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Encyclopedia ID: p24
Ned B. Klopfenstein, Mee-Sook Kim, Detlev R. Vogler, Bryce A. Richardson, Jane E. Stewart, and Paul J. Zambino
USDA Forest Service Rocky Mountain Research Station (1-2,4-6), Washington State University Department of Plant Pathology (4), USDA Forest Service Pacific Southwest Research Station (3)
Molecular genetic tools (e.g., genetic markers, DNA sequencing, and genomics) provide powerful methods for molecular diagnostics, genetic mapping, DNA fingerprinting, phylogenetic analysis, and population genetics of trees, pathogens, arthropods, invasive plants, and associated organisms in forest ecosystems. Such tools have become invaluable in diverse applications for detecting, assessing, and predicting environmental threats.
In recent years, molecular genetics has yielded a series of diagnostic tools that are essential for identifying, detecting, monitoring, and characterizing forest pathogens. These tools help to identify and monitor the spread of introduced, invasive, or evolving pathogens, and to determine their origins. Among introduced forest pathogens, molecular tools have been used to identify and/or detect Phytophthora ramorum (cause of sudden oak death), Discula destructiva (cause of dogwood anthracnose), Gremmeniella abietina (cause of Scleroderris canker of pines), and Fusarium circinatum (cause of pine pitch canker). Molecular markers have been used to distinguish aggressive races of forest pathogens (e.g., Sphaeropisis sapinea, the cause of diplodia tip blight of pines) and confirm interspecific hybridization among fungi causing poplar leaf rust, Dutch elm disease, Armillaria root rot, and Phytophthora disease of alder. Genetic markers can help identify virulence genes in forest pathogens and delineate pathogenic populations. Molecular genetic tools have been requisite for assessing disease threats, tracking epidemics, and monitoring pathogen change. This information is critical for effective disease management before and after a pathogen has invaded a forest. Similar approaches can be used to characterize arthropods, invasive plants, and nonpathogenic microorganisms associated with decomposition or biological control in forest ecosystems.
Molecular tools also provide essential information for assessing threats to forest trees. Various DNA markers can be used to characterize tree species, tree populations, and individuals. In genetic mapping, correlations between DNA markers and phenotypic traits are identified among progeny of crosses. With tree species, this allows identification of genetic loci controlling disease resistance or other phenotypic traits. At a broader level, genetic markers are useful to examine population structure and genetic diversity within forest tree species. Because genetically distinct tree populations can differ in their phenotypic responses, characterization of tree populations is necessary for meaningful assessment of abiotic and biotic environmental threats.
Recently, approaches that incorporate genetic marker technology, spatial modeling, and Geographic Information System data have been suggested for managing forest threats at the landscape level. Because population genetic structures vary across the environment and populations of forest trees and associated organisms often correspond to geographic features, the focus of management and threat response must be directed at the landscape level. Genetic structure and geographic distribution of pathogens, arthropods, invasive plants, beneficial organisms, and host-tree populations can be compared to site attributes such as temperature, moisture, soil properties, fire history, topographic characteristics, and management practices. Such analyses are critical in development of effective predictive models that will strengthen forest disease risk assessment.
For the near future, one can envision that the use of molecular genetic tools will be rapidly extended to many pathogens, arthropods, invasive plants, host trees, and beneficial microbes in forest ecosystems. Information derived from these molecular genetic tools will expand our understanding of threat assessment in forest management. One future challenge will be to integrate genetic, environmental, and landscape data in searchable databases that will provide end-users with valuable information for diverse applications.
corresponding author:
Ned Klopfenstein
USDA Forest Service
Rocky Mountain Research Station
1221 South Main Street
Moscow, ID 83843
208-883-2310
nklopfenstein@fs.fed.us
Encyclopedia ID: p115
Eric L. Smith and Andrew J. McMahan
The basis of assessing and predicting threats to forest health lies in being able to relate site and forest conditions to the likelihood and intensity of disruption by organisms and events. One major class of disruption agents are insects and pathogens: “pests” when and where the disruption decreases socially desired forest resource benefits. Since site and stand conditions have long been observed to influence the likelihood and intensity of impacts of a wide range of pests, a number of rating systems, simulation models, and related studied have been developed to assist managers in evaluating conditions, prioritizing treatment areas, and selecting treatments to be applied.
These models, hazard and risk rating systems and others, represent a quantification of a significant portion of the academic and applied knowledge of the nation’s forest pests, and pest risk response to management. These products are potentially useful tools in broad scale threat assessments. They are based on empirical data, knowledge of biological relationships, or constructed by experts with significant experience and insight. Many have been improved through testing or use; and many have some level of acceptance by natural resource professionals. The knowledge represented by these studies and tools represent an investment in time and resources, so if existing studies are not used it is not likely results from new studies would be available soon.
On the other hand, there are statistical, decision analytic, and other quantitative issues to consider when considering the use of these tools for broad scale assessments. These systems have usually been developed and calibrated for a limited geographical region or range of forest conditions. The systems may have been constructed as decision tools with imbedded management assumptions, not appropriate to current conditions. The analysis used in their construction may have been flawed or inappropriate; at least the goodness of fit of statistically-based models needs to be considered. In any case, the original data and analytical details of their construction may no longer be available to verify or modify the analysis. To apply the systems in broad scale assessments, the data for the model variables need to be available and of sufficient quality. Issues regarding the spatial scale of the original analysis relative to that of broad scale assessments should also be considered.
We have identified almost 200 published North American forest pest hazard and risk systems, and related studies and models, which could be considered for use in threat assessments. In this paper, we classify the relevant features of these systems which are needed to evaluate their potential usefulness in broad scale assessments. These features include scope of the original system (pest and host species, geographic or ecological range of application), original purpose (descriptive statistics of a sample, treatment priority ranking, marking or thinning guide, and others); method of analysis or model construction (regression-type analyses, scoring systems, expert opinion or multi-criterion approaches, complex computer simulation models, others); and other relevant factors. The systems and their features will be catalogued in a relational database and summary tables will be presented in this paper. The scope and applicability of existing published systems for specific pests will be compared to the recent and projected activity of these pests.
Additional issues concerning the application of single pest rating systems in ecosystem assessments will be addressed. Many systems provide an ordinal classification of stand hazard (high, medium, low, for example), or an index system which provides an ordinal scoring of conditions. Such systems for individual pests are not easily integrated into an assessment of multiple pests. Where systems produce impact outputs in absolute terms (BA mortality per area), a difficulty arises in representing positive interactions between multiple pest organisms, and consideration of the additivity of the impacts, so that the same tree is not projected as being killed more than once. Although many would consider empirical probability based models (for tree mortality, for example) to be superior to ordinal classification systems, it may be inappropriate to apply a probability model developed at one time and place to a different time and place.
Monitoring Methods Session - Tuesday Afternoon
corresponding author:
Eric L. Smith
USDA Forest Service
Forest Health Technology Enterprise Team
2150A Centre Avenue
Fort Collins, CO 80526-8121
970-295-5841
elsmith@fs.fed.us
Encyclopedia ID: p127
Kenneth Stolte and David Darr
A variety of forces and influences has shaped forest ecosystems throughout the evolutionary history of trees and forests. Native insects and pathogens, extreme weather events, and cyclic fires are part of normal ecosystem structure and function that includes weakening, death, regeneration, recycling, and replacement of trees and forests. Forests are adapted to endemic levels of native insects and pathogens that periodically become epidemic and temporally cause greater effects that recede with time. Periodic extremes of weather or long-term shifts in climate are also natural occurrences and forests adapt in a variety of ways. Fire is also an essential component of forest ecosystems, and provides many beneficial effects when it occurs within normal cycles of frequency and severity.
When these normal processes interfere with human use of forests, the condition may be undesirable but is not ecologically unhealthy or unsustainable.
Evaluating risk to forest health and sustainability necessitates enumeration of the type and magnitude of major stressors (national or regional-scale stressors), and knowledge of the impacts of stressors on forest ecosystems. Understanding the mechanism and severity of stressor effects facilitates understanding the effects of multiple stressors acting additively or synergistically on forest ecosystems. Exotic invasive species (particularly insects, pathogens, and plants); fragmentation and land-use change; air pollution (gases, acids, fertilizers, and climate change); changes in ecosystem processes due to management activities such as fire suppression and selective harvests; and exacerbated populations of native species due to compositional or functional changes in forest ecosystem comprise one list of the top 5 stressors that have, or have potential to, affect tens of millions of acres of forest lands in the U.S.
This paper evaluates the magnitude of effects on forests by many of these major stressors, and area and percent of forests where key ecosystem processes have been altered but the causal agent(s) are unknown. These stressors and effects on forest ecosystems are delimitated by Criterion 3 of the Montreal Process Criteria and Indicators (MPCI). Criterion 3 contains the biotic and abiotic stressors (Indicator 3.a.), air pollution stressors (Indicator 3.b.), and changes in biological indicators of ecological processes or continuity (Indicator 3.c.).
Relatively large areas of forestland in the
Globally, the period 1996 to 2000 was part of the warmest decade (1991–2000) in the historical record, and 1998 was the warmest year since 1861. This observation suggests that temperatures in
The introduction and spread of exotic, invasive species (insects, pathogens, plants, and animals) currently threaten many forest ecosystems. Exotic insects and pathogens have decimated native tree species such as American chestnut, butternut, American elm, eastern hemlocks, dogwoods, American beech, white pine, and others. An estimated 117 exotic insect species have been introduced into the
Exotic pathogens have greatly altered the composition, structure, and function of some forests. Introduced, nonnative pathogens have devastated several native
Sudden Oak Death disease, European pine shoot beetle, and Asian longhorned beetle are other recently introduced pathogens and insects that are damaging trees or forests in the
Kudzu, tree of heaven, and empress tree are a few examples of introduced plants that kill or replace native trees in Eastern forests and cause a general change in forest composition and function. New exotic species that change forest composition, structure, and function continue to be introduced into the U.S. as a result of ever-increasing global commerce despite our knowledge that these damaging agents have been negatively affecting forest health and sustainability for more then a hundred years.
Air pollutants that affect forest health and are of greatest concern fall into three broad categories: (1) acidifying agents (nitrates, sulfates, and other anions), (2) fertilizing agents (N-based compounds, nutrient cations, etc.), and (3) oxidizing agents (primarily ozone). Decreases in the protective stratospheric ozone layer by chlorides, methane, and other gases cause an increase in ultraviolet-B (a type of radiation from the sun) that is a related concern because sparse data is available to evaluate the nature and severity of effects on forest ecosystems, and the area of forests affected.
The response of forest ecosystem processes to known or unknown stressors relies on biological indicators as surrogate measures of effects on these processes because it is difficult or impossible to directly evaluate ecosystem processes at large spatial scales. Thus defoliation and crown dieback gives an estimate of the essential process of photosynthesis, carbon fixation, and photosynthetic efficiency (related to growth) since the amount of foliage is a limit on the amount of carbon that can be fixed. Similarly, mortality volumes are related to key processes such as reproduction, carbon cycling, and seral development. Significant changes in tree crown conditions and mortality volume indicators related to key ecological processes were found over large areas of Western and Eastern forests. It was not possible to associate all observed negative effects with specific causal agents at this time.
Changes in ecological condition from altered fire regimes affect many ecological processes. Changes in historic fire cycles affected all regions, with moderate (condition 2) to substantial (condition 3) changes in historic fire regimes affecting large areas. The absence of fire from many forests for nearly 100 years has exacerbated forest health problems including dwarf mistletoe in many western forests, oak decline in the Ozark and
Fire is sometimes a damaging agent that adversely affects forest productivity with respect to human values. During much of the 20th century, fire prevention and fire suppression greatly reduced tree mortality and soil erosion that had formerly occurred on vast areas of southern and western forests. Such management preserved forests for many desirable uses and contributed to the increasing timber productive capacity of forests throughout the
Monitoring Methods Session - Tuesday Afternoon
corresponding author:
Kenneth Stolte
USDA Forest Service
Southern Research Station
3041 E. Cornwallis Road
Research Triangle Park, NC 27709
919-549-4022
kstolte@fs.fed.us
Encyclopedia ID: p124
Frank H. Koch and William D. Smith
Historically,
Humans are increasingly the most important facilitator of forest pest introduction and spread, even at the landscape level. Moreover, with expanding global trade and interstate commerce, the number of potential forest invaders is likely to rise, making the analysis of human-mediated pathways particularly timely. In this synthesis, we present a number of spatial data sources that can be utilized to represent these human-mediated pathways. Collected by federal agencies and private companies for a range of purposes, these data sets can be manipulated to represent forest pest risks either directly or indirectly. Although general in nature, queries can often be used to tailor these data sets to address specific pests. Perhaps most importantly, the source data can usually be acquired for free or at negligible cost.
Using the sudden oak death pathogen (Phytophthora ramorum) and other pests as examples, we illustrate how some of these data sources can be used for mapping risks associated with human-mediated pathways. First, we demonstrate the use of foreign import cargo statistics, both marine and airborne, to assess the risk of introduction of new species at
While many of these data sets are imperfect depictions of human-mediated pathways, integration of several can add significant depth to early-detection/rapid-response projects. For instance, they can be used in conjunction with up-to-date climate and host species data to yield refined epidemiological maps, and as backdrops for simulated forest pest introductions. Furthermore, many of these data sets are applicable for forest threats other than pests. To facilitate further applications, we discuss current limitations, future information needs, and potential sources of additional data regarding human-mediated pathways.
Exotic Pests Session - Tuesday Afternoon
corresponding author:
Frank H. Koch
Department of Forestry and Environmental Resources
North Carolina State University
2028 Biltmore Hall
Campus Box 8001
Raleigh, NC 27695
919-549-4006
fkoch@fs.fed.us
Encyclopedia ID: p126
D.A. Weinstein and P. B. Woodbury
The USDA Forest Service has recognized a need to develop integrated approaches to assess the probable effects of multiple stresses. As part of this effort we conducted a state-of-the-science review of probabilistic regional risk assessment methodologies. The goals of this review were to: (1) Describe methodologies currently in use, identifying the methods that are capable of evaluating the threats to ecosystems from fire and fuels, invasive species, loss of open space, unmanaged outdoor recreation, and other key stresses; (2) Evaluate the usefulness of these methodologies for the Forest Service, including the advantages and disadvantages of each of these methods; and (3) Provide preliminary evaluation of the available databases as sources for these methodologies. This paper presents the conclusions of this analysis, highlighting methods useful for evaluating the risk to fire as an example. A companion paper presents the results of our survey of methods available for evaluating the risk of invasive species.
Much effort has gone into creating a capability of predicting fires throughout the region, both in their likely location and frequency. To create this capability, fire modeling systems have been established using a fine-scale grid of data on the landscape, such as fuel loads, vegetation, and climate trends. For example, LANDFIRE is a system that has been adopted by the Forest Service for assessing the risk of fire throughout the U.S. LANDFIRE depends heavily for this assessment on well-tested models such as FARSITE.
The great proliferation of fire modeling systems in different portions of the
Maintaining so many different types of models might be unwieldy and confusing to potential users. However, we strongly advocate that fire risk be estimated by a number of fire models run in parallel. If different models, especially those using different approaches and different data, predict similar patterns of risk, it will increase confidence in these predictions and make them more useful for management decisions.
corresponding author:
David Weinstein
Cornell University
Department of Natural Resources
8 Fernow Hall
Ithaca NY, 14853
607-351-4214
daw5@cornell.edu
Encyclopedia ID: p121
P.B. Woodbury and D.A. Weinstein
We conducted a state-of-the-science review of probabilistic regional risk assessment methodologies to identify the methods that are currently in use and capable of evaluating the threats to ecosystems from fire and fuels, invasive species, loss of open space, unmanaged outdoor recreation, and other key stresses. In a companion paper we highlight methods useful for evaluating the risk to fire. In this paper we give the results of our survey of methods available for evaluating the risk of invasive species.
The issue of invasive species is large and complex because there are thousands of potential invasive species, and there is constant movement of new and established plants, plant material, pests and pathogens. The most cost-effective approach is to control invasive species very early in the process of transport from the native range and entry. However, even a semi-quantitative “rule-based’ approach can help to identify locations that contain susceptible host species for specific pathogens or insect pests, and where propagules are more likely to enter based on the current locations of the invasive species, ports of entry, and methods of spread. Predicting long distance movement is much more difficult, as such events are rare, often poorly understood, and are often influenced by human behavior. Published methods to make probabilistic predictions of pest establishment could be expanded to provide quantitative estimates of spread beyond an initial port of entry. Many invasive species are transported along roads, and so road networks provide some information about the likelihood of introduction into a new region. Unmanaged recreation and land use change including forest fragmentation and ex-urban development are key interacting factors for assessing the risk of invasive species. .
Models based on fundamental biological and physical processes, such as population demographics and movement of organisms, are preferable to correlative statistical approaches. These may be useful to quantify the overlap in spatial distribution of stressors and ecological receptors. Process-based models may be extended with some confidence beyond the range of available data because they use predictor variables that represent physical and biological processes. The use of data on non-indigenous species to predict the occurrence of much rarer invasive species may be quite useful because the correlation is based on the key processes of human-influenced transport, establishment, reproduction, and dispersal of propagules. If the number of non-indigenous species in a region can be predicted based on some measure of the transportation network, or other environmental factor, one could extrapolate to future conditions with more roads or a higher traffic volume. Ecological niche modeling approaches are useful because they can use data from museum collections in other countries to make estimates of potential new range areas in the
As for any regional stressor, the use of multiple models and a weight of evidence approach would help to increase confidence in predictions of ecological risks from invasive species. Two approaches to predicting the risk of Asian long-horned beetle throughout
corresponding author:
P.B. Woodbury
Department of Crop and Soil Sciences
Cornell University
1017 Bradfield Hall
Ithaca, NY 14853
607-254-1216
pbw1@cornell.edu
Encyclopedia ID: p122
Brian W. Geils and Geral
Rocky Mountain Research Station
Managers of wildland ecosystems attempt to mitigate perceived risks, vulnerabilities and costs in the search for ecosystem sustainability. The science of risk analysis provides conceptual frameworks and assessment procedures for describing failure probabilities and consequences—usually with statistics and social-economic valuation. Risk analysis consists of three fundamental activities. On the basis of experience or expectation, a yet unrealized event is recognized as a potential threat to some management goal or value. When a warning from monitoring or research is received, event probability, extent, and severity are projected (e.g., a pest risk map). Concurrently, assessments are made of the values at risk and alternative costs of mitigation. For wildland managers values include such abstract goals as sustainability, forest health, resource productivity, and ecosystem integrity. The first challenge is to specified quantifiable objectives. Important considerations are estimation of uncertainty and the realization that intervention can modify but not completely determine the behavior of complex, natural ecosystems.
Although a diversity of users and context provides a rich source of ideas, all analysis is constrained by the world view of analysts and colored by their specific terminology (paradigm). Regarding management of wildland ecosystems, the extant world view favors equilibrium, historic conditions (or a range of reference conditions) and certainty of outcome. Ecological threats are viewed as those causing departures from the desired equilibrium and correction requires return the previous “natural” state. Management is perceived as an engineering problem of local and immediate control. An alternative view, however, recognizes that ecosystems are dynamic and connected—entrained by larger and slower systems of the hierarchy and resilient due to legacy structures and processes at the internal and lower levels. Ecosystem response after disturbance can be contingent on initial conditions and only predictable within a general (chaotic) or new (catastrophic) range. Ecological threats of special interest are those from eruptive populations (e.g., bark beetles and defoliators) and immigrant or emergent invasives (e.g., stem rusts or root diseases). The challenge of managers is how to facilitate the ecological and genetic accommodation of host and parasite populations with desirable outcomes. Promising new approaches for assessing risk are suggested from new multidisciplinary efforts under titles such as landscape genetics and landscape pathology.
In this synthesis, we present and support a conceptual framework for risk analysis based on the premise that system behavior (ecosystems or pathosystem) is determined by local conditions and specific historic and spatial connections. Spatial domains of various sizes are characterized by common environmental drivers such as temperature, rainfall, soil type, and insolation, Spatial domains are repeated across the landscape; their location can move with shifts of the environmental drivers (are sensitive to climate and land use changes). The biotic communities inhabiting these spatial domains have evolutionary histories influenced by varying time and spatial scales; and when perturbed, they exhibit the potential for multiple stable states. This new world view of ecosystems places a premium on an informed understanding of local dynamics and constraints. Certain forest insects, fungi, and other parasites or symbionts have an enduring, intimate association with their forest tree hosts (dominant vegetation and spatial domain partners). These associations have significant ecological and evolutionary significance that is meaningful for projecting the responses of wildland ecosystems to various disturbances.
We present evidence for the validity and utility of a model of evolutionarily significant units (ESU). These units represent long-term biotic interactions in a geographical location affecting ecological functions, resulting from persistent genetic discontinuities. We suggest these discontinuities are congruent over taxa, often form at geographic barriers, but can form in the absence of such barriers, and often have pervasive effects on host–parasite interactions. These zones may be demonstrated by changes in adaptive traits using techniques of landscape genetics (molecular makers). The ESU model provides an opportunity to more realistically map and project threats to wildland ecosystems from native and introduced forest pests. Specific examples are illustrated with white pine blister rust, fusiform rust, Armillaria root rot, budworm, and other disturbance agents.
corresponding author:
Brian W. Geils
USDA Forest Service
Rocky Mountain Research Station
2500 South Pine Knoll Drive
Flagstaff, AZ 86001
928-556-2076
bgeils@fs.fed.us
Encyclopedia ID: p123
Kurt Riitters, James Wickham, Timothy Wade, and John Coulston
USDA
Advances in landscape ecology, remote sensing, and geographic information systems have enabled status and trends reporting of forest fragmentation and other aspects of landscape spatial pattern at national to global scales. Until now, the information has been used mainly for ecological monitoring and for indicator-based environmental “report cards,” for example in international reports by the Montréal Process and the Millennium Ecosystem Assessment, and national reports by Forest Health Monitoring, the
The first part of this paper provides a synthesis of the science and technology of landscape pattern analysis as it relates to large-area ecological risk assessment. A key element of landscape assessment is the availability of consistent maps at national to global scales and we summarize the available data and prospects for improvements. A brief review of pertinent theory in landscape ecology will set the stage for a synthesis of our research over the past decade that has focused on advances in large-area landscape assessment protocols. Because future risk is tied directly to current conditions, we also provide an overall summary of forest spatial patterns in the
The second part of this paper focuses on the plan for a forward-looking risk assessment of landscape patterns in the 2010 RPA Assessment. The approach is motivated partly by our pragmatic perspective because this is a real-world risk assessment that must be completed in less than two years without substantial funding. The plan makes the best use of the available data and does not rely on data or research results that will not be available. Motivation comes also from a top-down assessment perspective that is consistent with a multiple-scale landscape ecological view of risk to all ecological endpoints in forested ecosystems. A novel feature of our approach is that it focuses on pattern itself, rather than on the endpoints that depend on pattern; if a landscape-scale forest pattern changes substantially, then all of the pattern-dependent ecological processes embedded in the landscape are at risk, even if all of the fine-scale details cannot be predicted. The plan is to use relatively coarse-scale data and models to identify specific locations at highest risk, and which aspects of forest pattern are at risk. The expectation is that local to regional cases of interest will receive more detailed follow-up investigation, if warranted. In summary, our assessment is designed to identify specific locations for remediation or prevention, to suggest general strategies for landscape pattern management that will be most effective at those locations, and to assist in prioritization of efforts by national policy formulators and land management agencies. We will use examples drawn from the literature of biodiversity, water quality, and invasive species to demonstrate these concepts and contrast them with traditional bottom-up approaches to ecological risk assessment.
corresponding author:
Kurt Riitters
USDA
3041 E. Cornwallis Road
Research Triangle Park,
919-549-4015
kriitters@fs.fed.us
note: oral presentation only
Encyclopedia ID: p111
Deborah Page-Dumroese, Martin Jurgensen, Carl Trettin, Mike Curran , and Dan Neary
USDA Forest Service Rocky Mountain Research Station (1,5) and Southern Research Station (3), Michigan Technological University (2), and British Columbia Ministry of Forests (4)
Maintenance of soil quality is an outcome government agencies and landowners strive to achieve after site management to maintain site productivity, hydrologic function, and ecosystem health. Soil disturbance resulting from timber harvesting, prescribed fire, or site preparation activities can cause declines, improvements, or have no effect on site productivity and hydrologic function. Soil resource information can be used to determine the stress level and ecosystem functions of stands and may be one method used to determine disease or insect outbreak risk. Soil physical properties, water regimes, and biogeochemical properties are key characteristics that can be affected by soil disturbance and in turn affect site quality and the susceptibility of stands to insects and disease outbreaks. In addition, overstocked stands, increased climatic variation, drought, type conversion, and susceptibility to wildfire can contribute to changes in soil quality that leads to outbreaks of insects and diseases in many ecosystems. For example, changes in ecosystem properties associated with changes in overstory properties alter the resilience of these stands. Similarly, loss of western white pine in the northwestern USA from blister rust infection has caused a type conversion to forest species that are not tolerant of root diseases, are not fire resistant and sequester nutrients in the surface mineral soil and tree crown that can later be lost through logging or fire. In the southwestern USA, overstocked ponderosa pine stands become water and nutrient stressed leading to insect outbreaks and catastrophic wildfires. These relationships and others can be used in conjunction with soil resource data bases to assess susceptibility to threats and to help develop management strategies to mitigate disturbances.
Land Session - Wednesday Afternoon
corrresponding author:
Deborah Page-Dumroese
USDA Forest Service
Rocky Mountain Research Station
1221 S. Main
Moscow, ID 83843
208-883-2339
ddumroese@fs.fed.us
Encyclopedia ID: p131
Virginia H. Dale
Department of Energy Oak Ridge National Laboratory
Ecological risk assessment (ERA) has been practiced for approximately 20 years in a variety of environmental applications. At a recent workshop sponsored by the Environmental Protection Agency, researchers and practitioners came together to discuss their cumulative experience, and suggest steps for improving the utility of ecological risk assessments in environmental decision-making. Workshop participants addressed ecological risk assessments in three decision-making contexts: product health and safety; management of contaminated sites, and natural resource protection. For each of the three decision-making applications, workshop participants evaluated four over-arching issues: problem formulation and hypothesis testing; spatial and temporal scale; biological scale; and decision-making in the presence of uncertainty. The workshop participants came to several conclusions. Problem formulation is a critical step in ERA and requires: improved communication between risk managers and risk assessors; careful consideration of critical ecological attributes; and moving beyond traditional null hypothesis testing and toward innovative analytical approaches (e.g., Bayesian analysis, causal argumentation). Current methods are available to conduct ERA’s at different spatial, temporal and biological scales. However, effective implementation of landscape level ERA’s requires more relevant data and explicit guidance to better integrate multiple lines of evidence for a range of biological responses. The utility of ERA’s for decision-making can also be increased by: probabilistic risk assessment methods that include quantitative uncertainty estimates. Finally, the uncertainty associated with ERA’s will also be assisted by systematic approaches in post-ERA monitoring, and data collection and storage.
corresponding author:
Virginia H. Dale
Oak Ridge National Laboratory
Bethel Valley Road, Building 1505, Room 200
P.O. Box 2008
Oak Ridge, TN 37831-6036
865-576-8043
dalevh@ornl.gov
note: oral presentation only
Encyclopedia ID: p132
T.L. Shore, A. Fall, W.G. Riel, J. Hughes, and M. Eng
Several bark beetle species, mostly in the family Scolytidae, have the potential for dramatic population increases under favorable forest and climate conditions which can result in landscape scale mortality to the host tree species. For example, the mountain pine beetle (Dendroctonus ponderosae Hopk.) has killed between 20% and 30% of mature lodgepole pine over 10 million ha in
Landscape-scale risk assessment of bark beetle infestation aims to quantify the spatial and temporal likelihood of attack extent and severity. We have developed and applied a range of methods from structural risk (i.e. strictly assessing patterns) to functional risk (i.e. assessing interactions and feedbacks between pattern and process).
Susceptibility and risk rating systems classify each stand or grid cell of a landscape according to local characteristics (e.g. stand age, distance to nearest attack). As such, these approaches are temporally static with limited spatial accounting, but have the benefit of limited data requirements and ease of application. Although likely pathways and interactions with management cannot be identified, the mountain pine beetle (MPB) susceptibility and risk rating system remains one of the most widely used tools.
Spatial connectivity assessment increases the spatial dimension from rating systems. Our approach to connectivity assessment uses spatial graphs to analyze scales at which patches of susceptible hosts are well-connected, in particular with existing attack. These methods are relatively easy to apply and data requirements are fairly modest (although information on movement cost/impedance is required). Although still static in nature, likely pathways can be identified, and large areas can still be processed efficiently.
Empirical information on infestation progression can be used to increase the temporal dimension with semi-Markovian projection models. These methods require moderate effort to develop and data requirements, requiring historical time series information. A key assumption is that future outbreak dynamics will mimic past trends. However, they allow trends to be identified and interaction with management scenarios to be explored.
Dynamic population models make a shift to a more process-oriented approach to modeling outbreak dynamics by explicitly capturing demographic changes in space and time with processes of mortality, birth, dispersal, etc. Such approaches require substantial effort to develop and have fairly high data requirements, in particular the need for a reasonable understanding of beetle biology and interactions with hosts at relatively fine scales. The advantage is a closer match with the ecological process, and greater ability to assess interactions with management.
Individual-based dispersal models allow more detailed exploration of how beetles may interact functionally with a landscape. However, such approaches are generally prohibitive at the landscape scale due to lack of sufficient data (both for details of landscape pattern and beetles) as well as computing power (especially for a large outbreak).
We have developed and applied the above methods, with the exception of the latter, for assessing MPB risk at landscape scales in pine forests of
corresponding author:
Dr. Terry L. Shore
Natural Resource Canada
Canadian Forest Service
506 W. Burnside Rd.
Victoria BC Canada V8Z 1M5
250 363-0666
tshore@pfc.forestry.ca
Encyclopedia ID: p114
Robert H. Beach, Erin O. Sills, Tzu-Ming Liu, and Subhrendu K. Pattanayak
RTI International, North Carolina State University, North Carolina State University and RTI International respectively
Severe weather events that bring high winds and/or heavy precipitation (e.g., hurricanes and ice storms) regularly cause major disturbances to U.S. forests, significantly impacting both ecological conditions and economic returns to forest landowners. Forest landowners may suffer from the loss of merchantable timber; increased risk of wildlife, disease, and pests in damaged stands; and depressed timber prices in the immediate aftermath of events that cause widespread damage. These risks have a substantial impact on the expected economic returns to forestry as well as leading to distributional impacts among producers and between consumers and producers. This has led to considerable interest in identifying factors that influence damage levels as well as ways to mitigate damages. Anecdotally, many forest managers associate damage with silvicultural activities such as thinning. However, previous studies have focused almost exclusively on biophysical properties of forest plots or individual trees to explain differences in damages without explicitly examining the role of landowners’ forest management decisions. Overlooking the impacts of management decisions on the risk of weather damages may lead to inefficient decision-making by policy-makers and private landowners.
Timberland throughout the U.S. South has been affected by a number of major hurricanes over the past century (Lutz 2005). Hurricane strength winds can cause severe defoliation and can directly damage and kill trees through uprooting, breakage and loss of minor and major branches, as well as stem breakage. For example, Hurricane Hugo damaged over one-third of South Carolina’s timberland in 1989. The damaged volume of timber was estimated to be 1.3 billion cubic feet (Remion, 1990). Major ice storms may also result in substantial damages or death for affected trees due to branch and stem breakage. In January of 1998, an ice storm hit southeastern Canada and the northeastern U.S. and damaged over 10 million hectares of forestland (Irland, 1998; Miller-Weeks, Eager, and Peterson, 1999).
The immediate loss of timber is not the only risk imposed by weather events. The increased number of broken and uprooted trees raises the risk of wildfires as well as disease and pest outbreaks for the surviving trees. Forest landowners also may be affected by depressed timber prices, at least in the short run. Production risk has an unambiguous negative impact on optimal rotation length, expected returns to forestland, and land value, although the effects of price risk are ambiguous (Prestemon and Holmes, 2000; Prestemon, Pye, and Holmes, 2001).
In this paper, we review and synthesize the literature on the risk of forest damages from severe weather, the factors that influence risk, and alternatives for mitigating risk. Damage severity depends on the interaction of numerous factors related to biological, topographical, and stand characteristics. For instance, although wind speed is the most important factor contributing to timber losses due to high winds, topography and soil conditions also determine a stand’s resistance to wind loading. From the perspective of forest managers, a key question is what they can do to decrease the risk to a given tract of timberland. Forest management can change susceptibility to wind damage through effects on stand characteristics such as tree species, tree height, tree diameter, crown area, rooting depth and width, and stand density (Kerzenmacher and Gardiner, 1998; Peltola et al., 1999; Peltola et al., 2000; Dunham and Cameron, 2000). Stand age and forest structure may also contribute to vulnerability of forest to high winds (Everham and Brokaw, 1996; Francis, 2000; Mitchell, 1995; Ruel, 1995). Similar factors have been related to the degree of ice damage to forests (Bragg, Shelton, and Zeide 2003). Thus, we can identify options for mitigating weather risk, including choices about tree species, silvicultural practices such as bedding and fertilization, and thinning regimes (Persson, 1975; Lohmander and Helles, 1987; Zeng et al., 2004; and Olofsson and Blennow, 2005).
To illustrate findings from the literature, we examine the impacts of Hurricane Fran on forests in North Carolina. Using Forest Inventory and Analysis (FIA) data and a simulated wind field generated with the Federal Emergency Management Agency’s HAZUS-MH model, we estimate the influence of forest management decisions on the probability and magnitude of storm damages, controlling for other biophysical factors. This type of empirical analysis can inform forest management decisions and increase the efficiency of public policy that encourages timber stand management and compensates landowners for weather damages.
Air and Water Session - Thursday Afternoon
corresponding author:
Robert H. Beach
RTI International
3040 Cornwallis Road
Research Triangle Park, NC 27709-2194
919-485-5579
rbeach@rti.org
Encyclopedia ID: p118
Alejandro A. Royo and Walter P. Carson
USDA Forest Service Northeastern Research Station and University of Pittsburgh Department of Biological Sciences
Exotic invasive plants are recognized as serious threats to forest ecosystems and have received considerable attention from the scientific community for decades. Less emphasized are the many native forest understory plants that rapidly increase their spatial distribution following multiple disruptions to an ecosystem’s natural dynamics. In many cases, these species expand and form persistent, monodominant thickets. No matter where these native plant invasions occur, they are characterized by one or more of the following: 1) The understory layer typically has greater vegetation cover and lower diversity than was common in forest understories in the past. 2) This layer can delay stand renewal and alter species composition by inhibiting tree regeneration. 3) Once this layer is formed it can resist displacement by other species and remain intact for decades. In this paper we evaluate the processes that trigger the expansion of several plant species native to temperate and boreal forests across North America and review their ecological characteristics to provide general guidelines in assessing native invasion risk in forest stands.
We argue that major anthropogenic changes to disturbance and browsing regimes bring about the monopolization of the forest understory by native plants. In all cases reviewed, aggressive understory plant expansion followed alterations in overstory disturbance regimes. Although these disruptions included predictable and manageable impacts such as tree harvesting, other less predictable overstory disturbance agents including catastrophic fires, insect outbreaks, and pathogens were involved. Assessing and managing risk from these alternative threats is challenging as their occurrence is often erratic, hard to control, and not limited by land ownership and administrative boundaries. In majority of the cases (>60%) the risk to forest understories was particularly acute if the effects of multiple stressors occurred in a stand, either in tandem or within a short period of time. Specifically, the synergy between overstory disturbance and uncharacteristic fire regimes or increased herbivory strongly controls species richness and leads to depauperate understories dominated by one or a few species.
We suggest that aggressive expansion by native understory plant species can be explained by considering their ecological requirements in addition to their environmental context. Some plant species are particularly invasive by virtue of having life-history attributes that match one or more of the opportunities afforded by multiple disturbances. Increased overstory disturbance selects for shade-intolerant species with rapid rates of vegetative spread over slower growing shade-tolerant herbs and shrubs. Altered fire regimes select for only those species that can survive the fire or resprout thereafter. Finally, overbrowsing selects for only those species that are well defended or tolerant to browsing. Ultimately, these processes create novel conditions that favor only a small subset of species that possess some combination of the following life-history characteristics: rapid vegetative growth, relatively shade-intolerant, fire-tolerant, and herbivore-tolerant. The result is a low diversity but dense understory that can persist for long periods of time even if the canopy closes.
The framework advanced by this review will help guide land managers in assessing the risk of native understory plant invasion within their stands. We suggest vigilant monitoring of stand conditions to ensure that alterations to the overstory and understory disturbance regimes do not operate concurrently, particularly when control over these factors falls under the purview of different management agencies (e.g. wild game vs. forestry management agencies). We caution that decisions regarding partial or complete overstory removals should consider a site’s understory conditions including inadequate advance regeneration, presence of clonal understory plants, fire history, and high herbivore impact. Finally, we suggest the implementation of management practices that more closely resemble natural disturbance levels.
Native Pests Session - Wednesday Afternoon
corresponding author:
Alejandro A. Royo
USDA Forest Service
Northern Research Station
P.O. Box 267
Irvine, PA 16329-0267
814-563-1040
aroyo@fs.fed.us
Encyclopedia ID: p117
Andrew Liebhold, Patrick Tobin, and Kurt Gottschalk
USDA Forest Service Northern Research Station
The process of biological invasion is recognized to be composed of three distinct phases: arrival, establishment and spread. In this review, we concentrate on spread which refers to the expansion of a newly established alien species into suitable portions of the exotic habitat. Understanding the processes that facilitate spread of an alien pest species is critical to the development of strategies for retarding or containing its expansion into new areas. Furthermore, prediction of spread may be of critical importance to development of forest management plans where the pest is expected to invade in the future. We present here a review of the literature on the population ecology of range expansion and provide a discussion, illustrated with examples, of how spread predictions can be integrated with landscape-level forest composition data to aid decision-making.
Most of our understanding of range expansion by alien species has it roots in two papers published in the 1950’s. The first of these was by Skellam who formed a simple reaction-diffusion model that combines exponential population growth with random (diffusive) dispersal. Around the same time, Fisher proposed a model for the spread of an advantageous allele by combining logistic growth with random movement. An elegant property that emerges from both of these models is that the asymptotic rate of radial expansion should be constant and can be predicted as 2 * sqrt(r * D), where r is the intrinsic rate of population growth and D is the diffusion coefficient. While these models greatly simplified many aspects of spread, they have performed remarkably well at capturing the dynamics of spread of many different types of organisms. They also provide an elegant representation of how spread is completely determined by either population growth or by movement; any characteristic of a species or a habitat that affect either of these will affect spread.
One feature of many alien species that has been found to greatly influence rates of spread is the mechanism of dispersal. Some species may be capable of more than one mode of dispersal (e.g., passive movement plus accidental movement by humans) and this feature, termed “stratified diffusion”, has been shown to greatly influence rates of spread. Instead of gradually expanding into contiguous areas, such species may “jump” ahead of the expanding population front and form isolated colonies that expand and coalesce. The movements that cause populations to “jump” ahead are thus of critical importance in determining where and how fast populations will spread. Furthermore, this population behavior provides opportunities for containing the spread of a species; any action that either diminishes jumping or retards the growth of isolated colonies may be an effective approach to limiting range expansion.
Without some understanding of the population biology of an organism, it is impossible to predict spread with any meaningful level of precision. In addition geographical variation in land use and forest composition may affect growth and dispersal of invading populations and thereby affect spread rates, but these effects may be complex and difficult to predict. Landscape-level data on forest composition may thus be of some value in predicting spread but may be even more useful for predicting impacts of pests once they have established in new areas. Bioeconomic models that incorporate geographical variability in forest composition may be of critical value in predicting pest impacts and identifying strategies for minimizing future impacts.
corresponding author:
Andrew Liebhold
USDA Forest Service
Northern Research Station
180 Canfield Street
Morgantown, WV 26505
304-285-1512
aliebhold@fs.fed.us
Encyclopedia ID: p112
USDA Forest Service Southern Research Station
Over 1.5 million fires are set by arsonists each year in the
Research since the 1980s has shown some scope for interventions into wildland arson wildfire processes, in order to reduce their frequency and social impacts. A study by Donoghue and
We also contend that advances in our understanding of this phenomenon can be obtained by evaluating how wildland arson fits into the broader picture of crime. Until recently, wildland arson research has ignored recent findings that have documented spatial and temporal autocorrelation of criminal activities (hotspots) (e.g., Bowers and Johnson 2004). An understanding of wildland arson could also be enhanced by incorporating ideas regarding how crime is related to economic conditions (e.g., Burdett et al. 2003, Gould et al. 2002) and social phenomena and deviance (e.g., Surrette 2002, Jacob and Lefgren 2003).
The objectives of this paper are to (1) place wildland arson into the context of other sources of wildfire ignitions and wildfire damages in various parts of the United States and other countries; (2) place wildland arson into the context of crime, especially how wildland arson activity is related to and compares with other criminal activity; (3) outline recent empirical research and the methods used to describe wildland arson, with a particular focus on the timing and spatial relationships of arson ignitions and how ignitions are related to socioeconomic variables, drawing upon research in the
Fire Session - Thursday Afternoon
corresponding author:
Jeffrey P. Prestemon
USDA Forest Service
Southern Research Station
PO Box 12254
Research Triangle Park, NC 27709
919-549-4033
jprestemon@fs.fed.us
Encyclopedia ID: p119
Paul G. Schaberg, Eric K. Miller, and Cristopher Eagar
USDA Forest Service Northeastern Research Station (1,3) and Ecosystems Research Group(2)
Considerable evidence now indicates that hydrogen ion (H+), nitrogen (N) and sulfur (S) additions from anthropogenic pollutant sources contribute to the leaching and depletion base cations such as calcium (Ca), magnesium (Mg) and potassium (K) from forest soils and ecosystems. Although the depletion of base cations can have varied and interacting influences on ecosystem function, it is the loss of Ca that may be particularly limiting to tree health and productivity. In contrast to other cations, Ca is not mobile in the phloem and is often immobilized in plant tissues in insoluble forms - processes that limit its biological availability and redistribution. In addition, Ca is often concentrated outside of cell membranes, uniquely increasing its vulnerability to direct leaching loss. Because Ca is an essential plant nutrient, Ca depletion raises important questions concerning the continued health and sustainability of forest ecosystems. Ca plays critical roles in plant cell function, including enhancing the stability of cell walls and membranes, and signal transduction processes that allow cells to sense and respond to stress. Considering these roles, Ca deficiency is expected to reduce tree growth and increase forest decline following exposure to even “normal” levels of stress that otherwise would pose no threat.
Controlled experiments with red spruce, sugar maple, and other species provide mechanistic support for theoretical expectations regarding the impacts of Ca depletion on tree health and productivity. For example, both H+ and N additions have been shown to reduce available Ca in red spruce foliage, simultaneously reducing foliar cold tolerance and increasing winter injury and crown degradation. New experimental evidence indicates that Ca depletion down-regulates another Ca-dependent process (stomatal closure), predisposing red spruce to drought damage. Data show that other tree species (eastern hemlock, balsam fir, and eastern white pine) experience the same mechanistic changes in Ca nutrition and physiology documented for red spruce. Importantly, many real-world examples for a variety of tree species (sugar maple decline, dogwood susceptibility to anthracnose, and hemlock susceptibility to the hemlock wooly adelgid) show that injury is often greater when Ca depletion and stress exposure co-occur.
Concerns about the influence of H+ and N deposition on Ca nutrition and forest health exist for industrialized regions around the world including eastern North America, Europe, and increasingly China. Indeed, especially in regions with low inherent soil fertility and/or high precipitation leaching, management options that either add Ca to systems or decrease its removal are being examined and sometimes employed. However, because not all tree species access, sequester or require Ca in equal levels, uniform standards for assessing thresholds in Ca depletion that require managerial actions remain elusive.
An alternative approach to defining plant-based thresholds for Ca deficiency is to model critical loads and exceedances in pollutant additions that likely disrupt ecosystem Ca cycles and lead to net losses in Ca pools within forests. For example, spatial associations of Ca cycling and loss to broad-scale data on forest health and productivity were recently conducted for portions of the northeastern United States. A steady-state ecosystem process model was coupled to extensive spatial databases and used to generate maps identifying forest areas likely to experience Ca depletion. Sustainable Ca supplies in forest ecosystems are functions of forest type, timber extraction intensity, prior land-use, atmospheric deposition rates, and site factors including climate, hydrology, and soil mineral weathering rates. Considering the unique vulnerability of Ca to leaching loss and its vital role in supporting tree stress response systems, the model focuses on how changes in Ca pools may influence forest health conditions. The model-based nutrient deficiency metric is a good predictor of independent “on-the-ground” indicators of current forest health and productivity. For oak and pine forests in Massachusetts, tree height and canopy transparency were significantly related to foliar Ca levels. A separate evaluation also showed promising results: a comparison of model results with multiple-year aerial surveys of forest damage in Vermont indicated that both the frequency of damage and size of damaged areas were related to modeled Ca deficiency. This model-based threat assessment identified 18-30% of NH and VT forests to be at risk of anthropogenic Ca depletion under current atmospheric deposition and harvesting rates.
Land Session - Wednesday Afternoon
corresponding author:
Paul Schaberg
USDA Forest Service
Northeastern Research Station
705 Spear Street
Box 968
Burlington, VT 05402-0968
802-951-6771 x1120
pschaberg@fs.fed.us
Encyclopedia ID: p130
Bernard R. Parresol
USDA Forest Service Southern Research Station
Uncertainties in models can be classified as natural, model, and data uncertainties. Environmental and biological systems are inherently stochastic. Some variables are random in principle, while other variables that are precisely measurable are modeled as random quantities as a practical matter due to the cost and/or effort involved with continuous measurement. Some quantities vary over time, over space, or across individuals in a population; this is termed variability. The differences in uncertainty and variability are relevant in decision making. The knowledge of the frequency distribution for variability can guide the identification of significant subpopulations which merit more focused study. In contrast, the knowledge of uncertainty can aid in determining areas where additional research or alternative measurement techniques are needed to reduce uncertainty. Mathematical models are simplified representations of the phenomena being studied. The structure of mathematical models used to represent biological systems is often a key source of uncertainty. Different sources of model uncertainties can be summarized as follows. (1) Model structure: uncertainty arises when there are alternative sets of assumptions for developing a model. (2) Model detail: often, models are simplified for purposes of tractability. (3) Extrapolation: models that are valid for one portion of input space may be completely inappropriate for making predictions in other regions of the parameter space. And (4) model resolution: selection of a spatial and/or temporal grid size often involves uncertainty. Uncertainties in data stem from a variety of sources. Some uncertainties arise from measurement errors such as random errors in analytic devices or systematic biases from imprecise calibration. Other potential sources of uncertainties include misclassification, estimation of parameters through a small sample, and estimation of parameters through non-representative samples. Uncertainty associated with model formulation and application can also be classified as reducible and irreducible. Reducible uncertainty can be lowered by better inventory methods, improved instrumentation, and improvements in model formulation.
Various approaches for representing uncertainty can be summarized as follows. (1) Classical set theory: uncertainty is expressed by sets of mutually exclusive alternatives in situations where one alternative is desired. This includes diagnostic, predictive and retrodictive uncertainties. (2) Probability theory: uncertainty is expressed in terms of a measure on subsets of a universal set of alternatives (events). The uncertainty measure is a function that assigns a number between 0 and 1 to each subset of the universal set. This number, called probability of the subset, expresses the likelihood that the desired unique alternative is in this subset. (3) Fuzzy set theory: fuzzy sets, similar to classical sets, are capable of expressing nonspecificity. In addition, they are also capable of expressing vagueness. Vagueness is different from nonspecificity in the sense that vagueness emerges from imprecision of definitions. In fuzzy sets, membership is a matter of degree. (4) Fuzzy measure theory: this theory considers a number of special classes of measures, each of which is characterized by a special property. Some of the measures used in this theory are plausibility and belief measures, and the classical probability measures. Fuzzy measure theory and fuzzy set theory are notably different. In fuzzy set theory, the conditions for the membership of an element into a set are vague, whereas in fuzzy measure theory, the conditions are precise, but the information about an element is insufficient to determine whether it satisfies those conditions. (5) Rough set theory: a rough set is an imprecise representation of a crisp set in terms of two subsets, a lower approximation and an upper approximation.
The aim of sensitivity analysis is to estimate the rate of change in the output of a model with respect to changes in model inputs. Such knowledge is important for evaluating the applicability of the model, determining parameters for which it is important to have more accurate values, and understanding the behavior of the system being modeled. Conventional methods for sensitivity analysis and uncertainty propagation can be broadly classified into three categories: (1) sensitivity testing, (2) analytical methods, and (3) sampling based methods. Sensitivity testing involves studying model response for a set of changes in model formulation, and for selected model parameter combinations. Some of the widely used analytical methods for sensitivity/uncertainty are: (a) differential analysis methods, (b) Green’s function method, (c) spectral based stochastic finite element method, and (d) coupled and decoupled direct methods. Sampling based methods involve establishing a relationship between inputs and outputs using the model results at the sample points. Some of the widely used sampling based sensitivity/uncertainty analysis methods are: (a)
Statistical Methods Session - Wednesday Afternoon
corresponding author:
Bernard R. Parresol
USDA Forest Service
Southern Research Station
200 WT Weaver Boulevard
Asheville, NC 28804
828-259-0500
bparresol@fs.fed.us
Encyclopedia ID: p125
Ralph J. Alig, Susan Stewart, David Nowak, David Wear, Susan Stein
Socio-economic forces drive forestland conversion, which is an issue because it results in substantial changes in ecosystem attributes. Landowners face increasing opportunity costs to keep land in forests as rising values for other land uses make forest ownership and return-on-forest investment less viable. When a forest is converted to a developed use, the loss of ecosystem services is direct and immediate, with some permanent habitat loss. For example, wildlife or fish species dependent on privately owned bottomlands at certain times of the year may disappear as these private lands are developed, regardless of quality of habitat remaining on adjacent public land.
Our synthesis paper examines trends in forest land conversions, use of theory in testing hypotheses and estimating models, empirical application of models in projections of forest land base changes, and policy implications of findings. Recent trends indicate the deforestation of more than one million
Land use theory guides research investigating determinants of forestland conversion. The conceptual model posits that landowners choose to develop land when the present value of the future stream of net returns generated by the land in a developed use exceeds the present value of the land remaining in forest use. Land markets demonstrate (via revealed behavior) what people are willing to pay to for alternative uses of land, such as for a developed use compared to forest use. With this economic theory as a foundation, impacts of population growth and rising personal incomes can be analyzed to model relationships between forest area change and other variables. Geo-referenced data now facilitates estimation of spatial land use change models.
Empirical applications of such models project land use change impacting forestry. The U.S. population is predicted to grow from 281 million in 2000 to 403 million by 2050, a major factor in projections that more than 50 million acres of nonfederal U.S. forests could be converted to urban and other developed uses in the next 50 years. In addition, tens of millions of acres of remaining private forests are projected to have increases in housing density. The Forests on the Edge project assessed threats to water quality and other forest benefits and impacts on nearby National Forests as more houses are built in private forests, and ranked watersheds by threat from development. Implications of these trends include greater edge effects that increase the risk of fire ignition, exotic species invasion, loss of wildlife habitat, and other disturbances.
We compare alternate projections to determine their sensitivity to model type and major assumptions; to assess uncertainty; and to compare them across spatial and temporal dimensions. From this we construct a composite outlook projecting near-term and long-term threats of forestland conversion, including identification of at-risk forests.
Policy implications and challenges include maintaining a robust suite of forest-based benefits (e.g., open space) in the face of continuing population growth. We discuss use of research-based findings to inform policy deliberations regarding risk mitigation alternatives pertaining to land use and forest benefits. Risk management involves intersectoral considerations; forestry is one of many possible land uses. Drivers of change such as urbanization affect many measures of resource condition, as examined in Renewable Resources Planning Act Assessments. Solutions to address conversions of forest land must be multi-faceted and should include improved valuation of forest-based environmental services. Land values provide important signals to land managers, and can be enhanced by wise management and by emerging markets for services such as carbon sequestration. Improving awareness and understanding of land values and their key role in the land conversion process is a goal of this research.
corresponding author:
Ralph Alig
USDA Forest Service
Pacific Northwest Research Station
3200 SW Jefferson Way
Corvallis, OR 97331
541-750-7267
ralig@fs.fed.us
Encyclopedia ID: p113
Shefali V. Mehta, Robert G. Haight, and Frances R. Homans
University of
Invasive species management relies considerably on assessing and managing risk. This arises from the inherent uncertainty of the invasion process, or the population dynamics of the invasive species. Managers face a daunting task as they incorporate the dynamic, spatial and stochastic aspects of invasive species into their decision making process. Numerous researchers have analyzed various components of risk and invasive species. Owing to the breadth of the issue, experts from many disciplines, including ecology, biology, economics, statistics and policy, have contributed to this extensive body of literature. This synthesis attempts to provide a comprehensive review and comparison the theory, evidence and application of risk analysis and invasive species management.
By its nature, risk analysis is the study of uncertainty and the attempt to qualify it, whether qualitatively or quantitatively. The uncertainty contributes to the lack of empirical evidence. In lieu of data, risk analysis literature often involves theory and numerical simulations. Additionally, the various disciplines propose different theories and applications. Understanding and reducing risk entails the study of these varied approaches and their interactions. Analyzing the interaction of ecological and biological knowledge, statistical analysis, and the allocation of limited resources, precipitates an understanding of risk analysis and its applications. However, the scope of this issue necessitates a narrower focus of risk analysis for invasive species.
Risk assessment and risk management are two different aspects of addressing risk. Often, these two are closely entwined. While this synthesis is not about risk assessment per se, the reliance of decision makers on risk assessment and its outcomes demands the inclusion of some aspects of risk assessment. As such, this synthesis discusses the major risk assessment outcomes and the methods for integrating risk assessment into the framework used by decision makers to mitigate risk.
This diverse literature requires a cohesive synthesis to unify these approaches. The invasion process provides a clear framework to present this synthesis. While the stages of the invasion process can be characterized in many ways, a widely accepted categorization divides the process into three main stages: introduction, establishment and spread. The accompanying management decisions are grouped into three main categories: exclusion, detection and management. Even though agencies engage in additional activities, these categories provide an adequate system with which to examine the decisions facing managers. Thus, the synthesis is arranged according to the chronological order of the stages of the invasion process. This provides an insightful comparison of the different approaches and applications of risk management at each stage. It also provides a sense of how these methods can be integrated to achieve effective outcomes.
For each invasion stage, the synthesis presents the key factors contributing to a species’ successful advance to each stage. These factors are determined by risk assessment using a variety of methods. The methods themselves are not explicitly discussed, but the relevant outcomes of the risk assessment are included. The synthesis then discusses the methods for incorporating the identified risk factors into a decision model for risk management. While the theory behind the risk management models is discussed, the emphasis is on the potential outcomes. After covering the simulated and empirical evidence, extant policies and applications are presented to illustrate the efficacy, or lack of, in the applications of the risk management theory and practices.
The dynamic nature of the invasion process frequently forces these management decisions to be taken simultaneously. Existing literature often analyzes the relationship between the management choices. Economics literature, for example, considers the optimal allocation between exclusion and management activities for the same species. The synthesis also integrates this literature into the framework; it provides the theory, and when available, the empirical evidence and applications of the theory.
By collecting and integrating the various approaches to risk management, this synthesis attempts to provide an in-depth review and comparison of current theory and its effective applications. Through the juxtaposition of various approaches, the synthesis also hopes to motivate further applications based on merging different strategies.
corresponding author:
Shefali V. Mehta
Department of Applied Economics
University of Minnesota
218d Classroom Office Building
1994 Buford Avenue
St. Paul, MN 55108
612-625-7242
meht0038@umn.edu
Encyclopedia ID: p129
Jay O’Laughlin
This synthesis paper provides guidance managers can use to conduct environmental analysis to support fuels treatment projects designed to reduce post-wildfire risks to ecological attributes. Wildfires burning in the uncharacteristic fuel conditions now typical of much of the western US pose risks to ecosystems and the valuable goods and services they provide, including aquatic and terrestrial habitats for fish and wildlife. One goal of the National Fire Plan (NFP) is hazardous fuel reduction. Fuels treatment can modify uncharacteristic wildfire behavior and the subsequent severity of post-wildfire effects, thereby providing benefits by reducing risks to firefighters, ecosystems, and structures. Implementation of fuels treatment projects also poses risks to ecosystems. Unless systematically analyzed and compared to risks of not doing treatments, project implementation risks can inhibit fuel treatment implementation, especially in areas inhabited by species protected by the federal Endangered Species Act (ESA). According to the US Government Accountability Office (2004), agencies recognize the need to better analyze the risk of acting to reduce fuels versus not doing so, but neither the NFP nor National Environmental Policy Act (NEPA) provide guidance specifying how to do this. How then can land managers determine whether the risk of actively treating fuels is greater than the risk posed by no action? The Environmental Protection Agency’s Guidelines for Ecological Risk Assessment (EPA 1998) can be adapted for this purpose. The key to analysis supporting fuel treatment decisions is the incorporation of the risk-reduction benefits of fuels treatment into a framework that facilitates comparison of alternatives. The resulting analysis can be used in NEPA environmental analysis documents to evaluate management alternatives, including no action. Comparing risks from uncharacteristically severe wildfire effects to potentially less severe net effects resulting from fuel treatments is consistent with NEPA’s requirement for public land managers to analyze short- and long-term environmental effects. Formulating the problem as a temporal comparison of adverse effects, however, often results in decisions to reject fuels treatment projects near imperiled species habitat. Adverse effects from fuels treatment are certain in the short term, whereas wildfire occurrence is uncertain. An alternative problem formulation focuses on the relative magnitude of adverse and beneficial effects from wildfire burning under different fuel conditions. By selecting a long-term planning horizon corresponding to fire return interval, wildfire and its effects become certainties. Instead of trying to confront the landscape-level uncertainties of if, when and where an uncharacteristically severe wildfire will occur, the environmental analysis question in the project area simply becomes, which pre-fire condition produces the more desirable post-fire effect: fuel treatment or no fuel treatment? Managers may accept the fuels treatment hypothesis: The adverse effects of short-term project implementation actions will result in substantial long-term net benefits from reduced severity of wildfire effects that outweigh the implementation risks. However, they need evidence to convince others who may be skeptical about this. A process developed from the EPA’s ecological risk assessment guidelines proceeds as follows. Risk problems are first formulated in a conceptual model comparing the relative magnitude of risks. This requires identifying a specific ecological entity to serve as the risk assessment endpoint, and the cause-and-effect relationships of various threats (i.e., hazards or stressors) that adversely affect the endpoint. The EPA cautions against using vague endpoints like integrity or sustainability, thus risk assessment enhances the clarity of objectives and transparency of decision processes. For example, fish are a risk assessment endpoint, and one stressor adversely affecting them is sediment from logging and/or wildfire burning under different conditions that vary according to fuel loadings. The model compares short-term sediment effects of implementing fuels reduction treatments to the longer-term post-wildfire sediment pulse effects with and without fuel treatments, including risk reduction benefits. The analytical model graphically answers the question: Which is worse for fish, wildfire burning under untreated conditions, or the treatments designed to reduce wildfire risks? Used quantitatively or qualitatively, this conceptual model may contribute to sustainable resource management decisions by improving communication among interested publics, risk managers in land and resource management agencies, and risk assessors in agencies responsible for enforcing the ESA.
corresponding author:
Jay OLaughlin
College of Natural Resources
University of Idaho
PO Box 441133
Moscow, ID 83844-1134
208-885-5776
jayo@uidaho.edu
Encyclopedia ID: p128
Jeffrey P. Prestemon and Thomas P. Holmes
USDA Forest Service Southern Research Station
The United States is experiencing a period of higher hurricane frequencies and intensities, affecting the largest single timber producing region in the world. Recent large hurricanes, including Katrina and Rita in 2005 and the Florida hurricanes of 2004, have resulted in timber mortality of several tens of millions of cubic meters. The effects of such large events are to swamp timber markets in the short run with salvable timber and reduce available timber inventories in the long run. Prestemon and Holmes (2000, 2004) trace the timber market impacts of such storms, particularly on prices and consumer and producer welfare. Research there shows how consumers may be benefited in the short-run but harmed in the long run, while producers of undamaged timber are harmed in the short-run and potentially benefited in the long run. Other research has examined the timber harvest timing impacts of hurricanes, considering timber salvage (Haight et al. 1996). Our paper consists of three main sections. First is a description of the biophysical risk process. Second is an overview of the timber market dynamics following hurricanes. Third is a discussion of what private and public decision makers should do to mitigate the negative economic effects of catastrophic wind storms given alternative management objectives.
The hurricane risk process is described for the U.S. South using information provided by the National Oceanic and Atmospheric Administration, with a focus on intense storms, which apparently cause most of the damage from hurricanes. This section includes a review of multiple risk interactions, such as the impact of hurricanes on the risk of wildfires, the impact of hurricanes on different forest types in the South, and research that may hint at trends and future risks. Timber market impacts from hurricanes are based on recent experience with three intense storms: Hugo (1989), Katrina (2005), and Rita (2005), for which substantial information exists, with emphasis on timber damages. This section quantifies their timber damages in physical and economic terms, placing them into perspective compared to the timber market overall. It describes the timber price dynamics and welfare effects following hurricanes. It also lays out what we know about mitigating the impacts of such storms through timber salvage. In our final section, we focus on the implications of existing research to improve management decision-making for governments, non-industrial private landowners, and the timber industry. We discuss the relative benefits from prioritizing salvage, the equity considerations of government assistance, optimal behavior for owners of undamaged timber and restoration options for private and public managers. This section contains results and information relevant not just to hurricanes but also to many kinds of large-scale natural disturbances involving extensive timber damage (ice, fire, insects and disease outbreaks), which involve salvage and consideration of timber decay (e.g., deSteiguer et al. 1987, Holmes 1991, Lowell et al. 1992), resulting salvage price depressions, and inventory loss-related long-run market price enhancements (e.g., Butry et al. 2001, Prestemon et al. [in press]).
corresponding author:
Jeffrey P. Prestemon
USDA Forest Service
Southern Research Station
PO Box 12254
Research Triangle Park, NC 27709
919-549-4033
jprestemon@fs.fed.us
Encyclopedia ID: p120
S. Hummel, G. Donovan, M. Hemstrom, T. Spies, and A. Youngblood
USDA Forest Service, Pacific Northwest Research Station
Summary: This paper contributes to the science of risk analysis by synthesizing the theoretical basis for its role in biodiversity management strategies. It contributes to the application of risk analysis in forest policy decisions by summarizing the current state of knowledge on estimating uncertainty at varying spatial and temporal scales in ways useful for simulation modeling. By considering both theoretical and applied aspects of risk analysis, the paper advances understanding of its strengths and limitations in forest ecology and management.
Approach: We summarize the key economic and ecological theories that underlie how risk is incorporated into contemporary strategies for managing biodiversity. By explaining the rationale for assessing risks to biodiversity associated with rare but severe disturbance events, the paper clarifies how these risks may change as the frequency and magnitude of the events change in different forest types. We use forest reserves in the interior northwestern US as an example to explore the implications of this change for land management. Reserves are one strategy for mitigating risks to biodiversity and in our example we explore the potential influence of altered fire regimes on the effectiveness of this strategy in interior, mixed-conifer forests.
Background: Risk analysis focuses on the problem of estimating the probabilities of rare events and the magnitude of their associated effects. One use of risk analysis is familiar to anyone who pays insurance premiums. Some types of insurance can be mandatory (malpractice, automobile), while other types are voluntary (life), and yet others subject to availability (flood, earthquake). Insurance doesn’t prevent loss. Instead, insurance spreads the risk of loss among members of a self-selected group who pool their funds so that compensation can be made to a member if an insured loss does occur. Funds come from premiums, which members pay based on calculations of the likelihood and damage of a specified future event and on their own personal risk factors. Insurance provides a way to manage risks that can be priced. The economic literature is replete with articles about risk management and ecologists have begun to borrow concepts from insurance when studying the contribution of biodiversity to ecosystem stability. Although no consensus has emerged, the ecological literature refers to biodiversity as a form of insurance. The insurance hypothesis proposes that ecosystems are insured against functional declines by the presence of many species, whose redundancies guarantee that some species will maintain key functions even if others fail. If this is true, then managing ecosystems to conserve biodiversity should help alleviate the deleterious consequences of natural and human-caused environmental threats. Many biodiversity conservation strategies are based – either implicitly or explicitly – on an assumption that the weight of evidence supports the insurance hypothesis. This paper examines the implications for biodiversity management if this assumption is wrong or if the frequency and severity of potential losses change with time and space.
Example: Forest reserves embody a biodiversity management strategy based on the insurance hypothesis. A decade ago, a network of reserves was established in the Pacific Northwest to conserve and develop a network of old-growth forests on federal land. Since then, increases in the amount of old forests in moist areas of the region have been documented. However, in drier areas east of the Cascade Range the amount of old forest is declining. We examine evidence for the adequacy of a reserve strategy to conserve the biodiversity of old forests in these drier areas, where changes in fire regimes and thus the probability of severe events directly affect key assumptions of the insurance hypothesis and calculations of risk. By reviewing the available literature on the variability of probabilities for disturbances like wildfire or insect epidemics at differing spatial scales we provide a summary that is of immediate value to anyone using simulation models for risk analysis.
Outcome: This paper will advance knowledge on the links among four of the conference topics: risk management across spatial and temporal scales, risk mitigation alternatives, uncertainty estimation and representation, and simulation modeling. It will show why this advance is important for contemporary land management decisions and environmental threat assessment by using forest reserves in the interior west as an example.
corresponding author:
Susan Hummel
USDA Forest Service
Pacific Northwest Research Station
620 SW Main Street, Suite 400
Portland, OR 97205
503-808-2084
shummel@fs.fed.us
Encyclopedia ID: p116