Intensive land uses over the past three centuries have altered the structure of the South’s terrestrial ecosystems. Forces of change continue to alter the region’s biota, and pressures are focused especially on several rare forest communities. These rare communities continue to be pressured by loss of area, fire exclusion, and disruption of hydrologic functions. Change has favored certain types of forests, such as loblolly pine and mixed upland hardwoods. Ongoing changes in these forest types also have implications for the structure and function of terrestrial ecosystems. We examine abundant and rare communities in the sections that follow. We then examine the effects of land use changes and forest management on terrestrial ecosystems. We conclude the section with a discussion of wildlife species of concern and conservation issues in the South.

Primary Question (chapter 17): How have biological agents, including insects and disease, influenced the overall health of the South’s forests, and how will they likely affect it in the future?

Related Questions (chapter 1): What are the history, status, and projected future of terrestrial wildlife habitat types and species in the South? (chapter 2): What are the history, status, and projected future of native plant communities in the South? (chapter 4): What are the historical and projected future impacts of forest management and access on terrestrial ecosystems in the South?

Analysis of changes in forest types indicates ongoing transformation of forest conditions. The area of upland hardwoods is forecast to decline somewhat between 1995 and 2040, but will remain the forest type with the greatest area. Pine plantation acreage is forecast to increase through planting of agricultural land and harvested natural pine and hardwood forests. Though these communities are considered abundant, they face continuing health challenges. Also, because of their extent, their structure and condition are especially important to the region’s wildlife. The value of these forest types as habitat for wildlife depends largely on how they are managed.

Pine types—Pine planting will continue to be focused in the Coastal Plain and parts of the Piedmont, but we expect planting rates to increase the most in the western half of the region. Forest structure in plantations differs from that found in naturally regenerated stands. Their management is designed to focus site potential to maximize the growth of trees of a single species, and trees are spaced to maximize fiber production over a 20- to 30-year period. Retaining a narrowly focused stand structure requires considerable management effort. This is evidenced by about 2.5 million acres of plantations transitioned to other forest types since the 1980s. Thus, over time and without intervention, plantations often become more diverse in terms of tree species composition. Their value as wildlife habitat will vary depending on the type and variety of vegetative species that diversify the stand. This increased diversity is greater in plantations established following harvest of natural pine or oak-pine forests, because they retain biological legacies from the preceding forest type, especially when plantations are mixed in with naturally regenerated forests and wetlands as in the Carolina Coastal Plain. Plantations established on converted agricultural sites can develop considerable grass and forb diversity in early stages, but because they lack the biological legacies of earlier forests, their vegetative diversity is limited for a longer period of time (chapter 4). Very dense stocking and use of herbicides can limit vegetative diversity throughout the entire rotation. The intensity of forest management has various effects on wildlife suitability. In addition to differences in forest structure, intensive pine management generally involves more frequent management activities. Depending on the circumstances (such as type of legacy, management strategy, density of stocking, use of herbicides, prescribed burning), these actions can disrupt, benefit, or have little effect on wildlife. Effects of management activities on wildlife are discussed in “Recreation.”

Another less commonly recognized phenomenon associated with intensively managed forests is their invasion by exotic plants; additionally, other land uses have contributed to the spread of exotics in the South. Privet, kudzu, and other exotic shrubs and vines displace native plant species and vary in their benefit to wildlife. Kudzu and Japanese honeysuckle alone now occupy more than 7 million acres of land each (chapter 3). In some areas, exotic vines can completely dominate the shrub and herb layer.

Expanded areas of pine forests in parts of the South have increased the availability and contiguity of host material for certain native pest insects and pathogens, especially southern pine beetle. However, short-rotation lengths and active management minimize what would otherwise be increased infestation risk. Damage from these pests is likely to be greatest in plantations that are not actively managed following establishment. These most commonly occur on nonindustrial private ownerships. Pest-appropriate management activities—which may include lower stocking rates, use of prescribed burning, active pest suppression, and sometimes reducing the frequency of stand-disturbing activities—may lower the risk of spreading infestations in these types of forests.

Overall mortality rates for softwoods have increased from about 0.6 percent of inventory per year in the 1960s to 1.0 percent per year in the 1990s. We expect pine mortality to remain high, especially at the periphery of the natural range of many pine species—for example, in Tennessee, Kentucky, and Virginia. In these areas especially, southern pine beetle will remain problematic for forest managers.

With respect to forest pests associated with pine types, we found that (chapter 17):

• Five native diseases in the South have substantial impact on forests and two—annosus root disease and fusiform rust—have substantial commercial impacts on pine species. Fusiform rust is in epidemic status along the Coastal Plain from Louisiana to South Carolina (fig. 41). It causes heavy mortality of slash and loblolly pines. Annosus is more localized and limited by site factors, but it can cause severe root disease in thinned stands if not treated. Littleleaf disease targets shortleaf pine and has encouraged the conversion of shortleaf sites to loblolly pine.

• Several native insects have substantial influence on forests. The insect with the most substantial economic impact and habitat impacts for the endangered red-cockaded woodpecker is the southern pine beetle, which reaches epidemic levels at irregular intervals and causes high rates of mortality over broad areas (fig. 11). It prefers shortleaf and loblolly pine forests, but also attacks other pine species. Longleaf pine, while susceptible, does not appear to be a preferred host species.

• Mature pine trees are more susceptible to damage from southern pine beetle than younger trees, so that public forests, with higher concentrations of older, more mature pine forests, are most likely to be attacked. Spillover of epidemics onto adjacent private land will continue to be a significant resource management issue for public forests in the South. Likewise, planted pine on nonindustrial private forest land with little management experiences higher mortality from southern pine beetle. The risk of damage can be reduced by utilizing management practices that reduce stocking.

Upland hardwoods—The upland hardwood type gradually expanded in the South between the 1950s and the 1990s but has been in a state of flux for more than a century. Many areas were permanently transformed by chestnut blight, which eliminated American chestnut from its dominant role in mountain forests in the eastern portion of the South beginning in the 1930s. Recent expansion of upland hardwood acreage has resulted from a combination of natural succession of pine forests and removal of the pine component from mixed pine-hardwood forests. Currently, the greatest expanses of the upland hardwood types (generally oak-hickory) are concentrated in the Piedmont, the Appalachian Mountains, the Ozarks, and the Cumberland Plateau. Urbanization, along with increased harvesting of hardwood timber, will continue to modify these forests in important ways, especially in the Piedmont. While the area of upland hardwoods is forecast to decline only slightly over the next few decades, it is likely that these forests will become more fragmented in some areas, and in these places, will provide less interior forest habitat. In addition, indirect human influences related to increased population density will also be felt in these areas.

As with softwood forests, pathogens and insects have had important effects in hardwood forests, and they continue to spread within the South. As was the case with chestnut blight, most of these organisms are nonnative, or exotic, and control options are either ineffective or limited in their potential application.

• Oak decline, a disease complex affecting oak species, could have long-term consequences for the species composition of hardwood forests in the South. It is prevalent in areas where oak species occupied the niche of American chestnut eliminated by the chestnut blight beginning in the 1930s. It is becoming especially widespread in the mountainous areas of the Southern Appalachians and the Ozark and Ouachita Highlands, on dry and infertile sites. Drought appears to worsen its effects.

• Four exotic diseases have had or will have substantial impact on southern forests (chapter 17). Each targets a single genus or species. Chestnut blight restructured Southern Appalachian forests, and the resulting trajectory of change has not completely played out. Based on current spread rates, beech bark disease is expected to cause substantial mortality to American beech and change its location in southern forests over the next 20 to 30 years. Butternut canker may completely eliminate butternut from southern forests. Dogwood anthracnose has already led to widespread decline of dogwoods with resulting aesthetic, economic, and wildlife implications (see fig. 42A, fig. 42B, fig. 42C and fig. 42D).

• The hemlock woolly adelgid kills both the eastern and the Carolina hemlock and is currently moving down the Blue Ridge from the Shenandoah Valley. It threatens both species’ occurrence in the wild. (chapter 3, chapter 17).

• The gypsy moth continues its steady march from the North and is currently moving from Virginia into North Carolina. Based on current spread rates, this insect is expected to progress across the South over the next 20 to 30 years. Epidemics can last several years in a particular location and lead to the defoliation of most species, but oaks are most susceptible. Considerable alteration to forested ecosystems, including loss of hard mast, is expected where gypsy moth damage coincides with oak decline (chapter 17).

Many of these forest health concerns can be complicated by the exclusion of fire. Absence of fire can alter species composition, but its reintroduction is difficult because much of the upland hardwood forest type occurs in or near heavily populated areas. Compounding the challenges of maintaining healthy hardwood forests is expected increased tree mortality that would increase fuel loadings and the risk of severe fires.

Primary Question (chapter 1): What are the history, status, and projected future of terrestrial wildlife habitat types and species in the South?

Related Question (chapter 17): How have biological agents, including insects and disease, influenced the overall health of the South’s forests, and how will they likely affect it in the future?

Several forest communities have become limited to only a tiny portion of their original range and thus may be disproportionately impacted by future changes. There are 14 critically endangered communities (where losses of more than 98 percent of their area have occurred since European settlement) and 25 endangered communities in the South (losses between 85 and 98 percent of area). Most of these communities are in the following seven classes (see chapter 1):

• Old-growth—Less than 586,000 acres of forest area (0.3 percent) in the South is in an old-growth condition. Old-growth assemblages are diverse, and they exhibit unique structural characteristics such as multilayered canopies and large accumulations of woody debris. The largest tracts of these remnant forests are limited to a few ecological provinces. Most are on public land such as the Great Smoky Mountains National Park and the region’s national forests. Some very small tracts occur on private land. While most publicly owned old-growth forest is administratively protected, factors such as air pollution and forest pests will continue to alter them.

• Spruce-fir forests—They are limited to high elevations in the Blue Ridge Mountains. These are very scarce ecosystems containing unique assemblages of species with a high degree of endemism. They are threatened by a combination of exotic pests and environmental factors. The exotic insect having substantial impacts on these forests is the balsam woolly adelgid, which has already eliminated 95 percent of the mature Fraser fir from high elevation forests of the Southern Appalachians. A significant restructuring of this type of forest is anticipated. Additionally, soils in this community predispose the area to changes in stream chemistry and other ecosystem damage from increased acid deposition derived from nitrous oxides (chapter 18).

• Wetlands, bog complexes, and pocosins—They have been reduced in total area by land use conversions and changes in hydrologic regimes. Bogs and pocosins provide habitat for many rare herpetofauna and birds. They also provide important refuges for species in landscapes that are dominated by agriculture and intensive silviculture. Fire regimes are crucial to the sustainability of many of these forests, and the exclusion of fire has substantially altered them.

• Bottomland and floodplain forests—Because they often occur on rich alluvial soils, a large share of these forests has been converted to agricultural uses, especially in the Lower Mississippi Alluvial Valley. Such forests, therefore, occupy only 20 percent of their original area. Certain forest pests can affect these forests. For example, the baldcypress leafroller, which defoliates and kills baldcypress, is prevalent in Louisiana swamps (chapter 17). Hydrologic alterations also alter the condition and structure of these forests.

• Glades, barrens, and prairies—They are naturally treeless areas in Piedmont, Interior Plateau, Ridge and Valley, and Coastal Plain ecoregions of the South. These areas evolved under extensive fire regimes, and fire exclusion has caused substantial ecological modification and continues to impact remnants of these systems.

• Longleaf pine ecosystems—They once covered much of the South’s Coastal Plain. They now occupy only 2 percent of their original range. The herb layer of these forests is one of the most diverse in the world. They are home to several threatened or endangered species, such as the red-cockaded woodpecker, and several species with high rates of endemism. Decline in these systems is attributable to several factors, including removal of original stands followed by fire exclusion, conversion to other pine species, conversion to other land uses, and the introduction of livestock. Brown-spot needle disease infects longleaf pine seedlings and therefore hampers efforts to restore the longleaf ecosystems across the South. Current concerns include continued urban development and difficulty in reestablishing fire regimes.

• Atlantic white cedar swamps–They have been reduced to 10 percent of their original range. They persist only in isolated small stands. As with pocosins, they provide for diverse wildlife refuges in intensively managed forest and agricultural landscapes.

Several increasingly rare types of wetlands—Atlantic white cedar swamps, bottomland forests, wetlands, bog complexes, and pocosins—are concentrated on private land, so their future condition is dependent on the decisions of their numerous owners. The spruce-fir and old-growth ecosystems are found mainly on public land. Old-growth is protected but is susceptible to invasion by exotic species, damage from air pollution, and restructuring due to fire suppression. Among rare forest communities, the spruce-fir ecosystem is currently under the most stress due to a combination of exotic insects and environmental stressors. Most remnant longleaf pine forests occur on private land and may be impacted by development, both directly through their conversion and indirectly due to the difficulty of providing the necessary fire regimes in areas of mixed ownership and high population density. Restoration efforts are underway, but challenges to restoring the longleaf pine ecosystem are great.

Primary Question (chapter 3): What are the likely effects of expanding human populations, urbanization, and infrastructure development on wildlife and their habitats?

Related Question (chapter 6): How have land uses changed in the South, and how might changes in the future affect the area of forests?

The use and configuration of forest land can influence the suitability of forests as habitats for wildlife species. However, at this time, there are no regional-level models for explicitly forecasting the effects of land use changes on wildlife. To address how land use could affect terrestrial ecosystems, we surveyed the body of research on the effects of various land uses and management on terrestrial animal species and found:

• Urban land uses have important impacts on bird populations. Urbanization restructures forest habitat by decreasing forest area and patch size while increasing edge relative to interior forest habitats (see chapter 1). As a result, avian species composition is altered, nest predation increases, and habitats become isolated. Often bird diversity remains high, but there is a shift in species represented. For example, urbanization generally leads to declining populations of forest insectivores, neotropical migrants, and forest interior specialists (chapter 3).

• While the greatest impacts of urbanization seem to be related to habitat fragmentation and loss, increased human presence also has indirect effects. Evidence suggests that the presence of houses adjoining forest tracts can reduce the habitat value of those tracts for sensitive neotropical migrant birds.

• Urban environments support fewer species of mammals than rural areas and tend to support habitat generalists rather than specialists. Highly urbanized settings support large populations of exotic species such as the house mouse and Norway rat. With green spaces in the urban area, many more species, especially small species, may persist. Mammalian predators such as bobcats and gray fox are generally excluded from habitat in highly developed areas. Urbanization also tends to exclude specialized species of reptiles, amphibians, and invertebrates while generalists can persist in even highly urbanized areas. Fragmentation can isolate otherwise suitable habitats. Examples of urban-sensitive species include the gopher tortoise and the timber rattlesnake in east Texas.

• As urbanization reduces and fragments some forest areas, the remaining large forest tracts on public and private lands may increasingly contribute to the conservation of many sensitive wildlife species. Given the importance of landscape structure in determining the suitability of habitats in urban and agricultural areas (chapter 3), maintaining habitat connectivity can enhance ecosystem function in these areas.

• Red imported fire ants have a substantial impact across an increasing range in the South. While most abundant in open habitats, they invade forests from along the margins created by roads and power lines. These ants displace and/or prey on native arthropods, reptiles, amphibians, and rodents, disrupting food webs and restructuring forested ecosystems (chapter 3).

• Several other exotic animals, such as feral pigs, cats, dogs, and exotic birds influence wildlife through predation, displacement of native species (especially birds), and habitat destruction (especially pigs). Localized impacts may be severe. For example, impacts of feral pigs have become very serious in rare wetlands in the Ozark-Ouachita Highlands. Population growth and expanding wildland-urban interfaces will result in growing problems with feral domestic animals (chapter 3).

• Agricultural land is often interspersed with woodlots and other forest habitat. Habitat connectivity, which is often provided by vegetated fencerows, greatly influences the presence of birds and other species in agricultural areas. Isolated forest habitats can serve as ecological traps for some species by focusing populations in small areas along with a high concentration of nest predators (chapter 3).

• Many bird species that depend on open habitats such as grasslands, prairies, savannas, glades, and barrens are now in serious decline in the Eastern United States. Declines are partially explained by the conversion of pastureland to cultivated row crops, the switch to “clean pastures” dominated by exotic cool-season grasses, and by the loss of fencerows as new agricultural technologies favor bigger fields.

• Forecasts of land use change and measures of forest fragmentation suggest that bird species may be subjected to the most change in the Piedmont subregion (chapter 1 and chapter 6). Accordingly, we anticipate declines of neotropical migrants and forest interior specialists in these areas. Implications for neotropical migrants may be especially important, since this group of birds is experiencing global decline.

Primary Question (chapter 4): What are the historical and projected future impacts of forest management and access on terrestrial ecosystems in the South?

Related Question (chapter 16): What are the history, status, and projected future of southern forests?

Forest management, by definition, affects the structure and distribution of forest conditions. Forest types have been dynamic in the South, with upland hardwood types increasing between the 1950s and the 1990s, lowland hardwood types essentially stable since the 1970s, and pine types in considerable flux. Net changes in forest are the result of several offsetting changes. For example, natural pine types are reclassified to upland hardwoods as a result of succession, while some upland hardwoods are converted to planted pine. All forest types are converted to urban uses, and agricultural fields are converted to planted pine (“Broad Forest Types” and chapter 16).

Silvicultural treatments can have important implications for wildlife. Timber harvesting, especially clearcutting, as well as afforestion of agricultural fields restarts successional processes. Young stands, especially those that follow timber harvesting, exhibit an increase in species richness and species diversity. Many wildlife species thrive in these early successional communities. After canopy closure, plant diversity generally decreases and wildlife use declines. Uneven-aged management that encourages several age classes of trees can sustain benefits for many but not all wildlife species due to the resulting stratified forest canopy. However, these benefits may lessen somewhat if stand entries are more frequent (chapter 4).

Planted pines, while sometimes characterized as monocultures, vary considerably in their composition. Wildlife species that thrive in early successional habitats use plantations heavily during the first few years after planting, although habitat values decline with heavy stocking, application of herbicides, and other intensive management practices. Browse is abundant, and several mammals graze these stands. Small mammals are abundant, thus raptor use is high. Many priority neotropical migrants use pine plantations after the first thinning or use lower stocked areas where hardwoods are allowed to thrive in the understory (usually stands managed for sawtimber). Several neotropical migratory birds use plantations early on, when insects and seeds are abundant. After canopy closure, plant diversity decreases and wildlife use declines.

Forest management can be augmented with techniques to directly enhance wildlife habitat. These include leaving mature trees in a stand to enhance structural diversity, application of streamside management zones to retain landscape diversity, and retention of snags to provide nesting habitat (chapter 4). Additional wildlife benefits may be obtained with natural regeneration techniques such as seed-tree cuts and shelterwoods, and with management practices such as midrotation thinning and prescribed burning.

Gauging the effects of forest management on mobile wildlife populations requires more than an understanding of stand-level dynamics. It requires insights into the overall landscape structure of forests within the region. Although this type of analysis is relatively new, several studies have examined the effects of forest fragmentation on wildlife species, especially birds. We found that (chapter 4):

• Studies have documented declines in migratory bird species from isolated forest patches, especially where agricultural and urban uses represent substantial components of the landscape. However, in heavily forested areas—70 percent or more forest—these negative effects do not occur. Accordingly, in large portions of the southern landscape, these fragmentation effects are not a substantial concern. They include the Southern Blue Ridge, Cumberland Plateau and Mountains, and Ozark and Ouachita Mountains.

• Forest fragmentation and negative edge effects are most prevalent in Ridge and Valley, Piedmont, Interior Low Plateau, and the Mississippi Alluvial Plain where agriculture and development dominate the landscape. In these areas, forest operations may impact fragmentation effects on wildlife.

• In heavily forested areas, forestry practices may provide important benefits for forest-breeding bird species through provision of early successional habitats. This is especially true for areas where existing hardwood forest structure is dominated by closed canopy stands and sparse understories or where dense pine stands and fire suppression exclude pine specialists.

Landscape configuration and fragmentation at fine scales may be critical for some species, especially amphibians, even in heavily forested areas. For example, persistence of pond-breeding salamanders requires access between terrestrial habitat and vernal ponds or Carolina bays. Roads and certain kinds of management practices can isolate these two habitat components. Spatial configuration of forest habitat is also an important factor in the recovery of federally listed subspecies of black bears in Louisiana and the black bear subspecies of conservation concern in Florida (chapter 4).

Across the South, more threatened and endangered species are affected by increased isolation of shrub-scrub and grassland habitats than are affected by scarcity or fragmentation of mature forests. The ultimate challenge for forest management then is to provide habitat conditions that support the array of grassland, shrub-scrub, and mature forest species occurring within the same landscape.

Primary Question (chapter 5): What conditions will be needed to maintain animal species associations in the South?

Related Question (chapter 2): What are the history, status, and projected future of native plant communities in the South?

Substantial alterations to forested communities have impacted several terrestrial species in the South. To enumerate and examine species of concern, the databases of the State Natural Heritage agencies were used to list species by their global conservation rank. The global ranks reflect scarcity for the entire range of the species. These ranks include presumed extinct, possibly extinct, critically imperiled, imperiled, vulnerable, apparently secure, and secure. Species of conservation concern include those that are critically imperiled (extremely rare—observed at 5 or fewer locations or fewer than 1,000 animals—or otherwise vulnerable to extinction), imperiled (rare—observations in 6 to 20 locations or fewer than 2000 animals—or otherwise vulnerable to extinction), or vulnerable (21 to 100 locations or 3,000 to 10,000 animals or found locally in a restricted area). Table 2 shows species of concern and critically imperiled species. In addition, data on the status of threatened and endangered vertebrate species were compiled from the Department of Interior. We examined the status of terrestrial wildlife species and found:

• Of the 1,208 vertebrate species known to exist in the South, 132 are considered to be of conservation concern. Twenty-eight species are classified as critically imperiled.

• Seven southern terrestrial vertebrate species are now presumed extinct.

• The South is a center of amphibian biodiversity in the United States. Fifty-four amphibian species are classified as species of concern, and 19 are critically imperiled. Many amphibians require both wet and upland habitats, emphasizing the critical biological importance of wetlands and of ecotones (the gradients between wet and dry habitats). Wetlands are discussed in more detail in “Forested Wetlands.”

The South contains several areas where the number of endangered species is high, including the Southern Appalachians, Atlantic and eastern gulf coast flatwoods, gulf coast marsh and prairie, and peninsular Florida. Loss of habitat is the primary cause of endangerment of terrestrial vertebrates. Forests, grasslands, shrublands, and wetlands have been converted to urban, industrial, and agricultural uses. Other factors include environmental contamination and commercial exploitation. Florida and Texas are the States with the greatest numbers of endangered vertebrate species (fig. 43).

The South also has a large complement of rare plants. Rare vascular plant species are not evenly distributed throughout the South. Concentrations of rare species diversity occur in the Southern Appalachians, the Florida Panhandle, and the Lake Wales Ridge region of Florida. Rare species are also concentrated in the Ouachita Mountains and on the Cumberland Plateau (chapter 2, fig. 44).

Management of public land includes protecting biodiversity through ecosystem or landscape-level management. About 11 percent of the South’s forests are in a public ownership, and these areas tend to be concentrated in mountainous areas (fig. 45). For some rare communities, public lands are critical to conservation—for example, for protecting old-growth areas and high-elevation spruce-fir ecosystems in the Southern Appalachians. Often, however, rare plant communities and critically imperiled species do not occur on public land. The management of private forests, therefore, will have a substantial impact on the persistence of many species of concern in the South.

In the Coastal Plain and Piedmont, large blocks of public land are scarce, so ecosystem management strategies can only succeed through the cooperation of multiple landowners. Such collaborations are beginning to emerge. Land trusts have acquired land with high ecological value. Landscape-level consortiums are emerging to address ecosystem maintenance and restoration. Coordinated research and conservation have focused on understanding and restoring longleaf pine ecosystems.

The conservation value of public land may be high in some areas because public land can provide scarce interior forest habitat and older forests.

In urbanizing landscapes, public tracts can be factored into conservation strategies pursued by local planners. The principal vector of ecological change in these areas is fragmentation, and efforts to design development so some forest connectivity is retained could provide important habitat and other benefits, especially for neotropical migratory birds.

The effects of human activities on forests are pervasive, even where there is no direct management activity. Hence, conservation requires careful monitoring of forest conditions and active management responses, even in remote areas.

The exclusion of fire remains a critical and widespread issue affecting the health of terrestrial ecosystems. The impacts of fire exclusion from longleaf pine communities are now well understood, not only for pine management, but also for other associated plant and wildlife species. The impacts on other systems, such as upland hardwoods, are less well known but likely linked to ongoing forest health problems. While some progress has been made, the effective reintroduction of fire into forest ecosystems remains a critical forest conservation challenge in the South.