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Part 2: Regional Trends of Biological Resources
Northeast: This region is the most heavily populated and hence has been negatively impacted by urbanization and fragmentation of remaining forests. Over the last century the region has become increasingly forested because of declines in agriculture. Consequently, populations of some woodland bird species have grown. The forests, however, are somewhat changed from the native forests not only in their size, but also in their composition; elm and beech have declined, and chestnut trees have disappeared-all due to nonindigenous diseases. As these forests have matured, there are fewer early successional forests, which has negatively affected birds that inhabit scrub habitats, such as the woodcock. (Fig. 4). Alterations of aquatic habitats in the Northeast have resulted in the listing of 13 species of freshwater mussels as endangered. In addition, nonindigenous species have also impacted aquatic habitats; purple loosestrife, for example, has degraded habitats in many wetlands, the zebra mussel is established in the Finger Lakes, and sea lamprey and several nuisance plants have invaded Lake Champlain. A number of valuable resources have severely declined in the Northeast because of the combination of harvest, lost or degraded habitat, and disease; these resources include the black duck (Fig. 5), blue crab, oysters, and submerged aquatic vegetation in the Chesapeake Bay. Conversely, some populations have made successful comebacks, such as striped bass. Many species that adapt well to urbanized environments, such as Canada geese, white-tailed deer, and beavers, are even becoming nuisance species because of their dense numbers.
Great Lakes: The biological resources of the Great Lakes and their connecting waterways have been drastically affected by nonindigenous species and historical commercial fishing. Non-native species entered the Lakes because of the man-made connections to the ocean. At least 25 non-native fish species, as well as numerous other invasive aquatic organisms, have become established in the Great Lakes, resulting in a fishery that is highly managed by stocking nonindigenous salmonids. While commercial fishing contributed to the demise of the native lake trout and whitefish fisheries, (Fig. 6) these two species are being restored. The Great Lakes have also suffered from environmental pollution; inputs of nutrients and toxic chemicals negatively affected a number of fish and wildlife species between the 1950's and 1970's. Clean-up efforts have been successful in reducing the levels of persistent toxic chemicals and have contributed to the restoration of bald eagles. Reduced nutrients in Lake Erie have also sparked the resurgence of burrowing mayfly populations, a critical food for vertebrates.
The coastal shore of the Great Lakes provides unique habitat in the dunes that are found in the upper lakes. Dune communities support more localized native species than any other part of the basin. Forests in the Great Lakes region have significantly changed. Much of the forest in the southern part of the region has been lost to agriculture and urban development, greatly affecting the native oak forest and savanna habitats. In the north, public ownership of lands has protected some forests, although the make-up of these forests has changed.
Southeast: Variation in climate, topography, and soil provide the Southeast with a rich diversity of habitats. The result is that a number of taxonomic groups reach continental high points of species richness. Amphibians, fishes, mollusks, aquatic insects, and crayfish have more species in the Southeast than anywhere else in North America. Because the Southeast has little public land and a fast-growing human population, this diversity is at significant risk due to land and water use. Nearly all major stream systems have been channelized or dammed, thus eliminating another important natural process-flooding-and adversely affecting stream habitat. As many as 144 major reservoirs have been built in this region, and the effects of these dams on the wealth of aquatic biodiversity are dramatic-19% of the freshwater fish species are threatened or endangered, and 73% of the freshwater mussels are at risk. Nonindigenous species have also had a great impact on aquatic habitats.
Although 55% of the land in the Southeast is forested, almost all is second-growth. Forests have been affected by nonindigenous species such as gypsy moths, wild pigs, and chestnut blight-an invasive disease that has decimated the American chestnut tree. Southeastern ecosystems have also been harmed by the absence of an important natural process, fire. Natural fires have been suppressed across the country, not only because of their potential Southeast and elsewhere. More than 50% of the rarest plants in the region depend on a natural frequency of fire.
Caribbean Islands: Island ecosystems are more vulnerable to change than continental systems, and land use and nonindigenous species have severely affected the Caribbean Islands. Forest habitats across much of the Caribbean were decimated by early settlement, but on some islands, most notably Puerto Rico and St. Johns, reforestation is occurring. These islands now have 38% and 75% forest cover, respectively. In Puerto Rico, 118 species of nonindigenous plants have become established, competing with native species and altering habitats. Almost two-thirds of Puerto Rico's endemic amphibians are declining, in part due to habitat destruction and introduced mammals such as the black rat. However, as in other locations around the world, some amphibian declines have been noted in areas with protected natural habitat, such as the Caribbean National Forest in Puerto Rico.
Puerto Rico and the Virgin Islands include significant marine resources that, similar to the marine resources of the mainland U.S.A., are increasingly stressed. Coral reefs of the Virgin Islands, for example, have declined because of diseases, hurricanes, sedimentation from coastal development, and destruction by boat anchors. Efforts to restore populations of threatened and endangered sea turtles that nest in the Virgin Islands have met with some success (Fig. 7), although commercial harvest in the British Virgin Islands remains a problem. Coastal habitats in Puerto Rico have also shown some improvement. Since 1974, mangrove forest acreage has increased by 40%, which will protect coastal erosion and provide nursery habitat for marine fish.
Mississippi River: The Mississippi River is one of the world's major river systems in size, habitat diversity, and biological productivity. Most of the river and its floodplain have been extensively modified for commercial navigation and other
human use. The 29 navigation dams constructed between Minneapolis and St. Louis have greatly altered natural features of the river and the floodplain forests that provide valuable bird habitat. Additionally, ecosystems have been lost to agriculture and urbanization such that forest cover now makes up only 14% of the Upper Mississippi River Valley. These alterations, combined with the effects of nonindigenous species and natural processes such as drought, are responsible for continued negative changes in this ecosystem. Wild celery, an important food for waterfowl, has declined significantly in Lake Onalaska since reaching peak abundance in the early 1980's. Similarly, the species richness of pearly- mussels has declined (Fig. 8). In some reaches, fingernail clams have declined, leading to decreases in scaup, which rely on these clams as food. Fish habitat is also diminishing in the system. Sedimentation has reduced water depth, which compromises overwintering habitat for fish. Loss of aquatic vegetation also reduces habitat for young fish. Like the Great Lakes, the Mississippi River suffers from pollution by toxic chemicals, which affected reproduction of eagles and mink, but with better controls of contaminant inputs, these populations have rebounded.
Coastal Louisiana: Coastal Louisiana ecosystems experience rapid changes due to topography, natural processes such as climate, and human modifications. The result is an annual loss of coastal wetlands of about 25 square miles per year. Most of this loss occurs when vegetated marshland sinks until it is below sea level; eventually the marshland reverts to open water. These wetlands have always been dynamic systems, expanding and shrinking over thousands of years, but human modification has pushed the natural processes into ever-shrinking coastal wetlands. Construction of the levees and associated navigational works of the Mississippi River prevent the overflow of fresh water and sediments from rebuilding marshes during spring floods, which threaten nearly 1200 square miles of habitat important to birds and marine species. A $900-million estuarine fishery and millions of waterfowl (Fig. 9) and other birds rely on this diminishing and rich coastal Louisiana habitat. This system is also impacted by nonindigenous species, such as water hyacinths which impede drainage and navigation and choke out native vegetation in lower reaches of rivers and freshwater marshes. Nutria, an introduced non-native species, are responsible for denuding the vegetation in intertidal flats and for stopping the regrowth of bald cypress.
Grasslands: Grasslands (Fig. 10) are among the most biologically productive of all communities within the United States, but they are also one of the most threatened habitats. In seven states, less than 1% of the native tall-grass prairie habitat remains; losses are due to agriculture and grazing, urbanization, and mineral extraction. Erosion threatens the sustainability of grassland soils, and the lack of fire has enabled invasion of nonindigenous species. Frequent fires are essential in maintaining native species diversity in grasslands. Waterways of the prairie potholes have been altered by drainage for agriculture. All of these changes contribute to a habitat loss that has resulted in significant declines in waterfowl breeding areas. Rainfall and predators are other important factors in determining the success of waterfowl in the prairie pothole region. Of the 435 bird species that breed in the United States, 330 breed in the Great Plains. Native grassland bird species have shown more consistent, widespread, and steeper declines than any other group of North American birds.
Rocky Mountains: This region is known for its natural beauty, as well as for its interesting array of biological resources: elk, gray wolves, grizzly bears, bald eagles, Douglas-fir, ponderosa pine, spruce-fir, and many others. Rapid population growth, nonindigenous species introductions, and urban expansion threaten the resources of the region, however. The population in the surrounding areas has greatly increased since 1950; for example, both Utah and Colorado have experienced a 150% population increase. This rapid population growth has increased demands for water and power and has altered habitats. Habitat loss and population-control programs are responsible for an estimated 98% decline in prairie dog populations. Prairie dog ecosystems are valuable in the Rocky Mountain foothills because they support 170 vertebrate species and contain more specialized plants and insects than adjacent areas.
While restoration of greenback cutthroat trout has been successful, three other native cutthroat trout subspecies are extinct. Introductions of nonindigenous fish severely threaten other native fish. The one remaining native trout species is threatened and is a primary post-hibernation food source for grizzly bears. As in other parts of the nation, bald eagles and peregrine falcons are recovering from declines caused by pesticides. At the same time, habitat loss, introduced species, and environmental contaminants are all contributing to declines of amphibians in the Rocky Mountains. For example, western toads now occupy less than 20% of their previous range. Although gray wolves were reintroduced into the Greater Yellowstone ecosystem in 1995 and their status is improving, the species occupies less than 10% of its historical range.
Great Basin-Mojave Desert: This area between the Sierra Nevada, the Transverse Ranges, the Rocky Mountains, and the Columbia and Colorado plateaus harbors a rich biological diversity. Great topographical relief and an arid, continental climate provide conditions for unique plants and animals. Because of the region's arid nature, aquatic habitats are at a premium and are very critical (Fig. 11). More than 75% of the species in the region are strongly associated with riparian, or streamside, vegetation. Unfortunately, much of this vegetation has been degraded by water diversions, agriculture, and grazing. Grazing, in particular, has changed the character of these habitats in the Great Basin, reducing biodiversity and enabling nonindigenous species such as the tamarisk to become dominant. Water diversions for irrigation and urban growth lower levels of surface waters and cause increases in total dissolved solids and some heavy metals, threatening biological resources of Mono and Great Salt Lakes. The unique plant diversity of this region's terrestrial ecosystems is threatened by urbanization, grazing, fire suppression, and nonindigenous species, such as cheatgrass. More than 99% of the sagebrush-grass zone, for example, has been negatively affected by livestock.
Biological populations reflect the impacts on habitats. Of 131 species and subspecies of fish that historically occurred in the Great Basin-Mojave Desert, 10 are extinct and 75 (62%) are listed, candidates for listing, or of concern. The Amargosa toad is a candidate for listing as endangered, but trends of other amphibians are still unknown. Trends in many bird species are unknown because of limited sampling and high variability. Still, because many of the region's species depend on wetland and riparian habitats, which are being destroyed and degraded, researchers are concerned that declines are widespread.
Southwest: The southwestern United States is a land of extremes, and as with the Great Basin, the variation in topography and climate has produced great biological diversity. Widespread grazing of domestic livestock, suppression of natural fire, and commercial forest logging have altered the biological resources of the Southwest. Because of the variation in habitats and their biotic communities, each responds differently to human-induced stress. For example, fire suppression in ponderosa pine forests, which cover extensive portions of the Southwest, have reduced understory plants and have caused a buildup of needles that disrupts nutrient cycling and contributes to poor tree growth. Grazing, which occurs in almost all of these forests, replaces palatable plant species with thorny or poisonous species, thus reducing diversity further. More than 85% of the ponderosa pine forests have been significantly and negatively impacted by grazing and fire suppression. In desert shrublands and semidesert grasslands, which form a diverse mosaic in the arid Southwest, grazing and fire suppression favor a vegetation shift from grasses to shrubland, thus inviting nonindigenous species to become established. Between 1974 and 1987, grassland cover declined by 35%; the nonindigenous honey mesquite shrub now dominates nearly 70 million acres.
As with other arid ecosystems, the Southwest aquatic and riparian habitats are invaluable. Habitat loss due to dams, groundwater pumping, and pollution have contributed to jeopardizing more than 48% of the region's fish fauna. Investigations have also indicated declines in the region's leopard frogs, but the status of many amphibians and reptiles is unknown. The Southwest has the largest number of native mammal species, although several have been extirpated, including the grizzly bear and gray wolf. Smaller mammals may be of even greater concern. For example, of the 30 species of bats, one-third to one-half are now considered sensitive.
California: Because parts of California are included in other chapters, this chapter focuses on westside California, a very distinctive region because of its topography and Mediterranean climate. Ecosystems in California have been heavily altered (Table 1) by agriculture, grazing, urbanization, and timber harvest. More than 85% of the old-growth coast redwood forests have been logged, reducing dependent species. Native California prairie has almost disappeared because it has been converted to agriculture or to nonindigenous annual grasslands. Similarly, more than 95% of the region's historical wetlands have been destroyed or modified. These habitat changes, along with nonin-digenous species, have negatively affected species trends-57% of fish species are extinct or on the road to extinction if present trends continue; 40% of the salamanders and 54% of the frogs are given or are in need of some sort of protection. Birds have also declined in California. In the 1970's, for example, 10-12 million waterfowl wintered in or migrated through California, with the great majority relying on Central Valley habitats. More recently, only 2.5 million waterfowl wintered in the Central Valley. Additionally, of the 342 species of land birds in this
region, 21.3% are listed as state or federally threatened and endangered species.
Pacific Northwest: The Pacific Northwest has a wealth of natural resources, which are used for a variety of purposes. This chapter addresses the status of four primary areas of resource concern: old-growth western forests, forests east of the Cascades, eastside rangelands, and aquatic ecosystems. Logging has drastically reduced the amount of old-growth forests; much of the remaining old-growth forests occur in stands smaller than 400 acres. The combination of old-growth forest removal and fragmentation has negatively affected many species. Three of the seventeen bird species that are closely associated with these forests and for which there is reliable population trend information have shown significant long-term downward trends, whereas none show upward trends. In eastside forests, selective harvest, grazing, and fire suppression have greatly altered the forests-in some areas as much as 98% of the old-growth ponderosa pine has been logged or lost. More than 99% of the fertile Palouse Prairie grasslands of southeastern Washington, as well as adjacent areas in Oregon and Idaho, were converted to agriculture, and 2-2.5 million acres of grassland and sagebrush steppe have been replaced by nonindigenous vegetation, primarily because of overgrazing.
Bird species have reacted differently to changes in rangelands. Whereas 25 bird species show downward population trends, especially in those species associated with grassland and shrub-steppe habitats, several raptor species show long-term upward trends. As of 1992, land managers listed 144 plant species in Oregon and Washington because of their rarity, but few were monitored for trend information. Aquatic habitats have been impacted as well. Ninety-five percent of the streams surveyed throughout Oregon had been moderately or severely degraded, primarily by logging activities, but potential for restoration of some of these streams remains high. The plight of salmon in the Pacific Northwest remains problematic
(Fig. 12). Habitat degradation, dams, overharvest, and ocean conditions all contribute to continued declines of salmon. Evidence of the widespread declines in frogs is also found in the Northwest. The spotted frog was once widespread in a variety of habitats on both sides of the Cascades but is now nearly extirpated on the westside.
Alaska: Alaska's vast size, small population, and cold climate have protected the state from many of the negative effects on biological resources seen in the conterminous United States. With limited development, biological resources mostly respond to natural processes-unsuppressed wildfires, climatic events, and natural population variability. However, for many biological resources in Alaska, trend information is nonexistent. Harvest has a major impact in this region, particularly on fishery resources. Freshwater fish stocks in the interior are declining, especially those reachable by road. In the Susina River drainage, for example, the harvest of wild rainbow trout declined by 50% during the last 10 years, despite a doubling of the time spent fishing. Harvests of whitefish in the Tanana drainage dropped from 26,810 fish in 1986 to 739 in 1991. Salmon populations seem to be stable, except for chum salmon in some areas. Wildlife species have experienced some negative effects due to harvest, but many populations, such as some caribou herds, are at record high numbers. Introduced species have caused some problems. For example, the Aleutian Canada goose was nearly extirpated because of predation from introduced foxes, and an introduction of caribou to Adak Island threatened habitat of endangered plants when the caribou population exceeded carrying capacity.
Hawaii and the Pacific Islands: The Hawaiian archipelago is the most isolated island group of comparable size and diversity on Earth. This isolation results in a high percentage of unique species. Oceanic islands, however, are quite vulnerable to biological invasions, and the Hawaiian archipelago has been severely affected by nonindigenous species. For example, wild pigs brought to the island cause significant damage to forests by eating tree fern trunks, rare plants, and earthworms, and by helping spread seeds of non-native plants (Fig. 13). Introduced goats also destroy native vegetation to the point where high goat densities can result in obliterated landscapes. Eradication efforts for both species are under way in several areas. Mosquitoes, which are not native to the region, are significant invaders because they help spread avian malaria, which has harmed many native birds. About 90 nonindigenous plant species pose significant threats to Hawaiian ecosystems. Some plants, such as miconia, can out-compete native species to create single-species stands or can even alter ecosystems processes.
The most spectacular land-bird assemblage ever found on any remote ocean archipelago evolved in the Hawaiian Islands, but this assemblage has been significantly depleted through human actions. Of the 76 species of perching birds or songbirds that lived in Hawaii, 31 are known only as fossils. Of the remaining 45, 19 are extinct and 18 are federally listed as endangered.
Marine Resources: A range of human activities affects living marine resources, including fishes, marine mammals, and marine birds. Increasingly intensive fishing efforts, in conjunction with the use of more sophisticated fishing gear and electronics, have resulted in gross overfishing of some marine populations. Associated with fishing is bycatch, when nontarget animals are taken in fishing operations. Both overfishing and bycatch are problems that have caused marine resource managers to create controlled access to fishing, whereby catch quotas are allocated to individual fishing vessels instead of allowing free and open access. Quota allocation to individual vessels is gaining acceptance.
Habitat alterations in rivers and estuaries, as well as in coastal zones, are a result of urbanization. Urbanization alters freshwater flows, increases erosion, introduces toxic chemicals and other contaminants into the waters, furthers the introduction of nonindigenous species, and degrades the marine habitats essential to living marine resources. Numerous demographic trends suggest that these conditions and threats are not likely to change soon. Some 50% of our population is estimated to live within a 2- or 3-hour drive of major freshwater systems (the Great Lakes) or coastal waters. As the nation grows, there will be further population growth in coastal zones. Our desire to live within sight of the ocean has never abated and, increasingly, urban dwelling areas are being developed on or near shorelines. Often these developments severely and negatively alter coastal and marine ecosystems and harm living marine resources.
Another major issue today is the mitigation necessary to protect endangered or threatened species. A recent example of this situation is with certain salmon runs in Pacific coast streams. The use of river waters for irrigation, power generation, and domestic consumption by large urban areas has compromised these streams and the survival of the salmon runs.
Many natural changes in the dynamics of ecosystems also may exacerbate the effects of the factors just listed. For instance, attention to global warming over the past two decades is now culminating in data that show widespread climatic effects on living marine resources. Articles in recent issues of major scientific publications indicate a progressive subtle warming of Pacific coastal waters and, consequently, an extirpation of certain species that would have been found in these waters a half-century ago. Similar trends have been speculated about and, to some degree, measured in shelf waters as well as in the coastal zone of the northwest Atlantic.
On the whole, the outlook for the welfare of the nation's living marine resources is guarded, with a need to remain vigilant. The crash of some groundfish fisheries, the poor welfare of some Pacific coast salmon stocks, and declines in some marine mammal populations are examples of situations that need special attention. Although many other of the nation's marine resources are in good condition, they too must be attentively managed and conserved under a suite of federal laws and international treaties. The science of the marine environment and the state of its resources must be improved, for without reliable scientific knowledge, resource use and management must necessarily be more conservative.
This is an executive summary and the full report may be cited as follows:
Mac, M.J., P.A. Opler, C.E. Puckett Haecker, and P.D. Doran. 1998. Status and trends of the nation's biological resources. 2 vols. U.S. Department of the Interior, U.S. Geological Survey, Reston, Va.
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