The report is organized into two parts. Part Two describes the status and trends of biological resources in different regions of the country, the ecosystems in that region, and how these resources have been affected by the factors described in Part One. The regions covered are the Northeast, Great Lakes, Southeast, Caribbean Islands, Mississippi River, Coastal Louisiana, Grasslands, Rocky Mountains, Great Basin-Mojave Desert, Southwest, California, Pacific Northwest, Alaska, Hawaii and the Pacific Islands, and Marine Resources. Factors Affecting Biological Resources Of the seven factors detailed in the report, six are human-induced and one, natural processes, covers natural events such as fire, hurricanes, and even precipitation extremes that induce changes in physical habitat. These natural processes, when not extremely severe or highly regular in their occurrence, can promote biodiversity by varying physical habitat.
Hurricanes can provide some benefits to ecosystems by distributing sediment to coastal wetlands.
Urbanization, conversion of lands to agriculture, draining of wetlands, and the fragmentation of forests are some of the land-use changes repeatedly cited in Part Two as major forces negatively affecting the health of biological resources. Changes in our nation's waterways to accommodate navigation, irrigation, hydroelectric power generation, and municipal use have drastically altered the biological integrity of aquatic environments. Consequently, aquatic organisms now dominate lists of imperiled species. Changes in land and water use have altered habitats so that they are more favorable for the establishment of nonindigenous species, which are posing increasing threats because of our more global economy and increased international travel. The impacts on biological resources due to environmental contaminants and climate change are often not as obvious as the effects of a dammed river or a drained wetland, but potential effects can be severe.