Defenders' Experts
Habitat Loss and Degradation
A 2002 publication by the Heinz Center, The State of the Nation's Ecosystems, provided an invaluable snapshot of the forests of the United States and the biological diversity these habitats support:
Forests cover almost 750 million
acres, about one-third of the U.S., down from about one billion acres at the
time of European settlement. The amount of forest land has remained relatively
stable in recent decades, but forest types have shifted in some areas.
About 20 percent of some 1,700 native animal species that depend on U.S. forests are considered to be at risk, and almost half of those are considered critically imperiled or imperiled. About 1.5 percent of forest species may already be extinct.
Most at-risk forest species are vulnerable largely because of habitat loss and degradation, much of it related to human activities, ranging from conversion to non-forests for urban and agricultural uses to invasion by non-native species and fire exclusion.
About three percent of eastern forests and 11 percent of the forests in the West were in "reserved lands" such as wilderness areas and national parks, where timber harvesting is prohibited by law. Intensively managed plantations accounted for four percent of western forests and 10 percent of forests in the East. However, the pervasive risks of biodiversity loss increasingly have shifted conservation biologists' thinking away from traditional "reserve / non-reserve" concepts toward broader biodiversity management strategies across the full range of ownerships and landscape allocations.
At the same time, public policy makers are increasingly recognizing that biodiversity benefits associated with healthy forest ecosystems extend far beyond the edge of the trees. Forests are the principal source of most of the nation's drinking water and have a profound effect on hydrology, air quality, and climate. Their economic, recreational, and aesthetic values are closely linked to the quality of their natural systems. Adverse effects on forest biodiversity can come from a variety of sources, including forest management.
Conversion of Forestland to Other Uses
One of the most obvious and dramatic is the conversion of forest land to other uses such as development (dwellings, etc.) or agriculture, which will generally render the land uninhabitable by forest-dwelling species.
Such changes can have influences beyond the absolute decrease in forested acres. Often, development proceeds in a way that creates a patchwork of forested areas and developed/ converted areas. The remaining forest "fragments' may be too small and isolated to provide full habitat benefits.
Roads
Roads contribute to fragmentation if they are a barrier to movement among forested areas. Roads can also facilitate the spread of invasive species , including plants, diseases and harmful insects. Unfortunately, many invasives can spread quite effectively even in the absence of roads - consider the chestnut blight that effectively eliminated the American chestnut from vast expanses of the eastern forest where it had previously been a dominant species.
Parcelization
Another trend that can contribute to forest fragmentation is "parcelization," the breaking up of contiguous forest land ownerships into ever smaller ownerships. Not only does this make it more difficult to strategically manage the larger area for a variety of values, each owner may want to build a residence or otherwise develop their parcel, furthering the trends of forest loss and fragmentation.
Development
A U.S. Forest Service study, Forests on the Edge: Housing Development on America's Private Forests published in June 2005 projected dramatic increases in housing development over the next three decades on more than 11 percent of the nation's private forests, more than 44 million acres. The agency estimates that private forests in the Southeast, where three-quarters of all U.S. private forests are located, will experience the most extensive changes. Forestland development pressures will also be high in parts of the Northeast, the Pacific Northwest and California.
Forest Simplification or
Homogenization
Intensive forest management often involves simplification or
homogenization of forests that can reduce the diversity they support.
Plantations of one or a few species, managed on short rotations, never develop
the variety of tree species, ages and sizes, and snags and fallen logs, that are
typical of natural forests. While this can lead to decreased diversity in these
intensively managed stands, enhanced timber production from such forests can, at
least theoretically, reduce the need to extract timber from other, more
sensitive areas, allowing less intensive, more biodiversity-friendly management
on these other lands. The challenges are to ensure that such trade-offs actually
occur and that allocations are made strategically to optimize production of both
timber and biodiversity.
Fire Exclusion
Exclusion of fire in some forests - typically drier types
that were historically maintained by frequent, low-severity fires - can have
detrimental effects on biological diversity and forest sustainability. Frequent
fires historically maintained Ponderosa pine forests in the West and long-leaf
pine in the Southeastern United States in an open, park-like, predominantly old
growth condition. Long-leaf pine has been extensively converted to plantations
of other species. Millions of acres of ponderosa pine on National Forests have
been altered by combinations of high-grade logging and fire exclusion. Dense
stands of smaller trees that have grown up in these forests pose a risk of
uncharacteristically severe (crown) fires and compete with remaining old pine
trees for moisture and nutrients, putting them at greater risk of being killed
by insects or disease. Even without crown fire or death of old pine trees, these
changes in forest structure and composition will lead to changes in populations
of wildlife and plants, often to the detriment of species of conservation
concern.
Management is a term that seems open to widely varying interpretations
For us, the essence of management is that it is informed and intentional. If one has a reasonable level of knowledge of an area of forest and how it functions, has objectives that are consistent with the ecological capacity of the land, and treats the land in a way that has a reasonable likelihood of achieving those objectives, then that treatment can legitimately be called management. Active management employs manipulation of one or more elements of the forest ecosystem (cutting trees, setting prescribed fire, etc.); passive management allows natural processes such as growth, mortality or succession to achieve objectives. Management can be contrasted with neglect or abuse, treating (or ignoring) the land without understanding how it works or without clear objectives that the land can sustainably provide, potentially losing crucial ecological elements or functions.Forests present immensely complex challenges for biodiversity conservation. Read some of the concepts scientists use to frame how we think about conservation of forest biodiversity.
Forests, in all their variety, provide benefits to biodiversity and management opportunities and challenges that are different from other ecosystem types.
Natural forests are a mosaic of stands of varying sizes and ages which supports a great diversity of wildlife.
Adverse effects on forest biodiversity can come from a variety of sources, including forest management.
Many conservation biologists are looking to the broader landscape for options to help conserve forest biodiversity.
Sources for further information on forest biodiversity and management strategies.
