Cougar, New Mexico
Courtesy New Mexico Dept. of Fish and Game
Watersheds: Deforestation of upland catchments often leads to disruption of hydrological systems, causing year-round water flows in downstream areas to give way to flood and drought. While forest cover remains intact, rivers not only run clear and clean, they also flow throughout the year. When the forest is cleared rivers turn muddy and swell or shrink.
Forests exert a “sponge effect,” soaking up water before releasing it a regular rates. The multistoried structure of the forest, together with its abundant foliage, helps break the impact of downpouring rains. Much of the water trickles down branches and tree trunks, or drips off leaves in a fine spray, so that when the rainfall reaches the ground, it percolates steadily into the soil or runs off into streams and rivers gradually.
The impact of downpours causes more erosion in deforested areas than anywhere on Earth. Washed away topsoil causes rivers to become burdened with sediment. Siltation becomes a problem for municipal water supply systems and impedes the ability of fish stocks to migrated and spawn.
Global Climate: Much of the energy that converts surface moisture into water vapor comes from the sun's heating of the land surface. Vegetation absorbs more heat than does bare soil. Over thick vegetation, such as forests, vigorous thermal currents take moisture, provided by the plant cover, up into the atmosphere where it condenses as rain. This effect constitutes a basic factor in controlling climate.
Still more important is the forest-climate linkage at the global level, through forests’ role as carbon sinks and hence their capacity to mitigate global warming (Apps and Price 1996, Woodwell and Mackenzie 1995). Forests currently hold some 1,200 gigatonnes (billion tons) of carbon in their plants and soils, by contrast with 750 gigatonnes in the atmosphere.
When forests are burned they release their carbon as carbon dioxide.
Globally, twice as much carbon goes into the atmosphere each year
due forest fires than is absorbed by the new growth of trees and
plants. Carbon dioxide is a major contributor to global warming.
Methane, which is another potent greenhouse gas, is also released in
forest fires. In addition, global warming itself will cause increased
die-off and decomposition of forest biomass, in turn triggering a further
release of carbon dioxide and methane (Houghton et al. 1995).
Global warming could lead to all manner of environmental discontinuities
that ecologist can only surmise about at present. It is plausible
that the world could eventually face a “runaway” greenhouse effect
as forests decline, taking with them their crucial function in the global
carbon budget. In the effort to halt global warming, it is likely
that much irreversible damage has already been done through the momentum
of climate change dynamics (Woodwell et al. 1995).
Biodiversity: Forests supply habitat for large numbers of plant and animal species. This biodiversity supplies abundant ecosystem services and functions as a “genetic library.” Genetic resources contribute to both modern and traditional agriculture, medicine and industry. All forms of biodiversity are both generated and maintained by natural ecosystems.
In the past two decades, the science of conservation biology has emerged.
Conservation biologists are in are in widespread agreement that the existing
network of protected lands, including wilderness, National Parks
and wildlife refuges are too small to address the preservation of ecosystems,
and hence biodiversity. Pioneering efforts, such as the Wildlands
Project in Tucson, Arizona, have designed large landscape level systems
of reserves, corridors, key watersheds, and buffer zones spanning all ownership's
which are needed to protect and restore what remains of native biological
diversity in the United States. Ending public lands logging is fully compatible
with this approach since public lands are the core reserves around which
wildlands recovery strategies should be designed.
Source: Daily, Gretchen C., ed. “Nature’s Service - Societal Dependence
on Natural Ecosystems,” 1997.