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Forests, wooded areas, and scattered trees have provided food, fuel, medicines, filtered water, shelter, and building materials throughout time. As countries with ample forests develop, they tend to emphasize timber production over other forest services; we've already seen this process occur in Canada and the US. Now, forests' timber production is similarly helping fuel economic development in many developing countries, where more than half of the world's remaining forests are located.
How much of the world's forests remain?
Forests are defined as land areas "dominated by trees where the tree canopy covers at least 10% of the ground area." By this definition, forests cover about 25% of Earth's land surface, excluding Antarctica and Greenland. Before people began clearing forests for agriculture, forests covered about 20% more land than they do now. Some estimates are as high as 50% more. Since 1980, forest area has decreased by about 10% in developing countries. In tropical regions, deforestation is currently estimated to exceed 130,000 square kilometers per year. In northern hemisphere countries, forest area is holding steady or increasing. In the United States and countries in Western Europe, where nearly all forests are managed to some degree, forest area increased as previously deforested areas were replanted for production or simply allowed to regenerate.
What are the primary goods and services forests provide?
We lose much more than trees when forests disappear.
In many parts of the world for example, New York City forest vegetation and soils are the primary or only filter for much of the water that people in the region use. But of the 145 watersheds around the world, 42 have lost more than 75% of their original forest cover. Fifteen have lost more than 95%. In Canada, Russia, Central and Eastern Europe, and most developing countries, annual timber harvests exceed what is regrown in available forest areas. The United States and Western Europe, two of the major producers of industrial timber, currently harvest less wood from available forest land than regrows annually, but in recent years the rate of regrowth has decreased. Growing trees take up more carbon than mature trees, but they store less until they reach full size, and loss of forest and decreased growth rate mean less carbon is stored. And more carbon in the atmosphere advances global warming. Clearly, trees are one of our most effective bulwarks against global warming.
But it is the biological richness and beauty of forest ecosystems that holds tremendous appeal to many environmentalists and the general public, as witnessed by worldwide appeals to "save the rainforest," even by people who don't live near and have no direct connection to rainforests.
What is the prognosis for the world's forests?
For frontier forests the principal threats are logging, mining, fragmentation by roads and other forms of infrastructure, and clearance for agriculture. Mining is stimulated by the lucrative industrial minerals located in developing countries' forests. Logging and mining operations, eager to move products to market, are often the initial road builders. Fragmentation by roads is important because they open remote forest regions to more logging and mining and to human settlement. Roads also increase hunting and poaching, sometimes of endangered species.
Clearance for agriculture is the primary cause of forest loss in Africa. Rural subsistence farming expands as populations grow. In Latin America, large-scale cattle ranching, government development programs, and hydroelectric projects are the main causes of forest loss. In Asia, loss results almost equally from expansion of farming and development projects. In the northern hemisphere, acid rain and other pollutants have taken their toll largely on boreal forests. The greatest threats, though, continue to be fragmentation and conversion.
Source: This profile is adapted from the companion book, World Resources 2000-2001.
The Value of Ecosystems
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