8.3.2. Ecosystems: Forested
The forests of North America north of Mexico occupy about 732 million hectares,
representing about 17% of all global forested lands. Approximately 60% of the
North American forests are Canadian (Brooks, 1993). The United States has about
13% of the world's temperate forests and almost half of the world's coastal
temperate rainforest (Brooks, 1993). Nearly half of U.S. forests are privately
owned, compared to only about 6% in Canada (Brooks, 1993).
Conifers constitute nearly 70% of the world's commercial timber harvest. In
North America, conifer species dominate the boreal forests of Canada, Alaska,
and the Pacific NorthWest and share dominance with hardwoods in the southeastern
and northeastern United States. Wood-based manufacturing accounts for about
2% (US$129 billion) of the U.S. gross domestic product (GDP) and about 3% (CAN$23
billion) of the Canadian GDP (Canadian Forest Service, 1996; International Monetary
Fund, 1996; U.S. Department of Commerce, 1996).
Forests provide habitats for wildlife and fish, store and regulate freshwater
supplies, are the repository of substantial plant and animal genetic resources,
and satisfy aesthetic and spiritual values. Recreation activity associated with
forests contributes to income and employment in every forested region of North
America. Nontimber commodities gathered in forests are sources of income and
Forests hold about 62-78% of the world's terrestrial biospheric carbon (Perruchoud
and Fischlin, 1995), about 14-17% of which is in the forests of North America;
about 86% of that is in the boreal forest (Apps et al., 1993; Heath et al.,
1993; Sampson et al., 1993).
Forests play a large role in global water and energy feedbacks (Bonan et al.,
1995) and account for most of the world's terrestrial evapotranspiration, which
is about 64% of the precipitation (Peixoto and Oort, 1992; Neilson and Marks,
1994). Most of the world's freshwater resources originate in forested regions,
where water quality is directly related to forest health.