Unsustainable harvesting rates

Biological resources include wild organisms harvested for subsistence, commerce, or recreation (such as fish, game, timber or furbearers); domesticated organisms raised by agriculture, aquaculture and silviculture; and ecosystems (such as rangeland) cropped by livestock. Irrespective of the condition of their habitats, excessive rates of harvesting, especially of animal species, can lead to their extinction for economic purposes, and in some cases their biological extinction. Intensive harvesting of species can also endanger their genetic diversity.

Wood, still mainly harvested from wild sources, is one of the most important commodities in international trade. Potentially valuable timber resources in many parts of the world are being degraded through excess harvesting, inadequate management and habitat loss. For example, of more than 600 large tree species in Ghana, around 60 are used in the timber trade and some 25 species have been identified as of conservation concern because of over-exploitation or rarity (WCMC 1992). Recent analysis (Oldfield and others 1998) of around 10 000 tree species (out of a possible world total of 100 000) found that nearly 6 000 met the criteria for threatened status defined by IUCN, with 976 categorized as Critically Endangered, 1 319 as Endangered and 3 609 as Vulnerable. Habitat loss or modification is the underlying source of risk, particularly for restricted range species but felling was the individual threat most often cited (for 1 290 species).

Asia's dominance of world trade in tropical hardwoods is likely to decline. At current rates of harvesting, remaining timber reserves in Asia will last for fewer than 40 years (ADB 1994).