Loss Of Biodiversity And Deforestation The Scale Of The Problem

Biological diversity is one of the management objectives for 25 percent of the world's forests. The area of forest within which conservation of biological diversity is the primary function has increased by 96 million hectares since 1990 and now accounts for 11.2 percent of total forest area,

Figure 4.1 The ten countries with the largest forest area account for two-thirds of the total forest area

Figure 4.1 The ten countries with the largest forest area account for two-thirds of the total forest area

Unknown, 7.8

Unknown, 7.8

Production, 34.1

Protection of soil and water, 9.3

Social services, 3.7

Conservation of biodiversity, 11.2

Source: FAO (2GG6: Figure 11).

Figure 4.2 Functions of forests globally, 2005, percent

Production, 34.1

Protection of soil and water, 9.3

Social services, 3.7

Conservation of biodiversity, 11.2

Source: FAO (2GG6: Figure 11).

Figure 4.2 Functions of forests globally, 2005, percent

Tropical forests

Source: Image courtesy of The Ozone Hole Inc. Figure 4.3 The world's tropical forests mostly in protected areas (FAO, 2006: xix). Despite this a large number of species have become extinct in recent history or are threatened with extinction. Reductions in populations are widespread, and genetic diversity is also widely considered to be in decline. These changes are more rapid than at any time in human history: 100-year records of known species indicate extinction rates around 100 times greater than is characteristic in the fossil record (Millennium Ecosystem Assessment, 2005: 43).

From 1990 to 2005 the world lost 35 percent of its forests mainly due to conversion to agricultural land in developing countries. This conversion continues at a rate of 13 million hectares a year, principally in the biologically diverse regions of South-east Asia, Oceania, Latin America, the Caribbean and sub-Saharan Africa (FAO, 2006: xiv, xv). Primary forest, mostly undisturbed and rich in habitat and vascular plant populations, covering 1.3 billion hectares and constituting 36 percent of all forests, is being lost at a rate of 6 million hectares a year (FAO, 2006: Table 1) (see Figure 4.4). While the information on primary forest is incomplete, there is no indication that this rate of loss is slowing (FAO, 2006: 13). On average, eight of the tree species native to a country are critically endangered and 20 are endangered (FAO, 2006: Table 3.9). In contrast, the temperate forests of the developed countries are expanding (FAO, 2006: xv).

The principal cause of forest and habitat loss is the conversion of forests to agriculture, while logging and over-exploitation, for such uses as fuel-wood, degrades them. Other factors adversely affecting forests to the tune

Area of primary forest

Area of other wooded laid

Area of forest Area of designated productive primarily for forest conservation plantations of biological diversity

Figure 4.4 Average annual change in forest area, 2000-2005, millions of hectares of over 100 million hectares a year are fire, pests or climate events, but their incidence and impacts are severely under-reported.

Forest plantations are increasing by 2.8 million hectares a year and now account for 4 percent of total forest area. Slightly more than 75 percent of all plantations are of introduced species for harvesting while the remainder consists of protective plantations mainly for conservation of soil and water. Asia reported a net gain of 1 million hectares a year from 2000-2005, primarily the result of large-scale afforestation reported by China (FAO, 2006: 82).

While extinctions in the heavily converted Mediterranean and temperate forests have reduced biodiversity, this was from a relatively low level of richness. Richness in terms of both species and families is greater by far in rainforests, which now contain the highest number of threatened species. Presently, 12 percent of bird species, 23 percent of mammals, 25 percent of conifers and 52 percent of cycads are threatened with extinction (IUCN, 2006; Millennium Ecosystem Assessment 2005: 44). The rate of forest loss for three biodiversity-rich countries is detailed in Table

At the rate of loss of forests indicated in Table 4.1, forests will have disappeared in the Democratic Republic of the Congo in 419 years, in Brazil in 154 years and in Indonesia in 46 years. As well as being lost, forests are also being degraded by factors such as logging roads and illegal extraction, but the extent of degradation is difficult to measure (FAO, 2006).

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