A/42/427
English
Page 153
16. Tropical moist forests cover only 6 per cent of the Earth's land surface but contain at least half the Earth's species (which totals 5 million at a minimum, but could be as many as 30 million). They may contain 90 per cent or even more of all species. The mature tropical forests that still exist cover only 900 million hectares, out of the 1.5-1.6 billion hectares that once stood. Between 7.6 million and 10 million hectares are eliminated outright each year, and at least a further 10 million hectares are grossly disrupted annually.[1] But these figures come from surveys of the late 1970s, and since then deforestation rates have probably accelerated.
17. By the end of the century, or shortly thereafter, there could be little virgin tropical moist forest left outside of the Zaire Basin and the western half of Brazilian Amazonia, plus some areas such as the Guyana tract of forest in northern South America and parts of the island of New Guinea. The forests in these zones are unlikely to survive beyond a few further decades, as world demand for their produce continues to expand and as the number of forestland farmers increases.
18. If deforestation were to continue in Amazonia at present rates until the year 2000, but then halted completely (which is unlikely), about 15 per cent of plant species would be lost. Were Amazonia's forest cover to be ultimately reduced to those areas now established as parks and reserves, 66 per cent of plant species would eventually disappear, together with almost 69 per cent of bird species and similar proportions of all other major categories of species. Almost 20 per cent of the Earth's species are found in Latin American forests outside of Amazonia; another 20 per cent are found in forests of Asia and Africa outside the Zaire Basin.[2] All these forests are threatened, and if they were to disappear, the species loss could amount to hundreds of thousands.
19. Unless appropriate management measures are taken over the longer term, at least one-quarter, possibly one-third, and conceivably a still larger share of species existing today could be lost. Many experts suggest that at least 20 per cent of tropical forests should be protected, but to date well under 5 per cent has been afforded protection of any sort – and many of the tropical forest parks exist only on paper.
20. Even the most effectively managed parks and protected areas are unlikely to provide a sufficient answer. In Amazonia, if as much as half the forest were to be safeguarded in some way or another but the other half were to be eliminated or severely disrupted, there might well not be enough moisture in the Amazonian ecosystem to keep the remaining forest moist.[3] It could steadily dry up until it became more like an open woodland – with the loss of most of the species adapted to tropical moist forest conditions.
21. More widespread climatic changes are likely to emerge within the foreseeable future as the accumulation of 'greenhouse gases' in the atmosphere leads to global warming early in the next century. (See Chapter 7.) Such a change will produce
- ↑ FAO/UNEP, Tropical Forest Resources, Forestry Paper No. 30 (Rome: 1982): J.M. Melillo et al., 'A Comparison of Recent Estimates of Disturbance in Tropical Forests', Environmental Conservation, Spring 1985; N. Myers, The Primay Source (New York: W.W. Norton, 1984); Myers 'The Latest News', op. cit.; J. Molofsky et al., 'A Comparison of Tropical Forest Surveys', Carbon Dioxide Program, U.S. Department of Energy, Washington DC, 1986.
- ↑ D. Simberloff, 'Are We On the Verge of a Mass Extinction in Tropical Rain Forests?' in D.K. Elliott (ed.), Dynamics of Extinction(Chicester, UK: John Wiley & Sons, 1986): Raven, op. cit.
- ↑ E. Salati and P.B. Vose, 'Amazon Basin: A System in Equilibrium', Science, 13 July 1984.
