Areas naturales para la conservacion

SCIENCE’S COMPASS
REVIEW: ECOLOGY

●

REVIEW

Andrew Balmford,1* Aaron Bruner,2 Philip Cooper,3 Robert Costanza,4† Stephen Farber,5 Rhys E. Green,1,6 Martin Jenkins,7 Paul Jefferiss,6 Valma Jessamy,3 Joah Madden,1 Kat Munro,1 Norman Myers,8 Shahid Naeem,9 Jouni Paavola,3 Matthew Rayment,6 Sergio Rosendo,3 Joan Roughgarden,10 Kate Trumper,1 R. Kerry Turner3 On the eve of the World Summit onSustainable Development, it is timely to assess progress over the 10 years since its predecessor in Rio de Janeiro. Loss and degradation of remaining natural habitats has continued largely unabated. However, evidence has been accumulating that such systems generate marked economic benefits, which the available data suggest exceed those obtained from continued habitat conversion. We estimate thatthe overall benefit:cost ratio of an effective global program for the conservation of remaining wild nature is at least 100 :1. matched estimates of the marginal values of goods and services delivered by a biome when relatively intact, and when converted to typical forms of human use. To ensure we did not neglect private benefits of conversion, studies were only included if they covered the mostimportant marketed goods, as well as one or more nonmarketed services delivering local social or global benefits. We cross-validated figures for individual goods and services with other estimates from similar places. Finally, we checked that the comparisons across different states of a biome used the same valuation techniques for particular goods and services. Our survey uncovered only five examplesthat met all these criteria. Here, we summarize their findings, with all figures expressed as net present values (NPVs, in 2000 US$ ha 1), and using the discount rates considered by the authors [see Fig. 1 and supplemental online material (10) for further details]. Two studies quantified net marginal benefits of different human uses of tropical forest areas. Kumari compared the values obtainedfrom timber plus a suite of nontimber forest products (NTFPs), as well as the values of water supply and regulation, recreation, and the maintenance of carbon stocks and endangered species, for forests under a range of management regimes in Selangor, Malaysia (11). Compared with two methods of reduced-impact logging, high-intensity, unsustainable logging was associated with greater private benefitsthrough timber harvesting (at least at high discount rates and over one harvesting cycle), but reduced social and global benefits (through loss of NTFPs, flood protection, carbon stocks, and endangered species). Summed together, the total economic value (TEV) of forest was some 14% greater when placed under more sustainable management (at $13,000 compared with $11,200 ha 1). A study from MountCameroon, Cameroon, comparing low-impact logging with more extreme land-use change again found that private benefits favor conversion, this time to small-scale agriculture (12). However, a second alternative to retaining the forest, conversion to oil palm and rubber plantations, in fact yielded negative private benefits once the effect of market distortions was

Economic Reasons for Conserving WildNature

H

umans benefit from wild nature (1) in very many ways: aesthetically and culturally; via the provision of ecological services such as climate regulation, soil formation, and nutrient cycling; and from the direct harvest of wild species for food, fuel, fibers, and pharmaceuticals (2). In the face of increasing human pressures on the environment, these benefits should act as powerfulincentives to conserve nature, yet evaluating them has proved difficult because they are mostly not captured by conventional, market-based economic activity and analysis. In 1997, Costanza et al. published a synthesis (3) of more than 100 attempts to value ecosystem goods and services using a range of techniques including hedonic pricing, contingent valuation, and replacement cost methods (4)....