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贡献背景材料
Each year the International Union for the Conservation of Nature (IUCN), the world's largest independent conservation organization, updates its Red Data Book which lists worldwide plant and animal species known to be endangered, vulnerable or rare. Out of approximately 950 species of bats in the world, the 1988 Red Data Book lists only 33 bat species in these categories— less than 4% of the total. This proportionately small number should lead anyone with even a remote awareness of the worldwide extinction crisis to be suspicious. Why then, does the red list stray so far from an accurate picture of the real problem?
First, consider that the IUCN red list has a substantial geographic bias toward North American species. There are 39 species of bats in North America (exclusive of Mexico),1 comprising about 5% of the worldwide bat diversity. However, five of the 33 species on the list are North American— thus a fauna comprising only 5% of the total accounts for 15% of the number considered threatened or endangered. Far from reflecting reality, the red list reflects our ignorance regarding the status of most species.
We simply have more knowledge about the status of bats in North America than we do for most other parts of the world. In fact, our ignorance is so extreme that we are not even certain how accurate the IUCN list is for many North American species. We simply do not have the data to determine whether they are stable, increasing or decreasing, and at what rates. Given this lack of information and the fact that most bats investigated are declining, the IUCN red list gives an inaccurate and minimal assessment of the current crisis.
A different approach Conservation biologists recently have suggested that constructing red lists has been a major tactical error. The mere existence of such lists can lead to the assumption that if a species is not listed, it is not in jeopardy. A great many species that are not on any threatened or endangered list, should be, but we do not know enough about them. A major problem is that to be included, the extent and rate of decline must be documented, but since in many cases, past populations have not been studied, this data is often not available. To correct this problem, it has been suggested that rather than putting together red lists, we should construct "green lists." Green lists would index species known to be secure. Species that are not green-listed would include those whose status is undetermined; given the grand scale of wildlife habitat loss throughout the world, we should consider all species not on a green list to be threatened and act accordingly. Thus, the burden of proof would be shifted to those who maintain that all is well with a species.
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发表于 2012-11-8 14:22:03
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发表于 2012-11-8 14:34:22
