生物谷报道： 据Scidev.net网3月11日报道，生物学家已经设计出一种新方法，可以快速评估人类活动对自然界的影响程度。他们说，这一方法有助于《生物多样性公约》实现到2010年减少物种灭绝的目标。
南非科学与工业研究委员会的斯格勒斯和比格斯于上周在《自然》杂志上公布了他们“零物种灭绝指标（BII）”。这一指标摒弃传统的统计物种清单并估算灭绝比例的方法，而是采用有关人类活动的增加或减少是如何影响相似物种群体的总量（例如食昆虫的鸟类或大型食草动物）的专业知识。通过一个简单的方程式，就能得出每个“功能群体”的数量与 前工业时代相比的相关程度。
总的来说，这一指标显示到2000年动植物数量已经下降，平均为前工业水平的84%。灭亡最多的是哺乳动物（71%）以及牧草地上的动植物。据该指标估算，牧草地上的动植物数量已经降到前工业水平的74%。目前大多数广泛使用的评估生物灭绝的物种清单显示，有99%的物种存活在研究区域。生物学家说，这一差别显示，仅看物种是否存在而不看存在的数量对当前展现生物多样性状况是不够敏感的。
188个国家加入2002年由《生物多样性公约》制定的2010年目标，但是生物多样性是一个很难定义的概念，因为它包含了地球多种生命的所有方面：从基因到物种再到整个生态环境。因此，仅仅统计物种数量和评估其灭绝风险并不能得出人类活动对自然界影响程度的详细程度。
斯格勒斯和比格斯说，他们的指标就克服了这一问题，并满足了公约测定生物多样性的标准，因为这一指标科学合理，灵敏地反应出时间或地区间的变化，而且准确、可行性强、易于理解。同时也是一个快速的方法，研究者们只花了几周时间来评估南部非洲的生物多样性状况，不过，详细的生物数量调查却要花几十年时间。但是他们注意到，该指标对气候变化或生活环境变化对生物多样性的长期影响十分敏感。
英联邦动物研究所科学主任乔治娜-梅斯女士说：“生物多样性评估需要抛开物种清单和物种灭绝率，因为每个物种现存的数量更为重要。” 她还说：“斯格勒斯和比格斯设计出的零物种灭绝指标（BII）满足了许多要求，并提供了一个灵敏的、有意义的指标。”
研究人员利用这一指标在非洲南部的波斯瓦纳、莱索托、莫桑比克、纳米比亚、斯威士兰和津巴布韦等国家进行测试。他们向专家们请教了人类活动对植物、哺乳动物、鸟类、爬虫动物和两栖动物等的影响和程度，包括农业和城市化等对相似物种在六种生活环境中所受的影响。结果发现，莱索托和斯威士兰的生物多样性减少最多，这两个国家人口都很密集。
该文发表在：NATURE |VOL 434 | 3 MARCH 2005 | www.nature.com/nature
详细内容参见：
Measuring loss of biodiversity the expert way
Mike Shanahan
Many plants in South Africa's fynbos are found nowhere else in the world
Biologists have devised a new method of rapidly assessing how much human actions are affecting the natural world.
They say their method will help in determining progress towards the internationally agreed target of significantly reducing biodiversity loss by 2010.
Bob Scholes and Oonsie Biggs of South Africa's Council for Scientific and Industrial Research published their 'biodiversity intactness index' last week in Nature.
The index discards the traditional approach of compiling lists of species and estimating the rate at which they are going extinct.
Instead, it draws on expert knowledge about how human activities increase or decrease the total populations of groups of ecologically similar species — such as insect-eating birds or large herbivorous mammals.
Using a simple equation, the index gives a measure of how close populations of each of these 'functional groups' are to those in pre-industrial times.
The researchers tested their index by looking at seven countries in southern Africa.
They asked experts on plants, mammals, birds, reptiles and amphibians about how different degrees of human impact, including agriculture and urbanisation, affected groups of similar species in six types of habitat.
The researchers used existing data sources to assess how much of the study area each of these habitats occupies and the patterns of land use in each.
Overall, their index suggests that by 2000, populations of the plants and animals assessed had declined, on average, to 84 per cent of their pre-industrial levels.
The greatest loss was among mammals (71 per cent) and in grasslands, where the index estimates that animal and plant populations have fallen to 74 per cent of former levels.
Species lists — currently the most widely used method for estimating biodiversity loss — show that 99 per cent of species remain across the area studied.
This difference, say the biologists, shows that only looking at whether a species still exists rather than the state of its population is not sensitive enough to accurately reveal the state of biodiversity.
The 188 countries that are party to the Convention on Biological Diversity set the 2010 target in 2002. But biodiversity is a difficult concept to define as it encompasses all facets of the variety of life on Earth: from genes to species to entire ecosystems.
It also covers the range of ways in which species interact, which together allow natural systems to continue functioning. Because of this, simply counting species numbers and assessing their risk of extinction does not give a detailed indication of how intact the natural world is as a result of human activities.
Scholes and Biggs say their index overcomes this problem and meets the convention's criteria for measuring biodiversity as it is scientifically sound, sensitive to changes over time or between locations, accurate, affordable and easy to understand.
As a method, it is also fast. Estimating the state of southern Africa's biodiversity took the researchers a few weeks of work, whereas detailed population surveys would have taken decades.
However, they note that the index might be insensitive to the long-term effects on biodiversity of climate change or habitat fragmentation.
"Biodiversity assessments need to move away from species lists and species extinction rates, because often the existence and proximity of local populations matters more," said Georgina Mace, director of science at the Institute of Zoology, United Kingdom, in the same issue of Nature.
"Scholes and Biggs' biodiversity intactness index (BII) makes a start in satisfying many requirements and provides a robust, sensitive and meaningful indicator," she said.
The index can be assessed for a single group of species, pooled for a specific habitat type, or combined further to give a picture of the state of biodiversity across entire regions.
For their study, the researchers assessed biodiversity in Botswana, Lesotho, Mozambique, Namibia, South Africa, Swaziland and Zimbabwe.
The greatest decreases in biodiversity, according to the index, were in Lesotho and Swaziland, the two countries with the greatest density of human population.
Link to full paper by Scholes and Biggs in Nature
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Link to full article by Mace in Nature 点击浏览该文件
Reference: Nature 434, 45 (2004)
