The key issue in the applicability of indicators is access to reliable and consistent information, particularly when we are attempting to apply indices at continental or global scales. The quality of knowledge varies greatly across biological groups (e.g., from very good for birds to very poor for soil microbes). This reflects not their relative ecological importance but their charisma and ease of study. This unevenness of observation has geographic consequences: The tropics and the oceans are less well inventoried than the temperate landmasses because they have a greater biodiversity and a shorter record of scientific study. To an extent, broadening the information sources to include traditional or indigenous knowledge can help alleviate the problem for the more prominent groups, but it is unreasonable to expect indigenous people to have knowledge about subjects that may not have seemed necessary or even visible to them.
The pragmatic solution is to confine biodiversity indicators to taxonomic groups or topics that are well known (i.e., plants and vertebrates) and to make use of both qualitative (including informal) and quantitative information sources, at least until some parity in knowledge is achieved. In well-studied ecosystem types, biodiversity loss can be measured based on all well-known taxonomic groups, provided that they are included in an unbiased fashion.
The unwillingness of much of the traditional scientific community in the biodiver sity domain to be pragmatic rather than perfectly rigorous is a significant impediment to addressing the urgent problem of biodiversity loss. Most indicators rely on very similar sets of input information, so the lack of consensus regarding the form of the indicator should not be an excuse to limit the collection and refinement of fundamental, spatially and temporally explicit data on
• Land cover and use and the spatial pattern of marine resource use
• The distribution of species, especially of plants and vertebrates
• Trends in the population size of key species
• The genetic diversity of domesticated species
• The impact of different land use activities on different species
A lesson in pragmatism can be drawn from the UN Climate Change Convention. When the Intergovernmental Panel on Climate Change was charged with developing performance indicators for greenhouse gas emissions, which can come from hundreds of activities and tens of thousands of individual sources, it chose activity-based approaches rather than full, source-by-source accounting. This approach establishes a statistical relationship between the intensity of an activity (e.g., agriculture) and its impact (in this case, on biodiversity). It calculates the score for a given geographic region by multiplying the area exposed to each activity by the impact factor. The Natural Capital Index and Biodiversity Impact Indices work in this way.
The increasing ease and decreasing cost of collecting genetic information may alter the emphasis currently placed on species-level information, especially for large groups of organisms whose taxonomy is poorly developed. For instance, in calculating endemism scores, the number of closely related species may be less important than the total genetic diversity in the system. In domesticated organisms, subject to intense breeding, the species concept is inapplicable in any case, and genetic methods are already widely applied. At present it is not practical to get full genetic profiles for all organisms. Community profiling is a method of choice for groups such as soil microbes, where a bulk sample is easily obtained.
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