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Box 1.2. Measuring and Estimating Biodiversity: More than Species RichnessMeasurements of biodiversity seldom capture all its dimensions, and the most common measure—species richness—is no exception. While this can serve as a valuable surrogate measure for other dimensions that are difficult to quantify, there are several limitations associated with an emphasis on species. First, what constitutes a species is not often well defined. Second, although native species richness and ecosystem functioning correlate well, there is considerable variability surrounding this relationship. Third, species may be taxonomically similar (in the same genus) but ecologically quite distinct. Fourth, species vary extraordinarily in abundance; for most biological communities, only a few are dominant, while many are rare. Simply counting the number of species in an ecosystem does not take into consideration how variable each species might be or its contribution to ecosystem properties. For every species, several properties other than its taxonomy are more valuable for assessment and monitoring. These properties include measures of genetic and ecological variability, distribution and its role in ecosystem processes, dynamics, trophic position, and functional traits. In practice, however, variability, dynamics, trophic position, and functional attributes of many species are poorly known. Thus it is both necessary and useful to use surrogate, proxy, or indicator measures based on the taxonomy or genetic information. Important attributes missed by species or taxon-based measures of diversity include:
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Millennium Ecosystem Assessment Related publication:
Other Figures & Tables on this publication: Direct cross-links to the Global Assessment Reports of the Millennium Assessment Box 1. Biodiversity and Its Loss— Avoiding Conceptual Pitfalls Box 1.1. Linkages among Biodiversity, Ecosystem Services, and Human Well-being Box 1.2. Measuring and Estimating Biodiversity: More than Species Richness Box 1.3. Ecological Indicators and Biodiversity Box 1.4. Criteria for Effective Ecological Indicators Box 2.1. Social Consequences of Biodiversity Degradation (SG-SAfMA) Box 2.2. Economic Costs and Benefits of Ecosystem Conversion Box 2.3. Concepts and Measures of Poverty Box 2.4. Conflicts Between the Mining Sector and Local Communities in Chile Box 3.1. Direct Drivers: Example from Southern African Sub-global Assessment Box 4.1. An Outline of the Four MA Scenarios Box 5.1. Key Factors of Successful Responses to Biodiversity Loss Figure 3.3. Species Extinction Rates Figure 1.3. The 8 Biogeographical Realms and 14 Biomes Used in the MA Figure 1.4. Biodiversity, Ecosystem Functioning, and Ecosystem Services Figure 2. How Much Biodiversity Will Remain a Century from Now under Different Value Frameworks? Figure 2.1. Efficiency Frontier Analysis of Species Persistence and Economic Returns Figure 3.3. Species Extinction Rates Figure 3.4. Red List Indices for Birds, 1988–2004, in Different Biogeographic Realms Figure 3.7. The Living Planet Index, 1970–2000 Figure 3.10. Main Direct Drivers Figure 3.12. Extent of Cultivated Systems, 2000 Figure 3.13. Decline in Trophic Level of Fisheries Catch since 1950 Figure 3.14. Estimated Global Marine Fish Catch, 1950–2001 Figure 3.15. Estimates of Forest Fragmentation due to Anthropogenic Causes Figure 3.15. Estimates of Forest Fragmentation due to Anthropogenic Causes Figure 3.15. Estimates of Forest Fragmentation due to Anthropogenic Causes Figure 3.15. Estimates of Forest Fragmentation due to Anthropogenic Causes Figure 3.15. Estimates of Forest Fragmentation due to Anthropogenic Causes Figure 3.15. Estimates of Forest Fragmentation due to Anthropogenic Causes Figure 3.16. Fragmentation and Flow in Major Rivers Figure 3.17 Trends in Global Use of Nitrogen Fertilizer, 1961–2001 (million tons) Figure 3.18 Trends in Global Use of Phosphate Fertilizer, 1961–2001 (million tons) Figure 3.20. Historical and Projected Variations in Earth’s Surface Temperature Figure 4. Trade-offs between Biodiversity and Human Well-being under the Four MA Scenarios Figure 4.3. Land-cover Map for the Year 2000 Figure 4.4. Conversion of Terrestrial Biomes Figure 4.5. Forest and Cropland/Pasture in Industrial and Developing Regions under the MA Scenarios Figure 4.6. Changes in Annual Water Availability in Global Orchestration Scenario by 2100 Figure 6.1. How Much Biodiversity Will Remain a Century from Now under Different Value Frameworks? Figure 6.2. Trade-offs between Biodiversity and Human Well-being under the Four MA Scenarios Table 1.1. Ecological Surprises Caused by Complex Interactions |
