Even for the taxonomic component of biodiversity, where information is the best, considerable uncertainty remains about the true extent and changes in taxonomic diversity ().
Given that cultivated systems alone now account for more than 24% of Earth’s terrestrial surface, it is critical that any decision concerning biodiversity or ecosystem services address the maintenance of biodiversity in these largely anthropogenic systems ().
Measuring Biodiversity: Species Richness and Indicators In spite of many tools and data sources, biodiversity remains difficult to quantify precisely.
More-complete biotic inventories are badly needed to correct for this deficiency ( While the data to hand are often insufficient to provide accurate pictures of the extent and distribution of all components of biodiversity, there are, nevertheless, many patterns and tools that decision-makers can use to derive useful approximations for both terrestrial and marine ecosystems.
North-temperate regions often have usable data on spatial distributions of many taxa, and some groups (such as birds, mammals, reptiles, plants, butterflies, and dragonflies) are reasonably well documented globally.
Because the multidimensionality of biodiversity poses formidable challenges to its measurement, a variety of surrogate or proxy measures are often used.
These include the species richness of specific taxa, the number of distinct plant functional types (such as grasses, forbs, bushes, or trees), or the diversity of distinct gene sequences in a sample of microbial DNA taken from the soil.This layer of living organisms—the biosphere—through the collective metabolic activities of its innumerable plants, animals, and microbes physically and chemically unites the atmosphere, geosphere, and hydrosphere into one environmental system within which millions of species, including humans, have thrived.Breathable air, potable water, fertile soils, productive lands, bountiful seas, the equitable climate of Earth’s recent history, and other ecosystem services (see ) are manifestations of the workings of life.Thus only a multidimensional assessment of biodiversity can provide insights into the relationship between changes in biodiversity and changes in ecosystem functioning and ecosystem services ().Biodiversity includes all ecosystems—managed or unmanaged. Sometimes biodiversity is presumed to be a relevant feature of only unmanaged ecosystems, such as wildlands, nature preserves, or national parks. Managed systems—be they plantations, farms, croplands, aquaculture sites, rangelands, or even urban parks and urban ecosystems—have their own biodiversity.Even among the larger and more mobile species, such as terrestrial vertebrates, more than one third of all species have ranges of less than 1,000 square kilometers.In contrast, local and regional diversity of microorganisms tends to be more similar to large-scale and global diversity because of their large population size, greater dispersal, larger range sizes, and lower levels of regional species clustering ( Biomes and biogeographic realms provide broad pictures of the distribution of functional diversity.Defining Biodiversity Biodiversity is defined as “the variability among living organisms from all sources including, inter alia, terrestrial, marine and other aquatic ecosystems and the ecological complexes of which they are part; this includes diversity within species, between species and of ecosystems.” The importance of this definition is that it draws attention to the many dimensions of biodiversity.It explicitly recognizes that every biota can be characterized by its taxonomic, ecological, and genetic diversity and that the way these dimensions of diversity vary over space and time is a key feature of biodiversity.It follows that large-scale human influences over this biota have tremendous impacts on human well-being.It also follows that the nature of these impacts, good or bad, is within the power of humans to influence ().