Biodiversity
 
Biodiversity is the sum total of life on Earth; the entire global complement ecosystem -        of terrestrial, marine, and freshwater biomes and ecosystems, and the Species plants, animals, fungi, and microorganisms—that live in them, in cluding their behaviors, interactions, and ecological processes. Biodiversity is linked directly to the nonliving components of the planet—atmosphere, oceans, freshwater systems, geological formations, and soils—forming one great, interdependent system, the biosphere.
Humankind’s Relationship to Biodiversity
Humans depend entirely on this biodiversity and are an integral part of it. Directly or indirectly, be it from wild or domesticated components of bio­diversity, humankind derives many goods critical to its sustenance, well­being, health, and enjoyment, such as food, medicine, building materials, and industrial products. Also, people enjoy many ecosystem services, in­cluding water regulation and supply, erosion control, soil formation, nutri­ent storage and cycling, pollination, pollution breakdown and absorption, climate stability, protection and recovery from natural disasters, and buffer­ing against the spread of disease. These services, provided by nature free of charge, have an estimated value of $33 trillion per year.
Even though continued human welfare depends on it, our knowledge of biodiversity is seriously inadequate. As of 1998, scientists have described between 1.4 and 1.8 million species. However, later estimates indicate that the total number of species ranges between 5 and 30 million, and some sci­entists believe it may be higher than 100 million.
Clearly, much more work is needed to quantify and describe all biodiversity at three main levels: genetic diversity, or the variation of genes within species; species diversity, or the variety of species within a biome or ecosystem, measured in species richness, species abundance, and taxonomic diversity; and ecosystem diversity, or the broad differences between ecosys­tem structures and biome types, and the diversity of habitats and ecologi­cal processes occurring within each of them. Taxonomists and other scientists in fields such as zoology, botany, ecology, and genetics study bio­diversity.
Threats to Biodiversity
Species are becoming extinct faster than scientists can discover them. The loss of biodiversity is an irreversible process: once a species becomes extinct its loss is permanent and irrevocable. Late-twentieth-century estimates cite the extinction rate between one thousand and ten thousand times greater than it would be naturally. This means that Earth is losing species at the fastest rate in the planet’s 4.5 billion-year history and, unlike prior extinc­tion episodes (such as the mass extinction of dinosaurs 65 million years ago), this extinction spasm is mainly the result of human activity and not of a cos­mic event. If extinctions continue at the current rate, in the next one hun­dred years humankind runs the risk of losing half of the planet’s biodiversity.
Most threats to biodiversity have to do with pressures on natural re­sources due to human activities. These include habitat destruction and con­version of natural ecosystems to agriculture; flooding for hydroelectric projects; large-scale extraction of natural resources such as mining and log­ging; excessive hunting and overfishing; pollution from agricultural pesti­cides, human waste, and industrial processes; and poorly planned urban and suburban sprawl.
Conserving Biodiversity
Conserving biodiversity is an urgent matter of common concern and should be an integral part of the development process, as was outlined in the Con­vention on Biological Diversity. This global, comprehensive agreement was drafted at the 1992 Rio de Janeiro Earth Summit and signed by 160 nations to address all aspects of biological diversity. Its objectives include “the con­servation of biodiversity, its sustainable use and the fair sharing of the ben­efits derived from the utilization of genetic resources.”
One conservation strategy aimed at reaching this goal recognizes that biodiversity is not evenly distributed over the planet: certain regions have higher species richness (the number of species in an area) and endemism (the number of species in that area that occur nowhere else) than others. Ironically, many of these sensitive areas are also preferred by humans to in­habit, placing tremendous pressure on local biodiversity. These areas are called the “biodiversity hotspots”; twenty-five of them have been described thus far, including Madagascar, the tropical Andes, the Philippines, and the Atlantic forest of Brazil. Conservationists believe that urgent conservation efforts should be targeted at these regions. Equally important are the so- called wilderness areas: Amazonia, the Congo Basin, and Papua New Guinea. These areas are also high in biodiversity but are not so immediately threat­ened.
 
References
Costanza, Robert, et al. “The Value of the World’s Ecosystem Services and Natural Capital.” Nature 387, no. 15 (May 1997): 253-260.
May, R. M. “How Many Species Are There on Earth?” Science 241 (1998): 1441-1449.
Mittermeier, Russell A., P. Robles Gil, and Cristina G. Mittermeier. Megadiversity: Earth’s Biologically Wealthiest Countries. Mexico: Cemex, 1997.
Terrestrial Ecorregions.Hotspots: Earth’s Biologically Richest and Most Endangered  Mexico: Cemex, 1999.
Stuart, S. Species: Unprecedented Extinction Rate, and It’s Increasing. Gland, Switzerland: IUCN, 1999.