Ecosystems are defined as communities that involve dynamic interactions among living elements (such as animals, plants, and microorganisms) and the inanimate elements of their environments. All parts of an ecosystem need to work together to maintain the proper balance of the system, and it is necessary for all ecosystems to function in conjunction to maintain balance.
The term ecosystem was first used in 1930 by Roy Clapham (1904–90), an appointee to the demonstratorship in botany at England's Oxford University. At the time, Clapham was studying plant ecology under the guidance of Botany Department Chair Arthur Tansley (1871–1955), a pioneer in the field of ecology. Two decades after Clapham and Tansley first articulated the concept of ecosystems, ecologists began including the study of ecosystems as a distinct field of study within the discipline of ecology. Scientists have since identified eight major ecosystems: the temperate forest,
tropical rainforests, deserts, grasslands, tundra, taiga, chaparral, and ocean.
An ecosystem may be as small as a tidepool or as large as the Sahara Desert or the Atlantic Ocean. The ecosystems of the tropical forests provide a classic example of the extent of ecosystems. In these forests, thousands of vegetable and animal species that live in the air and on the ground interact with millions of surrounding organisms. Within each ecosystem, the habitat is a physical element that combines the natural and adaptive conditions of particular species. All ecosystems are dynamic. Changes may be temporary in response to outside events such as forest fires or natural disasters, or they may occur according to established cycles.
Commonly occurring factors that affect changing ecosystems are nutrient availability, temperature, light intensity, grazing intensity, and species population density. Six ecosystems are identified as most necessary for supporting life on Earth; agroecosystems, forest ecosystems, freshwater ecosystems, grassland ecosystems, coastal ecosystems, and urban ecosystems. The integral relationship between these ecosystems and human life is demonstrated by the fact that half of the world's jobs are dependent on agriculture, forestry, and fishing. In the poorest sections of the world, 70 percent of all jobs are derived from these industries.
Biomes as Groups of Ecosystems
Biomes, sometimes confused with ecosystems, are in reality composed of a number of similar ecosystems that work together to maintain the critical balance of the environment. The Earth is a biome, as are the Great Basin, the High Plains, and the Kalahari Desert. Through global warming and climate change, human behaviors are altering vital ecosystems throughout the world, including those that make up the food chain, carbon cycle, nitrogen cycle, and water cycle. The critical nature of this dilemma is evident in the well-documented loss of species, their habitats, and ecosystems as a result of human pollution and overexploitation of resources. Particular attention is being paid to the ecosystems of Antarctica, the Arctic, the Bering Sea, and the greater Yellowstone ecosystem. In the Arctic, scientists have identified two major climate and ecosystem changes during the past 50 years, in part as a response to warming temperatures, that have precipitated a transition from primarily cold Arctic ecosystems of the pre-1970 period to sub-Arctic conditions during 1970–2000. The Bering Sea provides vast opportunities for studying the ecosystems of various bird and marine mammal populations.
In 1992, at the Earth Summit in Rio de Janeiro, member nations negotiated the Convention on Biological Diversity, popularly known as the Biodiversity Treaty. The treaty, which was signed by 196 countries, became international law on December 29, 1993. The treaty formally recognizes the interrelationship between human life and various ecosystems and encourages universal commitment to conserving biological diversity and using all biological resources responsibly. It also calls for equitable sharing of genetic resources among developed and developing countries.
In 2001, 1,300 scientists from 95 nations began working on the Millennium Ecosystem Assessment (MA) under the auspices of the United Nations. The assessment team is charged with identifying the effects of global warming and climate change on various ecosystems and determining ways to employ conservation and sustainable development to check the pace of ecosystem failure and environmental degradation, while improving human well-being. Between 2001 and 2005, the MA published five technical volumes and six summary reports. Scientists involved in the MA have concluded that 60 percent of the 24 ecosystems under investigation are being degraded as a result of human behavior. MA scientists have learned that this degradation is leading to the emergence of new and old diseases, abrupt alterations in water quality, the presence of dead zones in coastal waters, the collapse of fisheries in many sections of the world, and shifts in regional climate. While agreeing that the ecosystems of tropical forests and coral reefs are particularly vulnerable to global warming and climate change, the MA has identified degrading dryland ecosystems as the most significant threat to human health because these are the areas where poverty is greatest.
Elizabeth Rholetter Purdy
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