Glossary Kopbaeva Laura f1101

Biodiversity is the degree of variation of life forms within a given ecosystem, biome, or an entire planet. Biodiversity is a measure of the health of ecosystems. Biodiversity is in part a function of climate. In terrestrial habitats, tropical regions are typically rich whereas polar regions support fewer species. Biodiversity is the variability among living organisms from all sources, including terrestrial, marine, and other aquatic ecosystems and the ecological complexes of which they are part.

Ecosystem Functions Multiple stable states characterize most ecosystems. If disturbances or perturbations occur from either internal or external sources which tend to drive an ecosystem away from its current equilibrium state, then the ecosystem’s regulatory feedback mechanisms work to maintain the current state, or to bring the ecosystem to one of its other typical equilibrium states. Which state is prevalent at any particular time has an impact on related ecosystems. Depending on which equilibrium state is prevalent, there will be more or fewer plants or animals in that ecosystem (or more of one type and less of another), more or less food available, more or less waste absorption, more or less nutrient cycling, or more or less energy. 

Humankind benefits from a multitude of resources and processes that are supplied by natural ecosystems. Collectively, these benefits are known as ecosystem services and include products like clean drinking water and processes such as the decomposition of wastes. This grouped ecosystem services into four broad categories: provisioning, such as the production of food and water; regulating, such as the control of climate and disease; supporting, such as nutrient cycles and crop pollination; and cultural, such as spiritual and recreational benefits.

Ecosystems Provide Stability

Ecosystems are often characterized by one or more equilibrium states. An equilibrium state is a mildly fluctuating, relatively stable set of conditions that maintain a population or nutrient exchange at specific levels. Each equilibrium state is dynamic and undergoes periodic decline and resurgence depending on such factors as energy and nutrient inputs, predator-prey relationships (including diseases), or irregular disturbances. Even in its relatively stable condition an equilibrium state is dynamic in terms of the exchanges of nutrients and energy which occur, as well as the activities of its living components.  As ecosystems incorporate more components into their functioning, for example as a result of energy, nutrient or waste accumulations, or the introduction of new species, their biodiversity can increase.

Until the 1970s, ecologists agreed with what became known as the diversity-stability hypothesis: diverse ecosystems are more stable than ecosystems with fewer species. While Elton and his peers observed that less diverse communities are characterized by greater fluctuations in population density, the theory remained largely untested. In 1973, Robert May published a mathematically-based study that seemed to contradict the long-held hypothesis. May reported that communities with higher diversity tended to be less, not more, stable because higher diversity tended to undermine individual species. By the 1990s, field studies by Tilman et al. raised the possibility that the number of species in an ecosystem might greatly influence how that ecosystem functions by showing that the stabilizing effect of diversity on the whole ecosystem was much greater than the destabilizing effect of diversity on an individual species.

Resilience is the capacity of an ecosystem to respond to a perturbation or disturbance by resisting damage and recovering quickly. Such perturbations and disturbances can include stochastic events such as fires, flooding, windstorms, insect population explosions, and human activities such as deforestation and the introduction of exotic plant or animal species. Disturbances of sufficient magnitude or duration can profoundly affect an ecosystem and may force an ecosystem to reach a threshold beyond which a different regime of processes and structures predominates

Resistance is the adaptation of pest population targeted by a pesticide resulting in decreased susceptibility to that chemical. In other words, pests develop a resistance to a chemical through natural selection: the most resistant organisms are the ones to survive and pass on their genetic traits to their offspring. Resistance has developed in a variety of different pest species: Resistance to insecticides was first documented by A. L. Melander in 1914 when scale insects demonstrated resistance to an inorganic insecticide. Between 1914 and 1946, 11 additional cases of resistance to inorganic insecticides were recorded. The development of organic insecticides, such as DDT, gave hope that insecticide resistance was an issue of the past. Unfortunately, by 1947 housefly resistance to DDT was documented. With the introduction of every new insecticide class – cyclodienes, carbamates, formamidines, organophosphates, pyrethroids, even Bacillus thuringiensis – cases of resistance surfaced within two to 20 years.

Ecological health or ecological integrity or ecological damage are the symptoms of an ecosystem's pending loss of carrying capacity, its ability to perform ecological services, or a pending ecocide, due to cumulative causes such as pollution. it can also be defined as farming so as to minimize the negative effects of agricultural practices. The term health is intended to evoke human environmental health concerns, which are often closely related (but as a part of medicine not ecology). As with ecocide, that term assumes that ecosystems can be said to be alive (see also Gaia philosophy on this issue). While the term integrity or damage seems to take no position on this, it does assume that there is a definition of integrity that can be said to apply to ecosystems. The more political term ecological wisdom refers not only to recognition of a level of health, integrity or potential damage, but also, to a decision to do nothing (more) to harm that ecosystem or its dependents.