GRE写作Issue部分精品素材分享之生态系统的管理

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生态系统的管理

The conservation of biological diversity has become a global concern. Although not everybody agrees on extent and significance of current extinction, most consider biodiversity essential. There are basically two main types of conservation options, insitu conservation and ex-situ conservation. In-situ is usually seen as the ideal conservation strategy. However, its implementation is

sometimes infeasible. For example, destruction of rare or endangered species‟ habitats sometimes requires ex-situ conservation efforts. Furthermore, ex-situ conservation can provide a backup solution to in-situ conservation projects. Some believe both types of conservation are required to ensure proper preservation. An example of an in-situ conservation effort is the setting-up of protection areas. Examples of ex-situ conservation efforts, by contrast, would be planting germplants in seedbanks, or growing the Wollemi Pine in nurseries. Such efforts allow the preservation of large populations of plants with minimal genetic erosion.

生态系统的内在价值

Some people criticize the notion that the intrinsic value of ecological systems exists independently of humanity‟s recognition of it. An example of this approach is that one might say that a work of art is only valuable insofar as humans perceive it to be worthwhile. Such people claim that the ecosystem‟s value does not reach beyond our appreciation of it. Intrinsic value is a philosophical concept which some do not accept. However, intrinsic value defined as value existing separate from human thought may in this case be conflated with intrinsic value defined as natural worth existing independent of modification or application of a substance or entity, clouding the argument. This entire argument, however, assumes both the primacy and uniqueness of the ability of humans to create value, as opposed to a collection of sentient beings dependent on a perfectly ordered system for life or even a natural system devoid of sentient life being incapable of possessing inherent value. It also is a result of the confusion between anthropogenic—something being created by humans, and anthropocentric—exclusive value being given to humans.

生物多样性的定义

The most straightforward definition biodiversity is “variation of life at all levels of biological organization”. A second definition holds that biodiversity is a measure of the relative diversity among organisms present in different ecosystems. “Diversity” in this definition includes diversity within a species and among species, and comparative diversity among ecosystems.

A third definition that is often used by ecologists is the “totality of genes, species, and ecosystems of a region”. An advantage of this definition is that it seems to describe most circumstances and present a unified view of the traditional three levels at which biodiversity has been identified:

1. Genetic diversity—diversity of genes within a species. There is a genetic variability among the populations and the individuals of the same species.

2. Species diversity—diversity among species in an ecosystem. “Biodiversity hotspots” are excellent examples of species diversity.

3. Ecosystem diversity—diversity at a higher level of organization, the ecosystem.

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