GRE写作Issue部分精品素材分享之生物多样性的指标

2015年08月13日16:03 来源：小站整理

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生物多样性测量的三大指标

Biodiversity is usually plotted as taxonomic richness of a geographic area, with some reference to a temporal scale. Whittaker described three common metrics used to measure species-level

biodiversity, encompassing attention to species richness or species evenness:

1. Species richness—the least sophisticated of the indices available

2. Simpson index

3. Shannon index

There are three other indices which are used by ecologists:

1. Alpha diversity refers to diversity within a particular area, community or ecosystem, and is measured by counting the number of taxa within the ecosystem (usually species).

2. Beta diversity is species diversity between ecosystems; this involves comparing the number of taxa that are unique to each of the ecosystems.

3. Gamma diversity is a measure of the overall diversity for different ecosystems within a region.

生物多样性的衡量

Biodiversity is a broad concept, so a variety of objective measures have been created in order to empirically measure biodiversity. Each measure of biodiversity relates to a particular use of the data.

For practical conservationists, this measure should quantify a value that is broadly shared among locally affected people. For others, a more economically defensible definition should allow the ensuring of continued possibilities for both adaptation and future use by people, assuring environmental sustainability.

As a consequence, biologists argue that this measure is likely to be associated with the variety of genes. Since it cannot always be said which genes are more likely to prove beneficial, the best choice for conservation is to assure the persistence of as many genes as possible. For ecologists, this latter approach is sometimes considered too restrictive, as it prohibits ecological succession.

生物多样性与立法

Biodiversity is beginning to be evaluated and its evolution analyzed (through observations, inventories, conservation...) as well as being taken into account in political and judicial decisions.

The relationship between law and ecosystems is very ancient and has consequences for biodiversity. It is related to property rights, both private and public. It can define protection for threatened ecosystems, but also some rights and duties (for example, fishing rights, hunting rights).

Law regarding species is a more recent issue. It defines species that must be protected because they may be threatened by extinction. The U.S. Endangered Species Act is an example of an attempt to address the “law and species” issue.