生物多様性
生物多様性(せいぶつたようせい、英語ではbiodiversity, biological diversity)とは、多様な生物が存在しているさま、またはその度合のことである。
英語の biodiversity は、 国立研究協議会(National Research Council, NRC)が開催した 最初のアメリカ生物多様性フォーラムのための報告の中で 昆虫学者E.O. ウィルソンにより1986年に作られた。
英語の biological diversity はトマス・ラヴジョイにより1980年に作られた。
1986年以来生物多様性という用語とその概念は、生物学者、環境保護活動家、政治指導者、感心を持つ市民により世界中で広く用いられることになったが、これは20世紀の最後の10年間に見られた絶滅種に対する関心の広まりとよく一致している。
生物多様性の定義
生物多様性の三つのレベル
生物多様性(英語では 'biological diversity' あるいは 'biodiversity') には標準となる一義的な定義はない。ある定義は、生物多様性を「異なる生態系に存在する生物間での相対的な多様性の尺度」としている。この定義における「多様性」は、種間の多様性・種間の多様性・生態系間の多様性を含んでいる。
簡単かつ明瞭だが挑戦的な別の定義では、生物多様性を「ある地域における遺伝子・種・生態系の総体」とされている。この定義の長所は、うまく実態を表しているように思われることと、生物多様性として定義されてきた慣例的な3段階の切り口を統一的に扱える点である。
• 遺伝的多様性 - ある1種の中での遺伝子の多様性。同じ種の中での個体間の違いと、個体群間の違いがある（→集団遺伝学も参照されたい）。 • 種多様性 - 種間の多様性（簡単に言えば、多くの種が存在すること） • 生態系多様性 - より高次の多様性。異なる過程における豊富さであり、遺伝子が究極的に影響を及ぼす。
上記のうち最後の定義は、生物学における5つの組織の層と同じであり、複数のレベルでのアプローチに正当性を加えている。
ウィルソンが言うように遺伝子が自然選択における根本の単位であれば、生物多様性は実質的に遺伝的多様性であると言えるが、種多様性は研究を行なう際に扱いやすい。
生物多様性と取組
• For geneticists, biodiversity is the diversity of genes and organisms. They study processes such as mutations, gene exchanges, and genome dynamics that occur at the DNA level and generate evolution.
• For biologists, biodiversity is the diversity of populations of organisms and species, but also the way these organisms function. Organisms appear and disappear; sites are colonized by organisms of the same species or by another. Some species develop social organisations to improve their reproduction goals or use neighbor species that live in communities. Depending on their environment, organisms do not invariably use the same strategies of reproduction, .
• For ecologists, biodiversity is also the diversity of durable interactions among species. It not only applies to species, but also to their immediate environment (biotope) and the ecoregions the organisms live in. In each ecosystem, living organisms are part of a whole, they interact with one another, but also with the air, water, and soil that surround them.
生物多様性の役割
生物多様性は多くのやり方で、人類の文化の発展に貢献してきた。その一方、人類は遺伝的・種・生態系のレベルでの多様性の形成に重要な役割を果たしてきた。
すべての人類にとって、それは食料を供給し、衣料の原料となり、住居として、また薬として、エネルギー源としての第一の資源である。
Ecosystems also provide us various supports of production (soil fertility, pollinators, predators, decomposition of wastes...) and services such as purification of the air and water, stabilisation and moderation of the climate, decrease of flooding, drought and other environmental disasters.
If biological resources represent an ecological interest for the community, their economic value is also increasing. New products are developed thanks to biotechnologies, and new markets created. For society, biodiversity also is a field of activity and profit. It requires a proper management setup to determine how these resources are to be used.
Finally, the role of biodiversity is to be a mirror of our relationships with the other living species, an ethical view with rights, duties, and education.
See also: ecotourism, cultural diversity, local food.
生物多様性の評価
生物多様性をどう測定するか
From the viewpoint previously defined, no single objective measure of biodiversity is possible, only measures relating to particular purposes or applications.
For practical conservationists, this measure should quantify a value that is at the same time broadly shared among locally-affected people.
For others, a broader and more economically defensible definition is that measures should allow to ensure continued possibilities both for adaptation and future use by people, assuring environmental sustainability. As a consequence, biologists argued 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 approach is sometimes considered inadequate and too restricted.
生物多様性: 時間と空間
Biodiversity is not static: it is a system in constant evolution, from a species, as well as from an individual organism point of view. The average half-life of a species is around one million years and 99% of the species that have ever lived on earth are today extinct.
Biodiversity is not distributed evenly on earth. It is consistently richer in the tropics. As one approaches polar regions one finds larger and larger populations of fewer and fewer species. Flora and fauna vary depending on climate, altitude, soils and the presence of other species. For a listing of distinct ecoregions based on these distributions, see the WikiProject Ecoregions.
種の一覧
Systematics assesses biodiversity simply by distinguishing among species. At least 1.75 million species have been described; however, the estimates of the true number of current species range from 3.6 to more than 100 million. Some also say that the knowledge of the species and the families became insufficient and must be supplemented by a greater comprehension of the functions, interactions and communities. Moreover, exchanges of genes occurring between the species tend to add complexity to the inventory.
生物多様性の'ホットスポット'
• Brazil is said to represent 1/5 of the world biodiversity, with 50,000 plant species, 5,000 vertebrates, 10-15 million insects, millions of microorganisms, etc. • India is said to represent 8% of the recorded species, with 47,000 plants species and 81,000 animals.
See also: biogeography, Amazonian forest, species inventory, extinction.
生物多様性の経済的な価値
Ecologists and environmentalists were the first to insist on the economic aspect of biological diversity protection. Thus, Edward O. Wilson wrote in 1992, that la biodiversité est l'une des plus grandes richesses de la planète, et pourtant la moins reconnue comme telle.
Most people see biodiversity as a reservoir of resources to be drawn upon for the manufacture of food, pharmaceutical, and cosmetic products. This concept of biological resources management probably explains most fears of resources disappearance related to the erosion of the biodiversity. However, it is also is the origin of new conflicts dealing with rules of division and appropriation of natural resources.
Economic estimation of the value of biodiversity is a necessary precondition to any discussion on the distribution of biodiversity richnesses. This goal must also make it possible to determine financial means to devote to its protection. This new field of study is called: economic value of biodiversity.
生物多様性は危険にさらされているか
During the last decades, an erosion of biodiversity was observed. A majority of biologists believe that a mass extinction is under way. Although divided over the numbers, many scientifics believe that the rate of loss is greater now than at any time in history.
Some studies show that about one of eight known plant species is threatened with extinction. Every year, between 17,000 and 100,000 species vanish from our planet. Some people say that up to 1/5 of all living species could disappear within 30 years. Nearly all say that the losses are due to human activities, in particular destruction of plant and animal habitats.
Some justify this situation not so much by a species overuse or ecosystem degradation than by their conversion in very standardized ecosystems (e.g., monoculture following deforestation). Before 1992, others pointed out that no property rights or no access regulation of resources necessarily lead to their decrease (degrading costs having to be supported by the community).
Among the dissenters, some argue that there are not enough data to support the view of mass extinction, and say abusive extrapolations are being made on the global destruction of rainforests, coral reefs, mangrove swamps, and other rich habitats.
生物多様性の経営: 保全、維持、保護
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, in-situ and ex-situ conservation. In-situ conservation. In-situ is usually seen as the ultimate conservation strategy. However, its implementation is sometimes unfeasible. 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. An example of an ex-situ conservation effort, by contrast, would be planting germplasts in seedbanks. Such efforts allow the preservation of large populations of plants with minimal genetic erosion.
The threat to biological diversity was among the hot topics discussed at the UN World Summit for Sustainable Development, in hope of seeing the foundation of a Global Conservation Trust to help maintain plant collections.
See also: conservation, seedbank, IUCN, Global 200.
生物多様性の法律における位置付け
Biodiversity must be evaluated and its evolution analysed (through observations, inventories, conservation...) then it must be taken into account in political decisions. It is beginning to receive a juridical setting.
• "Law and ecosystems" relationship is very ancient and has consequences on biodiversity. It is related to properties rights, private and public. It can define protection for threatened ecosystems, but also some rights and duties (for example, fishing rights, hunting rights). • "Laws and species" is a more recent issue. It defines species that must be protected because threatened by extinction. Some people question application of these laws. • "Laws and genes" is only about a century old. While the genetic approach is not new (domestication, plant traditional selection methods), progress made in the genetic field in the past 20 years lead to the obligation to tighten laws. With the new technologies of genetic and genetic engineering, people are going through gene patenting, processes patenting, and a totally new concept of genetic resource. A very hot debate today seeks to define whether the resource is the gene, the organism, the DNA or the processes.
The 1972 UNESCO convention established that biological resources, such as plants, were common heritage of mankind. These rules probably inspired the creation of great public banks of genetic resources, located outside the source-countries.
New global agreements (Convention on Biological Diversity), now gives sovereign national rights over biological resources (not property). The idea of static conservation of biodiversity is disappearing and being replaced by the idea of a dynamic conservation, through the notion of resource and innovation.
The new agreements commit countries to conserve the biodiversity, develop resources for sustainability and share the benefits resulting from their use. Under these new rules, it is expected that bioprospecting or collection of natural products has to be allowed by the biodiversity-rich country, in exchange for a share of the benefits.
Sovereignety principles can rely upon what is better known as Access and Benefit Sharing Agreements (ABAs). The Convention on Biodiversity spirit implies a prior informed consent between the source country and the collector, to establish which resource will be used and for what, and to settle on a fair agreement on benefit sharing. Bioprospecting can become a type of biopiracy when those principles are not respected.
関連記事
• 生態学 • Convention on Biological Diversity • International Treaty on Plant Genetic Resources for Food and Agriculture • Fair trade • Environmental economics • Global 200 • List of environment topics
