Biodiversity

Viewed from the air, the tropical forest of Brazil, Indonesia, or Zaire is still a vast carpet of green, broken by occasional village clearings, rivers, and hills. These forests and waters support a great diversity of species. They have evolved there to live as communities of interdependent plants, animals and microbes in ecosystems. An ecosystem becomes a natural resource when people begin to appreciate its potential utility. Problems of sustaining the resource arise when governments and/or local people increase their demands on the resources, and exploit them faster than they can be replenished.

Britain's wildlife resources have been declining even from the time when they were first beginning to be appreciated. In 1874, James Harting, in his preface to his edition of Gilbert Whites writings said:-

If any apology be deemed necessary for the appearance of a new edition of one of the most delightful books in the English language, the reader need only be reminded of the physical changes which have taken place since Gilbert White's day in the district of which he wrote, and of the vast additions which are daily being made to our knowledge in almost every branch of natural history.

Wolmer Forest, which eighty years ago was "without one standing tree in the whole extent", is now partly enclosed, and planted to the extent of several hundred acres with oak, larch, and Scotch fir. Bin's Pond, a "considerable lake," which at one time " afforded a safe and pleasing shelter to wild ducks, teals, and snipe", has long since been drained, and cattle now graze on its bed. The covert in which foxes and pheasants formerly abounded has almost entirely disappeared.

The variety of plants and animals in an ecosystem, and the area it occupies, is a measure of its potential value, and its long-term stability. Depletion of natural resources is costly to society at large, and the concept of biodiversity is central to managing ecosystems to sustain their yields and stabilise other systems which depend upon them. The Biodiversity Convention of the Rio Environment Summit is an agreement of world leaders that the management of biodiversity should be given high priority in our systems of economic planning and education.

Biodiversity is a word invented by scientists as short-hand for 'biological diversity'. It includes all kinds of variation in living things; what they look like, and how they live-in other words the variety of life. 'Biodiversity' is now commonly used to describe the list of all living things found in a particular place.

In 1992, at the Rio de Janeiro 'Earth Summit', a contract was signed by 150 countries to treasure their biodiversity, and protect it against any activity that would diminish it. Protection requires the support of everybody, but unfortunately, biodiversity is a difficult idea to grasp. People have much to learn before they can value all living things, and choose to pay for their protection, rather than buy a 'new car, or 'air conditioning'.

Biodiversity, simply stated, is the variety and variability among living organisms and the communities in which they occur. Measurements of biodiversity define the level of nature's variety. It can be measured in terms of the number and frequency of ecosystems, species, or genes in a given space. It is usually considered at four different levels, ecosystem diversity", community diversity", "species diversity," and "genetic diversity." Action plans to support the Biodiversity Convention are now being produced for ecosystems and species at national and local levels.

Ecosystem Diversity

Ecosystem diversity is a concept of spatial diversity of group of species. It recognises that species are dependent upon a particular kind of physical/biological habitat which supports an ecosystem (e.g. tropical rain forest and northern deciduous forest).

The diversity of ecosystems relates to the diversity and health of the communities to which species belong. Ecosystems provide natural cycles of nutrients (from production to consumption and decomposition), of water, of oxygen and carbon dioxide (thereby affecting the climate), and of other chemicals like sulphur, nitrogen, and carbon. Ecological processes govern primary and secondary production (i.e. energy flow), mineralization of organic matter in the soils and sediments, and storage and transport of minerals and biomass. Efforts to conserve species must therefore also conserve the ecosystems of which they are a part.

Community diversity

Community diversity is a concept of the diversity of the inter-relationships between species within a particular ecosystem (e.g. lime woods, and ash woods, within northern deciduous forest).

Species diversity

Species diversity is a concept of the variety of living organisms on earth, and is measured by the total number of species in the world or in a given area under study (e.g. the total number of world species has been variously estimated as from 5 to 30 million or more, though only about 1.4 million have actually been described), .

Genetic diversity

Genetic diversity is a concept of the variability within a species, as measured by the variation in genes within a particular population, variety, subspecies, or breed (e.g. the chemical units of hereditary information as DNA that can be passed from one generation to another).

In general, the larger the population size of a species, the greater the chance of there being high genetic diversity. But population increase in some species may lead to a population decline in other species, and even to a reduction in species diversity. Since it is usually not possible to have both maximum species diversity and maximum genetic diversity, national policy-makers are trying to define the optimum biological diversity consistent with their objectives for economic development. One key element is to ensure that no species falls below the minimum critical population size at which genetic diversity is lost rapidly.

Advantages of Conserving Biodiversity Insurance

There is a considerable uncertainty about the values, including economic values, that future generations may attach to biodiversity. Since our knowledge is so limited, it makes sense to preserve as many species as possible, since we do not yet know which are potentially useful. Biodiversity should be maintained because future practical needs, and values are unpredictable. Our understanding of ecosystems is insufficient to be certain of the impact of removing any component.

Stability

Genetic diversity provides the variability within which a species can adapt to changing conditions. The less diverse environmental systems are less likely to have genetic variability of all kinds available to substitute for others that are depleted. Furthermore, if the effective population size falls below a certain level, the species is likely to die out. Diverse environmental systems normally enhance the resilience to cope with ecological stresses. Many losses are irreversible.

Interdependence of organisms

No organism lives in isolation from other living things and each has its own way of life which contributes to the balance of nature. The inter-dependence and successful functioning of all these parts is a key contributory factor to the stability of the planet as a whole. If we continue to pollute the atmosphere, contaminate land and water, and degrade our ecosystems by, for example, destroying forests, wetlands and marine environments, then the planet will suffer accordingly. The totality of the problem is addressed by a government's sustainable development strategy, but the harmonious and healthy functioning

of all the organisms which constitute "life" is the concern of the Biodiversity Convention, and hence of the national and local biodiversity action plans.

New crops

Genetic variability in cultivated and domestic species is, and probably always will be, an extremely important social and economic resource. It was genetic variability which enabled early peoples to develop the crops and livestock which were a pre-requisite of settled agriculture. The remaining variability is all that is available to enable breeders to develop new varieties. The continued development and stability of agriculture, especially in the longer term, depend to no small extent on our capacity to continue doing this.

Cultural enrichment

We conserve species and habitats because they are beautiful or because they otherwise enrich our lives. The culture of a nation is closely allied to its landscapes and wildlife. A moral argument adds to this perspective the view that we should hand on to the next generation an environment no less rich than the one we ourselves inherited. To support conservation means to act on a belief that a culture which encourages respect for wildlife and landscapes is preferable to one that does not.

Loss of biodiversity

Biological diversity is not spread evenly across the planet. In general, well-watered lowland tropical terrestrial ecosystems have the greatest diversity, which declines with rainfall and latitude (or elevation). Oceanic islands, or small areas of a restricted habitat on land, tend to have fewer species than large areas of the same habitat type. On the other hand, isolated islands tend to have endemic species which are found nowhere else. Therefore, conserving the entire range of the world's biological wealth requires protecting the endemic species on islands, as well as those in larger areas of higher biodiversity. Increasingly, as more and more ecosystems are destroyed, the diverse seminatural habitats associated with older cultures, (e.g. small fields, wood pasture, and sacred sites) become very valuable as characteristics of the local landscape.

They require protection.

Human influences tend to reduce diversity, particularly where they are intensive and long-standing (as in permanent agriculture), but limited human activities can actually increase diversity (as in some tropical village systems of shifting cultivation at low human population densities). Aquatic habitats parallel these generalisations, with the tropical systems-especially coral reefs, and large old lakes (as in the African Rift Valley lakes)-having greater diversity than temperate systems.

Within these broad trends, some areas are more diverse than others. These patches of high biodiversity are due to such factors as:-

• • complexity of soils and other geological factors;

  • altitudinal variation (areas with considerable variation in elevation containing greater diversity and being better able to adapt to climate change);

  • history (some areas having served as "refugia" during drier or cooler periods).

Most diversity tends to be found in extensive tropical habitats which are little affected by humans, so relatively large protected areas are likely to be the most effective way of conserving maximum biological diversity. But the real situation is far more complex than that, because diversity also occurs in managed forests, secondary forests, and agro-ecosystems. Conserving biological resources therefore requires a wide range of management tools, varying from complete protection to intensive management alongside industrial production systems.

Sustainability

Current processes of economic development are depleting many biological resources at such a rate that they are rendered essentially non-renewable. Experience has shown that too little biological diversity will not be conserved by market forces alone, and that effective government intervention is required to meet the needs of society. Economic inducements are likely to prove the most effective measures for converting over-exploitation to sustainable use of biological resources. .