Frequently Asked Questions

What is Biodiversity?

Overview

The diversity of life

Biodiversity is the totality of genes, species, and ecosystems in a region.

The wealth of life on earth today is the product of hundreds of millions of years of evolutionary history. Over the course of time, human cultures have emerged and adapted to the local environment, discovering, using, and altering local biotic resources.

Many areas that now seem "natural" bear the marks of millennia of human habitation, crop cultivation, and resource harvesting. The domestication and breeding of local varieties of crops and livestock have further shaped biodiversity.

Biodiversity can be divided into hierarchical categories that describe quite different aspects of living systems that scientists measure in different ways.

• Genetic diversity

  Genetic diversity refers to the variation of genes within species.

  This covers distinct populations of the same species (such as the thousands of traditional rice varieties in India) or genetic variation within a population (which is very high among Indian rhinos, for example, and very low among cheetahs).

  Until recently, measurements of genetic diversity were applied mainly to domesticated species and populations held in zoos or botanic gardens, but increasingly the techniques are being applied to wild species.

• Species diversity

  Species diversity refers to the variety of species within a region.

  Such diversity can be measured in many ways, and scientists have not settled on a single best method. The number of species in a region -- its "species richness" -- is one often-used measure, but a more precise measurement, "taxonomic diversity," also considers the relationship of species to each other.

  For example, an island with two species of birds and one species of lizard has greater taxonomic diversity than an island with three species of birds but no lizards.

  Thus, even though there may be more species of beetles on earth than all other species combined, they do not account for the greater part of species diversity because they are so closely related.

  Similarly, many more species live on land than in the sea, but terrestrial species are more closely related to each other than ocean species are, so diversity is higher in marine ecosystems than a strict count of species would suggest.

• Ecosystem diversity

  Ecosystem diversity is harder to measure than species or genetic diversity because the "boundaries" of communities -- associations of species -- and ecosystems are elusive.

  Nevertheless, as long as a consistent set of criteria is used to define communities and ecosystems, their number and distribution can be measured.

  Until now, such schemes have been applied mainly at national and sub-national levels, though some coarse global classifications have been made.

  Besides ecosystem diversity, many other expressions of biodiversity can be important. These include:

  • the relative abundance of species,
  • the age structure of populations,
  • the pattern of communities in a region,
  • changes in community composition and structure over time, and
  • ecological processes as predation, parasitism, and mutualism.

  More generally, to meet specific management or policy goals, it is often important to examine not only compositional diversity -- genes, species, and ecosystems -- but also diversity in ecosystem structure and function.

• Cultural diversity

  Human cultural diversity could also be considered part of biodiversity.

  Like genetic or species diversity, some attributes of human cultures (say, nomadism or shifting cultivation) represent "solutions" to the problems of survival in particular environments.

  And, like other aspects of biodiversity, cultural diversity helps people adapt to changing conditions.

  Cultural diversity is manifested by diversity in language, religious beliefs, land-management practices, art, music, social structure, crop selection, diet, and any number of other attributes of human society.

Biological diversity: What it is and why it is important

Our species entered the industrial age with a population of one billion and with biological diversity -- the total of genes, species, and ecosystems on earth -- possibly at an all-time high.

Biological resources -- the portion of diversity of actual or potential use to people -- were freely available for exploitation to support development.

Biological resource limits

In the early 21st century, we are coming to realize that biological resources have limits, and that we are exceeding those limits and thereby reducing biological diversity. This is therefore a time of extraordinary change in the relationship between people and the biological resources upon which their welfare depends.

Each year, more people are added to the human population than ever before, species are becoming extinct at the fastest rate known in geological history, and climate appears to be changing more rapidly than ever.

Human activities are progressively eroding the earth's capacity to support life at the same time that growing numbers of people and increasing levels of consumption are making ever greater demands on the planet's resources.

The combined destructive impacts of a poor majority struggling to stay alive and an affluent resource-consuming minority are inexorably and rapidly destroying the buffer that has always existed, at least on a global scale, between human resource consumption and the planet's productive capacity.

The erosion of the planet's life-support systems is likely to continue until human aspirations come more into line with the realities of the earth's resource capacities and processes, so that activities become sustainable over the long term.

The problems of conserving biological diversity therefore cannot be separated from the larger issues of social and economic development.

Maintaining Diversity

Maintaining maximum biological diversity assumes far greater urgency as rates of environmental change increase.

Diversity in genes, species, and ecosystems provides the raw materials with which different human communities will adapt to change, and the loss of each additional species reduces the options for nature -- and people -- to respond to change conditions.

The tropics harbor a major proportion of the planet's biological diversity. The industrialized countries also depend on tropical resources, as industrial materials, sources of breeding material, pharmaceuticals, tourism sites, and a wide range of other tangible and intangible benefits.

So far, however, the exploitation of the tropics by the industrialized societies has yielded great benefits without making commensurate investments in conservation and without paying the environmental costs of over-exploitation.

Cheap labor, raw materials with low prices that do not reflect their true value, inappropriate development aid, and the control of commodity prices and interest rates, among other factors, have encouraged much more rapid levels of resource depletion and destruction than would otherwise be the case.

The situation is continually worsening through the ramifications of the developing world's debt crisis and related high interest rates.

Governments, industry, development agencies, and the general public are therefore becoming increasingly concerned about the depletion of biological resources, with the growing awareness that development depends on their maintenance.

Issues in conservation

• How can scientific knowledge be mobilized that will best enable the planet's biological diversity to be conserved?
• How can the process of change be managed so that biological resources can make their best contribution to sustainable development?
• What information is required to address the problem of conserving biological diversity?
• Which problems need to be addressed first?
• How can the many initiatives in conservation of biological diversity be coordinated most effectively?
• Where can the financial resources be found to respond to these issues at a scale that will be commensurate with the problems?

How many species are there?

Estimates

Surprisingly, scientists have a better understanding of how many stars there are in the galaxy than how many species there are on Earth. Estimates of global species diversity have varied from 2 million to 100 million species, with a best estimate of somewhere near 10 million, and only 1.4 million have actually been named. The problems stemming from the limits of current knowledge of species diversity are compounded by the lack of a central database or list of the world's species.

Terrestrial and freshwater species

New species are still being discovered--even new birds and mammals. On average, about three new species of birds are found each year, and since 1990, 10 new species of monkeys have been discovered. Other vertebrate groups are still far from being completely described: an estimated 40 percent of freshwater fishes in South America have not yet been classified.

Scientists were startled in 1980 by the discovery of a tremendous diversity of insects in tropical forests. In one study of just 19 trees in Panama, fully 80 percent of the 1,200 beetle species discovered were previously unknown to science. At least 6 million to 9 million species of arthropods--and possibly more than 30 million--are now thought to dwell in the tropics with only a small fraction currently described.

As scientists begin investigating other little-known ecosystems, like the soil and the deep sea, "surprising" discoveries of species become commonplace. Small wonder. A single square meter of temperate forest can hold 200,000 mites and tens of thousands of other invertebrates. A similar-sized plot from tropical grasslands can hold 32 million nematodes, and one gram of the same soil might hold 90 million bacteria and other microbes. How many species these communities contain is still anyone's guess.

Marine Species

Marine systems too are revealing an unsuspected diversity. Scientists believe that the deep sea floor may contain as many as a million undescribed species. Entirely new communities of organisms--hydrothermal vent communities--were found less than two decades ago. More than 20 new families or subfamilies, 50 new genera, and 100 new species from these vents have been identified.

The Fundamental Values of Biodiversity

Biological resources provide the basis for life on earth, including that of humans. The fundamental social, ethical, cultural, and economic values of these resources have been recognized in religion, art, and literature from the earliest days of recorded history. The great interest that children have in nature, the numerous wildlife clubs, the generous donations made to non-governmental conservation organizations, the political support for "Green Parties," and the popularity of zoos and wildlife films are economic expressions of preference and show that the general public does not think of biological resources merely in terms of cash value.

Biodiversity in Economic Terms

But in order to compete for the attention of government and commercial decision-makers in today's world, policies regarding biological diversity first need to demonstrate in economic terms the contribution biological resources make to the country's social and economic development. Even partial valuation in monetary terms of the benefits of conserving biological resources can provide at least a lower limit to the full range of benefits and demonstrate the conservation can yield a profit in terms that are meaningful to national accounts.

Three main approaches have been used for determining the value of biological resources:

 

• assessing the value of nature's products--such as firewood, fodder, and game meat--that are consumed directly, without passing through a market ("consumptive use value");
• assessing the value of products that are commercially harvested, such as timber, fish, game meat sold in a market, ivory, and medicinal plants ("productive use value"); and
• assessing indirect values of ecosystem functions, such as watershed protection, photosynthesis, regulation of climate, and production of soil ("non-consumptive use value"), along with the intangible values of keeping options open for the future ("option value") and simply knowing that certain species exist ("existence value").

Biodiversity assessments, strategies, and action plans

source: WRI

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