- In our biosphere immense diversity (or heterogenecity) exists not only at the species level but at all levels of biological organisation ranging from macromolecules within cells to biomes.
- The Biodiversity is the term popularised by the sociobiologist Edward Wilson.
- Genetic diversity: A single species might show high diversity at the genetic level over its distributional range.
- The genetic variation shown by the medicinal plant Rauwolfia vomitoria growing in different Himalayan ranges might be in terms of the potency and concentration of the active chemical (reserpine) that the plant produces.
- In India has more than 50,000 genetically different strains of rice, and 1.000 varieties of mango.
- Species diversity: The diversity at the species level. For example, the Western Ghats have a greater amphibian species diversity than the Eastern Ghats.
- Ecological diversity: At the ecosystem level. India, for instance, with its deserts, rain forests, mangroves, coral reefs, wetlands,
- estuaries, and alpine meadows has a greater ecosystem diversity than a Scandinavian country like Norway.
- It has taken millions of years of evolution, to accumulate this rich diversity in nature, but we could lose all that wealth in less than two centuries if the present rates of species losses continue.
- Biodiversity and its conservation are now vital environmental issues of international concern as more and more people around the world begin to realize the critical Importance of biodiversity for our survival and well-being on this planet.
PATTERNS OF BIODIVERSITY
- (Latitudinal gradients. The diversity of plants and animals is not uniform throughout the world but shows a rather uneven distribution.
- For many group of animals or plants, there are interesting patterns in diversity, the most well-known being the latitudinal gradient in diversity.
- In general, species diversity decreases as we move away from the equator towards the poles.
- With very few exceptions, tropics (latitudinal range of 23.5° N to 23.5° S) harbour more species than temperate or polar areas.
- Colombia located near the equator has nearly 1.400 species of birds while New York at 41° N has 105 species and Greenland at 71°N only 56 species.
- India, with much of its land area in the tropical latitudes, has more than 1,200 species of birds.
- A forest in a tropical region like Equator has up to 10 times as many species of vascular plants as a forest of equal area in a temperate region like the Midwest of the USA.
- The largely tropical Amazonian rain forest in South America has the greatest biodiversity on earth-it is home to more than 40.000 species of plants
- More than 3,000 of fishes, 1.300 of birds, 427 of mammals, 427 of amphibians, 378 of reptiles and of more than 1.25.000 invertebrates.
- The Scientists estimate that in these rain forests there might be at least two million insect species waiting to be discovered and named.
- During his pioneering and extensive explorations in the wilderness of South American Jungles.
- the great German naturalist and geographer Alexander von Humboldt observed that within a region species richness increased with increasing explored area, but only up to a limit.
- In fact, the relation between species richness S = CA and area for a wide variety of taxa Log S – log C+Z log A (angiosperm plants, birds, bats. freshwater fishes)
- It turns out to be a rectangular hyperbola On a logarithmic scale, the relationship is a straight line described by the equation
log S = log C+ Z log A
S=Species richness A= Area Area
Z = slope of the line (regression
Species richness log-log scale
- The importance of Species Diversity to the Ecosystem Does the number of species in a community really matter to the functioning of the ecosystem?
- This is a question for which ecologists have not been able to give a definitive answer.
- It’s for many decades, ecologists believed that communities with more species, generally, tend to be more stable than those with less species.
- What exactly is stability for a biological community.
- A stable community should not show too much variation productivity from year to year, it must be either resistant or resilient to occasional disturbances (natural or man-made), and it must also be resistant to invasions by alien species.
- We don’t know how these attributes are linked to species richness in a community, but David Tilman’s long-term ecosystem experiments using outdoor plots provide some tentative answers.
- Tilman found that plots with more species showed less year-to-year variation in total biomass.
- He also showed that in his experiments, increased diversity contributed to higher productivity.
LOSS OF BIODIVERSITY
- While it is doubtful if any new species are being added (through speciation) into the earth’s treasury of species, there is no doubt about their continuing losses.
- The biological wealth of our planet has been declining rapidly and the accusing finger is clearly pointing to human activities.
- The colonization of tropical Pacific Islands by humans is said to have led to the extinction of more than 2.000 species of native birds.
- The IUCN Red List (2004) documents the extinction of 784 species (including 338 vertebrates, 359 invertebrates and 87 plants) in the last 500 years.
- Some samples of recent extinctions include the dodo (Mauritius). quagga (Africa). thylacine (Australia). Steller’s Sea Cow (Russia) and three ubspecies (Bali. Javan. Caspian) of tiger.
CAUSES OF BIODIVERSITY LOSSES
- The accelerated rates of species extinctions that the world is facing now are largely due to human activities.
- There are four major cause (The Evil Quartet” is the mobiquet used to describe them).
- This is the most important cause driving animals and plants to extinction. The most dramatic examples of habitat loss come from tropical rain forests.
- Once covering more than 14 per cent of the earth’s land surface, these rain forests now cover no more than 6 percent.
- They are being destroyed fast. By the time you finish reading this chapter 1000 more hectares of rain forest would have been lost.
- The Amazon rain forest (it is so huge that it is called the ‘lungs of the planet harbouring probably millions of species is being cut and cleared for cultivating soya beans or for conversion to grasslands for using beef cattle.
- Besides total loss the degradation of many habitats by pollution also threatens the survival of many species.
- When large habitats are broken up into small fragments due to various human activities.
- The mammals and birds requiring large territories and certain animals with migratory habits are badly affected, leading to population declines.
- Over exploitation: Humans have always depended on nature for food and shelter, but when ‘need turns to ‘greed’.
- Alien species invasions: When alien species are introduced unintentionally or deliberately for whatever purpose, some of them turn invasive, and cause decline or extinction of indigenous species.
- The Nile perch introduced into Lake Victoria in east Africa led eventually to the extinction of an ecologically unique assemblage of more than 200 species of cichlid fish in the lake.
- Co-extinctions: When a species becomes extinct, the plant and animal species associated with it in an obligatory way also become extinct. When a host fish species becomes extinct, its unique assemblage of parasites also meets the same fate.
Why Should We Conserve Biodiversity?
- There are many reasons, some obvious and others not so obvious, but all equally important.
- They can be grouped into three categories: narrowly utilitarian, broadly utilitarian, and ethical The narrowly utilitarian arguments for conserving.
- biodiversity are obvious: humans derive countless direct economic benefits from nature- food (cereals, pulses, fruits). firewood, fibre, construction material,
- The industrial products (tannins, lubricants, dyes, resins, perfumes ) and products of medicinal importance.
- It has More than 25 per cent of the drugs currently sold in the market worldwide are derived from plants and 25.000 species of plants contribute to the traditional medicines used by native peoples around the world.
- Nobody knows how many more medicinally useful plants there are in tropical rain forests waiting to be explored.
- Its With increasing resources put into ‘bioprospecting” (exploring molecular, genetic and species-level diversity for products of economic importance).
IN SITU CONSERVATION
- It Faced with the conflict between development and conservation, many nations find it unrealistic and economically not feasible to conserve all their biological wealth.
- Invariably, the number of species waiting to be saved from extinction far exceeds the conservation resources available. On a global basis, this problem has been addressed by eminent conservationists.
EX SITU CONSERVATION
- In this approach, threatened animals and plants taken out from their natural habitat and placed in special setting where they can be protected and given special care.
- Zoological parks, botanical gardens and wildlife safari parks serve this purpose. There are many animals that have become extinct in the wild but continue to be maintained in zoological parks.