Biodiversity and Conservation

Since life on earth evolved around 3.8 billion years ago, there have been diversification of all kinds of organisms in their effort to survive. Eventhough, there must be more than 7 million types of species, only 1.5 million have been recorded

Biodiversity

• Biodiversity means diversity or heterogeneity at all levels of biological organization, i.e., from macromolecules of the cells to the Biomass. 
• The term Biodiversity was popularised by the sociologist- Edward Wilson.
• Edward Wilson to describe the sum total of the diversity of biological organisation at all the  levels.
• The important levels of biodiversity are

1. Genetic diversity,

2. Species diversity,

3. Ecological diversity

Genetic diversity

• It is the diversity at genetic (gene and chromosomal) level, or at subspecies level, i.e. below species level, in a single species. 
• The genetic variation (in terms of allelic forms of the same gene) expressed by the medicinal plant Rauwolfia vomitoria growing in different Himalayan ranges is in terms of the potency and concentration of the active chemical (reserpine) that the plant produces. There are variations in the concentration of chemical in the medicinal plants.
• Other animal groups Crustaceans Molluscs 
• India has more than 50000 genetically different strains of rice  and 1000 varieties of mango. 
• The genetic diversity helps the population to adapt. If a population has more diversity it can adapt better to the changed environmental conditions. The low diversity leads to uniformity. The genetic variability is therefore, considered to be the raw material for speciation

Species diversity 

• It is the measure of the varieties of species and their abundant presence within a region, e.g. Western Ghats have more amphibians than Eastern Ghats. Species richness and species evenness are the two important measures of species diversity.
• The measurement of species diversity is its richness, i.e. the number of species per unit area. The greater is the species richness the more will be the species diversity. In nature, the number and kind of species, as well as the number of individual per species, vary, and this leads to greater diversity.

Ecological diversity 

• It refers to the diversity at ecosystem level. It makes communities more productive and stable, e.g. India has a greater ecosystem diversity (in terms of variety of habitats in deserts, rainforests, mangroves, coral reefs, wetlands, estuaries and alpine meadows) than a Scandinavian country like Norway
• It is the diversity at community level. It can be of 3-types

1. Alpha (α) diversity -

• It is the diversity of organisms within the same community or habitat.

2. Beta (β) diversity -

• It is the diversity between communities or different habitats. Higher the heterogenecity in the altitude, Humidity and Temperature of a region, the greater will be the dissimilarity between communities, and higher will be the β diversity.

3. Gamma ( (γ) ) diversity -

• It is the diversity of organisms over the entire geographical area, covering several ecosystems or habitats and various trophic levels and food webs. Such diversity is most stable and productive

Number of species on earth

It is difficult to believe that there are 20,000 species of orchids, 20,000 species of ants, 28,000 species of fi shes and about 3,00,000 species of beetles on earth. According to IUCN (International Union for Conservation of Nature and Natural resources) estimates, the total number of animal and plant species, described so far, is more than 1.5 million. Due to project ‘Species 2000’ and ‘Global Biodiversity Information’, the new species are being discovered faster than ever before. However, the discovery and description of species is more complete in temperate than in tropical countries. A large number of species are waiting to be discovered from tropics.

According to estimates of Robert May

• The global species diversity is about 7 million (1.5 million, i.e. 22% reported till now and 78% are yet to be discovered). More than 70% of all the species recorded are animals. Plants are not more than 22% of the total.

 Among animals also, about 70% are insects.

 The Fungi have more species than all the vertebrates species combined.

 In case of vertebrates, the species of fi shes are more than that of birds, and of latter, more than

reptiles.

In case of plant species, the species of fungi > species of angiosperms > species of

algae.

The all above estimates do not give any idea for the number of species of prokaryotes,

whose species diversity may run in millions.

 

How Many Species are There on Earth and How Many in India?

• According to the IUCN 2004, more than 1.5 million species have been recorded in the world, but we have no idea of how many species are yet to be discovered and described. A sound estimate of global species diversity of about 7 million was given by Robert May.

• More than 70% of all the species recorded are animals, while plants comprise no more than 22%. Out of total animals recorded, 70% are insects (i.e. out of every 10 animals on this planet, 7 are insects).

• The number of fungi species is more than all the vertebrate species of fishes, amphibians, reptiles and mammals combined in the world and it is interesting to know that the diversity of microbial species alone might run into millions.
• Indian biodiversity India is one of the 12 mega diverse countries of the world. Though India has only 2.4% of the world’s land are but it shares an impressive 8.1% of the world’s species diversity.
• There are about 45,000 species of plants and twice as many of animals have been recorded in India.
• India probably has more than 1,00,000 species of plants and 3,00,000 species of animals yet to be discovered and described. If we apply Robert May’s global estimate then only 22% of species of the world have been recorded.

Patterns of Biodiversity

• The diversity of plants and animals, throughout the world, is not evenly distributed and shows some interesting patterns of distribution.
• The patterns of biodiversity are, latitudinal gradients and species-area relationships.

Latitudinal Gradients

• It means that species diversity decreases as we move away from the equator and towards the poles (low to high latitude).
• Generally, tropics (latitudinal range of 23.5°N to 23.5°S) have more species than temperate or polar areas, e.g. Colombia near the equator has nearly 1, 400 species of birds. India has more than 1,200 species, while New York at 91°N has 105 species and Greenland at 71°C has 56 species.
• The largely tropical Amazonian rainforest in South America has the greatest biodiversity on the earth using more than 40,000 species of plants, 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.
• Some hypothesis proposed by scientists to explain the rich biodiversity in tropical regions are

• The temperate regions were subjected to frequent glaciations in the past, whereas tropical latitudes have remained relatively undisturbed for millions of years.
• Tropical environments are less seasonal, relatively more constant and predictable. This promotes niche specialisation and leads to a greater species diversity.
• Availability of more solar energy in the tropics, contributes to higher productivity, this in turn might contribute indirectly to greater diversity.

Species-Area Relationships

• German naturalist and geographer Alexander von Humboldt observed that within a region, species richness increased with the increasing available area, but only up to a limit.
• The relation between species richness and area, for a wide variety of taxa (angiosperm plants, birds, bats, freshwater fishes) 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 .

Where, S = Species richness, A = Area, Z = Slope of the line

(regression coefficient) and C = y-Intercept.

• Ecologists have discovered that the value of Z lies in the range of 0.1 to 0.2, when analysis is done in small areas regardless of the taxonomic group or area. But the species-area relationships among very large areas (continents), will give a much steeper slope and Z values in the range of 0.6 to 1.2, e.g. for frugivorous birds and mammals in the tropical forests, the slope is found to be 1.15. Thus, it can be said that the larger the area, the steeper is the slope.

Importance of Species Diversity to the Ecosystem

• Stability Communities with more species diversity, generally, tend to be more stable than those with less species. This is because such communities are more resistant or resilient to occasional distrubances (natural or man-made) and invasions by alien species.
• These communities do not show much variation in productivity from year to year.
• David Tilman discovered that increased diversity contributed to higher productivity and also proved that species richness is the key to the well-being of any ecosystem. It is also essential for the survival of man on this planet earth.
• Ecosystem health Ecologist Paul Ehrlich gave an analogy, Rivet Popper hypothesis, to help understand the effect of loss of species biodiversity. He compared each species with a rivet in the body of an airplane.
• This hypothesis explain that ecosystem is an airplane and the species are the rivets joining all the parts together.
• If every passenger travelling in the airplane starts taking rivets home (causing a species to become extinct), initially it may not affect flight safety but as more and more rivets are removed, over a period of time the plane becomes weak and poses threat to flight safety. However, if rivets on wings (keystone) species are removed, it would pose a more serious threat to flight safety.