Geography · Ch 20 — Biodiversity and Conservation
Introduction
Introduction
The story of biodiversity begins with the ground beneath your feet. Weathering, the breakdown of rocks, creates a mantle of soil whose depth and character vary from one climatic zone to another. This weathering mantle is the very foundation on which vegetation grows, and where vegetation thrives, biodiversity follows. The real drivers behind these variations are solar energy and water — the more generous their supply, the wider the spectrum of life you find. That is why the richest biodiversity on Earth is concentrated in areas that receive abundant sunlight and rainfall.
Life itself is ancient. The biodiversity we see today is the product of roughly 2.5 to 3.5 billion years of evolution. Before humans appeared, the Earth supported more biodiversity than at any other time in its history. Since our emergence, however, that richness has been in rapid decline. Species after species has faced extinction, largely because of overuse by humans. The global number of species is uncertain — estimates range from 2 million to as many as 100 million, with 10 million considered the best guess. New species are still being discovered regularly, and many remain unclassified. For instance, an estimated 40 per cent of freshwater fish from South America have not yet been classified. Tropical forests stand out as exceptionally rich in biodiversity.
Biodiversity is not a static collection of organisms; it is a system in constant evolution, both at the level of species and at the level of the individual organism. The average half-life of a species is estimated at between one and four million years. A sobering fact follows: 99 per cent of all species that have ever lived on Earth are now extinct.
Life is also not spread evenly across the planet. Biodiversity is consistently richer in the tropics. As you move toward the polar regions, you find larger and larger populations of fewer and fewer species — the variety shrinks even as the numbers of certain hardy organisms grow.
The word itself is a combination of two terms: bio, meaning life, and diversity, meaning variety. In simple terms, biodiversity is the number and variety of organisms found within a specified geographic region. It covers the varieties of plants, animals and micro-organisms, the genes they contain, and the ecosystems they form. It relates to the variability among living organisms on Earth — variability within and between species, and within and between ecosystems. Biodiversity is our living wealth, the result of hundreds of millions of years of evolutionary history.
Biodiversity can be discussed at three levels:
- Genetic diversity — the variety of genes within a species
- Species diversity — the variety of species within a region
- Ecosystem diversity — the variety of ecosystems in which these species live and interact
Biodiversity as we have today is the result of 2.5-3.5 billion years of evolution. Before the advent of humans, our earth supported more biodiversity than in any other period. Since, the emergence of humans, however, biodiversity has begun a rapid decline, with one species after another bearing the brunt of extinction due to overuse. The number of species globally vary from 2 million to 100 million, with 10 million being the best estimate. New species are regularly discovered most of which are yet to be classified (an estimate states that about 40 per cent of fresh water fishes from South America are not classified yet). Tropical forests are very rich in bio-diversity.
You have already learnt about the geomorphic processes particularly weathering and depth of weathering mantle in different climatic zones. You should know that this weathering mantle is the basis for the diversity of vegetation and hence, the biodiversity. The basic cause for such weathering variations and resultant biodiversity is the input of solar energy and water. No wonder that the areas that are rich in these inputs are the areas of wide spectrum of biodiversity.
Biodiversity is not found evenly on the earth. It is consistently richer in the tropics. As one approaches the polar regions, one finds larger and larger populations of fewer and fewer species.
Biodiversity itself is a combination of two words, Bio (life) and diversity (variety). In simple terms, biodiversity is the number and variety of organisms found within a specified geographic region. It refers to the varieties of plants, animals and micro-organisms, the genes they contain and the ecosystems they form. It relates to the variability among living organisms on the earth, including the variability within and between the species and that within and between the ecosystems. Biodiversity is our living wealth. It is a result of hundreds of millions of years of evolutionary history.
Biodiversity can be discussed at three levels: (i) Genetic diversity; (ii) Species diversity; (iii) Ecosystem diversity.