Class 12 Biology

Biodiversity and Conservation

The importance of Species Diversity to the Ecosystem

Scientists have yet to properly understand the relation between species diversity and health of an ecosystem. But it beyond doubt that rich biodiversity is not only essential for ecosystem health but imperative for the very survival of the human race on the earth.

Rivet Popper Hypothesis

Stanford based ecologist Paul Ehrlich explained the possible implications of reduction in species diversity by using this analogy.

He compared the ecosystem with an airplane and compared the species with rivets. We know that thousands of rivets are used in an airplane to join various parts. If every passenger starts popping a rivet to take home a memento, it may not affect flight safety initially. But as more and more rivets are removed the plane becomes dangerously weak in the long run.

Some of the rivets may be more critical than others. For example, loss of rivets on the wings can be more dangerous, compared to loss of rivets on the seats.

Similarly, extinction of a few species may not be harmful for the ecosystem. But extinction of a critical species may play havoc with the ecosystem.

Loss of Biodiversity

The colonization of tropical Pacific Islands by humans has resulted in extinction of more than 2,000 species. The IUCN List (2004) documents extinction of 784 species in the last 500 years. Some taxa are more vulnerable to extinction than other taxa. At present, more than 15,500 species in the world are endangered. At present, 12% of all bird species, 23% of all mammal species, 32% of all amphibian species and 31% of all gymnosperm species in the world are facing the threat of extinction.

Mass extinction has happened in the past as well. But the current rate of extinction is estimated to be 100 to 1,000 times faster. Ecologists predict that nearly half of all the species on the earth would be wiped out within the next 100 years.

Loss of biodiversity in a region may lead to

Causes of biodiversity losses

There are four major causes which are taken as The Evil Quartet.

  1. Habitat loss and fragmentation: Large scale deforestation to make way for human activities is resulting in habitat loss. This has also resulted in fragmentation of habitats into small parts. Habitat loss and fragmentation is the most important cause that is resulting in extinction of plants and animals.
  2. Over-exploitation: Human need for natural resources has turned into greed. It results in over-exploitation of natural resources. Many species of plants and animals have become extinct due to overexploitation.
  3. Alien species invasions: Some of the alien species turn invasive; resulting in decline or extinction of indigenous species. For example; introduction of carrot grass (Parthenium), Lantana and water hyachinth (Eichhornia) has caused damage to many indigenous species of plants in India.
  4. Co-extinctions: Some species of plants and animals are associated in obligatory way. Extinction of one species results in extinction of the associated species. For example; when a host fish becomes extinct, the parasites which are dependent on it also become extinct.


Why Should We Conserve Biodiversity?

There are many reasons for conservation of biodiversity. These reasons can be grouped into three categories, viz. narrowly utilitarian, broadly utilitarian and ethical.

Narrowly Utilitarian Arguments: Nature fulfills numerous human needs by providing food, firewood, fibre, construction material, industrial products and medicinally useful products. Bioprospecting is related to exploring molecular, genetic and species-level diversity for products of economic importance.

Broadly Utilitarian Arguments: This argument says that biodiversity plays a major role in many ecosystem services. Let us take example of pollination. It is essential for crop production, and crop has significant economic importance for us.

Ethical Arguments: Human beings share this planet with millions of plant, animal and microbe species. Every species has an intrinsic value. Some of it may not be of economic importance for us. But it is our moral duty to protect all of these species.

Methods of Conservation

In Situ Conservation: The onsite conservation of ecosystem is called in situ conservation. Protecting and maintaining wildlife sanctuaries and national parks is the method of in situ conservation.

Ex Situ Conservation: The offsite conservation of ecosystem is called ex situ conservation. In this method, threatened plants and animals are taken out from their natural habitat and placed in special setting for better protection. Zoological parks, botanical gardens and wildlife safari parks serve this purpose. Cryopreservation techniques are utilized to preserve gametes of threatened species.