Unit 3
Definition and Levels of Biodiversity

Learning Outcomes

Prerequisites

Key words

Species richness, Species Evenness, Genetic diversity, Aesthetic value, Option value.

Discussion

2.3.1 Biodiversity

Biodiversity describes the richness and variety of life on the earth. It is the most complex and important feature of our planet. Without bio-diversity, life would not sustain. The term bio-diversity was coined in 1985. It comes from a combination of two words “Bio”,means living and diversity means variation. Hence, put simply, variation among the living beings is called biodiversity. It is important in natural as well as artificial ecosystems. It deals with nature’s variety, the biosphere. It refers to variabilities among plants, animals and mi-croorganism species. Biodiversity includes the number of different organisms and their relative frequencies in an ecosystem. It also reflects the organization of organisms at different levels. Biodiversity holds ecological and economic significance. It provides us with nourishment, housing, fuel, clothing and several other resources. It also brings in monetary benefits through tourism. Therefore, it is very important to have a good knowledge of biodiversity for a sustainable livelihood. Bio-diversity is the variety of plant and animal life in the world or in a particular habitat. It is a key measure of the health of any ecosystem, and of our entire planet. Every organism in an ecosystem, or biome, relies on other organ-isms and the physical environment. For example, plant and animal species need each other for food, and depend on the environment for water and shelter. Biodiversity describes how much variety an ecosystem has, in terms of resources and species, and also genetically within species. A more diverse ecosystem will have more resources to help it recover from famine, drought, disease or even the extinction of a species. There are several levels of biodiversity, each indicating how diverse the genes, species and resources are in a region. Biodiversity is measured by two major components: species richness, and species even-ness.

Species richness: It is the measure of the number of species found in a community. It takes in to account only the numbers and not the abundance of the species.

Species Evenness: Species evenness takes into account the number of species and the relative abundance of species in a community. Several indices have been proposed. Two of the commonly used measures of evenness are the

1. Shannon- Weiner- index (H): It quantifies the entropy or degree of surprise
2. Simpson index (D) : It was introduced in 1949 by Edward H Simpson to measure the degree of concentration when individuals are classified in to types.

Alpha diversity: It refers to the diversity within a particular area or ecosystem and is usually expressed by the number of species (i.e., species richness) in that ecosystem.
Beta diversity: It is a comparison of diversity between ecosystems, usually measured as the change in the number of species between the ecosystems.
Gamma diversity: It is a measure of the overall diversity for the different ecosystems with-in a region.
Genetic diversity: Genetic diversity is the total number of genetic characteristics in the genetic makeup of a species. A single species might show high diversity at the genetic level (e.g. Homo sapiens: Chinese, Indian American, African etc.). Genetic diversity allows species to adapt to changing environments. This diversity aims to ensure that some species survive drastic changes and thus carry on desirable genes. Species that differ from one another in their genetic makeup do not inter-breed in nature. Closely-related species have in common much of their hereditary characteristics. For instance, about 98.4 per cent of the genes of humans and chimpanzees are the same. Each member of any animal or plant species differs widely from other individuals in its genetic makeup because of the large number of combinations possible in the genes that give every individual specific characteristic. Thus, for example, each human being is very different from all others. This genetic variability is essential for a healthy breeding population of a species. If the number of breeding individuals is reduced, the dissimilarity of genetic makeup is reduced and in-breeding occurs. Eventually this can lead to the extinction of the species. The diversity in wild species forms the ‘gene pool’ from which our crops and domestic animals have developed over thousands of years. Today the variety of nature’s bounty is being further harnessed by using wild relatives of crop plants to create new varieties of more productive crops and to breed better domestic animals. Modern biotechnology manipulates genes for developing better types of medicines and a variety of industrial products.

2.3.2 Species diversity

It is the ratio of one species population over the total number of organisms across all species in the given biome. ‘Zero’ would be in-finite diversity, and ‘one’ represents only one species present. Species diversity is a measure of the diversity within an ecological community that incorporates both species richness (the number of species in a community) and the evenness of species. 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 temper-ate or polar areas. The number of species of plants and animals that are present in a region constitutes its species diversity. This diversity is seen both in natural ecosystems and in agricultural ecosystems. Some areas are more rich in species than others. Natural undisturbed tropical forests have a much greater species richness than plantations developed by the Forest Department for timber production. At present conservation scientists have been able to identify and categorise about 1.8 million species on earth. However, many new species are being identified, especially in the flowering plants and insects. Areas that are rich in species diversity are called ‘hotspots’ of diversity. India is among the world’s 15 nations that are exceptionally rich in species diversity.

2.3.3 Ecosystem Diversity

An ecosystem is referred to as ‘natural’ when it is relatively undisturbed by human activities, or ‘modified’ when it is changed to other types of uses, such as farmland or urban areas. Ecosystems are most natural in wilderness areas. If natural ecosystems are overused or misused their productivity eventually decreases and they are then said to be degraded. India is exceptionally rich in its ecosystem diversity. A region may have several ecosystems, or it may have one. Wide expanses of oceans or deserts would be examples of regions with low ecological diversity. A mountain area that has lakes, forests, and grasslands would have higher biodiversity in this sense. A region with several ecosystems may be able to provide more resources to help native species survive, especially when one ecosystem is threatened by drought or disease. Ecosystem diversity deals with the variations in ecosystems within a geographical location and their overall impact on human existence and the environment. It is a type of biodiversity which refers to variation in species rather than ecosystems.

There are a large variety of different ecosystems on earth, which have their own complement of distinctive inter linked species based on the differences in the habitat. Ecosystem diversity can be described for a specific geo-graphical region, or a political entity such as a country, a State or a taluk. Distinctive eco-systems include landscapes such as forests, grasslands, deserts, mountains, etc., as well as aquatic ecosystems such as rivers, lakes, and the sea. Each region also has man-modified areas such as farmland or grazing pastures. The diversity of life at all three organizational levels, genetic, species and ecosystem, is thus being rapidly modified by modern man. This is a great loss to the future generations who will follow us.

2.3.4 Values of Biodiversity

Biodiversity provides a variety of environmental services from its species and ecosystems that are essential at the global, regional and local levels. Biodiversity is essential for preserving ecological processes, such as fixing and recycling of nutrients, soil formation, circulation and cleansing of air and water, global life support, maintaining the water balance within ecosystems, watershed protection, maintaining stream and river flows throughout the year, and erosion control and local flood reduction. Food, clothing, housing, energy, and medicines are all resources that are directly or indirectly linked to the biological variety present in the biosphere

2.3.4.1 Consumptive use value

A straight consumptive use is the direct utilization of timber, food, fuel wood and fodder by local communities. The diversity of organisms provide food, clothing, shelter, medicines, proteins, enzymes, papers, sports goods, musical instruments, beverages, narcotics, pets, zoo specimens, tourism and raw material for business etc. The direct utilization of timber, food, fuel wood and fodder is done by local communities. The biodiversity held in the ecosystem provides forest dwellers with all their daily needs, food, building material, fodder, medicines and a variety of other products. Fisher folk are highly dependent on fish and know where and how to catch fish and other edible aquatic animals and plants.

2.3.4.2 Productive use value

The biotechnologist uses bio rich areas to ‘prospect’ and search for potential genetic properties in plants or animals that can be used to develop better varieties of crops that are used in farming and plantation programs or to develop better livestock. To the pharmacist, biological diversity is the raw material from which new drugs can be identified from plant or animal products. To industrialists, biodiversity is a rich storehouse from which to develop new products. For the agricultural scientist the biodiversity in the wild relatives of crop plants is the basis for developing better crops. Genetic diversity enables scientists and farmers to develop better crops and domestic animals through careful breeding. Originally this was done by selecting or pollinating crops artificially to get a more productive or disease resistant strain. Today this is increasingly being done by genetic engineering, selecting genes from one plant and introducing them into an-other. New crop varieties (cultivars) are being developed using the genetic material found in wild relatives of crop plants through biotechnology. Even today, new species of plants and animals are being constantly discovered in the wild. Thus these wild species are the building blocks for the betterment of human life and their loss is a great economic loss to mankind. Among the known species, only a tiny fraction has been investigated for their value in terms of food, or their medicinal or industrial potential. Preservation of biodiversity has now become essential for industrial growth and economic development. A variety of industries such as pharmaceuticals are highly dependent on identifying compounds of great economic value from the wide variety of wild species of plants located in undisturbed natural forests. This is called biological prospecting.

2.3.4.3 Social values

While traditional societies which had a small population and required less resources had preserved their biodiversity as a life supporting resource, modern man has rapidly depleted it even to the extent of leading to the irrecoverable loss due to extinction of several species. Thus, apart from the local use or sale of products of biodiversity there is the social aspect in which more and more resources are used by affluent societies. The biodiversity has to a great extent been preserved by traditional societies that valued it as a resource and appreciated that its depletion would be a great loss to their society. The consumptive and productive value of biodiversity is closely linked to social concerns in traditional communities. ‘Ecosystem people’ value biodiversity as a part of their livelihood as well as through cultural and religious sentiments. A great variety of crops have been cultivated in traditional agricultural systems and this per-mitted a wide range of produce to be grown and marketed throughout the year and acted as an insurance against the failure of one crop. In recent years farmers have begun to receive economic incentives to grow cash crops for national or international markets, rather than to supply local needs. This has resulted in local food shortages, unemployment (cash crops are usually mechanized), landlessness and increased vulnerability to drought and floods.

2.3.4.4 Ethical and moral values

Ethical values related to biodiversity conservation are based on the importance of protecting all forms of life. All forms of life have the right to exist on earth. Man is only a small part of the Earth’s great family of species. We do not know if life as we know it exists else- where in the universe. Apart from the economic importance of conserving bio-diversity, there are several cultural, moral and ethical values which are associated with the sanctity of all forms of life. Indian civilization has over several generations preserved nature through local traditions. This has been an important part of the ancient philosophy of many cultures. India has a large number of sacred groves or ‘deorais’ preserved by tribal people in several states. These sacred groves around ancient sacred sites and temples act as gene banks of wild plants.

2.3.4.5 Aesthetic value

Knowledge and an appreciation of the presence of biodiversity for its own sake is an-other reason to preserve it. Quite apart from killing wildlife for food, it is important as a tourist attraction. Biodiversity is a beautiful and wonderful aspect of nature. Sit in a forest and listen to the birds. Watch a spider weave its complex web. Observe a fish feeding. These are magnificent and fascinating. Symbols from wild species such as the lion of Hinduism, the elephant of Buddhism, the eagles and foxes of Egyptian, Roman and Greek civilizations, have been venerated for thousands of years.

2.3.4.6 Option value

Keeping future possibilities open for their use is called option value. It is impossible to predict which of our species or traditional varieties of crops and domestic animals will be of great use in the future. To continue to improve cultivars and domestic livestock, we need to return to wild relatives of crop plants and animals. Thus the preservation of biodiversity must also include traditionally used strains already in existence in crops and domestic animals. Environmental economics (or ecological economics) provides methods of assigning economic values to species, communities and ecosystem. These values include the harvest (or market place) value of resources, the value provided by un-harvested resources in their natural habitat, and the future value of resources. For example, the Asian wild guar could be valued for the meat harvested from its current populations, its value for eco-tour-ism, or its future potential in cattle breeding.

Recap

Objective type questions

Answer to Objective type questions

Self Assessment Questions

Assignment

Suggested Reading

Reference