BIOLOGICAL DIVERSITY: Biological diversity or biodiversity, refers to the variety of life in all its forms including plants, animals and microbes that exist and interact in the various biological communities and ecosystems. The levels of biodiversity necessary to preserve ecological diversity are genetic diversity, species diversity and eco systems diversity.
Genes are the units for transferring characteristics from one generation to another. For example, a child may have her father’s eye colour and mother’s build because he or she inherits genes responsible for those features from her parents.
Genetic diversity is the diversity of genes within a species. It is a measure of the variety of different versions of the same gene within individual species.
For instance although all human beings belong to the species Homo sapiens, the Africans, Asians, and Americans differ from each other owing to genetic diversity. Genetic diversity is a prerequisite for all other forms of biodiversity and the basis for evolution.
Species diversity refers to the variety of living organisms on earth that are found within individual communities or ecosystems. It is measured by counting the total number of species. For instance, the leopard, the grey horn bill, the Asian elephant, and purple-faced leaf monkey belong to different species. The most common gauge of biodiversity is the number of species in a given area. This is called species richness.
Different groups of species are found in different places on the earth. The distribution and the patterns of richness are determined by evolution, ecological processes and human activities. Species interact with other species for survival. An interacting group of different species is called a community.
Biodiversity of Sri Lanka
The species diversity of Sri Lanka shows that we have 4000 species of flowering plants, 107 species of freshwater fish, 59 species of amphibians, 174 species of reptiles, 435 species of birds, 140 species of mammals and several thousand invertebrates. Within the Asian region Sri Lanka has the highest species density for flowering plants, amphibians, reptiles and mammals. Sri Lanka also has the second highest population density of humans. Species density is the number of a particular species per 1000 sq. km.
A species can be either introduced or indigenous. Indigenous means native to an area. Those found only in one area or only in a country is known as endemic species. There are a large number of endemic species in Sri Lanka. This means that these species are found only in this country and in some instances only in particular areas or ecosystems. If any of these endemic species become extinct, they cannot be retrieved from any other part of the world since they do not exist anywhere else.
Percentage of our endemic species
The following are the details of the percentage of each species that is endemic to the island. Fish – 41%, Amphibians – 65%, Reptiles – 52%, Birds – 10%, Mammals – 5%, Land Snails – 80%, Freshwater crabs – 100%, Flowering plants 28%.
Areas that carry an unusually high number of endemic species world wide are referred to as biodiversity hotspots. Sri Lanka, with the Western Ghats of India, is endowed with a rich biodiversity and considered, one of the 25 biodiversity hotspots in the world.
Ecosystem diversity refers to the variety of ecological areas within which different species occur. An ecosystem can be described as a community of species, occupying a given area, interacting together and with the physical environment within which it exists. This is an interconnected network of biotic and abiotic components comprising a given area or region. Biotic is living and abiotic is non living components of an ecosystem. The abiotic components are soil, air, water etc. An ecosystem process is this interaction.
There are two categories of ecosystems, aquatic ecosystems and terrestrial ecosystems. Some are natural and others man made.
Examples of natural aquatic ecosystems are marshes, streams, rivers, estuaries, lagoons, coastal seas, sea grass beds and mudflats, mangroves and salt marshes, coral reefs, sandstone reefs and villus. Man-made aquatic ecosystems are tanks, reservoirs, canals, ponds and lakes.
Examples of natural terrestrial ecosystems are tropical wet evergreen forests, tropical submontane and montane forests, mixed evergreen forests, grasslands, scrub forest, Savannah, Sand dunes and beaches. Man-made terrestrial ecosystems are home gardens, agriculture fields, botanical gardens, monocultures and mixed plantations.
Uses and values of biodiversity
We need to protect our biodiversity because there are compelling economic, scientific, aesthetic and ethical reasons or values attached to biodiversity. Our natural resources, which stem mainly from our rich biodiversity, have great economic value through direct use. They are used for food, medicine, timber/fuel wood, clothes, recreation, biological control, ornamental and industrial processes. When direct uses are for non market purposes they are called consumptive values. When resources are extracted for commercial purposes they are called productive use values.
Sri Lanka’s biodiversity has much value to man both in direct terms and in indirect terms.
The direct value comes from the exploitation of our biodiversity for our food both which grows naturally and that which is taken as genetic material to improve our food crops. Certain species of plants are used for conversion to drugs and medicines.
Our needs of firewood and timber is extracted from our forests and timber plantations. Certain types of clothes are made from natural fibres etc. Parks, botanical gardens, protected areas and other areas, with our fauna and flora are used for recreational purposes. There are other areas of natural beauty which we enjoy and should not be destroyed.
Certain living species are used to control or kill other species that have gone out of control. For instance a beetle was brought from Australia to clean up the salvinia (Salvinia molesta ) which was brought to Sri Lanka during the 2nd World War and spread to cover all the water bodies and canals so that the Japanese hydroplanes could not land. This water weed spread very fast in lakes and slow moving rivers, choking up all the canals and waterways and caused flooding in many areas. It also competed with the paddy by competing for water, nutrients and space in paddy fields. This beetle consumed all the salvinia and died out soon after, since it feeds only on salvinia.
There are a lot of benefits that man derives indirectly from our biodiversity. The indirect values arise from the fact that biodiversity can be beneficial to people, but do not necessitate the consumption of resources. These benefits include eco system functions like maintaining water quality, recycling nutrients, soil conservation, protection of our watersheds, regulation of climate, in carbon sequestration, pollination and also education and scientific values.
There are also indirect values of maintaining options for the future. Hidden within the diversity rich rainforest may be a vast array of plants that could be used to develop drugs for presently incurable diseases etc in the future. To many people, the value of biodiversity goes beyond an opportunity to photograph or provide a daily meal. The indirect existence value comes from the fact that being aware that a species exist is reason enough to protect biodiversity. Some people, who may never get a chance in their life time to see a wild elephant, are willing to spend money to conserve them because they are happy and attach a value to the knowledge that these species exist in the world.
Most of the endangered species in this country and probably in the rest of the world, are birds, mammals and amphibians. These are the animals that are displaced by the activities of man or are hunted by him. They are also more visible and of greater interest to us. There may be many life forms that have been destroyed or pushed to the brink of extinction, which we are not aware of.
High population density and expansion of the human environment have increasingly threatened Sri Lanka’s biodiversity, which may lead to extinction of species.
If a species is said to be extirpated it means that this species has died out in a particular area. It has not died out completely but exists in other areas. For example the Comb duck is extirpated from Sri Lanka but is found in India. A species is declared extinct when there is no reasonable doubt that the last individual has died. Also a species is deemed to be extinct if it has not been recorded during the last 50 years even after extensive surveys.
Extinction is a natural process that has occurred throughout the evolutionary history of organisms. When some species become extinct new species evolve to take their place, just as mammals replaced dinosaurs. The problem today is that species are becoming extinct at an alarming rate and most of it occurs due to human mismanagement of biological resources. The evolutionary process is thus hampered.
Loss of biodiversity
There are several reasons for the loss of biodiversity. Some of the major reasons for these losses are detailed below.
a) Habitat loss and habitat degradation.
The habitats of many species are lost due to agriculture and farming, land fills in low lying areas, human settlements, forest fires, encroachment, timber extraction, and irrigation projects.
The loss of habitat quality or habitat degradation is due to haphazard tourism, pollution of land, water and air, use of pesticides and fertilizers, mining of corals, gems, and minerals and introduction of exotic or invasive species
The disposal of industrial waste into waterways contributes to the poor quality of the island’s water resources. Algae blooms and many dead fish have been reported in the Kotmale reservoir and more recently in the Kandy Lake. Pesticides harm the natural biodiversity of these systems indirectly, through their effect on food chains. Acid rain has also been reported in Horton Plains
b) Over exploitation
If any of our natural resources are used in excess or in a manner that these resources cannot sustain themselves, there is a likelihood of those species becoming either extirpated or extinct. The use of any species must be in a manner that they can breed or regenerate so that their numbers or populations do not diminish. Over exploitation can be for food and medicine, use of recreational areas, timber extraction, export of aquarium fish, and use of animal parts as ornaments.
Wild species have been increasingly collected for commercial purposes. Ornamental aquatic fish and plants for the aquarium trade, ornamental plants like orchids and ferns, and wild relatives of agricultural and medicinal species are now being collected, Kekatiya and Kothala himbutu for instance. Over 75% of the indigenous freshwater fish species, including 21 endemic species are collected from our waters for sale. When a species is protected by law, harvesting of that species is called ‘poaching’.
Since we do not fully understand the complex interrelationships between organisms, we are often surprised and dismayed at the ill-effects of removing seemingly insignificant members of biological communities.
c) Introduced species
Over the years, a large number of exotic plants and animal species have been introduced into Sri Lanka either accidentally or intentionally. Some of these species have escaped into natural ecosystems and are now overrunning the indigenous species.
An invasive species can be alien in that it is introduced from another country or area.
It can also be an ordinary member of the community suddenly becoming invasive due to a change in environmental conditions. An invasive species takes over the habitats of other species and multiply at an alarming rate thus suppressing the native species and in the case of faunal invasives, feeding on natives species.
In addition to these, global climatic changes, a lack of awareness and proper scientific management, are also some of the causes for the loss of biodiversity. Deficiencies in our knowledge of some species and their role in the ecosystem, legal and institutional systems that promote unsustainable exploitation and the under-valuation of our biodiversity also cause losses.
Conservation of our biodiversity
Conservation can be carried out in situ through legal protection – Ordinances, like the Fauna & Flora Protection Ordinance & Conventions like the Convention on Biodiversity, establishment of protected areas, environmental rehabilitation, reforestation, reintroduction of species to their habitats and the sustainable utilization of these resources.
Ex situ conservation can be carried out in zoological gardens, botanical gardens, medicinal plant gardens, using field gene banks, through reproduction programmes under captive conditions, conserve germ plasm and with tissue and seed banks.
Conservation is defined as the management of the use of biosphere in a way that it may yield the greatest sustainable benefits to the present generation while maintaining its potential to meet the needs and aspirations of the future generations. The basis for the conservation of biodiversity is the value of our biodiversity to human beings.
Conservation has to be through planned management to prevent over exploitation, destruction or neglect.
There has to be conservation of the different species, the conservation of their habitats and the conservation of the genetic diversity. The relevant government agencies, together with selected non-governmental agencies, should formulate an overall plan for the conservation of our biodiversity.
The Department of Wildlife Conservation, the Forest Department, the Coast Conservation Department, The Department of National Zoos, The Botanical Gardens and the Central Environment Agency are the leaders in this respect.