Wednesday, July 09, 2008

Biodiversity Conservation of biotic-abiotic and biotic-biotic interactions

Plant-ecology is serving as shelter and secure place for wild birds. There is no trophic relation of the birds with the sal plant, but in ecological-niche function they are very much related (left); This is mating behaviour of birdwing butterfly (Troides) by hanging with the specific plant the Aristolochia.
BY now the term 'biodiversity conservation' has become very popular but the meaning of it is not clear even to many educated people in the society. It is generally understood that the conservation of living organisms is the conservation of biodiversity. But actually the conservation of the biodiversity is the conservation of interactions in an ecosystem.

Biodiversity means the variability among living organisms from all sources including, inter alia, terrestrial, marine and other aquatic ecosystems and the ecological complexes of which they are parts. This includes diversity within species, between species and of ecosystems. Biodiversity has three main components: ecosystem biodiversity; species diversity; and genetic diversity.

  • Ecosystem biodiversity describes the variety of different ecosystems found in a region. A categorisation of the combination of animals, plants, micro-organisms and the physical environment with which they are associated, is the basis for recognising ecosystems.

  • Species diversity describes the number and variety of species in a given area.

  • Genetic diversity describes the range of genetic characteristics found within a species and among different species.
Ecosystem is a system or phenomenon of interaction between abiotic and biotic factors in a certain area of the biosphere. The biosphere may be divided into smaller ecological units each of which is termed as an ecosystem. This is a term first to describe a natural unit that consists of living and non-living parts, interacting to form a stable system. The ecosystem may then be defined as a unit of the biosphere consisting of organisms and their physical and chemical environment tuned in a machine-like organization and driven by an external energy source, the solar radiation. So long as the system receives energy, it is self-sustaining. Fundamental concepts include the flow of energy via food chains and food webs and the cycling of nutrients biogeochemically.

Ecosystem principles can be applied at all scales equally, for instance, to a lake, an ocean, or the whole planet. The ecosystem represents a distinct combination of air, soil and water (habitat), along with vegetation, animal and microbial life, making it self-sustaining. An ecosystem is any spatial or organizational unit which includes a community of living organisms and non-living substances of environment interacting to produce materials between the living and non-living parts. Further, an ecosystem may be natural as a pond, a lake, a river, an estuary, an ocean, a forest, or it may be man-made or artificial like an aquarium, a dam, a cropland, a city and so on.

As the ecosystem is to harbour both species and genetic diversity, so it holds the conservation strategies and the conservation of three types of biodiversity as a whole. Let us see how the biodiversity conservation itself interprets the conservation of biotic-biotic and biotic-abiotic interactions. The interaction between biotic and abiotic factors means the interaction between living organisms (plant and animals) and the atmospheric non-living materials. On the other hand, biotic-biotic interaction means the interactions among the living organisms i.e. between plant and animals or among animals or among plants. Biodiversity conservation holds the conservation of energy-flow in nature among the living organisms in the living form. “Conservation of ecosystem is the vital part of the conservation of biodiversity” because ecosystem diversity is one of the three biodiversity types.

Biodiversity conservation is the assemblage of enhancement of species richness, maintenance of species richness, sustenance of species richness, and survival of species richness in an ecosystem. This means the conservation of interaction of all dynamism of interactions among species diversity, genetic diversity and ecosystem diversity. In the hierarchy of interactions plants occupy the first position and characteristically designated as the first trophic level in the system of energy-flow when biotic factors are in the ladder-steps of the energy-flow in the form of “being eaten”.

Trophic level is the position of an organism in the food chain, determined by the number of transfers of energy that occur between the nonliving energy source and that position. Trophic levels include producers (photosynthesizers and chemosynthesizers that convert light or chemical energy into living material) and several levels of consumers (animals eating plants, animals eating animal, etc. The trophic level of an organism describes how far it is removed from plants in the food chain. Autotrophs constitute the first (producer) trophic level. The second trophic level contains herbivores (primary consumers) and so forth. An organism cannot always be assigned to one trophic level. Thus, some plants, such as sundews, are carnivores (third or fourth trophic level) as well as autotrophs (first trophic level). Many mammals, such as pigs and humans, are omnivores and also belong to several trophic levels because they eat both plants and animals.

Ecosystems seldom have more than five trophic levels. This is because there is not enough food or energy in the top trophic level to feed another level. First, not all the food available at one trophic level is actually eaten by animals at the next level. At each level, the biomass, the total mass of all organisms present, is only partly consumed. Second, most of the energy an animal eats does not go to make it fatterit is used in respiration; for the maintenance and repair of body tissues; and for locomotion, circulation and feeding. As we will expect from the laws of thermodynamics, none of these processes is very efficient. Some useful energy is lost as heat and as entropy each time energy is converted from one form to another. Because of these energy losses from one trophic level to the next, there is not enough energy left to support higher trophic levels. Energy from the sun enters an ecosystem during photosynthesis. Then it passes from one to five trophic levels in the ecosystem's food web.

Now question comes 'whether conservation of biodiversity is the mere conservation of plantation or not'. It is already stated that in the energy-flow system, plant is the basic structural form and first trophic level. This first trophic level is characterized by three characters at a time, whereas the other trophic levels (the animals/different consumers) in an ecosystem are the successive ones and having only two characters. Among the three characters, the plant can convert abiotic energy into biotic molecules and can manufacture its own food (first character); the plant can store the energy in the biotic form (second character); and the plant can transfer the energy to the other trophic levels (to the consumers) (third character) which is occurred by the process of “being eaten”.

In an ecosystem, all other trophic levels (the consumers) are only having with the second and third characters of the first trophic level. So, it is evidenced scientifically that no animals can exist and multiply in an ecosystem if the first trophic level is absent. Directly or indirectly an animal has to depend on the plant in an ecosystem. If plants are available, animals get nutrition first and then can take shelter, can mate, can prepare for nesting, can produce offsprings, can perform social activities (where necessary and essential), can cause the speciation, can enrich the species richness, and can sustain the species richness. This sustenance is the conservation of all living organisms in an area; and then the conservation of biodiversity.

The plants are not only used as the nutritional sources for animals, but they are also used as ecological sources and as the ecological niche-sources. The birds are found to take characteristic rest in the trees, even if these trees are not found to supply them food materials. So need for the trees is multidimensional, many of the needs have yet not been identified and discovered. Another interesting example of the plant association is birdwing butterfly (Troidesscientifically named) with the specific plant (the Indian birthwort, Aristolochiascientifically named). It is to be noted that birdwings are the largest butterflies in the world. Some of the species of the butterfly are available in Bangladesh. They do not found to copulate without the Aristolochia plant. If the specific plant is not found, the butterfly cannot go for successful breeding. For progeny-maintenance of this species, association with the plant is absolutely necessary. This peculiar mating behaviour is a simple example of an interaction of the biotic-biotic factors in an ecosystem.

Fast decrease of Modhupur forest biodiversity has been blamed on the “shrinking of forest”. Many kinds of wild animals including leopard, wild buffalo, wild cow, wild hog, wild cock, peacock, spotted deer, jackal, wild cat, mongoose, wild goat, red mouth monkey, black mouth baboon, porcupine, squirrel, hare and bocat were found in Modhupur forests only a few decades ago(as reported by the Forest Department). Birds including hawks, kites, vultures, mynah, nightingale, swallow, owl, pigeon, dove, skylark, sparrow, wood-pecker, parrot, different vaieties of martin, kingfihers were available in the forest in high population. Of the reptiles, snakes were most available like python and poisonous cobra. Different varieties of frogs were described as amphibian fauna. Number of varieties of environment friendly invertebrates included worms (earthworms), white ants, different kinds of soil dwelling carabeids, most decorative butterflies were mostly available in the Modhupur forests.

To save Modhupur forest-biodiversity it is highly necessary to save the forests meaning as save the plant population and increase the sustenance of plant species richness.

Now the question is why plants and plantation are the major event to go for biodiversity conservation. Because if plant is there initiation of bio-conservation is there, if plant is not there no initiation of bio-conservation. Plantation is the stimulation of the fact-initiation. If there is no stimulation, there is no response; if there is no response there is no fact for happening; if there is no happening (specially among the living beings) there will be no behavioural aspects and then there will be no appearance of conservation functionality in nature.

Dr M A Bashar is Professor Department of Zoology and Ex-Dean, Faculty of Biological Sciences, University of Dhaka.

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