- 1 Causes for Biodiversity Loss – Conservation Challenges in the Sundarbans
- 1.1 1. Latitudinal and Altitudinal Gradients:
- 1.2 2. Species-Area relationships:
- 1.3 Rivet Popper Hypothesis
- 1.4 Importance of Biodiversity
- 1.5 Causes of Extinction of Biodiversity
- 1.6 Environmental Problems of Sundarbans
- 1.7 Ecological Condition of Sundarban
- 1.8 Factors of Environmental Problems of the Sundarbans
- 1.9 Loss of Biodiversity
- 1.10 Types of Extinction
One of the most pressing Biology Topics of our time is the conservation of endangered species and habitats.
Causes for Biodiversity Loss – Conservation Challenges in the Sundarbans
According to Reice (1994), a heterogenous environment promotes biodiversity. The tropical rain forests, for example, are the richest in biodiversity, even though the region experiences very little seasonal variations. Two distinct patterns of biodiversity have been observed. They are:
1. Latitudinal and Altitudinal Gradients:
Except for the arid areas and the aquatic habitats, biodiversity shows a definite trend to increase as we move from the poles towards the equator. The poles have very harsh cold climates throughout the year thus, have very low biodiversity, but the temperate regions and mostly the tropical regions of the earth show the highest biodiversity. Statistics say that number of vascular plants in tropics may range upto 118-236 species per 0.1 hectare, while the number of the same may be just 21-48 species in temperate regions and only 0-10 species in arctic regions.
A similar trend can also be seen with the increase in altitude. This occurs due to the phenomenon of Lapse temperature, in which for the increase of every kilometer of height, the temperature drops at the rate of about 6.5°C. Such climatic gradations also influence the living entities which show a decreasing trend with increasing height.
2. Species-Area relationships:
Species richness, the number of different taxa present in an area is indicative of biodiversity. German naturalist Alexander von Humboldt found that such richness of species increases with increasing area but upto a certain limit, after which the number of species observed becomes constant. The hyperbolic relationship is observed in the case of species-area interactions. While in a logarithmic scale, the relationship depicts a straight line.
Importance of Latitudinal and Altitudinal Gradients and Species Area Relationship:
These are integral concepts in the field of biodiversity that help us in determining various ecological patterns that exist on Earth. Determining biodiversity patterns across the earth is an essential requirement to understand the ecosystems.
log S = log C + Z log A
Here, S = Species richness
Z = Regression coefficient (usually 0.1-0.2)
A = Area
Rivet Popper Hypothesis
It is a theoretical demonstration that entails the conditions of the ecosystem wherein a significant loss of a certain species affects the functions and diversity of an ecological community.
This hypothesis presupposed that communities consist of relatively specialized species with limited ability to compensate each other thereby the vanished of certain species is important to the performance of the ecosystem. Rivet’s hypothesis asserts that each species loses to an ecological unit, which can decrease ecosystem functions although the decrease is rather slow as more species are eliminated. In this concept, any loss of diversity is clearly noticeable. According to it, an airplane has thousands of rivets as an ecosystem with different species. If a few rivets are removed, it will not affect flight safety initially but the airplane will become weak and will destabilize at some point in time.
Importance of Biodiversity
The importance of biodiversity in the environment may be discussed in the following manner:
- Man depends solely on different plants and animals for food, clothing, and shelter. Besides to be rescued from diseases he needs different types of medicines, for comfort and pleasure there is the need for cosmetics and household goods even arms for self-protection and all these materials come from the living world. However most of the articles of these categories we get from plants. There are about 25000 plant species that are cultivated for foods, cosmetic substances, and medicines.
- Different plant and animal species maintain their existence through comparative interaction between them. This relation is expressed through the food chain and food web. Every organism may be considered as the aggregate of energy. Through the accumulation of energy, its storage, and utilization the existence and development of an organism become possible. The source of this energy is the sun and the plants can use this energy as food. The animals at different trophic levels obtain this energy from plants. Therefore the loss or extinction of any form of life is antagonistic to the existence of living forms.
- By using different organisms and their functional attributes man has developed techniques to promote smooth livelihood. For example with the application of biotechnology, we can produce curd from milk, develop ladders by using techniques of echolocation from bat, production of multiple copies of DNA in PCR by using enzymes from Thermus aquaticus, etc, these are different examples of the use of biodiversity in human welfare.
- Various forms of organisms are actually the representation of different gene pools. This gene pool has been a precious property to us. We can use this gene pool for our benefit, for example production of transgenic animals and plants by genetic engineering, and the formation of hybrids through mating between different organisms, have given us some promising concepts in order to achieve benefit.
- In the environment, the plants control different environmental conditions. There is no controversy regarding the fact that plants keep the environment cool and they promote rain on the land. Therefore we have been very cautious regarding the destruction of plants from nature. Considering all of these, it may be said that for economic development and comfort, we need our biodiversity preserved.
Many biologists who study biodiversity confine themselves to the objective assessment of ecological processes. Biodiversity has an intrinsic value i.e., worth protecting regardless of its value to humans.
- Stability: Biodiversity is the basis of the stability of an ecosystem. The greater the number of species of a community, the more is its stability. It is observed that in a species-rich community, alien species can not establish themselves and they can also resist any kind of environmental disturbance. The community has the ability to resist ecological disbalances.
- Productivity: The productivity of an ecosystem is also dependent on its species richness. The more species present in an ecosystem more will be its productivity.
- Ecosystem Health: Biodiversity is the base for a stable ecosystem. Various interactions, feedback controls, critical links, and keystone species maintain the health and stability of ecosystems. Extinction and removal of a few species may destabilize the system. This effect was put forward by Paul Ehlrich as he proposed the Rivet Popper Hypothesis. According to it, an airplane has thousands of rivets as an ecosystem with different species. If a few rivets are removed, it will not affect flight safety initially but the airplane will become weak and will destabilize at some point in time. Biodiversity, besides its ecological significance, provides a socio-economic and monetary asset to the nation. Human society depends on biological resources, their diversity, and the ecosystems that sustain them to provide essential goods and services.
Causes of Extinction of Biodiversity
Human activities are a major threat to biodiversity. It is caused by the elimination of species from the earth. The rate of extinction of species from Earth is accelerating. There are four major causes of extinction referred to as “the evil quartet’’. These are:
- Habitat Loss and Fragmentation
- Over Exploitation
- Alien Species Invasion
- Intensive Agriculture
- Hunting and International Business
The extinction factors of biodiversity are mentioned below:
1. Habitat Loss and Fragmentation:
Natural habitat which protects natural flora and fauna are being converted to human settlements, harbours, dams, reservoirs, croplands, grazing grounds, and mining sites. Deforestation deprives animal life of shelter and food. This decreases the population of many species. Fragmentation means a large continuous area of habitat is divided into two or more fragments. It results in the disruption of complex interactions amongst species, and the destruction of species restricted to deeper undisturbed parts of the forest. Animals requiring large territories are badly affected. The Amazon rain forest was so large that it used to be called the ‘lungs of the planet’. Millions of species were in existence there. Now it is being cut and cleared for cultivating soybeans and developing grasslands for raising beef cattle.
2. Over Exploitation:
Excessive exploitation of plant or animal species beyond their renewability results in degradation and extinction of the resource. Excessive felling of trees in the forest, overgrazing, hunting of animals, D uprooting of medicinal plants, etc., have resulted in degradation of habitats and extinction of many species, e.g., Cheetah from India, Dodo from Mauritius, and Passenger pigeon from America. Many marine fish populations are declining around the world because of over-harvesting. A number of economically important species are likely to become endangered.
3. Alien Species Invasion:
The introduction of alien or exotic species may cause significant loss to the biological communities. They often become invasive and drive away the local species. They may alter the habitat in such a way that many natives are no longer able to persist. Island ecosystems are the most vulnerable due to their small size and small number of species. A few examples of the introduction of exotic species and their effects are
- Lantana camara, an exotic shrub strongly competes with the native species and has eliminated many of them. It has also invaded many forests in different parts of our country.
- Water hyacinth (Eichhornia crassipes) was introduced in several tropical countries including India. It has clogged water bodies and wet lands resulting in the death of several aquatic plants and animals.
Many species live in obligate associations in ecosystems. When one of them becomes extinct, the others associated with it would also die, e.g., Pronuba yuccaselles and Yucca. If the host becomes extinct, all the parasites exclusively found on it will also become extinct.
Natural as well as man-made disturbances such as fire, tree fall, defoliation by insects, etc., affect communities adversely. Man-made disturbances and degradations are more severe. They include the falling of trees, use of fire for clearing, collection of litter, and over-exploitation for other economically important products.
6. Intensive Agriculture:
To meet the expanding demand for food grain it is required to increase the agricultural land area. In most cases, it is done by reclamation of wet lands, use of fallow lands, destruction of grasslands and forests, etc. Destruction of habitats results in extinction of species. Intensive agriculture is based on a few selected crops and their high-yielding varieties. This leads to the fast disappearance of other varieties. For example, at one time about 308 varieties of maize were grown in the U.S.A. Today their number is only 12.
Pollution may reduce and eliminate populations of sensitive species. Excessive use of pesticides has polluted both groundwater and surface water bodies. Many sensitive populations have disappeared. The populations of fish-eating birds and falcons have declined. Lead poisoning is another major cause of mortality of many aquatic birds like ducks, swans, and cranes. Eutrophication leads to depletion of oxygen, fouling of water, and death of animals. Spillover of oil in the sea causes the death of several marine algae, fish, and sea birds.
Growing economically important plants for commercial purposes reduces the number of other species in the forest. In silviculture, the cultivation of forest plants like Teak, Sal, Kel, Sheesham, etc., is in practice. Such pure strands are liable to be attacked by insects and pathogens.
9. Hunting and International Business:
All kinds of hunting methods for international business or any purposes like for food, recreation, fur, hide, musk, plumage, tusk, horn, etc., have caused extinction or destruction of wildlife as well as the balance of nature.
The wild plants of forests destroyed for timber, charcoal, and firewood often deprive wild animals of their most palatable food and affect their survival. Due to the high percentage of deforestation, there are reduction in the area for the free movement of wild animals well as disturbs the ecological balance.
Environmental Problems of Sundarbans
Sundarbans represent the Sundarban Biosphere Reserve which was constituted by the Government of India in 1989 and Biosphere Reserve received recognition from UNESCO under the Man and Biosphere Programme in November 2001. The total area of Sundarban Biosphere Reserve measures about 9600 sq. km. However, Sundarban also extends in Bangladesh, and including the portion of Sundarban in Bangladesh its area will be about 10200 sq. km. In India, the Sundarban Reserve Forest covers about 4200 sq. km and the non-forest area covers about 5400 sq. km containing habitation of people. Indian Sundarban is bound by river Muriganga on the west and river Hariabhahga and Raimongal on the east.
Ecological Condition of Sundarban
Sundarban is rich in aquatic flora and fauna. It is highly productive for as natural fish nursery. The region is famous for its Mangrove forest where the Sundari trees grow. The name Sundarban is derived from the name of the Sundari plant.
The dominant mangrove species Heritiera fomes is locally known as sundri or sundari. Mangrove forests are not home to a great variety of plants. They have a thick canopy, and the undergrowth is mostly seedlings of mangrove trees. Besides the Sundari, other species that make up the forest include Avicennia sp., Xylocarpus mekongensis, Xylocarpus granatum, Sonneratia apetala, Bruguiera gymnorrhiza, Ceriops decandra, Aegiceras corniculatum, Rhizophora mucronata, and Nypa fruticans plams.
Sundarbans is famous for the Royal Bengal Tiger. Besides the area contains many species of birds, spotted deer, crocodiles, and snakes. The ecosystem provides yellow monster, Indian flaptailed turtle, Indian python, wild pig, rhesus maccaque, estuarine crocodiles, and horseshoe crabs.
Factors of Environmental Problems of the Sundarbans
1. Destruction of Mangroves:
The mangrove forest is an important component of the Sundarban ecosystem. Their plants are specially adapted to saline environments. Therefore, if mangrove plants are destroyed the whole ecosystem will be affected. The plants with the prop roots can protect against land erosion when tidal water is very active on the banks of rivers. Due to the extension of agricultural land and urbanization in the forest area, such an effect occurs.
2. Crisis of Freshwater:
Fresh water availability is short in the total Sundarban delta area. High tides sometimes bring salt water to the cultivated land causing floods in the whole Sundarban area. This causes destruction of vegetation and productivity of the area.
3. Destruction of Habitats:
Because of the loss of Sundari trees and mangroves from this forest area a shrinkage of the habitats occurs affecting to habitation of the wild animals. Due to natural calamities such as cyclone and flood, when sea water submerges the water bodies on the land, this not only destroys to growth of the plants but also destroy many freshwater communities.
Pollution is a threat to any place in the globe nowadays. Sundarban is also no exception to this. The increase in population has been enhanced by the use of cars and fossil fuels and as a result, CO2 production and lead liberation in the environment has also increased.
5. Disbalance of Prey-Predator Number:
In the environment, prey-predator proportion is very important. Poaching and hunting kill the tigers, so it is expected that the population of deer will increase. In a similar fashion, if the deer population is reduced, tigers will come out of the forest to localities in search of food.
6. Submergence of Islands due to Rising Sea Level:
Submergence of the island Sundarban has been a great problem for the habitats of all animals including man. It is reported that in past days the area of Sundarban was smaller than of the present day. Due to the rise of new land masses new islands were established and plants and animals developed habitation in the newly formed island. Presently due to global warming sea level is rising and as a result some islands have gone under sea water causing some destruction of Sundarban.
Loss of Biodiversity
Biodiversity is lost due to extinction. Extinction is the total elimination or dying out of species from the earth. The loss of biodiversity can be attributed to the influence of human activities on the global ecosystem. Actually, the human community has deeply altered the natural environment, modified the territory, and exploited the species directly.
Various causes for the loss of biodiversity are:
- Degradation and destruction of habitats due to colonization and clearing of forests for settlement or agricultural expansion, commercial expansion, hydraulic schemes, fire, human, etc.
- Hunting and over-exploitation, mainly for commercial (and often illegal) purposes.
- Introduction of exotic species accidentally or deliberately, that threaten native flora and fauna directly by predation or by competition and also indirectly by altering the natural habitat or introducing diseases.
- Pollution and poisoning stress the ecosystem.
- Due to global warming, the suitable climate for a given species is changed, putting pressure on species with regard to their adaptability, thus making them vulnerable to extinction.
- Improper use of agrochemicals and pesticides, increase in human population, inequitable land distribution, and economic and political policies and constraints.
Susceptibility to Extinction
A species becomes prone to extinction due to two categories of factors environmental changes and population characteristics. Population characteristics are
- Large body size, e.g., elephant, rhinoceros.
- Small population size.
- Low reproductive potential, e.g., blue whale, giant panda.
- Higher status of trophic level, e.g., bald eagle, Bengal tiger.
- Fixed migratory route and habitat, e.g., blue whale.
- Narrow range distribution, e.g., Woodland caribou.
- Island species.
- Lack of genetic variability.
- Inability to switch over to alternate food.
Types of Extinction
Species become extinct through three types of extinction processes.
1. Natural Extinction:
It is the extinction of species from the earth due to changes in environmental conditions. Some species disappear and the others which are more adapted to changed conditions, take their place. Many species have become extinct in the geological past by this process.
2. Mass Extinction:
Mass extinction occurs due to environmental catastrophes. A mass extinction occurred about 225 million years ago in the Permian when 90% of shallow-water marine invertebrates disappeared. Another mass extinction occurred between Cretaceous and Tertiary over 60 million years ago when dinosaurs and a number of other organisms disappeared. It is also called the K-T boundary. During the Pleistocene Wooly Mammoth, Mastodon, Giant Sloth, and many other mammal species became extinct.
3. Anthropogenic Extinction:
It is the extinction of species caused by human activities like hunting, overexploitation, habitat destruction, pollution, etc. The colonization of tropical Pacific islands by humans has resulted in the extinction of more than 2,000 species of native birds. According to the World Conservation Monitoring Centre (WCMC), 533 animal and 384 plant species have become extinct since the year 1600. Some examples of important recent extinctions are the Dodo (Raphus cucullatus) of Mauritius, the Tasmanian wolf (Thy- lacinus cyanocephalus) of Australia, the Quagga of Africa, Stellers’s sea cow of Russia, and three subspecies of tiger (Bali, Javan, and Caspian).
Loss of biodiversity is leading to
- Decline in the productivity of plants.
- Living organisms including plants are losing resistance to environmental disturbances like drought, flood, etc.
- Drastic changes in ecosystem and environment.