Disadvantages of agroecosystem:
• Wind erosion: Tiling causes large amount of wind erosion.
• Irrigation: Large quantities of water are required for irrigation.
• Pollutants: Agricultural practices can pollute the air with microorganisms like fungi, algae, bacteria, viruses, pesticides, weedicides and increase soil salinity.
• Susceptibility to disease: Hybrid varieties are more susceptible to disease, e.g.
smut of sugarcane, maize and sorghum and rust of wheat and bajra are common in crop plants and they are resistant to fungicides so the yield is affected.
• Loss of biodiversity: High yielding varieties are encouraged as a result of which the naturally occurring varieties of crop are getting depleted.
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• Animal and plant diseases: Animals and humans consuming ergot infected bajra suffer from ergot poisoning. It causes serious diseases of the nervous system.
Spore dust in heavily rust infected wheat field results in severe lung diseases.
Plantation Forests: Planting of selected species of trees over a piece of land resulting into tree cover which resembles forest is called plantation forest. These are significantly different from the natural forests as they are highly simplified and lack biodiversity. Fast growing trees like neem, teak and shisham are generally planted.
Dams, Reservoirs and Diversions:
Dams, reservoirs and diversions capture and store run off water and release it as needed. A dam is a structure built in order to restrict the flow of river or tidal water and provide fresh water for following purposes :
• Producing hydroelectric power. This alternative source of energy reduces carbon dioxide emission into the atmosphere.
• Supplying water for irrigation and other uses to rural, suburban and urban regions.
• Controlling floods.
• Reservoirs also provide recreational activities such as swimming and boating. Dams have increased the annual run off available for human use nearly by one-third.
Disadvantages of dams:
• Dams cause permanent submergence of crop land and forests.
• Dams destroy farm lands and displace large number of local people.
• They increase water pollution because of reduced water flow. In the tropical regions there is an increase the water born diseases. The local populations suffer from water born diseases such as malaria, schistosomiasis and botulism ( a nervous diseases resulting from blue green algae).
• Nutrients in the soil are reduced.
• The natural water flow regimes are disrupted, since it is a regulated flow of water the spawning and migration of some fishes is affected.
• There is high cost of building the dams.
• Large dams which are more than 15 meters high (492 feet) increase earth quakes in the seismically active areas.
• In arid region dams are resulting in increase in water salinity as the reservoirs (formed by dams) have more exposed surface area and have a higher rate of evaporation than the river.
• A dam has a limited life span usually 50 to 200 years. Because over the time the reservoir fills with silt and it can not hold enough water to generate electricity.
AQUACULTURE:
Aquaculture is defined as the breeding, rearing and harvesting of plants and animals in all types of aquatic environment including ponds, rivers, lakes, estuaries and oceans. It can take place in the natural or in man made environment. It is a major source of global food supply. The marine aquaculture deals with the production of oyster, clams, mussels, shrimps and salmon whereas, freshwater aquaculture operations produce catfish, trout and tilapia and some more freshwater
fish and plants. Contribution of aquaculture to global food production depends on development of present and future technology in mimicking the natural ecosystems. Aquaculture industry should be able to recycle the nutrients and generate less waste like natural ecosystem.
From the economics point, aquaculture products can be grouped into two types: one high valued species such as shrimps and salmon that are frequently grown for export. And second, low valued species such as carp, tilapia, milk fish, clams and oyster. Carps accounts for more than one- third of the world’s aquaculture production. Carp farming is easy to integrate with other conventional farm activities as well as they are herbivorous and can survive on low cost readily available feed material. Tilapia is a good source of food but, they are among the serious invasive species in subtropical and tropical regions. They are rapid breeders under captivity, resistant to diseases but, fighters and affect the growth of other species of fish.
Tilapia is omnivorous and even digs soil to eat up detritus. Tilapia culture has been banned in India since it is a prolific breeder and destroys the biodiversity of the ecosystem.
Aquaculture in India:
Marine: India has a very long coast line for tapping sea food. Marine resources include Bay of Bengal, Arabian Sea, Indian ocean, numerous gulfs , coral reefs, mangroves and brackish waters like lagoons and Chilka lake.
Fresh waters: India’s inland waters occupy a very large area (about 1.6 million hectares).
They are in the form of major river systems such as Ganges, Yammuna, Brahmputra, Narmada, Mahanadi, Cauvery and Krishna. Besides this there are wetlands, canals, ponds, lakes, and irrigation channels where culture fishery can be practiced. The fresh water fishes are various species of carps such as Chinese carp, green carp, mirror carps, cat fish etc.
The culture fisheries ( aquaculture) has been started in ponds, artificial enclosures and net pens providing fertilizers such as cowdung, domestic waste and other animal excreta. The pond cultures can be of the following types:
1. Monoculture: This involves production of only one species. Usually trouts, eels and cat fish are produced in monoculture. .
2. Polyculture: The culture of more than one compatible aquatic species is called polyculture. Common combinations are milk fish with prawn, Chinese carp with Indian carp and carp with Tilapia.
Tilapia , trouts, salmon and some more species of fish are cultured in net pens. Milk fish and mullets are cultured in enclosures or bamboo fences.
Environmental Impact of aquaculture
Aquaculture has many advantages. It provides improved qualities of fish with respect to nutrients by crossing over and genetic engineering. It also reduces the over harvesting of conventional fisheries. But both these profits are at the cost of environmental degradation.
• Aquaculture requires both land and waters resources, which are already in short supply.
• More man power is required for their maintenance.
• Large amount of concentrated wastes are produced.
• Coastal habitats with mangrove swamps are removed for the shrimp farming in Asia and Africa . Destruction of Mangroves in coastal region has made them more prone to cyclones, tornados and flooding. Thailand has lost 17% of its Mangrove forests.
• Aquaculture fish are very sensitive to pesticide runoff from the croplands (biomagnification).
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• Dense populations are more vulnerable to diseases. Since the fish are reared under highly controlled conditions they become more sensitive and prone to diseases.
URBAN ECOSYSTEM
An urban place is a city where many people live close together and the population density is high. They consume a major part of the earth’s resources and produce more waste. The earth is witnessing urban revolution as the people all over the world crowd into towns and cities. In 1800 only 5% of the world population were urban dweller (50 million people) and in 1985 it increased to 2 billion. At present 45% is urban population and by 2030 there will be more than 60% people living in cities.
Characteristics of urban ecosystem and their impact on the environment:
• Population density is high. There is too much of congestion (due to high population density) that create inhumane conditions.
• It survives on major input of energy and natural resources.
• The economic growth of urban ecosystems is at the cost of environmental degradation.
• They are highly polluted since there are many industries releasing pollutants and very few or no green plants to absorb them.
• Noise pollution is more severe due to more number of industry and noisy means of transport.
• Urban ecosystems have water and other resource problem because of high population density. They consume 75% of the earth’s resource and produce 75% of the waste.
• There is more crime and unrest due to unemployment with population increase beyond the carrying capacity. Increasing population density in the mega cities of the world compels some people to live in slums (periphery of the city) e.g. 3 million people in Mumbai live in slum and shanty town which lack basic services.
Urbanization is taking place more rapidly in the developing countries. The increase of city dwellers in a developed (industrialized) country is only 0.8% whereas it is 3.6 % in the developing country.
RURAL ECOSYSTEM
Rural ecosystems are between natural and urban ecosystems since, the exploitation of nature and natural resources by man is relatively much less. People live here under comparatively more natural conditions in simple life style.
Characteristics of Rural Ecosystem and their Impact on the Environment:
• In rural areas people live in small clusters surrounded by farm lands.
• In the villages people are mostly dependent on cultivation or farming.
• Clean water supply to them is in the form of wells, canals, lakes or rivers directly. These sources may be quite far from the living place. Ladies and children spend a lot of their time in fetching water and fire wood .
• Schools and modern sources of entertainments are beyond their reach.
• Transportation is poor.
• They are polluted by domestic sewage effluent and fossil fuel burning.
• Poor sanitation and hygienic conditions.
• Houses are small and without ventilation.
The government policies to reduce the migration of people from villages to cities are to increase the cost of land in the cities and reduce it in the villages. More employment should be created in the villages. Some incentives should be given to the people working in the villages. More facilities should be provided to the villagers so that they are not pushed towards the cities.
METHODS TO MINIMIZE HUMAN IMPACT ON NATURAL ECOSYSTEMS Natural ecosystems are our resources especially for food, fuel and water. To protect them from human impact it is essential to change our habits, curtail our needs and try to conserve them for the future generations and to maintain the ecological balance in nature. This can be done at the individual, community, national and global level.
Individual level: School and college students should take various initiatives to protect the natural ecosystems. They should participate and organize seminars, camps and conferences on various environment related issues. Their aim is to educate and inculcate environment friendly attitude in people of all professions. People should be made aware of the consequences of climate change and environmental degradation. They should be taught to economize the use of energy and bioresources .
Plant trees in the neighbourhood and nurture them well.
Install energy efficient lightening system. Replace incandescent bulbs by compact fluorescent bulbs. That last four times longer and use one- fourth of the electricity used by the former.
Turn off all lights, fans, televisions air conditioners, computers and other electrical gadgets when not in use.
Recycle all cans, bottles and plastic bags. Generate as little trash as possible. Trash in landfills emits large quantities of methane and when incinerated releases carbon dioxide.
Use of electrical gadgets like washing machines, dish washing machine and iron should be minimized.
Keep cars well tuned, get them serviced regularly. Try to pool cars. Use public transport as far as possible.
Use cycle or walk for short distance shopping and visits.
Community level: At community level the concept to protect environment is very old in India. It is observed in all the communities as most of them worship jal (water), vasu (air) and prithvi (earth) on auspicious occasions.
i) Sacred groves in India are the ancient natural sanctuaries where all forms of life are given natural protection by deity (saints or the tutelary who protect). These sacred groves are still found in Himachal Pradesh, Maharashtra and Meghalaya.
ii) Bishnois of Rajasthan are Hindus that believe in protecting all kind of animals and plants around them (especially khejri tree i.e. Prosopis cinera and black buck). They do not even cut tree until it dies its natural death and only then they use it.
iii) Van Gujjars are indigenous forest dwellers living at the foot hills of Himalayas. They live in full harmony with the natural ecosystem of forest. They lop off the branches of the trees below the nodal points only at the time when the trees are shedding their leaves so that the tree growth is not affected. Buffalo dung is used as a natural manure.
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iv) Chipko movement, name of the movement comes from a Hindi word meaning to
‘embrace’. The Mandal village women and local, Gram Swarajya Sangh (Dasoli) headed by Mr. Chandi Prasad Bhatt to protect Aaknanda valley from deforestation.
They formed a human chain around the trees, hugged the trees and prevented them from being felled in 1973. The success achieved by this act encouraged similar protest movements in other parts of the country to protect forests and other natural ecosystems.
v) Narmada Bachao Andolan was initiated by Ms Medha Patkar to stop the construction of dams on India’s largest westward flowing river Narmada. In 1992 she was given Goldman Environment Award for her dedicated effort to protect environment.
National level:
India is the seventh largest country of the world and second largest in Asia. It is the second most populous country of the world with more than a billion people. India is the first country to amend its constitution to give the state government the power to protect and improve their environment. This 42nd amendment was adopted in 1976 and came into effect in 1977. The department of environment was created in 1980 and it became the Ministry of Environment and Forests in 1985. There after various steps have been initiated for preservation, conservation and mitigation.
The Energy and Research Institute (TERI), Headed by Dr. R.K. Pachauri is playing a vital role in several environment related issues at students, community , national and international level. Dr. R.K. Pachauri is also the chairman of IPPC and has been awarded Nobel prize in 2007.
India has one of the largest renewable energy program in the world and has made progress in the field of wind, solar , geothermal and biomass energy. Use of solar cookers, solar heaters, lanterns are encouraged . At Solar Energy Centre, Department of non- conventional sources of energy, Gwalpahri several solar devices are being designed. In the rural areas (like Bakoli village) many families are supplied with improved biogas stoves, biogas plants and other cleaner sources of energy to reduce the emission of green house gases.
CNG (compressed natural gas) has replaced diesel and petroleum in many metro cities in public and private transport vehicles.
For the conservation of natural biodiversity, the government along with NGOs and universities has started establishing biodiversity restoration parks like Yammuna Biodiversity Park in Jagatpur near Wazirabad, Aravalli Biodiversity Park,Vasant Vihar in Delhi and Asola Bhatti Wild Life Sanctuary on the northern terminal of Aravalli hills near Gurgaon.
Asola- Batti wild life sanctuary is the only man made sanctuary which represents northern flat topped hill form of country’s oldest hill ranges – the Aravalli. This region is over exploited for the extraction of quartzite, Badarpur or “bajri” by the mining communities.
Yammuna biodiversity park project is initiated by joint collaboration of Delhi Development Authority and Centre for Environmental Management of Degraded Ecosystems in June 2002. It is an excellent example of planners working in tandem and close association with scientists. In the last four years it has shown a great progress in terms of improving the habitat for the growth of 20 different communities. 51000 trees have been planted. Many species of migratory birds which had reduced in number in India have started returning to this wetland.
Global level: Following conferences / and protocols are adopted at the international level to protect our environment.
1972: The Stockholm conference on Human Environment.
1988: The intergovernmental Panel on climate change (IPCC).
1990: IPCC released its first assessment report.
1922: UN framework convention on climate change (UNFCCC) was held at Rio de Janeiro.154 countries participated in this convention.
1994: The convention entered into force.
1995, COP 1 (Conference of parties) held at Berlin Germany, IPCC finalized its second assessment report.
1997, The Kyoto protocol was adopted at COP-3 in Japan.
2001, IPCC Finalized its third assessment report.
2005,UNFCCC, COP 11 \ MOP 1 (28 Nov. to 9 Dec.2005 ): Two meetings were held simultaneously - the eleventh conference of the 189 parties to the 1992, UNFCCC on climate change( COP 11) and the first meeting of 156 parties to the convention’s 1997 Kyoto protocol (MOP 1), which entered into force in February 2005. The important agenda was to make Kyoto protocol fully operational by 2008 and decisions were taken to strengthen the functioning of its innovative mechanisms. Another important issue was to develop global climate change policies beyond 2012, when the Kyoto emission targets expire.
2006, UNFCCC: United Nations Environment Programme conference (16 Nov. 2006 ): was held in Narobi to discuss the consequences of climate change on biodiversity and melting of Glacial.
2007, UNFCC COP 13 (3-14 December): Conference was held at Bali , hosted by Government of Indonesia.
India is a party to UNFCC and signed the multilateral treaty on June 10. 1992. Several
Ecoindustrial Revolution:
Ecoindustry or industrial ecology is to make industrial manufacturing processes more
sustainable by redesigning them to mimic how nature sustains them. The solution to many of above problems is ecoindustrial revolution which will take place in another 50 years. It will help to achieve industrial, economic and environmental sustainability. One way is by recycling or reutilizing most of the chemicals.
• Industries interact in complex resource exchange web where the waste of one manufacturer becomes the raw material for the other.
• Industry should be made far away from rural, urban or natural ecosystems . SUMMARY
1. Ecosystem is a interacting unit of abiotic and biotic components of the biosphere.
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2. Climatic regime, inorganic substances, organic compounds, producers, macroconsumers and microconsumers are the structural components of the ecosystem
3. Functional processes of the ecosystem are food chains, energy flow, nutrient cycles, ecological succession (ecosystem development) , and homeostasis.
4. All the abiotic factors such as light, temperature, pressure , humidity, salinity, topography and the availability of various nutrients limit the growth and distribution of animals and plants.
5. All the living organisms of an ecosystem are interdependent through food chains and food webs. Removal of any single species of the community results in ecological imbalance.
6. Source of energy for all the ecosystems is solar radiations which is absorbed by autotrophs and passed on to the heterotophs in the form of food (organic substances).
Energy flow is always down hill and unidirectional.
7. Gross primary productivity (GPP) is the total amount of solar energy captured and stored in the form of organic substances by the green plants. Net primary productivity (NPP) is the amount of organic substances left in the plant after its own metabolism i.e. GPP = NPP + plant respiration.
8. Trophic structure of the ecosystem can be represented graphically in the form of ecological pyramids the base of the pyramid represents the producers and successive tiers represent subsequent higher levels.
9. The nutrients move from the nonliving to the living and back to the nonliving component of the ecosystem in a more or less circular manner. These nutrient cycles are known as biogeochemical cycles.
10. The main components of all the biogeochemical cycles are:
a. the reservoir pool that contains the major bulk of the nutrients like soil or atmosphere
b. cycling pool which are the living organisms (producers , consumers and decomposers) , soil , water and air in which it stays temporarily for a short period.
11. Human modified ecosystems are created by man for his own benefits. They may or may not depend on solar energy and require fossil fuel or electrical energy generated by human.
All man made ecosystems have some advantages to the human beings but many disadvantages to the natural ecosystems and environment.
GLOSSARY
Community: It is an assemblage of species populations that occur together in the same place at the same time. Its characteristics are determined by the interactions among the individuals such as competition, predation, parasitism, energy flow and species diversity.
Food Chain: Transfer of food energy from the source in plants through a series of organisms with repeated eating and being eaten is called food chain.
Food Web: In a community food chains are interconnected and interlocked to form a food web.