Major Environmental Problems of Lithosphere

This subdivision of the biosphere plays two vital roles in metabolism.

First, it is the only source of most mineral metabolites for all the organisms, terrestrial as well as aquatic; and second, it forms the bulk component of soil (pedosphere), required particularly by the terrestrial plants.

Soil is formed from disintegration of rocks by the action of running water and weathering. Living organisms also contribute to soil formation. Their decay produces organic fractions of soil, collectively called humus. Humus mixed with sand and clay constitutes the soil. Soil is affected by climate (temperature and rainfall), vegetation and human activities.

Major Environmental Problems of Lithosphere:

Major environmental problems of lithosphere may be as follows:

(1) Soil degradation, erosion and pollution,

(2) Deforestation,

(3) Landslides and earthquakes, and

(4) Loss of agricultural land for nonagricultural purposes.

1. Soil Degradation:

It has been reported from many parts of the country that agricultural intensification, faulty irrigation techniques, deforestation and excessive use of pesticides and herbicides have lead to widespread soil degradation. According to one estimate, about 300 million ha of land is now highly degraded and about 1.2 billion ha or 10% of the earth’s vegetated surface is described as moderately degraded. In India, the worst examples of soil degradation have been observed in Gujarat, Rajasthan and Bihar.

The desertification of soil in Rajasthan is attributed to deforestation and cattle grazing. Agricultural land is also highly susceptible to degradation in arid and semiarid regions. Both overgrazing and excessive cultivation expose the soil directly to erosion by the wind.

In the process of desertization, arid and semiarid land that has supported subsistence or nomadic agriculture gives way to desert. The process may be slowed by irrigating the land, which gives a temporary remission but lowers the water table, and salts accumulate in the topsoil (salinization). Once salts have started to accumulate, the process of salinization tends to spread and leads to sterile white salt deserts. This has been observed in many areas of India and Pakistan.

However, the degradation of soil by intensive agriculture can be prevented or slowed by:

(a) Returning the land to grazed pasture or rangeland;

(b) Use of farmyard manure, crop residues and animal wastes and

(c) Alternating years under cultivation with years of fallow.

2. Soil Erosion:

Soil erosion is a process in which useful land is washed off through excessive rains and soil runoff. The Rio conference, 1992 also adopted Agenda 21 for soil conservation and recommended measures, now coordinated by the United Nations Commission on Sustainable Development, to prevent soil erosion, in particular minimizing soil runoff and sedimentation. The main factors or forces responsible for removal or displacement of soil from one place to another are water and wind.

Water erodes and removes soil mainly in the following four ways:

(i) Sheet Erosion:

The soil is removed in small but uniform amounts from all over and therefore does not leave a mark behind. The evidence of this type of erosion can be seen in the heavy quantity of silt that is deposited elsewhere.

(ii) Rill Erosion:

The runoff water moves rapidly and cuts several stream-like structures. As the water moves very rapidly, its cutting effect is quite visible.

(iii) Gully Erosion:

In this process, several rills converge towards the steep slopes and join to form broad channels of water called gullies. When rills and gullies are formed in abundance, ploughing becomes impossible due to uneven topography and cultivation of crops cannot be done.

(iv) Riparian Erosion:

It takes place on the banks of fast running rivers. The fast flowing waters cut the margin of the bank laterally. Once much of the soil from beneath is cut away, the top soil of the river banks tumbles down into the water with big splash.

Soil Erosion Due To Wind:

During some parts of the year soil erosion due to wind is very common. In a dust storm, huge quantity of dust is raised high and transported to great distances. The wind lifts finer particles high up whereas the large particles roll along the surface. The rolling particles rub the ground and due to abrasive action help in loosening the soil. The process continues and more dust particles gather as the storm advances with speed.

Measures to check Soil Erosion:

The principal methods to check soil erosion aim at reducing the physical and biological forces that cause erosion and protecting the soil by plant cover. However, the plant cover should be such as to yield food, fodder and other resources. A cost-effective technology used in reducing soil erosion is contour – based cultivation (contour-farming). In India, contour ditches have helped to increase four times the survival chances of tree seeding. Deeply rooted, hedge-forming vetiver grass, planted in contour strips across hill slopes, slows down water runoff efficiently, reduces erosion, and increases moisture content for crop growth.

Therefore, currently 90 per cent of soil conservation efforts in our country are based on such biological systems. Ramakrishnan (2001) stated that in the north-eastern parts of India shifting agriculture (Jhum) helps in sustainable production as the soil fertility is recovered during its vegetational fallow phase.

Simple technology involving rock embankments (bunds) constructed along contour lines for water and soil conservation greatly succeeded. Such bunded fields yield average of 10 per cent more than traditional fields in a normal year and almost 50 per cent more in dry years (UN, 1998). Such terracing provides a very high quality of soil conservation, but is possible at a place where labour is cheap.

Contour farming is recommended on lands with gentle slopes. But on somewhat greater slopes, strip cropping is done where strips of land are ploughed at right angles of the direction of the slope and different crops are raised in adjacent strips. On less steep slopes, by ploughing and cultivating in strips along the contour, soil runoff can be reduced significantly. Singh, Misra and Ambasht (1980) have shown that plants play a very significant role in soil conservation. They have quantified their soil binding efficiency, which was regarded above 95 per cent for dominant grasses.

Plant cover is also the most efficient method for checking soil erosion due to wind. Tree plantations in short blocks are called wind breaks. Extensive tree plantations are called shelter belts. These are planted in rows at right angles to the direction of the wind.

The wind breaks and shelter belts reduce the wind velocity on wind-ward side up to about the distance equivalent to 5 times the height of trees and on lee-ward side to about 30 times the tree height (Ambasht, 1990). It may be concluded that proper soil conservation strategy may help not only in achieving sustainable agriculture but also in checking soil degradation and erosion.

3. Soil Pollution:

Almost all the sources that pollute inland water bodies also pollute agricultural land and other soils.

These are:

(a) Sewage And Domestic Wastes:

In villages, only few houses have septic tanks for treatment of sewage and domestic wastes. Many people go to open fields for easing out; such faecal matter of human origin pollutes both soil and air.

(b) Industrial Wastes and Effluents:

Industrial wastes and effluents that are discharged to some water bodies also pollute the adjoining lands. The toxicity of these industrial pollutants to crop plants and soil organisms is variable but all of them contaminate the soil environment.

(c) Pesticides:

Pesticides are synthetic chemicals used for pest control. They are classified as insecticides (organochlorines such as DDT, organophosphates such as Malathion and Carbamates such as Carbary1), (Fig. 6.5), rodenticeds (such as Sodium fluoroacetate), molluscicides (such as Sodium pentachlorophenate), and piscicides (such as Toxaphene). Besides pesticides, a variety of other synthetic chemicals called fungicides (such as Phenylmercury, Carboxin,) and herbicides (such as Paraquat, 2, 4-D) (Fig. 6.6) are also used in modem agriculture for killing fungi and herbs and weeds respectively.

Pesticides may also be grouped on the basis of their mode of action as fumigants, contact poisons, repellents, systemic poisons and growth regulators. Of all the insecticides, the mode of action of organophosphoras compounds is better known. They function by blocking acetylcholine – esterase. They effectively poison the enzyme by phosphorylation and thus block hydrolysis of acetylcholine into choline. The inhibition results in accumulation of acetylcholine at the postsynaptic membrane, which is then unable to return to its original state and takes some time to regain its activity.

Pesticides reach soil through spraying, runoff, rain, atmospheric fall out, and industrial effluents. Pesticides used on the crops or agricultural land may reach the aquatic systems and also the atmosphere. The biogeochemical cycle of a pesticide (Fig. 6.7) shows that after entering the environment, a pesticide cycles like a mobile substance. The hazards of pesticide pollution are alarming since many pesticides are highly persistent. They remain in the environment through bio-concentration and bio-magnifications (Flint and Van den Bosch, 1981) However, the use of synthetic pesticides and fertilizers is a necessary evil of modem agriculture.

Effects of pesticides on the living forms are too many. Though pesticides have made enormous contribution to the green revolution and economic development, their indiscriminate and widespread use has caused several life threatening health hazards to humans and other animals.

Their use is directed against economic pests, but they also affect a wide range of non-target organisms, including desirable animals and plants. The chlorinated hydrocarbons may reach such high levels in animals at the summit of the aquatic food web that they are unable to reproduce or they may be poisoned outright. Many pesticides affect the reproduction of fish-eating birds and other higher animals DDT affects the steroid sex hormones in birds.

The herbicides 2,4-D and 2,4,5-T at relatively high doses lower reproductive activity in chickens. Pesticides can change the growth rate and also produce some behavioural changes in non-target organisms. The most widely known harmful effect of broad spectrum pesticides is that their use may not kill only the target insects, but also the predatory forms that may have been keeping the pest species at reasonably low levels.

In this way, new man-made pests are created. Another negative aspect of pesticide use is that repeated applications of a given pesticide may result in the development of resistant strains of target pests. The development of such genetic resistance in pest populations is well-known. It is documented that by 1980s more than 60 species of malaria mosquitoes had developed resistance to DDT. There are examples of multiple – pesticide failure in some cases of mosquito pest.

Instances of direct killing of humans through consumption of heavy doses of pesticides such as DDT, Gamaxine or other poisonous chemicals used in the manufacturing of pesticides are not uncommon. The memory of the so-called ‘Bhopal Tragedy’ is still fresh. The leakage of methyl isocynate (MIC) from the Union Carbide Factory, Bhopal in 1984 caused over 2500 deaths and other ailments in thousands of people. MIC is an intermediate chemical used in the production of carbamate pesticides such as Carbary1 and Aldicrab. Many cases of pesticide poisioning do occur almost every day in the country and many such cases go unreported.

More than 5 million of deadly pesticides, most of which already banned in Europe and USA, are used by farmers in Asia. These are believed to cause an estimated one million deaths yearly, especially among pesticide handlers (FAO,1995). In India, several women who experienced still births were found to have high levels of pesticides such as aldrin and DDT in their maternal blood and umbilical cords.

The observed DDT residues in the fat of Indian population are very high, ranging from 12.5 ppm for Gujarat to about 30.0 ppm for Delhi. High infant mortalities have been reported from places where high residues of DDT were found in human milk. A study from Punjab revealed high levels of DDT and BHC in breast milk samples.

A recent study conducted by Greenpace International has reported on health-effects of chlorinated pesticides such as DDT, BHC and Endosulphan. Indian men exposed to these pesticides while working in cotton fields were found to have decreased fertility. Accumulation of these pesticides in vital organs such as liver, kidney, gonads, lungs, adrenal glands, and blood causes histopathological changes and carcinogenic, mutagenic and teratogenic effects.

However, the management of pesticide risks in non-human species is even less studied excepting in veterinary medicine. In pesticide threatened ecosystems, its reversal and subsequent rehabilitation needs a better understanding of pesticide risk management. The same applies to environmental friendly disposal of pesticides including land fill and incineration (Misra et al, 1998).

4. Forest and Related Problems:

During past 50 years forests have suffered serious depletion. At present forests constitute only 19.4% of the total geographic area of the country as against the target of 60% as laid down by the National Forest Policy 1952 (revised in 1988).

The preamble of National Forest policy (NFP), 1988 says that forest depletion is attributable to relentless pressures arising from ever-increasing demand for fuel-wood, fodder and timber, inadequacy of protection measures, diversion of forest lands to non- forest uses without ensuring compensatory afforestation and the tendency to consider forests as revenue earning resource. Therefore, NFP 1988 has suggested a new strategy of forest conservation.

According to the State of Forest Report, 1999, the forest cover of the country has been estimated to be 631,291) sq km, which is 19.39% of the geographic area of the country. The dense forest, open forest and mangrove constitute 11.48%, 7.76% and 0.15% of geographic area respectively. Scrub and non-forest are the other classes in the scheme of classification (Table 6.3). Between 1997 and 1999 the net increase in the forest cover of the country was 3,896 sq.km. The dense forest has increased by 10,098 sq km and mangrove by 44 sq km, whereas open forest has decreased by 6,246 sq.km. (Table 6.4).

The recorded forest area of the country, as reported by the State Forest Departments, is 7652 million ha, which constitutes 23.28% of the total geographical area of the country. This area has been classified into Reserved, Protected and Un-classed forests, which constitute 54.44%, 29.18% and 16.38% of the forest area, respectively.

Protected Areas:

For in situ Conservation of bio-diversity of the country, 87 National Parks and 485 Wildlife Sanctuaries have been created so far. They cover a total area of 4.06 million ha and 11.54 million ha, respectively. These together constitute 15.60 million ha and form 4.75% of the geographic area of the country and referred as Protected Areas (PA). However, the protected area network at present is unevenly distributed over State-‘ and Biogeographic Regions.

Some of the PAs are too small to maintain viable populations of wildlife, while majority have not been integrated through forested corridors to maintain genetic continuity. The Project Tiger, a pioneering effort to protect one of the most important animal species of the country, was lunched in 1973. At present, there are 23 Tiger Reserves spread over 3.30 million ha. The areas of these reserves overlap National Parks/ Wildlife Sanctuaries and are included in the Protected Areas Network. India now has the largest tiger population in the world.

Biosphere Reserves:

Biosphere reserves, a concept originated in 1974, are a set of unique ecosystems identified on the basis of their bio-diversity, naturalness and effectiveness as a conservation unit. There are 13 Biosphere Reserves (Table 6.5) with a geographical area of 52459.61 sq km. A large part of this area spreads even beyond protected areas and they are distinct geographic entities. Six internally important wetlands of India have been declared as “Ramsar Sites” under Ramsar Convention (1971).

These are Keoladeo National Park (Rajasthan), Lake Chilika (Orissa), Lake Sambhar (Rajasthan), Lake Loktak (Manipur), Lake Harika (Punjab) and Lake Wular (J & K). For intensive conservation and management eleven more wetlands have been identified in the country. Wetlands are increasingly threatened by anthropogenic activities. Ramsar Convention promotes the concept of “wise use”, which refers to “sustainable utilization for the benefit of humankind in a way compatible with the maintenance of the natural properties of the ecosystem”.

The Ministry of Environment and Forests, the nodal agency for wetland conservation in India, constituted in 1993, a National Wetland Committee (National Committee for Wetlands, Mangroves and Coral Reefs, since 1992), which advises the Government on research, conservation and management of wetlands in the country.

Deforestation:

Deforestation means felling of tress or cutting of forests without regard to their vital role in the life support system and ecological balance and environmental stability. Deforestation is a worldwide phenomenon. Forest losses may be attributed to ever-increasing demand for timber, fuel-wood and fodder and pressures on forest land for creating space for agriculture and industries.

Forest areas in the proximity of the villages are reported to be degrading faster due to collection of fuel wood and cattle grazing as compared to forests located in inaccessible areas. For centuries, forests have been looked upon as revenue earning resource and this concept has promoted deforestations all over the world.