HUMAN ACTIVITIES AND THEIR IMPACT ON ENVIRONMENT
For economic development and better living, man has sacrificed forest land for agriculture, industries, urbanization etc. This has brought in to trail environmental disaster and back fired on man himself endangering his existence on earth.
The dawn of human civilization can be traced back to the discovery of agriculture almost 10,000 years ago. In the early period, man used the primitive practice of slash and born cultivation or shifting cultivation, which is still prevalent in many tribal areas, as in North East in the hill regions.
The two modes of agriculture—traditional and modern—are described below along with their impacts.
(i) Traditional Agriculture and its Impact:
It involves small plots, simple tools, natural water, organic fertilizer and several crops. The yield is,
however, low but it is still used by about 50% of the world population. The impacts of this type of agriculture are as follows:
(a) Depletion of Nutrients:
During slash and burn of trees in forests, the organic matter in soil is destroyed and within a short period most of the nutrients are taken up by the crops. Thus the soil becomes deficient in nutrients and compels the cultivators to shift to another area.
Forest land is cleared by slash and burn of trees in forest for cultivation purposes. Frequent shifting of cultivation plots leads to deforestation i.e., loss of forest cover.
(c) Soil Erosion:
As a result of deforestation, soil gets exposed to the weathering forces i.e., rain, wind
and storms and is subjected to erosion. The net result is loss of top fertile soil.
(ii) Modern Agriculture and its Impact:
It is based on high input–high output technique using hybrid seeds of high-yielding variety and abundant irrigation water, fertilizers and pesticides. This is the basis of “Green Revolution” which boosted the production of wheat and India became self-sufficient in food. But the fallout from Green Revolution has become evident since the 90s (1990) as shown below:
(a) Impacts from HYV (High-Yielding Varieties):
Application of seeds of HYV gave rise to mono-culture i.e., the same species (genotype)
grown over vast areas, such monoculture is vulnerable to attack by some pathogen, which
spreads like wild fire, devastating crops over large areas.
(b) Fertilizer Problems:
Essential micro-nutrients nitrogen, phosphorus and potassium (NPK) are supplied by chemical fertilizers. Indiscriminate use of chemical fertilizers causes micro-nutrient imbalance in the soil which ultimately loses productivity.
(c) Nitrate Pollution:
From agricultural fields nitrogenous fertilizers leach into the soil and finally contaminate groundwater. When the nitrate level of groundwater exceeds 25 mg/l, they can cause a serious health hazard known as “Blue Baby Syndrome”, which affects mostly infants even leading to their death.
Agricultural run-off water contains fertilizer components, particularly nitrogen and phosphorus, which reaches nearby water bodies and causes their over nourishment. Excessive use of these fertilizers leads to overnourishment of the lakes/water bodies and gives rise to the phenomenon of eutrophication (eu = more, trophication= nutrition).
As a result, there is excessive growth of algal species, which is known as algal bloom. The water body or lake soon gets filled up with algal species which quickly complete their life cycle and die thus adding a lot of organic matter. Dissolved oxygen in the lake is consumed and fish get killed so that the lake becomes a dead pool of water devoid of plants and animals. Thus the lake ecosystem gets degraded due to eutrophication.
(e) Pesticide Side Effects:
Several thousand pesticides are used in agriculture for destroying pests and boosting crop production. In the early period of human civilization arsenic, sulphur, lead and mercury were used to kill pests. From 1940 synthetic organic pesticides have been used. Among these, DDT (dichlorodiphenyl trichloroethane), discovered by Paul Mueller (1939), deserves special mention. During 1940-1950, it saved 5 million lives from malaria, typhus etc. and also protected crops from huge losses. But DDT and other pesticides show a number of harmful side-effects on environment.
Inducing Pest Resistance and Yielding New Pests:
In course of time new generations of pests develop resistance to pesticides so that they survive even after pesticide spray. At present,about two dozen pest species are known to be immune to all types of pesticides.
Many pesticides including DDT are non-biodegradable so that they persist in the food chain. At each step of the food chain the pesticide level gets more and more concentrated. This is the process of biological magnification or amplification. Thus, DDT builds up from 0.04 ppm in plankton to 75 ppm in fish-eating birds. Man occupies a high trophic level in the food chain and hence gets a high dose of pesticide, which is quite harmful.
Excessive irrigation of croplands for good growth of crop leads to waterlogging. In the absence of adequate drainage, excess water is accumulated which seeps into the underlying water table. Pore spaces in the soil get fully drenched with water and soil air becomes deficient. The water table rises and the roots of plants have insufficient air for respiration. There is decline in crop yield with decrease in soil strength.
In addition to waterlogging, salinity also rises from excessive irrigation water. The latter contains dissolved salts which under dry conditions evaporates leaving behind salts in the upper soil profile. Saline soils are characterized by accumulation of soluble salts such as sodium chloride, sodium sulphate, calcium chloride, magnesium chloride etc. in the soil profile. Salinity causes stunted plant growth and reduces crop yield. Thousands of hectares of land in Punjab have been affected by soil salinity.
The best method for getting rid of salinity is to flush out by applying freshwater to such soils.
Industries produce environmental hazards everywhere. They consume 37 per cent of world’s energy and emit 50 per cent of world’s CO2, 90 per cent of SOx and almost all the chemicals now threatening O3 layer with depletion. Every year, they produce 2100 million tonnes of solid waste and 350 million tonnes of hazardous waste. In developing countries, small as well as big industries discharge untreated waste.
There is world-wide concern about the disposal of radioactive wastes from nuclear reactors. Nuclear reactor accidents are expected to increase over the years. The stock of nuclear power stations is also ageing. In developed countries, industries have enforced economy during the last two decades in the use of resources and energy consumption.
It is a common practice for these industries to recycle and reuse water. The average person in a developed country still consumes 15 times more energy than in a poor country. However, in a developed country energy is being used more efficiently and the expected rate of increase of energy
consumption is only 1.3 per cent per year.
Transport is a great consumer of land and energy. The length of motor ways has almost doubled in developed countries over the past two decades, reaching 1,500,00 km. in 1990. Transport consumes 30 per cent of world’s energy (of which 82 per cent is consumed on roads) and produces 60 per cent CO-emissions, 42 per cent of NOx and 40 percent of hydrocarbon emissions.
But there is a hope of new cleaner transport becoming popular in future. Almost one-third of Brazil’s cars run on pure ethanol, obtained from specially grown crops and many cars run on ethanol/petrol mixture. Natural gas is being used as a fuel in several countries including Italy where 3 lakh cars run on compressed natural gas (CNG).
Major efforts have been made in developed countries in reducing petrol consumption by 50 per cent of the amount used two decades ago. Auto-emissions have also been cleaned up. Use of lead-free petrol has curtailed Lead (Pb) emission by 87 per cent during 1980-1990.
Minerals find extensive use in domestic, agricultural, industrial and commercial sectors and thus form a very important part of any nation’s economy. Minerals are broadly of two types:
(a) Non-metallic minerals e.g., graphite, diamond, quartz, feldspar etc.
(b) Metallic minerals e.g., bauxite, laterite, hematite etc.
Since the early days of human civilization man has used metals extensively. That is why history labelled the eras as Bronze Age and Iron Age. The most abundantly used metals are Iron and Steel (Annual use 750 million tonnes) followed by Manganese, Copper, Chromium, Nickel and Aluminium. Mining and processing of minerals involve major environmental concerns including disturbance of land, air pollution from dust and smelter emissions and water pollution from disrupted aquifers.
Six major mines are known to cause severe environmental problems.
(a) Jadugoda Uranium Mine, Jharkhand: Exposing local area and the population to radioactive hazards.
(b) Jharia Coal Mines, Jharkhand: Underground fire causing land subsidence and displacement of people.
(c) Sukinder Chromite Mine, Orissa: Seeping of hexavalent chromium into river posing serious health
hazard. Chromium Cr+6 (hexavalent) is highly toxic.
(d) Kudremukh Iron Ore Mine, Karnataka: Causing river pollution and threat to biodiversity.
(e) East-Coast Bauxite Mine, Orissa: Land encroachment and rehabilitation issue.
(f) North-Eastern Coal Fields, Assam: Very high sulphur contamination of groundwater.
Impacts of Mining:
Mining involves extraction of minerals/fossil fuels from deep deposits in soil employing the techniques of sub-surface mining or surface mining. The former method is more dangerous and expensive including risks and accidents. The environmental damages are described
(a) Devegetation and Defacing of Landscape:
Large-scale devegetation or deforestation leads to ecological imbalances besides disfiguring the landscape. The huge debris and tailings spoil the environment of the region and make it vulnerable to soil erosion.
(b) Subsidence of Land:
Underground mining (e.g., coal) causes subsidence of the soil above resulting in tilting of buildings, cracks in soil/road, bending of rail tracks etc.
(c) Groundwater Contamination:
Mining disturbs the hydrological processes and also pollutes the ground water. Sulphur impurity in many areas gets converted into sulfuric acid through microbial action, which makes the water acidic. The acid mine drainage often contaminates the nearby streams and lakes and damages aquatic life
(plants and fish).
(d) Air Pollution:
Smelters in metal extraction processes in metallurgical industries emit huge volumes of air pollutants—sulphur oxides, soot, arsenic, lead, cadmium particles etc. These have public health hazards for local residents.
(e) Occupational Health Hazards:
Most of the miners suffer from various respiratory and skin diseases due to constant exposure to the suspended particulate matter and toxic substances. Such diseases include asthma, bronchitis, black-lung disease, asbestosis, silicosis etc.
As per the definition of the then director of World Health Organization (WHO), Prime Minister G.H. Bruntland (Norway), sustainable development means “meeting the needs of the present without compromising the ability of future generations to meet their needs”! Nowadays sustainable
development is the keynote of many projects but only few of them achieve sustainable growth.
The important components of sustainable development are:
• Population stabilization (growth below 0.5 per cent)
• Integrated land-use planning
• Conservation of biodiversity
• Air and water pollution control
• Renewable energy resources
• Recycling of wastes and residues
• Environmental education and awareness at all levels.
- Give a short account of the impacts of agriculture on environment.
- What is meant by
(c) Salinity of soil?
- Enumerate the impacts of mining.
- What is the significance of sustainable development? What are its main components?