Sunday, August 08, 2010
Monoculture and Agro-chemicals: impacts on natural environment
Dr. M. P. Mishra Sunday, August 08, 2010 ECOSENSORIUM KNOWHOW
The practice of producing or growing one single crop over a wide area, again and again, is called as monoculture. There may be two distinct definitions of monoculture: Vegetation composed of a single species and, Field composed of a single crop rather than multiple crop species. During the days of green revolution, farmers had to practice monoculture due to its beneficial effects like –
1. Reduced plant competition for nutrients, space and solar radiation,
2. Control of undesirable or unprofitable organisms,
3. Reduction of costs by limitation of specialized machinery required for arable operations,
4. Maximise profit from the growing of high gross margin crops.
In spite of above benefits, monoculture has many adverse impacts on agriculture as well as on environment on the whole. Some of these impacts are mentioned below-
1. In monoculture, a vast area is cleared to convert it into a big farm. For this, all the trees and bushes are to be cleared without leaving any obstruction in between. This exposes the soil to the battering action of rain, wind and water current. Extensive soil erosion follows in such an area. We have been losing about 7 million hectares of useful cropland every year due to soil erosion as per the reports of the U N and FAO (1980).
2. The monoculture provides ideal conditions for development of a vast variety of insect pests and diseases. More and more pesticides are needed for their control and eradication. Thus a lot of money is wasted in purchasing synthetic pesticides.
3. High yielding crop varieties drive away a number of indigenous crop varieties. For example, there were about 40,000 indigenous varieties of rice before the green revolution. But, due to monoculture, most of these indigenous varieties have disappeared and only 50 of these have remained in Indian fields by now. Thus this method of agriculture wiped away most of our indigenous genetic resources.
4. Most of the oil seeds and pulses have been neglected through monoculture as only wheat, rice and maize occupied major areas of farmlands. These crops make the soil fertile by enriching it with nitrogen. As such farmers have to purchase more and more nitrogenous fertilizers from the markets. This results into a pressure o he national economy.
5. The cultivation of only dwarf varieties of wheat and rice created the problems of straw fodder. Thus farmers have to invest more money in making arrangements of feed for cattle.
6. Little fallow periods are to be left in between two crops. So it does not consume much time to recoup the lost fertility. So, more and more fertilizers have to be added, with each group. But gradually, the organic matter appears and soil is converted into a heap of sand silt and clay, mostly deficient in nutrients.
Agrochemicals and environment
Synthetic chemical fertilizers and natural environment
· Synthetic Fertilizers alter the composition of soil and make it infertile.
· Synthetic fertilizers cause eutrophication when they join the waters of water bodies after being washed away during rains.
· These fertilizers accumulate in fruits, grains and seeds; and affect the community health.
· Excessive use of synthetic fertilizers makes plants susceptible to damage from wind and diseases.
Poor farmers cannot afford purchasing costly agrochemicals while rich farmers enhance their agricultural production by proper and timely application of these chemicals in their crops. Many poor farmers become labourers after leaving agricultural works.
Pesticides and natural environment
The High Yielding Varieties of Crops remain vulnerable to a variety of pests and diseases due to their poor resistance. So a variety of pesticides are needed to be used to prevent and care the infestation or the outbreak of pests. However after some time, the pests develop resistance to pesticides due to which the intensity and frequency of pesticides have to be increased every time. This results to the investment of good sum of money, which can be afforded by rich farmers only. Thus green revolution has been favouring the growth and prosperity for rich farmers only.
Over 90 percent of the sprayed pesticides reach a destination other than their target species, including undesired species of plants and animals, air, water, bottom sediments, and food. In many ecosystems it has been found that pesticides kill both the pests and natural predators. This condition creates secondary outbreak of pests which usually remains most damaging.
Pesticides, after they join the food chain and travel to the top consumer cause serious biomagnification. They get deposited in the fatty tissues of animals and human beings where their potency goes on increasing. Severe cases of renal failure, brain damage, blindness and impotency have been reported due to biomagnification of pesticides. Even the smallest quantity of these chemicals can cause long term and widespread impacts as they are in the food chain connected to a vast variety of birds and amphibians.
Here are some examples of how some pesticides are harmful to the biotic components of the environment –
1. Pesticides, when sprayed, or dusted on crop plants or garden plants, they cause adverse impacts on honey bees, other pollinators, parasites and predators. Continuous use of pesticides leads to development of pesticide-resistance in different pests. This adversely affects the non-target organism that is the organisms that the pesticide is not meant for.
, Malathion, Chloropyriphos, and many others are highly poisonous to aquatic organisms like amphibians and fish, and also to some terrestrial animals like birds, bees and wildlife. These pesticides cause acute toxicity to liver and kidney, heart, blood, lungs and skin. Linden
3. Aldrin, Di aldrin, Endrine etc. are a group of highly toxic chemical pesticides that join the food chain and cause serious ailments in the bodies of consumers. Some of the minor troubles caused by traces of these pesticides are –loss of memory, mental retardation, loss of weight, and impotency.
The Chlorinated Hydrocarbons are other group of pesticides that are deposited in the fatty (Adipose) tissues of animals where they are magnified gradually, and cause serious conditions in the later course.
Phytohormones and environment
Plant hormones sprayed on plant parts or mixed in soil, are easily absorbed by producers. Then they move through entire biosphere by way of food chains and create chemical imbalance in the bodies of consumers.
Image 1 Monoculture of garlic