It is mainly the solar energy which gives rise to most of our renewable resources. Solar energy heats earth's surface and evaporates water which condenses and comes down to earth as rain, dew or snow. Green plants trap this energy during photosynthesis.
All worlds use this energy. Green plants, therefore, constitute a biotic system which supplies a constant source of energy to the biosphere including man. The productivity of this system is, however, limited by availability of water, nutrients or the chemical building blocks and conditions of the environment. For sustainable development we have to ensure proper functioning of this system and for future needs we have to strengthen and widen this vital resource base. Sustainable management of our renewable resources involves:
1. Avoiding over-exploitation and pollution of biotic systems:
There is a limit upto which natural systems can provide resources to mankind. Withdrawl beyond this limit tends to damage the productivity of the system. So also is the stress caused by unhealthy conditions like pollution, temperature changes etc. which impair the proper functioning and thereby the productivity of the system. Modern practice of intensive agriculture tends to over-exploit the system.
High yielding varieties, large amounts of fertilizers and energy inputs, pesticides etc. depress microbial life which is the basis of regenerative capacity of our soils. These results in loss of soil's capacity to retain water recycle nutrients and desertification follows.
Over-exploitation of aquatic systems leaves little from which fresh stocks can be built up for the next harvest. Too much extraction of timber and fuel wood from a forest damages its regenerative capacity causing the system to turn into unproductive wasteland. For management of natural systems on a sustainable basis it is essential that we extract only that much which its productivity permits.
Both the affluence of developed countries as well as abstract poverty in under-developed countries is detrimental to the productivity of biotic systems. The root cause of environmental damage lies in want and misery of masses which inhabit developing countries of the world. We cannot expect much from people whose main concern for a day's grueling labour is just to earn enough to feed himself and his family.
They are forced to till any land, cut down any tree and poach any animal if it fetches something to satisfy their necessities, regardless of long term consequences. As long as gross injustices in the distribution of resources prevail and there is a wide gap between the standards of life in developed and developing countries of the world environmental issues shall continue to be ignored. While a little restrain is required on over indulgence and consumption of resources in developed countries, proper environment-friendly development is necessary for the developing countries of the world.
This alone can halt environmental degradation and create the capacity to face and solve environmental problems. United Nations system and many international agencies have realized the importance of economic development in under-developed countries of the world and are now directing their attention to the problem.
2. Strengthening the resource base and augmenting regenerability of biotic systems:
So far man has endeavoured to manage the biotic systems in such a way as to produce maximum yield in the process of which health and self-regeneration capacity of the system is ignored. The system is weakened - its biotic component degenerate and degradation follows. Successive harvests are reduced or require more and more material and energy input for sustained productivity. The system is made unsustainable as in the absence of these inputs it could collapse. The objectives of the / management of the biotic systems should change now. While High Yield is very much desired, it should not be at the cost of regenerability or health of the system. The three important sectors which feed the mankind are:
1. Agricultural sector.
2. Live-stock and fisheries.
3. Forest and wild life.
Agro-ecosystems which man sets up have to be provided fresh-water nutrients or fertilizers, chemicals to suppress insects and pests and suitable hybrid varieties. The heavy reliance of modern agriculture on material and energy inputs makes it unsustainable.
The supplies of freshwater are limited. About 1,13,500 cubic kms of freshwater is received by land surface through precipitation out of which about 72,500 cubic kms is lost through evapo- transpiration. The net gain of freshwater on land surface annually is about 41,000 cubic kms which trickles down and flows back to the sea.
This is the total amount of water which mankind can use without causing any adverse impact on ecology and environment. Of this 41,000 cubic kms, 27,000 cubic kms. is lost as flood flow and about 5,000 cubic kms is in inhabitable area where it is of little use to the mankind. The remaining 9,000 cubic kms is the total amount which serves the mankind. According to an earlier estimate, we shall need about 11,250 cubic kms of freshwater by the year 2000 A.D. which is more than the actual supplies.
Naturally the excess demand shall be met either by recycling and re-use or by heavy over-drafts on ground water deposits which could be ecologically detrimental to the locality. Much of the surface flow available to the mankind is, however, grossly polluted which further aggravates the problem. Naturally the management of water resources today involves:
1. Promote economic use of freshwater and its recycling and re-use.
2. Reduce pollution of surface water by treatment and control of sewage and industrial effluents.
Augment ground water supplies by proper land use planning and reforestation to recharge the ground water table.
Raise the surface water storage capacity and hence utilize some of the 27,000 cubic kms of water which flows quickly down to sea as flood flow.
Supplies of fertilizers and chemicals on which modern agriculture relies heavily are also not going to last forever. Both fertilizers and pesticides are neither cheap nor their frequent use healthy for soil fertility. Even today many of the farmers in developing countries are unable to afford fertilizers and pesticides even though their governments provide generous subsidies.
So also is the energy required for agricultural purposes which is largely met with fossil fuels - oil or natural gas - which is neither going to last forever nor is cheap. With widespread loss of genetic resources it may also be difficult to arrange for hybrid varieties suitable for agroclimatic conditions of times to come.
The best strategy for sustainable management of agro-ecosystems appears to be the promotion of a healthy microbial community which augments nutrient regeneration capacity, water holding potential and porocity of soils. This can be done by avoiding chemical stresses caused by pollution of soils and providing adequate amounts of organic matter which serves as a food for microbial life.
Crop rotation and infusion of diversity in our agro-ecosystems is another promising method of ensuring sustainable agriculture. For reducing damages caused by insects and pests there are a number of alternatives available which are friendly to the environment. No doubt this may cause a reduced productivity and call for a better and deeper understanding of environment friendly technology. However, for sustained productivity we shall have to be content with whatever we get from such systems.
Live-stock and fisheries provide to the mankind rich high quality proteins. Since times immemorial both live-stock and fisheries have been an important subsediaries of agricultural activity. Today, however, these have acquired an industry like dimensions which is in fact a drain on the limited resources of mankind. A heavy demand of energy and material resources is imposed by animal husbandry.
Instead of utilizing waste organic matter and left over biomass from agricultural fields, large livestock populations are maintained on carefully measured diets grown on about 55 million hectares of productive land all over the world. More than 38% of the total global grain production is fed to livestock population while 12 out of every 100 people in the world go hungry.
The faecal matter and excreta produced by these animals create problems of waste disposal. The large herd of animals, thus, maintained give rise to problems of over-grazing which is a major threat to forests in a number of developing countries of the world.
A diet rich in animal proteins is neither healthy for man nor it is a wise development strategy. Meat, eggs, fishes etc. come from secondary trophic levels whereas grains, vegetables, fruits and nuts come from primary trophic levels. Transfer of energy from primary trophic level to secondary one involves a loss of about 88-90% - to produce 100 gms of animal biomass about 1000 gms of plant biomass is needed. This makes using organic matter at primary trophic level more economical than converting it to animal biomass and then using it as food.
For sustainable management of our livestock population we should adopt our traditional ways which served as means to convert useless organic matter left after the removal of grains from crop plants into a source of useful material and energy. The livestock raised on waste organic matter also serve the man to produce milk, meat, eggs, hide, woollens, and manures and is a source of cheap labour. The livestock and poultry should be maintained as a useful nutrient loop between agricultural crop and man.
World Fisheries constitute a very important supplement to human food supplies. However, full potential of world fisheries has not been utilized so far. Water subjected to regular fishing operations are over-exploited while many productive areas are ignored for want of proper means, disputed jurisdictions or such political reasons. It is mainly the pollution of natural waters and over-fishing which is responsible for increasingly lower harvest from our aquatic systems.
Aqua-culture, which is a promising method of supplementing world's food supplies in developing countries, is also hampered by lack of resources and technical know-how. To put world's fishing industry on a sustainable footing it is necessary that we check pollution of aquatic systems, avoid concentrated fishing and over-exploitation, develop versatile, effective and mobile fishing machinary to cover as much productive areas as possible and develop aquaculture as a productive enterprise.
Forests and wild life provide a variety of useful products to the mankind. For thousands of people living in world's developing countries resources of local forest and wild life products constitute an important source of livelihood. In addition to this forests are helpful in checking erosion and degradation of soils, in shaping natural environment and local climatic conditions by maintaining humidity, regulating temperatures impeding wind velocity and influencing precipitation. With destruction of forests natural habitats for wild life are lost. The enormous capacity of forest soils and vegetation to absorb, transform and accumulate various pollutants of the environment, which we drastically need today, is lost. Deforestation, therefore, seriously affects our capacity to maintain viable biotic systems which are essential for the mankind. For sustainable society, we have no other option but to maintain healthy forests and wild life for which efforts being undertaken today involve:
i. Prevent deforestation by controlling unregulated expansion of agriculture and cattle ranching at the expense of forests, unregulating grazing, destruction of green cover and unregulated fuel wood collection and timber harvesting.
ii. Extend our forest wealth by planting carefully selected species suited to the local conditions on land which have lost their plant cover. This will widen the resource base and provide additional habitats for wild life.
3. The use of alternative food sources:
In pre-historic times man used about 5,000 species and varieties of edible plants. Today about a dozen of species only provide 90% of the world food supplies and only 150 species of plants are cultivated on large scale. There are thousands of species of plants with edible parts which can serve as a food source for the mankind.
There are many species of birds, fishes and mammals which can serve the mankind as a source of food. The cultivation of many of these species is simple and productivity higher. With a little change in our food habits and a little adjustment these species may also be used to supplement the human food. This will widen our resource base and add sustainability to supplies by reducing the dependence on a few species.