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Vol. 17 No. 3 - July 2011

Sustainable Carrying Capacity Without Inputs of Fossil Energy
and Minimal Adverse Environmental Impact

By: C.R. Bhatia*

Ecologists define carrying capacity as the maximum number of individuals that an area can support without detrimental effects on the environment – soil, water, air and the life forms.  In natural as well as agro-ecosystems, humans and animals are dependent on the primary productivity in the area. The latter utilize the free resources of CO2 and sunlight to convert into chemical bond energy in the form of carbohydrates, proteins and lipids that are utilized as food by humans and animals. Plants from the forests also provide firewood, the traditional source of energy for heating, and timber for housing.  However, to utilize the two free resources, land area, water, plant nutrients and growth periods with moderate temperatures suitable for plant growth are essential. Before the start of agriculture some ten thousand years back, humans subsisted as hunter and gatherer of food.  Their numbers were small and the primary productivity of the plants in nature was adequate to meet the modest demands of a small population. 

Change, however, is part of the evolutionary processes.  The first major change started some ten thousand years back when the humans discovered that the grains they have been collecting from natural growth of cereals like barley, wheat and rice can be grown in their own backyards.  This was the beginning of agriculture. It led to a major change in life style from food gathering to growing food. Human settlements, domestication of animals and growth of civilization followed.  Since then, humans have been striving to increase the productivity of the cultivated plants to harvest more and more.  Earlier, they moved to virgin lands, kept their fields’ fallow for few years, initiated crop rotations with leguminous crops to improve soil fertility and crop productivity.  Later they started using animal dung, garbage, fish meal, bones, saltpeter (sodium and potassium nitrates) to increase the harvest.

The second breakthrough came with the development of chemical processes for the production of synthetic ammonia utilizing abundant nitrogen in the air. The application of synthetic fertilizers, along with mechanization of farm operations, and genetic enhancement of plants increased crop productivity several fold.  The common denominator was the increased inputs of fossil fuels in farm operations and production of fertilizers. All this happened in just about 200 years, starting with the industrial revolution in the nineteenth century, first in the agricultural production systems of the developed regions and later in the developing countries.

Industrialization, increased food production, control of infectious diseases and other factors contributed to increased population growth rate.  The World population that was 1.55 billion in 1900 reached 6.22 billion in the year 2000 and is expected to reach 7 billion in October 2011. The projections for 2050 are 9 billion.  Addition of another billion, from 6 to 7 has taken only 12 years.  That the world is able to currently feed 7 billion people is a great achievement which goes against the arguments of Malthus, who in 1798, said that population will grow geometrically while the production will increase in arithmetic proportion. Technology and energy inputs made this possible. However, currently annual population growth rates in many regions including India are higher that productivity growth rates.

The first oil crisis of 1970s initiated analyses of the energy input / output into all human activities including the food production, transport and utilization. It emerged that the spectacular increases in crop productivity have been achieved by large fossil energy inputs in the form of fertilizers, fuel and power.  There have been no gains in net energy return, estimated as the ratio of energy input and output. The high quality energy of fossil fuels enhanced the harvest of solar energy.  In simple words, crop plants converted fossil fuels into food. 

As the input intensive, green revolution technology that contributed to self sufficiency in food production in high population growth areas like India, the adverse environmental effects such as, increase in nitrate content in water bodies, decline in water table and pesticide residues became apparent in many parts.

The environmental impact of the human activities is well expressed by the formula given by Ehrlich and Holdren1.

I = P x A x T


I = Impact on the environment,

P = Population,

A = Affluence of the population,

T = Technology factor (the available technologies for food production and other human activities).

The environmental impact involves complex interactions between P - the population numbers and consumption of natural resources including food (quantity and quality) dependent on the affluence of the population.  Technologies used for food production as well as all other human activities and their energy use efficiency make an important component of T.

It is apparent that tradeoffs are involved, and large populations with high consumption of natural resources cannot be sustainable. It is important to recall that agriculture was possible only after destruction of the natural vegetation that must have caused loss of considerable biodiversity.  Till recently, forests were cleared to provide land for settling displaced persons.  Thus the Carrying Capacity (CC) depends on the natural resources and levels of environmental degradation acceptable to the society. Reducing the consumption of resources by changing the life styles and food habits are the other options for increasing the CC which may not always be socially acceptable.

Ecologists have widely different views on the world’s CC; some say that 2 billion is the right population for the world.  Others argue that we already have over 6 billion, and earth can support 40 billion, provided the consumption and life style are altered. It has been suggested that a much larger world population can be supported by reducing the consumption of meat, fats and sugars.  Carrying capacity without the inputs of fossil energy would be less than two billion.

It is now widely accepted that the known resources of fossil fuels may be exhausted in the next fifty years. Hence, in future, plants will be a large source of renewable energy, different starting materials for chemical industry, presently obtained from fossil fuels, besides food, feed and fiber. All these must come from shrinking land and depleting water resources on a sustainable basis. Indeed, it is a tall order and a great challenge for plant scientists.  It is obvious that all cannot get everything; for sustainable development either the number of people, or the life styles and consumption levels will have to change for minimizing the environmental impact. Sustainable agriculture is possible only for a sustainable population. Scientific advances and new energy efficient technologies will certainly play key role in ameliorating the environment and sustaining human populations. It is, therefore, important to estimate human CC of different agro-climatic regions under various possible scenarios for the future. 

Summing up, carrying capacity of the world increased when humans started growing plants that provide food, instead of gathering grains from natural stands. Industrialization, development of synthetic fertilizers and other agrochemicals further enhanced productivity through large inputs of fossil energy. This made it possible to support even larger population. Then came the realization that the known fossil energy sources are limited and will be exhausted in the next fifty years. Further, the adverse environmental impact of intensive farming became apparent in many areas. In future, plants will be the source of liquid fuels and other starting materials for chemical industry besides much more diversified food, feed and fodder. All this, must come from shrinking cultivable land and water resources on a sustainable basis without damaging the resource base.

*Former Secretary, Department of Biotechnology, Govt. of India, 17, Rohini, Plot No. 29-30, Sector 9-A, Vashi, New Mumbai-400073.

E-mail: [email protected]

This article has been reproduced from the archives of EnviroNews - Newsletter of ISEB India.

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