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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
Where:
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.
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