| Population
Growth and Environmental Concerns Environmental
limits to growth?
The 200-year-old apocalyptic prediction 41and more recent warnings 42 that human population growth would
eventually outstrip the capacity of land to produce food have thankfully not come true.
Human ingenuity and continued improvements in agricultural technology have thus far
ensured that global food supplies have grown at least as fast as population. But as the
20th century ends scientists are still pondering the underlying question: are there
environmental limits to the number of people and the quality of life that the earth can
support?
Because natural conditions, technology, and consumption and distribution patterns are
constantly in flux, and there is no universal agreement as to the definition of
"carrying capacity", it is unlikely that there will ever be a definitive answer.
Most scientists who have pondered the issue have predicted that there are natural limits,
but the predicted limits fall within a broad range: 4-16 billion people.43 What will happen as human population approaches
those limits, either globally or locally, will depend on human choices — about
lifestyles, environmental protection and equity.
Water, Land and Food
In sub-Saharan Africa and parts of the Indian subcontinent, which together contain about
one third of the world’s population, mortality rates are increasing and are
responsible for one third of the fall in long-range population projections.44 Birth rates in these areas have not declined as
rapidly as they have elsewhere, and aquifer depletion and decreasing per capita crop land
are central players in projected demographic and resource trends.
An urgent concern for many rapidly growing countries is shrinking crop land per person.
In Nigeria, per capita grain land is projected to shrink from 0.15 to 0.07 28 hectares per
person by 2050. Pakistan’s grain land per person would drop from 0.09 to 0.04
hectares in the same period.45 Countries
that currently have 0.03 hectares or less of grain land per capita, such as South Korea
and Japan, import about 70 per cent of their grain. Because global per capita grain output
has been stagnant for more than a decade and world grain carryover stocks have been
dropping, these trends pose critical questions as to their effects on international food
supply, markets and distribution. Will the countries and people who need to import food in
the future be able to afford it?
In many parts of both the more- and less-developed world, water demand already
substantially exceeds the sustainable supply.46
In India, for instance, water withdrawals are now estimated to be twice the rate of
aquifer recharge, with the result that water tables are falling by one to three metres per
year.47 The International Water Management
Institute estimates that the eventual lack of water for irrigation could cut India’s
grain production by 25 per cent. This is a grave issue in a country whose population
reached 1 billion in 1999 and is expanding at the rate of 18 million per year, and where
53 per cent of all children are currently malnourished.48
Rising population has reduced world grain area per person by 50 per cent since 1950. 49 Little viable agricultural land remains
unexploited, and existing crop land continues to be lost to industrial expansion and
residential development. If the quantity of agricultural land is not increasing, grain
yield improvements must keep pace with population growth, currently 1.3 per cent per year,
just to maintain the status quo in per capita food output.
Continued improvements in agricultural technology and crop productivity may well result
in further increases in grain yield, but these are not likely to be on the same scale as
the gains made in the "green revolution" of recent decades; there is evidence
that there may be biological limits to crop yields.
Climate Change, Natural Resource Degradation and
Biodiversity
Continued population growth will affect other environmental trends, including collapsing
fisheries, shrinking forests, rising temperatures, and the wholesale loss of plant and
animal species.
Global warming is a wild card inextricably linked to population-related issues,
including fuel consumption, land use tradeoffs and the potential limits on food and water
supplies. The Intergovernmental Panel on Climate Change, a United Nations-sponsored panel
of 2,500 scientists, has projected that, if current greenhouse gas emission trends
continue, the mean global surface temperature will rise from 1 to 3.5 degrees Celsius in
the next century.50 The panel’s
"best estimate" scenario projects a sea-level rise of 15 to 95 centimetres by
2100. The ecological and human impacts of rising oceans would include increased flooding,
coastal erosion, and salinization of aquifers and coastal crop land, and the displacement
of millions of people living near the coast.
Patterns of precipitation are also likely to change, which combined with increased
average temperatures, could substantially alter the relative agricultural productivity of
different regions.
Greenhouse gas emissions are closely linked to both population increases and
development. Slower population growth would make emission reductions easier to achieve and
provide more options for adaptation to climate change.
BOX 10
--------------
One Person in Four
May Face Water Shortages by 2050
One fourth of the world’s people are likely to live in countries facing chronic or
recurring shortages of fresh water by the year 2050, according to a recent study by
Population Action International. Already, more than 430 million people — 8 per cent
of the world’s population — are living in countries affected by water stress or
out-right scarcity, the study found. That is expected to increase four-fold, to nearly 2
billion by mid-century.
There is already fierce national competition over water for irrigation and power
generation — most notably in the Tigris-Euphrates and Nile river basins. Along the
Euphrates River, Iraq, Syria and Turkey compete for one primary water source. This
competition will worsen if, as projected, their combined populations grow by some 50 per
cent over the next 30 years.
While the Middle East and North Africa are the regions most affected by water scarcity
today, sub-Saharan Africa will be increasingly affected over the next half century, as its
population doubles or even triples. In several countries, water supply is already
inadequate to meet the demands of a growing industrial sector. Within the next 10 years,
Kenya, Morocco, Rwanda, Somalia and South Africa are projected to join the ranks of the
water scarce.
On the other hand, slower population growth than previously projected may reduce the
threat of water shortages and allow more time to develop conservation strategies in India,
Pakistan, Jordan, Sri Lanka and El Salvador, the study found.
The study is based on a widely used methodology developed by Swedish hydrologist Malin
Falkenmark. It holds that countries with annual, renewable fresh water of less than 1,700
cubic metres per person will begin to experience periodic or regular "water
stress" and those with less than 1,000 cubic metres per person will face "water
scarcity", hindering economic development and threatening human health and
well-being.
Source: Population Action International. 1997. Sustaining Water, Easing
Scarcity: A Second Update. Washington, D.C. Population People’s Choices |
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