Population and Human
Production and Consumption
Resources at Risk
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Trends Point to Gains in Human Development, While Many Negative Human
Impacts on Vital Ecosystems are Increasing
The past 100 years have brought unprecedented gains in many of the
indicators that we use to gauge progress in human development, from life
expectancy to per capita income to education.
During the same period, however, human impact on the natural world has
risen dramatically as the scope and intensity of human activities has
increased. Although there has been progress recently in tackling air and
water pollution problems in some countries, many negative trends, such as
the loss of tropical forests and the buildup of greenhouse gases in the
atmosphere, continue unabated.
An overview of environment and development trends yields the following
- World population now at nearly 6 billion is growing more slowly than
experts predicted just a few years ago but is still expected to increase
substantially before stabilizing. Projections of future population,
which are always highly uncertain, put world population at between 8 and
12 billion in 2050, with nearly all of this growth expected in the
developing world. An increasing number of the world's people are
receiving some degree of education, a factor closely tied to human
well-being. During the past 30 years, a higher proportion of children
have been attending school, and adult literacy has climbed.
- The economic fortunes of a number of developing nations have risen
steadily in the past two decades (although the recent downturn in Asian
economies shows this growth may be fragile), but many other nations have
experienced economic decline and falling per capita incomes since 1980.
The disparity in incomes between the rich and poor within nations and
between wealthy and poorer nations in general continues to widen,
meaning that a relatively small percentage of the world's people and
nations control most of the world's economic and natural resources.
- Global food production is generally adequate to meet human
nutritional needs, but problems with distribution mean that some 800
million people remain undernourished. World food production is still
rising, but several trends will make it more challenging to feed an
additional 3 billion people over the next 30 years. Yields of the major
grain crops are rising more slowly now than in the past, and postharvest
losses remain high. Soil degradation from erosion and poor irrigation
practices continues to harm agricultural lands, jeopardizing production
in some regions. In general, without a transition to more
resource-efficient and less toxic farming methods, it will be difficult
to meet world food needs in the future without increasing agriculture's
- Consumption of natural resources by modern industrial economies
remains very high---in the range of 45 to 85 metric tons per person
annually when all materials (including soil erosion, mining wastes, and
other ancillary materials) are counted. It currently requires about 300
kilograms of natural resources to generate US$100 of income in the
world's most advanced economies. Given the size of these economies, this
volume of materials represents a truly massive scale of environmental
alteration. For this reason, extending this kind of resource-intensive
economic model to developing nations as is now occurring around the
world is not environmentally viable.
- Global energy use, which has increased nearly 70 percent since 1971,
is projected to increase at more than 2 percent annually for the next 15
years. This increase will bring more energy services such as
refrigeration and transportation to people but will raise greenhouse gas
emissions about 50 percent higher than current levels, unless a
concerted effort takes place to increase energy efficiency and move away
from today's heavy reliance on fossil fuels. The low price and
familiarity of fossil fuels work against the switch to renewable energy
sources, such as wind, solar, geothermal, hydro, and others, but these
clean energy sources are nonetheless undergoing considerable expansion
and technical progress.
- Nations have cut consumption of ozone-depleting substances some 70
percent since 1987, demonstrating that they can work together to address
an environmental crisis, such as the depletion of the stratospheric
ozone layer. However, the ozone layer is still not safe. Phaseout of
chlorofluorocarbons (CFCs) and other ozone-destroying chemicals is not
complete, and a significant black market in illegal CFCs has sprung up,
endangering some of the gains already made.
- In the past 50 years, excess nitrogen, principally from fertilizers,
human sewage, and the burning of fossil fuels, has begun to overwhelm
the global nitrogen cycle, with a range of ill effects ranging from
reduced soil fertility to eutrophication in lakes, rivers, and coastal
estuaries. The amount of biologically available ("fixed") nitrogen may
double over the next 25 years, increasing the current excess.
- Acid rain is a growing problem in Asia, with sulfur dioxide
emissions expected to triple there by 2010 if current trends continue.
- Deforestation continues to shrink and degrade world forests, with
deforestation rates in most countries surveyed increasing from 1990 to
1995 despite a surge of public awareness about the loss of forests,
especially in the tropics. Deforestation in the Amazon doubled from 1994
to 1995 before declining in 1996, and forest fires in both Indonesia and
the Amazon took a heavy toll in 1997. The world has lost half its
forests over the past 8,000 years through conversion to farms, pastures,
and human settlements or commercial sites.
- Competition from nonnative plant and animal species "bioinvasions"
represents a relentless and growing threat to natural ecosystems, with
some 20 percent of the world's endangered vertebrate species threatened
by exotic invaders. Burgeoning world trade is one of the prime agents in
the increasing pace of bioinvasions, which are now considered the second
greatest threat to global biodiversity after habitat loss.
- Risks to the world's ecosystems are nowhere greater than in aquatic
environments such as coral reefs and freshwater habitats in rivers,
lakes, and wetlands. These fragile zones face an array of assaults from
dams to land-based pollution to destructive fishing techniques. Some 58
percent of the world's reefs and 34 percent of all fish species may be
at risk from human activities.
- Global water consumption is rising quickly, and water availability
is likely to become one of the most pressing and contentious resource
issues of the 21st Century. One third of the world's population lives in
countries already experiencing moderate to high water stress, and that
number could rise to two thirds in the next 30 years without serious
water conservation measures and coordinated watershed planning among
What do these trends portend for the global environment? On the
surface, they paint a troubling picture of the future, with many critical
environmental indicators continuing to decline at their current pace or at
increasing speed. Although global food supply and economic growth appear
robust in the short term, such accumulating environmental harm ultimately
puts at risk the ecosystems and environmental processes such as climate
that form the basis of human health and well-being. Yet, interpreting
environmental trends requires care. Environmental threats are not always
comparable or additive, since they differ greatly in terms of scale,
effect, and the time frame in which they act, from the local and immediate
threats of overfishing or deforestation, to long-acting and global-scale
threats such as climate change.
Overall, the trends sketched above and detailed in the following pages
support some important conclusions. First, changes to natural ecosystems
are occurring on a larger scale than ever before, involving entire
landscapes. Such large-scale landscape changes---through deforestation,
expansion of agricultural land, and urban and suburban growth---will
likely dictate the physical condition and extent of terrestrial ecosystems
in the next several decades. Progressive fragmentation of the world's
remaining forest blocks; buildup in coastal areas; and the spread of
cities, suburbs, and attendant roads and infrastructure over once-rural
tracts will do much to degrade the habitat and watershed values of these
areas. The map showing the current extent of "domesticated" land (see
Chapter 5) indicates the extent to which these landscape-level changes
have already altered the Earth's surface.
Second, the very scale of these landscape-level changes, as well as the
increasing intensity of industrial and agricultural processes, are
inducing changes in the global systems and cycles---such as the atmosphere
and the nitrogen cycle---that underpin the functioning of ecosystems.
These changes in what can be called the "global commons" represent
long-term environmental threats of a profound and far-reaching nature.
Global warming from the buildup of greenhouse gases is the best-known
example, with the potential for large-scale disruption of natural
ecosystems, agriculture, and human settlements due to changes in rainfall
and temperature patterns and rising sea levels. Disruption of the global
nitrogen cycle through extensive use of fertilizers, the burning of fossil
fuels, and other activities also has the potential to change the structure
and composition of terrestrial and aquatic ecosystems.
Third, threats to biodiversity from all sources are quickly reaching a
critical level that may precipitate widespread changes in the number and
distribution of species, as well as the functioning of ecosystems. Current
extinction rates are 100 to 1,000 times higher than prehuman levels, and
projected losses of habitat from land conversion, as well as increasing
competition from nonnative species, will probably push this rate higher
Even as these trends indicate the environmental challenges ahead, it is
important to remember that they can be modified with human resolve.
Already, the transition to more environmentally benign ways of growing
food, producing goods and services, managing watersheds, and accommodating
urban growth has begun in many far-sighted communities and companies. How
fast this transition to more "sustainable" forms of production and
environmental management will proceed, and whether it can effectively
mitigate the effects of large-scale environmental change, is the real