This article throws light upon the eight main determinants of earth’s carrying capacity. The determinants are: 1. Growing Inequality in Income 2. Economic Growth 3. Population Growth 4. Cropland 5. Pasture and Rangeland 6. Fisheries 7. Fresh Water 8. Forests and Woodlands.
Determinant # 1. Growing Inequality in Income:
Of the three principal driving forces, the growing inequality in income between rich and poor stands out in sharpest relief. In 1960, the richest 20 per cent of the world’s people absorbed 70 per cent of global income; by 2010 (the latest year for which comparable figures are available), the wealthy people’s share had climbed to nearly 86 per cent.
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The poorest 20 per cent, meanwhile, saw their share of global income drop from an already meager 2.3 per cent to just 1.29 per cent. The ratio of the richest fifth’s share to the poorest does thus grew from 30 to 1 in 1960 to 75 to 1 in 2010 .
Disparities in food consumption are revealing as well (Table 1.2). As many as 700 million people do not eat enough to live and work at their full potential. The average African, for instance, consumes only 87 per cent of the calories needed for a healthy and productive life Meanwhile, diets in many rich countries are so laden with animal fat as to cause increased rates of heart disease and cancer.
Moreover, the meat-intensive diets of the wealthy usurp a disproportionately large share of the earth’s agricultural carrying capacity, since producing one kilogram of meat takes several kilograms of grain. If all people in the world required as much grain for their diet as the average American does, the global harvest would need to be 2.6 times greater than it is today—a highly improbable scenario.
Determinant # 2. Economic Growth:
The second driving force—economic growth—has been fuelled in part by the introduction of oil onto the energy scene. Since mid-twentieth century, the global economy has expanded fivefold. As much was produced in two-and-a-half months of 1990 as in the entire year of 1950. World trade, moreover, grew even faster. Exports of primary commodities and manufactured products rose eleven fold.
Unfortunately, economic growth has most often been of the damaging variety—powered by the extraction and consumption of fossil fuels, water, timber, minerals, and other resources. Between 1950 and 1990, the industrial round wood harvest doubled, water use tripled, and oil production rose nearly six fold. Environmental damage increased proportionately.
Determinant # 3. Population Growth:
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Compounding the rises in both poverty and resource consumption in relation to the worsening of inequality and rapid economic expansion, population growth has added greatly to pressures on the earth’s carrying capacity.
The doubling of world population since 1950 has meant more or less steady increases in the number of people added to the planet each year. Whereas births exceeded deaths by 37 million in 1950, the net population gain in 1993 was 87 million—roughly equal to the population of Mexico.
The current world population is around 7 billion, the pattern of world population growth to date and the projections-based on the growth trends allows one to speculate about the implications associated with it. Fig. 1.5 shows the growth of human population from the origin to the present times.
We can see, for example, the dramatic reduction in the time required for the population to increase in increments of 1 billion if present trends Continue.
It also depicts that the population growth rates have increased tremendously from a doubling time of 150 years (1750- 1900) to a doubling time of 35 years (1930 – 1965), and considering the present rate of growth (with downward trends) the next doubling in 2010, that is within a time span of 45 years (1965-2010).
The annual growth rate was 1.7 per cent in 1982, peaked in 1965 at 2 per cent and the present rate is about 1.5 percent. It is expected that with this rate the world population will cross the 8 billion mark (box 1.2) by the year 2025 (Fig. 1.5).
The U.N. median population projection now shows world population reaching 8.9 billion by 2030, and leveling off at 11.5 billion around 2150.
The outer limit of the planet’s carrying capacity is determined by the total amount of solar energy converted into biochemical energy through plant photosynthesis minus the energy those plants use for their own life processes. This is called the earth’s net primary productivity (NPP), and it is the basic food source for all life.
Prior to human impacts, the earth’s forests, grasslands, and other terrestrial ecosystems had the potential to produce a net total of some 150 billion tons of organic matter per year.
Stanford University biologist Peter Vitousek and his colleagues estimate, however, that humans have destroyed outright about 12 per cent of the terrestrial NPP and now directly use or co-opt an additional 27 per cent. Thus, one species—Homo sapiens—has appropriated nearly 40 per cent of the terrestrial food supply, leaving only 60 per cent for the millions of other land-based plants and animals.
It may be tempting to infer that, at 40 per cent of NPP, we are still comfortably below the ultimate limit. But this is not the case. We have appropriated to 40 per cent that was easiest to acquire.
It may be impossible to double our share, yet theoretically that would happen in just 60 years (i.e., between 1900 to 1960) if our share rose in tandem with population growth. And if average resource consumption per person continues to increase, that doubling would occur much sooner.
Determinant # 4. Cropland:
Cropland area worldwide expanded by just 2 per cent between 1980 and 1990. That means that gains in the global food harvest came almost entirely from raising yields on existing cropland. Most of the remaining area that could be used to grow crops is in Africa and Latin America; very little is in Asia.
The most sizable near-term additions to the cropland base are likely to be a portion of the 76 million hectares of savanna grasslands in South America that are already accessible and potentially cultivable, as well as some portions of African rangeland and forest. These conversions, of course, may come at a high environmental price, and will push our 40 per cent share of NPP even higher.
Moreover, a portion of any cropland gains that do occur will be offset by losses. As economics of developing countries diversify and as cities expand to accommodate population growth and migration, land is rapidly being lost to industrial development, housing, road construction, and the like.
Canadian geographer Vaclav Smil estimates, for instance, that between 1957 and 1990, China’s arable land diminished by at least 35 million hectares—an area equal to all the cropland in France, Germany, Denmark, and the Netherlands combined. At China’s 1990 average grain yield and consumption levels, that amount of cropland could have supported some 450 million people, about 40 per cent of its population.
In addition, much of the land we continue to farm is losing its inherent productivity because of unsound agricultural practices and overuse. The “Global Assessment of Soil Degradation,” a three-year study involving some 250 scientists, found that more than 550 million hectares are losing topsoil or undergoing other forms of degradation as a direct result of poor agricultural methods (Table 1.4).
On balance, unless crop prices rise, it appears unlikely that the net cropland area will expand more quickly over the next two decades than it did between 1980 and 1990.
Assuming a net expansion of 5 per cent (which may be optimistic), total cropland area would climb to just over 1.5 billion hectares. Given the projected 33-percent increase in world population by 2010, the amount of cropland per person would decline by 21 per cent (Table 1.5).
Determinant # 5. Pasture and Rangeland:
They cover some 3.4 billion hectares of land, more than twice the area in crops. The cattle, sheep, goats, buffalo, and camels that graze them convert grass (which humans cannot digest) into meat and milk (which they can).
The global ruminant livestock herd, which numbers about 4.4 billion, thus adds a source of food for people that does not subtract from the grain supply, in contrast to the production of pigs, chickens, and cattle raised in feedlots.
Much of the world’s rangeland is already heavily overgrazed and cannot continue to support the livestock herds and management practices that exist today.
According to the “Global Assessment of Soil Degradation,” overgrazing has degraded some 680 million hectares since mid-twentieth century. This suggests that 20 percent of the world’s pasture and range is losing productivity and will continue to do so unless herd sizes are reduced or more sustainable livestock practices are put in place.
During the 1980s, the total range area increased slightly, in past because land deforested or taken out of crops often reverted to some form of grass.
If similar trends persist over the next two decades, by 2010 the total area of rangeland and pasture will have increased 4 percent, but it will have dropped 22 percent in per capita terms. In Africa and Asia, which together contain nearly half the world’s rangelands and where many traditional cultures depend heavily on livestock, even larger per capita declines could significantly weaken food economies.
Determinant # 6. Fisheries:
Another natural biological system that humans depend on to add calories, protein, and diversity to human diets is our fisheries. The annual catch from all sources (including aquaculture) is about 150.0 million metric ton in 2000. — about 7 per cent of the protein humans consume. Fish account for a good portion of the calories consumed overall in many coastal regions and island nations.
The world fish catch has climbed rapidly in recent decades, expanding nearly fivefold since 1950. But it peaked at just above 100 million tons in 1989. Although catches from both inland fisheries and aquaculture (fish farming) have been rising steadily, they have not offset the decline in the much larger wild marine catch, which fell from a historic peak of 82 million tons in 1989 to 77 million in 1991, a drop of 6 per cent.
With the advent of mechanized hauling gear, bigger nets, electronic fish detection aids, and other technologies, almost all marine fisheries have suffered from extensive overexploitation. Under current practices, considerable additional growth in the global fish catch overall looks highly unlikely.
Indeed, the U.N. Food and Agriculture Organization (FAO) now estimates that all seventeen of the world’s major fishing areas have either reached or exceeded their natural limits, and that nine are in serious decline.
FAO scientists believe that better fisheries management might allow the wild marine catch to increase by some 20 per cent. If this could be achieved, and if the freshwater catch increased proportionately, the total wild catch would rise to 102 million tons; by 2010, this would nonetheless represent a 10 per cent drop in per capita terms.
Determinant # 7. Fresh Water:
It may be even more essential than cropland, rangeland, and fisheries:
Without water, after all, nothing can live. Signs of water scarcity are now pervasive. Today, twenty-six countries have insufficient renewable water supplies within their own territories to meet the needs of a moderately developed society at their current population size.
And populations are growing fastest in some of the most water-short countries, including many in Africa and the Middle East. Rivers, lakes, and underground aquifers show widespread signs of degradation and depletion, even as human demands rise inexorably.
Water constraint already appears to be slowing food production, and those restrictions will only become more severe. Agricultural lands that receive irrigation water play a disproportionate role in meeting the world’s food needs.
The 237 million hectares of irrigated land account for only 16 per cent of total cropland but more than one-third of the global harvest (2010). For most of human history, irrigated area expanded faster than population did, which helped food production per person to increase steadily. In 1978. however, per-capita irrigated land peaked, and it has fallen nearly 6 per cent since 2010.
Determinant # 8. Forests and Woodlands:
They are the last key components of the biological resource base. They contribute a host of important commodities to the global economy—logs and lumber for constructing homes and furniture, fibre for making paper, fruits and nuts for direct consumption, and, in poor countries, fuel wood for heating and cooking.
More important even than these benefits, however, are the ecological services forests perform—from conserving soils and moderating water cycles to storing carbon, protecting air quality, and harboring millions of plant and animal species.
As on 2000, forests cover 24 per cent less area than in 1700—3.4 billion hectares compared with an estimated 4.5 billion about 300 years ago.
Most of that area was cleared for crop cultivation, but cattle ranching, timber and fuel wood harvesting, and the growth of cities, suburbs, and highways all claimed a share as well. In 1990s, assessments suggest that the world’s forests declined by about 130 million hectares between 1980 and 1990, an area larger than Peru.
A successful global effort to lighten humanity’s load on the earth would directly address the three major driving forces of environmental decline—the grossly inequitable distribution of income, resource-consumptive economic growth, and rapid population growth—and would redirect technology and trade to buy time for this great movement.
Although there is far too much to say about each of these challenges to be comprehensive here, some key points bear noting.
Wealth inequality may be the most intractable problem, since it has existed for millennia. The difference today, however, is that the future of rich and poor alike hinges on reducing poverty and thereby eliminating this driving force of global environmental decline. In this way, self- interest joins ethics as a motive for redistributing wealth, and raises the chances that it might be done.
Important actions to narrow the income gap include greatly reducing Third World debt— much talked about in the 1980s but still not accomplished—and focusing foreign aid, trade, and international lending policies more directly on improving the living standards of the poor.
If decision-makers consistently asked themselves whether a choice they were about to make would help the poorest of the poor—that 20 per cent of the world’s people who share only 1.4 per cent of the world’s income—and acted only if the answer were yes, more people might break out of the poverty trap and have the opportunity to live sustainably.
A key prescription for reducing the kinds of economic growth that harm the environment is the same as that for making technology and trade more sustainable—internalizing environmental costs. If this is done through the adoption of environmental taxes, governments can avoid imposing heavier taxes overall by lowering income taxes accordingly.
In addition, establishing better measures of economic accounting is critical. Since the calculations used to produce the gross national product do not account for the destruction or depletion of natural resources, this popular economic measure is extremely misleading.
It tells us we are making progress even as our ecological foundations are crumbling. A better beacon to guide us toward a sustainable path is essential. The United Nations and several individual governments have been working to develop better accounting methods, but progress with implementation has been slow.
In September 1994, government officials gathered in Cairo for the “International Conference on Population and Development,” the third such gathering on population. This is a timely opportunity to draw attention to the connections between poverty, population growth, and environmental decline; and to devise strategies that simultaneously address the root causes.
Much greater efforts are needed, for instance, to raise women’s social and economic status and to give women equal rights and access to resources. Only if gender biases are rooted out will women be able to escape the poverty trap and choose to have fewer children.
The challenge of living sustainably on the earth will never be met, however, if population and environment conferences are the only forums in which it is addressed. Success hinges on the creativity and energy of a wide range of people in many walks of life.
The scientists “Warning to Humanity” ends with a call to the world’s scientists, business and industry leaders, the religious community, and people every where to join in the urgent mission of halting the earth’s environmental decline.