In just a few decades the world’s population will hit nine billion, leading to the essential question: Can this many humans survive and try to improve their lives without depleting the planet? here are too many people demanding too much from the earth! The world’s human population is currently increasing by about 90 million people a year. All these new arrivals require food, energy, clean water, sanitation, clothing, housing, schooling, healthcare and employment. This, plus the waste and pollution they produce, puts a greater strain on the environment and squeezes other species into zoos and small areas of parkland.
The population is growing at a rate that cannot be sustained! We do not have the environmental resources to cope with the standard of living, which people in developed countries are accustomed to and which those in developing countries aspire to. We are currently increasing the world population at rates that are outstripping any reasonable expectation of maintaining, or improving, our requirements for living. The issue is not just about the number of people, but also how this number relates to the consumption of available resources.
In 1999 the world’s human population was 6 billion. It is growing at a rate of 1.9% per year, in comparison with 0.8% per year prior to 1950. Between 1950 and 1987 it doubled from 2.5 to 5 billion. In 1950 there was an addition of 50 million people per year to the world. In 1975 this had increased to 72 million and by 1992 it had further increased to 93 million people per year. For perspective, this means the combined populations of the UK, Ireland, the Netherlands and Greece are added to the global population each year; 386,921 people each day or 269 people every minute! The United Nation estimates that in 2050, the world population could range from 7.9 to 10.9 billion, depending on the actions we take today.
The poorest countries have the fastest growth rates with over 90% of population growth occurring in developing countries. This will result in a massive shift in the geo-political balance. Developed countries which made up one third of the world population in 1950, now constitute less than a quarter and will dwindle down to only 13% by the year 2100.
Increasing population is partially caused by people living longer due to improved food, health care and sanitation. Over the past 30 years life expectancy has increased by 30 years in East Asia and 15 years in Africa. However, family planning is not accessible to between 300 and 400 million couples.
In the developed world, increasing populations are growing at a slower rate than in previous decades. Between 1950 and 1990, the population increased by 43%, compared with 150% in developing countries. AIDS has not had a significant impact on population growth.
Population growth results in:
1. Poverty – Countries have to spend more of their resources on importing food.
2. Unemployment – More people have to compete for jobs and there is a fall in wages.
3. Environmental destruction – Each year an area the size of Austria and Belgium combined is cleared for new farms, and huge areas are being turned into deserts because of over-use by people and grazing animals. Even the most sustainable methods of land management are unable to cope with the demands of an ever growing population. The number of people living in countries where cultivated land is critically scarce is projected to increase to between 600 and 986 million in 2025. Today over 1.8 billion people live in countries with critically low levels of forest cover. By 2025 this could nearly double to 3 billion
THESE ASSERTIONS IN RELATION TO THE PRESENT EXPONENTIAL POPULATION OF THE WORLD
Obviously the earth cannot continue indefinitely to sustain population growth at the current rate. How many people can it support? Ecologists have often made use of the concept of carrying capacity in addressing the pressures that populations put on their environments. Carrying capacity is simply the largest number of any given species that a habitat can support indefinitely.
Primary Productivity of the Earth
One way of analyzing carrying capacity of the earth is to calculate its net primary productivity (NPP). This is the total amount of solar energy converted into biochemical energy through plant photosynthesis, minus the energy needed by those plants for their own life processes. It represents the total food resource on earth.
It has been calculated that, prior to human impact, NPP was about 150 billion tons of organic matter per year. By deforestation and other forms of destruction of vegetation, humans have destroyed about 12% of the terrestrial NPP, and now directly use (for food and fiber) or co-opt (by converting productive land to other uses) an additional 27%. Thus we have already appropriated about 40% of the terrestrial food supply, leaving only 60% for the other terrestrial plants and animals. You might conclude from this that we are at 40% of the carrying capacity and that the theoretical maximum human population would therefore be 2.5x the current level i.e. 2.5×5.9 = 15 billion, a number that will be reached within the next century if present trends continue. This is the number the earth could support if all of the plant growth on earth were used to support the human population, and if we were not also limited by waste buildup and non-renewable resources. It assumes that we forget about conserving biological diversity for its own sake, forget about preserving any natural habitat, and forget about saving natural ecosystems for the many benefits they provide (like producing oxygen, preventing CO2 buildup, cleansing water supplies, etc.). If we set aside enough of the earth’s primary productivity for these other essential purposes, then the predicted carrying capacity for humans is much less than 15 billion; in fact, probably less than the current population.
Another way of looking at global capacity is to examine the degree to which humans already dominate the Earth’s ecosystems. Estimates indicate that:
we have already transformed or degraded 39-50% of the Earth’s land surface (agriculture, urban).
we use 8% of the primary productivity of the oceans (25% for upwelling areas and 35% for temperate continental shelf areas).
we have increased atmospheric CO2 concentration by 30%
we use more than half of the accessible surface fresh water
over 50% of terrestrial nitrogen fixation is caused by human activity (use of nitrogen fertilizer, planting of nitrogen-fixing crops, release of reactive nitrogen from fossil fuels into the atmosphere)
on many islands, more than half of plant species have been introduced by man; on continental areas the fraction is 20% or more
about 20% of bird species have become extinct in the past 200 years, almost all of them because of human activity
22% of marine fisheries are overexploited or depleted, 44% more are at the limit of exploitation
70% of the earth’s surface is covered by oceans, and the oceans provide a significant fraction of total primary productivity. Most of the conversion of inorganic compounds (such as carbon dioxide and water) into organic material is done by the phytoplankton: microscopic drifting plants that exist everywhere in the oceans and are the primary source of food for all of the higher levels of the food chain. The phytoplankton gives the ocean its blue/green color, and so measurements of that color can be used to estimate the amount of phytoplankton. This is the rationale behind NASA’s Coastal Zone Color Scanner (CZCS) carried on a satellite that was launched in 1978 and worked until 1986. The first image shows cumulative results from imaging over the entire period, and the next image shows results from September 97 to August 98. Green indicates high concentrations, and red indicates very high concentrations of phytoplankton, revealing differences in the productivity of different regions. The North Atlantic and North Pacific are large areas of high productivity, and there are regions of very high productivity along the coasts and at areas of upwelling where extra nutrients are brought to the surface.
Calculations have been done of the amount of Primary Productivity that is required to support fisheries. The results show that humans use about 8% of the primary production of the oceans, but that the fraction is more than 25% for upwelling areas and 35% for temperate continental shelf areas.
Declining per capita Resources and Productivity
Another way to analyze the global situation is to examine the resources on which we depend and try to estimate how much we can increase their productivity:
Fisheries. The estimate of 20% increase in fish catch was made before the alarming decline in Atlantic Cod and other major fisheries. Nine of the seventeen major fishing areas of the world are in serious decline, and all of them have either reached or exceeded their limits. So the predicted increase of 20%, and per capita decline of 10%, is based on some imaginary improvement in fisheries management, and is probably unrealistic.
Irrigated land – accounts for 17% of cropland but contributes more than a third of the global harvest. Predicted per capita change is -12%.
Cropland. Between 1980 and 1990, cropland area worldwide expanded by 2%. It is unlikely that it could be expanded any more quickly, given that the areas already taken are the ones that are easiest to cultivate, and given that land is being rapidly lost to various kinds of development. The optimistic estimate is that cropland could be increased by 5% over the 20yr period shown on the table. This will mean the conversion of huge areas of South America and Africa to agriculture, at a very high environmental price. Given the predicted 33% increase in population, even this increase represents a decline of 21% in cropland per person.
Rangeland and Pasture. Similar calculations show a decline of 22% (and about 20% of this area is declining in productivity because of overgrazing).
Forests. Due to a combination of deforestation and population growth, the per capita change in forests is -30%!
All of these statistics show that we are already stretching these resources to the limit, and that the 33% increase in population will be very difficult to accommodate.
As the century begins, natural resources are under increasing pressure, threatening public health and development. Water shortages, soil exhaustion, loss of forests, air and water pollution, and degradation of coastlines afflict many areas. As the world’s population grows, improving living standards without destroying the environment is a global challenge.
We’ve been on a big growth spurt during the past century or so. In 1900, demographers had the world’s population at 1.6 billion, in 1950 it was about 2.5 billion, by 2000 it was more than 6 billion. Now, there are about 7.2 billion of us.
In recent years we’ve been adding about a billion people every 12 or 13 years or so. Precisely how many of us are here right now is also a matter of debate, depending on whom you consult: The United Nations offers a range of current population figures and trends, the U.S. Census Bureau has its own estimate, and the Population Reference Bureau also tracks us.
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