Human Pressure on Earth's Carrying Capacity Rises

OAKLAND, California, November 28, 2002 (ENS) - Humanity is putting increasing pressure on global ecosystems, with consumption exceeding the Earth's biological capacity by 20 percent, according to a new report from the Sustainability Program of Redefining Progress, a nonprofit, nonpartisan public policy organization.

The biosphere needs about one year and three months to renew what humanity consumes in a year, the report found.

The organization's latest "Ecological Footprint of Nations" report analyzes the ecological impact of 146 of the world's nations, demonstrating to what extent a nation can support its resource consumption with its available ecological capacity.

The report uses ecological footprint accounts to provide a measurable estimate of humanity's pressure on global ecosystems.


Vegetable farmers in Sudan are planting coriander to repel insect pests. (Photo courtesy FAO)
"The 'Ecological Footprint' accounts show us that humanity's consumption and waste production today exceed the Earth's capacity to create new resources and absorb waste," the report says. "We are, as a result, liquidating certain natural capital to support current resource use, thereby reducing the Earth's capacity to support future life."

The Redefining Progress report expresses ecological footprint in terms of global acres. Each global acre, the report explains, corresponds to one acre of biologically productive space with world average productivity.

The "Ecological Footprint" measures the biologically productive area required to produce the food and wood people consume, to supply space for infrastructure, and to absorb the greenhouse gas carbon dioxide emitted from burning fossil fuels.

The global ecological footprint in 1999 was 5.6 global acres per capita, while the Earth's biocapacity was 4.7 global acres. In metric terms, these measurements are 2.3 global hectares per capita and 1.9 global hectares per capita.

According to the report, "The bottom line for sustainability thus becomes - how can each person have a satisfying life within the average of 4.7 global acres per person or less? This is the most significant challenge for research, business and politics."

The analysis is primarily based on data published by the United Nations and the Intergovernmental Panel on Climate Change. The data from 1999 is the most recent available to scientists.

"Humanity's Ecological Footprint exceeds the Earth's biological capacity by 20 percent," said Sustainability program director Mathis Wackernagel, one of the report's three authors. "Many nations, including the United States, are running even larger ecological deficits. As a consequence of this overuse, the human economy is liquidating the Earth's natural capital."

The United States recorded an ecological footprint of 24.0 global acres (9.7 hectares) per capita, nearly doubling its national biocapacity of 13.0 global acres (5.3 hectares) per capita.

Long Beach

Long Beach, California (Photo courtesy City of Long Beach)
The U.S. deficit of 10.9 global acres (4.4 hectares) per capita is among the highest, only exceeded by Belgium and Luxembourg taken as a unit, which has a deficit of 14 global acres (5.6 hectares) per capita.

New Zealand had by far the largest surplus at 35 global acres (14 hectares) per capita, with Australia second on the list with a surplus at 17 global acres (7 hectares)per capita.

The report details these individual measurements, but emphasizes the need to take a global perspective on this issue. In 1999, there were 28.2 billion acres, or 11.4 billion hectares, of biologically productive land on Earth, covering some 25 percent of the planet's surface.

This consists of 22.5 billion acres (9.1 billion hectares) of usable land, and 5.7 billion acres (2.3 billion hectares)of water that provide economically useful resources that can be considered biologically productive. The world population in 1999 was 5.9 billion.

Based on the assumption that 12 percent of all biologically productive space should be left undisturbed for other species, the report found that the available space per person worldwide shrinks from 4.7 global acres (1.9 hectares) to 4.1 (1.7 hectares). This measure of 4.1 global acres, or 1.9 global hectares, is then the "ecological benchmark" for comparing peoples' ecological footprints.

Reaching this ecological benchmark will get more difficult in the future as the global population increases and further resource degradation occurs, the report found.

"Assuming on further ecological degradation, the amount of biologically available space will drop to 2.8 global acres (1.1 hectares) per capita once the world population reaches its predicted 10 billion. If current growth trends continue, this will happen in about 30 years."

"Sustainability talk is meaningless unless it is backed up by specific measurable commitments and timetables for implementation," said Wackernagel. "We will achieve sustainability only when every person can lead a satisfying life within the Earth's biological capacity. People can use the ecological footprint to hold individuals, organizations, businesses, and governments accountable for their sustainability performance."


Wellington, New Zealand. New Zealand had the largest surplus at 35 global acres (14 hectares) per capita. (Photo courtesy Discover New Zealand)
Calculations for these accounts make five assumptions. First, that it is possible to keep track of most of the resources people consume and the wastes they generate. Redefining Progress also assumes that resource and waste flows can be "converted into the biologically productive area required to maintain these flows."

The third assumption is that different types of biologically productive areas can be expressed in the same unit "once they are scaled proportionally to their productivity."

In addition, the calculations assume that since these areas represent mutually exclusive uses and are standardized to represent the same amount of productivity, they can be added to a total that measures humanity's demand.

The fifth core assumption in calculating an ecological footprint is that the area of total human demand can be compared with nature's supply of ecological services, "which may also be expressed in standardized units of productivity."

The authors say the footprint calculations are conservative measures. The report underestimates human impact and overestimates the available biological capacity in several ways, its authors wrote.

First, it counts each area only once, even if the area provides two or more ecological services. In addition, the authors choose the conservative estimates when in doubt and include current agricultural practices as if current industrial yields would not caused any significant long term damage to soil productivity.

Some human activities for which the authors have insufficient data are left out, and they have excluded activities that systemically erode nature's capacity to regenerate, such as plutonium, polychlorinated biphenyls (PCBs) and other materials for which the Earth has no significant assimilation capacity.

Nonrenewable resources from the Earth's crust are included in these accounts only to the extent that their use damages the biosphere, such as through mining and burning of fossil fuels. These assets appear in the carbon dioxide component of the ecological footprint accounts.

Neither fresh water nor the release of solid, liquid and gaseous waste other than carbon dioxide are included in the accounts.

The calculations include six types of bioproductive areas used to support the human economy - cropland, grazing land, forests for harvesting timber and fuelwood, fisheries, built up areas for accommodating human infrastructure, and forests to sequester carbon dioxide from fossil fuels or to replace fossil fuels with biomass.

Improvements have been made to their measuring techniques, the authors said, largely thanks to better data and databases. In earlier accounts, agricultural production statistics were separate from trade statistics. Units for production, generally measured in metric tons, were difficult to equate with trade figures reported in dollars. The United Nations Food and Agriculture Organization now has all of its statistics available in tons.

"These accounts show the importance of addressing the current population dynamic to avoid future human suffering," the report says. "If the lack of affordable, safe, and effective family planning leads to a human population of 10 billion people, we implicitly condemn large segments of future generations to harsh lives."

The report is available for download at: