By Shawn Dell Joyce

April 9, 2013 4 min read

Some scientists say we are not only living beyond Earth's carrying capacity but also eating up future generations' ability to live within Earth's means. We are emptying the Earth's bank account rather than living off the interest as our ancestors have done and leaving a "balance due" for future generations.

British geographer Ernst Georg Ravenstein is credited with first estimating the carrying capacity of the Earth to be about 6 billion people. Presently, at almost 7.1 billion, our population includes at least a billion people who do not receive enough food energy to carry out a day's work. Even through Ravenstein was operating on statistics from the 19th century, he hit fairly close to home.

Before Ravenstein, English clergyman Thomas Robert Malthus argued that human population always increases more rapidly than food supplies and that humans are condemned to breed to the point of misery and starvation. The 200 years since Malthus' essay was first published have proved him wrong. We can artificially increase food production above birth rates and even decline in numbers in the presence of plenty.

The World Hunger Program at Brown University estimated, based on 1992 levels of food production and an equal distribution of food, that, in the words of Discover magazine, "the world could sustain either 5.5 billion vegetarians, 3.7 billion people who get 15 percent of their calories from animal products (as in much of South America), or 2.8 billion people who derive 25 percent of their calories from animal products (as in the wealthiest countries)."

Clearly, we have passed all sustainable estimates and are now entering the "borrowed time" area of the population chart. In order to provide the projected 9 billion people in 2050 with 2,100 calories per day (what food aid agencies declare as the minimum caloric intake), we would have to double our global agricultural production. Humans already have plowed over most of the usable farmland on the planet, and there is a limit to any field's fertility. Could Malthus be right after all?

This is not a new chapter in human history. We have faced starvation before and triumphed. According to environmental analyst Lester Brown, "in the 15th century, Icelanders realized that overgrazing of their grasslands was leading to soil erosion. Farmers then calculated how many sheep the land could sustain and allocated quotas among themselves, thus preserving their grasslands and a wool industry that thrives today."

Here are some steps you can take to reduce your ecological footprint:

--Measure your ecological footprint at http://www.myfootprint.org.

--Walk, bike or share a ride instead of driving or flying.

--Have a home energy audit, and increase your home's efficiency.

--Adopt energy-saving habits -- e.g., using low-tech clotheslines and curtains.

--Eat local, in season and organic.

--Eat less meat.

--Have smaller families and support zero population growth.

Shawn Dell Joyce's weekly column, "Sustainable Living," can be found at creators.com.

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