If the whole world lived like the average Israeli, another two or three planet Earths would be needed to support the human race, according to a calculation based on the resource management tool known as the Ecological Footprint. The latter term, which is becoming increasingly popular, measures the amount of land and water a population needs to produce the resources it consumes and to absorb the waste it creates.

We live in a relatively limited sphere that includes our home, the road leading to work or leisure-time activities, etc. But, in fact, we "occupy" a much greater area - that which is utilized to grow our food, for factories to produce the materials to build our homes, for transportation and other purposes. The Ecological Footprint calculates the acreage used by each person, and the amount of carbon dioxide emissions dictated by the person's lifestyle. The calculation does not take into consideration other types of pollutants, and so is an underestimation.

Western lifestyle causes a particularly large Ecological Footprint. For example, for an American, the average Ecological Footprint is huge - about 96 dunams (23.72 acres). In contrast, the Ecological Footprint of the average Indian is 8 dunams (1.97 acres). The Ecological Footprint of the average Israeli is about 46 dunams (11.36 acres). In other words, to sustain ourselves, Israelis need an area more than 10 times the size of the country.

According to the NGO Global Footprint Network, humanity's Ecological Footprint is 23 percent greater than the planet's production ability. In other words, each year the human race uses what it takes from nature about a year and three months to produce. According to Dr. Lia Ettinger of the Heschel Center for Environmental Learning and Leadership, the situation can be compared to an overdraft in our bank account, where we are already seriously overdrawn. However, this overdraft can only only go on for so long.

"We have only one planet Earth, and we are already living not on the interest but on the principal," Ettinger says. A depletion of the principal will lead to bankruptcy in a few decades, since the rising rate of consumption is greater than nature's ability to renew its resources. "The point is that it is impossible to go on with business as usual," Ettinger says. "Our social and economic systems must take into account the free services nature gives us, and understand that even things that are given at no monetary cost have great value," she says.

The results can already be seen in the collapse of essential systems, damage to sources of livelihood, habitat destruction, soil that can no longer produce and resources that become more expensive or unavailable.

The concept of the Ecological Footprint was coined about 15 years ago by Mathis Wackernagel, who developed it as his doctoral thesis, together with his advisor, Professor William Rees, as a system for measuring sustainability. According to Dan Gottleib, who is writing his doctoral thesis on the Ecological Footprint, advised by Professor Abraham Haim and Professor Eran Vigoda-Gadot of the University of Haifa, the innovation in thought brought about by the concept has led a number of governments, businesses and communities throughout the world to use it to estimate the extent to which their policies are sustainable. There are even firms that specialize in Ecological Footprint consultation. "I have not yet come across the use of this tool in government ministries," Gottleib says, "but it is slowly trickling down to the environmental community."