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Easter Island was one of the last places on Earth to be settled by human beings. First reached by Polynesians 1,500 years ago, this small island 3,200 kilometers west of South America supported a sophisticated agricultural society by the 16^th century. Easter Island has a semiarid climate, but it was ameliorated by a verdant forest that trapped and held water. Its 7,000 people raised crops and chickens, caught fish, and lived in small villages. The Easter Islander's can be seen in massive 8– meter –high obsidian statues that were hauled across the island using tree trunks as rollers.

By the time European settlers reached Easter Island in the 17^th century, these stone statues, known as ahu, were the only remnants of a once impressive civilization – one that had collapsed in just a few decades. As reconstructed by archeologists, the demise of this society was triggered by the demotion of its limited resource base. As the Easter Island human population expanded, more and more land was cleared for crops, while the remaining trees were harvested for fuel and to move the ahu into place, the lack of wood made it impressible to build fishing boats or houses, reducing an important source of protein and forcing the people to move into caves. The loss of forests also led to soil erosion, further diminishing food supplies. As pressures grew, armed conflicts broke out among villages, slavery became common, and some even resorted to cannibalism to survive.

As an isolated territory that could not turn elsewhere ran out, Easter Island presents a particularly stark picture of what can happen when a human economy expands in the face of limited resources. With the final closing of the remaining frontiers and the creation of a fully interconnected global economy, the human race as a whole has reached the kind of turning point that the Easter Islanders reached in the 16th century.

For us, the key limits as we approach the 21st century are fresh water, forests, range land, oceanic fisheries, biological diversity, and the global atmosphere. Will we recognize the world's natural limits and adjust our economies accordingly, or will we proceed to expand our ecological footprint until it is too late to turn back? Are we headed for a world in which accelerating change outstrips our management capacity, overwhelms our political institutions, and leads to extensive breakdown of the ecological system on which the economy depends?

Although our ancestors have struggled with water shortages from ancient Mesopotamia onward, the spreading scarcity of fresh water may be the most underestimated resource issue facing the world as it enters the new millennium. This can be seen both in falling water tables and in rivers that run dry, failing to make it to the sea. As world water use has tripled since mid – century, over – pumping has led to falling water tables on every continent.

China and India, the world's two most populous countries, depend on irrigated agriculture for half or more of their food supply. In China, water tables are falling almost everywhere that the land is flat. The northern half of the country is quite literally drying out. The water table under much of the north China Plain, a region that accounts for nearly 40 percent of China`s grain harvest, is falling by roughly 1.5 meters a year. Projections by the Sandia National Laboratory in the United States show huge water deficits emerging in some key river basins in China as the new millennium begins.

In India, the water situation may be deteriorating even faster. As India's population approaches the 1 billion mark, the country faces steep cutbacks in the supply of irrigation water. David Seckler, head of the International Water Management Institute in Colombo, the world's premier water research body, observes: "The extraction of water from aquifers in India exceeds recharge by a factor of 2 or more. Thus almost everywhere in India, fresh – water aquifers are being pulled down by 1-3 meters per year. " Secler goes on to speculate that aquifers are depleted, the resulting cutbacks in irrigation could reduce India`s harvest by 25 percent – in a country where food supply and demand are already precariously balanced and where another 600 million people are expected over the next half – century.

At present, 70 percent of all the water worldwide that is diverted from rivers or pumped from underground is used for irrigation, 20 percent is used for industry, and 10 percent goes to residences. The economics of water use do not favor farmers. A thousand tons of water can be used in agriculture to produce one ton of wheat worth $ 200, or it can be used to expand industrial output by $ 14,000-70 times as much. As the demand for water in each of these three sectors rises and as the competition for scarce water intensifies, agriculture almost always loses.