Environmental Problems, Their Causes, and Sustainability 1

3Science,Systems,Matter, and EnergyAirWaterSoilEnergyMineralsCASE STUDYAn Environmental Lessonfrom Easter IslandEaster Island (Rapa Nui) is a small, isolated island inthe great expanse of the South Pacific. Polynesiansused double-hulled sea-going canoes to colonize thisisland about 2,500 years ago. They brought along theirpigs, chickens, dogs, stowaway rats, taro roots, yams,bananas, and sugarcane.Evidence from pollen grains found in the soil andlake sediments and in artifacts shows that the islandwas abundantly forested with a variety of trees—includingbasswoods (called hauhau) and giant palms.The Polynesians developed a civilization based on theisland’s trees. The towering palm trees were used forshelter, tools, and fishing boats. Hauhau trees werefelled and burned to cook and keep warm in the island’scool winters, and rope was made from thetree’s fibers. Land was also cleared of trees to planttaro, sugarcane, bananas, and yams.Using these abundant tree resources, thePolynesians developed an impressive civilization.They also developed a technology capable of makingand moving large stone structures, including theirfamous statues (Figure 3-1). The people flourished,with the population peaking at somewhere between7,000 and 20,000 by 1400. However, they used up theisland’s precious trees faster than they were regenerated—anexample of the tragedy of the commons.By 1600, only a few small trees were left.Without large trees, the islanders could notbuild their traditional big canoes for huntingporpoises and catching fish in deeper offshorewaters, and no one could escape the island by boat.Without the once-great forests to absorb and slowlyrelease water, springs and streams dried up, exposedsoils eroded, crop yields plummeted, and faminestruck. There was no firewood for cooking or keepingwarm. The hungry islanders ate all of the island’sbirds. Then they began raising and eating rats, descendantsof hitchhikers on the first canoes.Both the population and the civilization collapsedas gangs fought one another for dwindling food supplies.Bone evidence indicates that the islanders beganhunting and eating one another.Dutch explorers reached the island on Easter Day,1722, perhaps 1,000 years after the first Polynesians hadlanded. They found about 2,000 hungry Polynesians,living in caves on a shrubby grassland.Like Easter Island at its peak, the earth is an isolatedisland in the vastness of space with no othersuitable planet to migrate to. As on Easter Island, ourpopulation and resource consumption are growingand our resources are finite.Will the humans on Earth Island re-create thetragedy of Easter Island on a grander scale, or will welearn how to live more sustainably on this planet thatis our only home? Scientific knowledge is a key tolearning how to live more sustainably. Thus we needto know what science is, understand the behavior ofcomplex systems studied by scientists, and have abasic knowledge of the nature of the matter and energythat make up the earth’s living and nonlivingresources, as discussed in this chapter.Figure 3-1 These massive stone figures on Easter Islandare the remains of the technology created by an ancientcivilization of Polynesians. Their civilization collapsed becausethe people used up the trees (especially largepalm trees) that were the basis of their livelihood. Morethan 200 of these stone statues once stood on hugestone platforms lining the coast. At least 700 additionalstatues were found turned over, abandoned in rock quarriesor on ancient roads between the quarries and thecoast. No one knows how the early islanders (with nowheels, no draft animals, and no sources of energy otherthan their own muscles) transported these gigantic structuresfor miles before erecting them. We presume theyaccomplished it by felling large trees and using them toroll and erect the statues.