There is a risk of water shortages in the near future, and many sources of water are polluted. Humanity may also be close to running out of oil and other important materials.
There is a limit to the numbers of people that can be supported by the earth. A higher population requires more land to be used for food, and more chemical fertilizers and intensive cultivation to be used on existing agricultural land. If a high standard of living is maintained, a high population will also require more energy and resource use and it will usually create more pollution and waste. The world population was six billion in 2000, and it is projected to rise to almost nine billion by the year 2040. In 10,000 B.C. the maximum estimated world population was around ten million (U.S. Census Bureau-International Database, 2007). There are currently signs that the current population is reaching the limits of the carrying capacity of the world. There are constant famines in some parts of Africa. Rising oil prices may signal an impending oil shortage. Consumption of oil has risen throughout the world and there have been few significant new discoveries. Deforestation is a major problem as poor countries cut down their forests to provide new land for agriculture. There are large "dead zones" in some coastal areas due to pollution. Damage to the environment will eventually lower the carrying capacity of the earth as agricultural yields will fall if topsoil is eliminated because of the erosion that occurs with constant monocropping and the destruction of the forests. Overfishing can cause fish stocks to collapse, and they may not recover for a long period of time even if fishing is temporarily halted. If the world population outgrows the carrying capacity of the earth, the results could be a rapid population collapse as wars, famines, and major epidemics occur in many places at once. There is evidence that the society on Easter Island collapsed due to overpopulation and the overconsumption of resources. "Apparently the islanders were greeted with a lush tropical paradise when they first discovered it. It must have seemed inexhaustable. The trees were cut for lumber for housing, wood for fires, and eventually for the rollers and lever-like devices used to move and erect the moai" (Wassmann, 1996). Eventually, the clear-cutting caused erosion and the permanent loss of the original forest on the island. The island could no longer support its population, and there was constant warfare and cannibalism. The society collapsed, and the population of the island is estimated to have dwindled from about 7,000-9,000 to about 750.
Overdevelopment has damaged the environment in many places. Human needs and wants should not be the only thing that determines where new housing developments and cities are constructed, as development can cause important species to lose land in their habitats; and it can cause other problems, such as the loss of topsoil and pollution. The loss of some species in a region can cause other species to either die off or over-reproduce. Other species could enter the region, and they could become pest species. Land in some types of developments also becomes eroded easily. Highways and developments also create large amounts of pollution and waste.
Pollution has always been a major problem throughout history. The industrial revolution added many new types of pollution to the environment