Human Influence on Ecosystems

Humans have evolved from a few small populations of hunter-gatherers to a sprawling population that has altered the landscape wherever they have settled. As a result of human development, ecosystems have been manipulated and exploited, threatening their sustainability and production. Some key causes of this destruction are exploitation, introduction of foreign species, habitat conversion and irrigation practices.

Overexploitation

• Consumption of natural resources through activities such as fishing, hunting, livestock grazing, fuel wood consumption and logging puts a strain on ecosystems. If too many of an animal or plant species are killed, or too much of a habitat is destroyed through these exploitative human practices, the ecosystem's ability to function is compromised.

Non-Native Species

• Ecosystems maintain a delicate balance in the form of mutualism between organisms, food chain structure and habitat maintenance. However, human introductions of foreign species to ecosystems around the world threaten that balance. Humans have intentionally and unintentionally brought plant and animal species with them when traveling to new lands. European colonization around the world rapidly increased the spread of non-native species. This caused problems in the new ecosystems such as over-consumption of native populations and competition for food sources with native populations. The effect of a non-native species on an ecosystem is not always negative. However, the result of such introductions of foreign species is difficult to predict.

Habitat Conversion

• A common agricultural practice is the conversion of a natural habitat to a crop-producing plot of land to meet human needs. Such conversion threatens the survival of an ecosystem. When forests are removed and replaced with farmland, the soil loses the productivity it once had in the forest ecosystem. Without the root structure to hold the soil in place, nutrient regeneration is reduced and the overall productivity of the soil is much less than it had been prior to tilling.

  Habitat conversion also takes place whenever a natural ecosystem is converted into an unnatural structure. Pavement in the form of roads and parking lots as well as buildings are forms of habitat conversion.

Irrigation

• Although irrigation has long been used as a method of moving water from its source to an agricultural area, the overuse of the method during the 20th and 21st centuries has led to ecological destruction of the soil. Irrigation has made agricultural practices possible in otherwise impossible environments, such as desert ecosystems. These practices, however, have required ecologically harmful construction of dams, wells, canals and dikes. Water tables have been lowered to support the crop's need for water and as a result, the quality of groundwater has significantly diminished. Fertilizer, pesticides and other harmful contaminants have been introduced to the water supply through irrigation.

Conservation

• During the 20th and early 21st centuries, the practice of conservation regarding the world's ecosystems began to increase. Agricultural practices were introduced that had less impact on the long-term health of the environment. Regulations were introduced to control the transport of invasive species. Also, exploitative practices such as hunting, fishing and logging were more tightly regulated to conserve populations of species for future use.