Humans have had an impact on the environment since the dawn of their existence by utilizing the Earth's resources for food, shelter, tools, firewood, etc. Impacts on the environment are wide and varied from location to location, however the most severe impacts on the global ecosystems and sustainability have been due to global warming, acid rain, overhunting and overfishing, habitat loss, and invasive species.
The burning of fossil fuels is a major problem to the environment because of the carbon dioxide emissions contributing to the greenhouse effect. Other air pollutants released may affect human health and the environment; for example, sulphur and nitrogen may react with water to produce acid rain.
Global warming will result in drastic changes to global ecosystems as habitats are altered; many animals will be forced to shift their ranges north. One concern that many scientists have is the ability of the animals to shift and or adapt to the rapidly changing conditions.
Human activities, such as the burning of fossil fuels in factories, power stations, and automobiles, release nitrogen and sulphur oxides into the atmosphere and are the leading cause of acid rain. When these air pollutants react with rain, water sulphuric and nitric acid are produced. Some of the potential effects of acid rain on the environment are listed below.
As the water pH approaches 6, insects begin to disappear and other aquatic organisms are not able to survive because the pH continues to decrease and become more acidic. Terrestrial animals, such as wetland birds, lose their food sources. Waxy surfaces of leaves are degraded lowering the resistance to disease, cold, and drought. Soil loss and removal of nutrients is accelerated, slowing the growth rates.
Both fishing and hunting could be sustainable practices; for example, fish can be harvested forever if the number of fish caught each year does not exceed the number reaching maturity and reproducing in that year.
Overfishing and overhunting have caused many species, such as the passenger pigeon and woolly mammoth, to become extinct. In some cases the population dynamics of an ecosystem are dramatically altered by removing too many prey or too many predators.
Habitats can be destroyed by: Habitat Loss - the clearing of land and change in land use. Habitat Fragmentation - the splitting of large areas of land for societal purposes, such as roads and buildings, preventing animals from moving between habitats and limiting their ability to find food, reproduce, and colonize new areas. Habitat Degradation - loss of biological functioning due to pollution.
Invasive species are defined as organisms that are transported from one ecosystem to another by humans with the potential to cause harm to society and the environment. Invasive species are problematic because they are able to out-compete the native plants and animals for nutrients and other resources. As a result, the invasive populations grow rapidly and alter the natural functioning of the ecosystem. In addition the “new” species in the environment does not have any local natural predators.
A mass extinction occurs when a large percentage of living organisms go extinct over a short period of time. Each of the previous five major mass extinction events has been due to natural changes to the environment on a global scale. The most famous and the last mass extinction event (but not the largest) occurred 65 million years ago when the dinosaurs were wiped off the face of our planet due to a large asteroid impact that changed global conditions.
Many scientists speculate that we are now in the middle of the next mass extinction in which many species are becoming extinct due to humans many impacts on ecosystems.