Environmental problems can be found in all areas of the world, and they affect land, water and air. Some result from what humans take from the environment, in the form of land for agriculture, and accommodation for a rapidly increasing population; mineral and fossil fuel resources; and timber. These problems include deforestation, erosion, damage to ecosystems and reductions in biodiversity. Other problems stem from what humans put into the environment, in the form of various pollutants. These issues include climate change, damage to the ozone layer, urban pollution, and acid rain.
One of the most publicized aspects of degradation is deforestation. In the Amazon rainforest in particular, trees are being felled at an alarming rate to provide more land for agriculture. This is threatening the survival of many animal species, for example the jaguar. In Borneo and Sumatra, another forest animal, the orang-utan, is under threat for the same reason.
Deforestation can also lead to soil erosion. Trees stabilize the soil with their roots, reduce the intensity of rainfall that hits the ground, and help soils retain moisture. When they are removed, heavy rain can quickly wash soil away, and, during dry periods, bare, desiccated soil may be removed by wind. Deforestation on hill and mountainsides can lead to flooding, as water is then able to run unimpeded down the slopes, and can also result in disastrous mudslides.
In some cases, successful campaigns have been launched to alleviate some of these problems. For example, in the United States, logging of forest land was destroying the habitat of the Northern Spotted Owl, a threatened species. After a lengthy lawsuit, however, logging was curtailed in those areas. As of 2013, there are campaigns in progress to save a variety of endangered animals.
This is a global problem that affects the atmosphere, oceans, lakes and rivers, and also land. Many human activities result in the release of toxic chemicals into the air or into water, which can go on to damage the environment or cause ill health in people. Two of the worst air pollutants are sulfur dioxide (SO2) and nitrogen dioxide (NO2). SO2 is produced by sulfur compounds in fossil fuels, particularly coal, while NO2 comes mostly from car exhausts. Both are toxic, and high levels in urban environments can cause, or aggravate, respiratory problems in humans.
These gases are also responsible for acid rain. Both undergo reactions in the atmosphere that produce strong acids, which dissolve in rainwater. The resulting rain can increase the acidity of soils and lakes, killing off sensitive species, and may directly damage trees and other plants. It can also damage some stone buildings and monuments.
Another cause for concern is depletion of the ozone layer, high in the atmosphere. This layer absorbs ultraviolet light, particularly the most damaging forms, minimizing exposure at ground level. The release of chemicals known as chlorofluorocarbons (CFCs), used in aerosol sprays, is blamed for damaging this layer, and potentially increasing exposure of humans, animals and plants to dangerous levels of ultraviolet light. These chemicals have been banned in the USA and Canada, but many other countries are still using them.
Air pollution can also take the form of tiny particles. Many combustion processes, such as wood and coal fires, wood stoves, and the burning of fuel in cars produce minute particles of carbon, in the form of soot and smoke. These may affect climate, by reducing the transparency of the atmosphere, and by acting as “condensation nuclei,” which encourage water vapor to condense into droplets, increasing cloud cover. At lower levels, these “particulate” pollutants may contribute to respiratory problems in people.
One of the biggest environmental problems facing mankind is due to a pollutant that is not normally directly harmful to humans. Carbon dioxide (CO2) is produced in huge quantities by the burning of fossil fuels, for example by cars, industrial processes, and airplanes. It traps heat in the Earth’s atmosphere, and is the most important “greenhouse” gas. Increased levels resulting from human activities are thought to be raising air and ocean temperatures across the planet, a phenomenon known as “global warming” or “climate change.” This, in turn, seems to be causing melting of glaciers and ice sheets on a large scale, which may lead to rises in sea level and the consequent loss of large areas valuable, low-lying agricultural land, and the displacement of huge numbers of people.
Climate change may also have a drastic effect on agriculture due to changes in temperature and rainfall. Many crop plants may be unable to adapt to drier or wetter conditions. Droughts may affect some areas, while others may suffer from flooding, due to increased rainfall. It may be that warming of the oceans will lead to more frequent, and more severe, hurricanes.
This can occur through the release of industrial waste, for example from mining and metal refining activities, into streams and rivers, from where it may make its way into the ocean. A variety of toxic metals can affect aquatic and marine life and may accumulate in the food chain, posing a threat to humans. Another major source of water pollution is fertilizers, which can be washed into rivers and lakes from farmland, causing a phenomenon known as eutrophication. Nitrates and phosphates, present in fertilizers, and essential for plant growth, can also promote uncontrolled multiplication of algae in lakes, causing an “algal bloom.” This reduces water quality and oxygen levels, and may kill fish.
Humans often introduce animal and plant species to areas outside their natural range. Sometimes this is done intentionally and sometimes not, but often it can lead to serious environmental problems. Domestic pets may kill local wildlife, while non-native garden plants may escape and become established in a new area, taking over from native species, perhaps because they have no natural predators in their new environment. Increased international travel means that disease-causing organisms can easily be introduced to new areas, where they may cause devastation among species that have no natural resistance.
Solutions to many of these problems will require action by governments across the globe, for example, to reduce burning of fossil fuels and develop renewable energy resources. Ordinary people, however, can make their own contributions; for example, cutting down on car journeys helps reduce levels of carbon dioxide, nitrogen oxides and soot. Avoiding long haul flights wherever possible may also help. Companies can play a role by using teleconferencing facilities so that employees do not have to travel to meetings, and allowing staff to work online from home, where practical. Individuals can also help in many small ways, such as minimizing their use of garden fertilizers, not using them when rain is forecast, picking up litter and rubbish that might harm wildlife, and properly disposing of harmful chemicals.