10.5: Pollution

Pollution occurs when chemicals, particles, or other materials are released into the environment, harming the organisms there. For many thousands of years, ever since they built the first campfire, human activity has generated air, water, and soil pollution. For most of human history, however, these contaminants had relatively little environmental impact. But over the last few centuries, pollution levels skyrocketed as a result of population growth and the Industrial Revolution. As a result, regulations have been enacted to control emissions. Even where these are effective in curbing current pollution sources, high levels of contamination may exist from past activity. And new contamination can occur through industrial accidents or other inadvertent releases of toxic substances.

Pollution has contributed to the decline of many threatened species. For example, a 2007 study by Kingsford and colleagues found that pollution was a major pressure on 30% of threatened Red List species in Australia and surrounding regions. 

Power plants, factories, and vehicles are common sources of air pollution. In some cases, the pollutants are directly toxic (for example, lead), but in other cases the pollutants indirectly cause ecological harm when they are present in unnaturally large quantities (for example, carbon dioxide emissions leading to climate change). Not only can air pollutants directly harm animals by causing respiratory issues and cancer as well as damage vegetation, but some interact with the atmosphere to form acid deposition (commonly called acid rain). Acid deposition disrupts aquatic ecosystems as well as soil communities and plant growth.

Heavy metals, plastics, pesticides, herbicides, fertilizers, and sediments are examples of water pollution. Heavy metals (including copper, lead, mercury, and zinc) can leach into soil and water from mines. Furthermore, acid mine drainage is caused by reaction of mine wastes, such as sulfides, with rainfall or groundwater to produce acids, like sulfuric acid. The Environmental Protection Agency estimates that 40% of the watersheds in the western United States are contaminated by mine run-off. Plastics harm shorebirds, turtles and aquatic invertebrates that ingest and accumulate them. Nutrients, such as nitrate and phosphates, are healthy in bodies of water to an extent, but when fertilizer pollution adds too many of these nutrients at one time, algal blooms can result. This has cascading effects that can ultimately shade and kill aquatic plants and deplete oxygen needed by fish and other animals (eutrophication). A particularly concerning water pollution problem is micropollutants. For examples, some chemical residues affect growth, cause birth defects, and have other toxic effects on humans and other organisms even at very low concentrations.

Figure \(\PageIndex{a}\) summarizes the effects of air and water pollution on biodiversity, and the chapters about Solid Waste Management, Water Pollution, and Air Pollution explain these threats in more detail.

Figure \(\PageIndex{a}\): Some sources of water and air pollution and their major effects on biodiversity. Sources of pollution include industry, car emissions, power plants, pesticides, fertilizers, and drugs. Some major consequences of air pollution include respiratory problems, acid precipitation, plant damage, ozone depletion, and climate change. Water pollution can bioaccumulate and can lead to eutrophication, death by plastic, reduced photosynthesis, and hormone disruption. Image by Leafcutter Media (CC-BY-SA).

References

Kingsford RT, Watson JEM, Lundquist CJ, Venter O, Hughes L, Johnston EL, Atherton J, Gawel M, Keith DA, Mackey BG, Morley C, Possingham HP, Raynor B, Recher HF, Wilson KA. Major conservation policy issues for biodiversity in Oceania. Conservation Biology 2009;23(4):834–40.

Attributions

Modified by Melissa Ha from the following sources:

• Issues and Opinions from AP Environmental Science by University of California College Prep, University of California (licensed under CC-BY).  Download for free at CNX.
• Biodiversity 2011- Pollution and Biodiversity 2016- Pollution from Australia State of the Environment by Commonwealth of Australia (licensed under CC-BY)