The connection between pollution and conservation is often one of direct conflict, with conservation normally being assumed to be the preservation of the environment in its natural state, and pollution as the introduction of harmful substances into the environment. The environment is often divided into major sectors that may have delayed affects on one another, however, through pollution, such as air pollution, water pollution, and land pollution. Pollution and conservation can also be largely concerned with the state of animal wildlife in an environment. Animals can have more robust abilities to adapt to pollution through means such as migration, greater tolerance for adverse chemicals in the ecosystem than plants, and through very gradual mutation and natural selection processes. While most pollution is caused by human industrial activity, pollution and conservation can also be at odds where the human population itself is looked at as an example of an invasive species that encroaches on and destroys natural habitats as it multiplies out of control.
One of the most critical and far-reaching areas of the environment due to its natural cycle of intertwined changes involves the worldwide resource of available fresh water. Water cycles through the land via river watersheds and rain to purify it of chemical salts and pollutants that can harm plant and animal life, and it is vaporized by ground heat to serve as a natural cleanser of air pollutant particles. Conserving water is also important because many industries rely upon large quantities of fresh water to function, as well as most types of agriculture. Among the complex issues of pollution and conservation involving water, threats exist to the fresh water supply from contamination by germ-based diseases and water-borne parasites that are often increased as the human residential population grows, as well as contamination by synthetic chemical pollution from commercial activity. The United Nations has estimated that, as of 2011, more people die on Earth every year from polluted water than from all forms of violence on the planet including any currently active states of war.
While saving water from pollution processes can indirectly improve air quality, reducing pollution in the air has to be made a priority as well. Air quality can, in some cases, be poorer in the wild than in urban environments. A 2001 report on the state of US National Parks found that air quality in some of the large conversation areas of the US parks system was worse than in many cities. An example of how conservation practices have to be tied together in the report showed that mercury pollutants from waste incinerators and electrical power plants fueled by coal have contaminated over 18,000 lakes in the central United States. These bodies of fresh water, including the Great Lakes themselves, were polluted by mercury carried through the air.
Where pollution and conservation involve contamination of the land, resolving such problems may be the most difficult of all. Many proponents of green conservation suggest that protecting the land is best done through resource conservation, or reducing the need for natural resources beyond the ability of the environment to replenish them over time. This is difficult to promote in practice, however, as many growing nations are committed to harvesting their natural resources as quickly and cheaply as possible, which often includes releasing pollutants into the environment that can be carried for thousands of miles or kilometers by air and water.
The US Department of State has estimated that 22,000,000 acres of forest are cut down each year on a global basis to be used for fuel, shelter, and other purposes. Pollution and conservation also has an impact on coral reefs, which are considered to be the rainforests of the sea for their ability to host thousands of ocean species. Though they provide over $375,000,000,000 US Dollars (USD) per year in commercial products as of the year 2000, they are also disappearing at a rapid rate due to pollution. Estimates as of 2000 are that 30% to 60% of all coral reefs around the world will be gone by the year 2050.
Habitat loss that affects animal species in general is the most visible evidence of the tradeoff between pollution and conservation. While land and water development for a growing human population contribute to habitat loss as well as agricultural and industrial interests, other often unseen factors affect the trend as well. These include the fragmentation of habitats from human encroachment, which can cause local ecosystems to lose their ability to survive next to civilization. Examples of habitat fragmentation can occur from such activities as the building of roads, dams on rivers, or through the destruction of small regions that migratory species use along their annual routes.