Pollution is the introduction of contaminants into a natural environment that causes instability, disorder, harm or discomfort to the ecosystem i.e. physical systems or living organisms. Pollution can take the form of chemical substances or energy, such as noise, heat or light.
Contaminants can be either foreign substances/energies or naturally occurring contaminants. Pollution is often classed as point source pollution where there is a single identifiable source of contamination such as an industrial chimney stack or sewage outfall, or non-point source pollution where there are multiple diffuse sources such as agricultural run-off.
The effects of pollution on ecosystems are numerous and varied but can be broadly grouped into four main categories:
1) changes to water quality which may lead to reductions in aquatic biodiversity;
2) damage to terrestrial habitats and soils;
3) alterations to atmospheric conditions leading to climate change; and
4) direct impacts on individual species including human beings. There are many different types of pollution with varying levels of impact on the environment but some of the more commonly discussed forms include: air pollution, water pollution, soil contamination and light pollution.