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Last changed: 4/04/11
Air pollutants are transported through the atmosphere and deposited into ecosystems which are sometimes far away from the sources. They have various impacts on the biogeochemistry, the flora and fauna and its diversity.
Deposition of sulphur and nitrogen compounds leads to soil acidification, altering the balance between and budgets of soil nutrients. Plants and plant communities that only thrive in neutral soil conditions have no chance of survival in the long term. Such types of ecosystem then disappear, and the biodiversity of ecosystems is diminished.
Nitrogen compounds can also have eutrophication effects on semi-natural terrestrial ecosystems. Long-lasting high levels of airborne nitrogen deposition disrupts the balance between nitrogen and other nutrients such as magnesium, phosphorus and potassium in the soil and thereby affects a balanced uptake by plants. An imbalanced nutrient household in the ecosystem leads to lower tolerance of short-term interferences or stress (frost, dry periods, pests). Nitrogen deposition is a major cause of the loss of biodiversity in Europe.
If concentrations of heavy metals exceed critical limits, they are toxic to organisms and can disrupt the functioning of an ecosystem.
Ground-level ozone also is harmful to vegetation. Direct effects can lead to yield or quality loss (e.g. discolouration and death of parts of leaves). In the case of trees, long-term effects are possible (e.g. increased sensitivity to pests).
In summary, long periods of stress exerted through pollutant input lead to destabilisation of ecosystems (e.g. forest damage), which are then more vulnerable to natural stress factors and changes in climate.
The mentioned anthropogenic (i.e. caused by human activity) stress factors have local effects which vary with natural site conditions: their mutual impact can either be amplified (synergistic effects) or weakened (antagonistic effects).
The changes in ecosystems brought about or aided by air pollutant input can ultimately result in an impairment of their functions, which also means diminished ability to serve mankind, e.g. by providing clean groundwater and other resources, flood protection, acting as areas of rest and recreation, etc.