Why is ecology not limited only to the forces of nature ?

1. Over time, however, ecology has been modified by human actions. What appears to be a natural feature of the environment — aridity or flood-proneness, for example, is often produced by human intervention. Deforestation in the upper catchment of a river may make the river more flood-prone.

2. Climate change brought about by global warming is another instance of the widespread impact of human activity on nature. Over time, it is often difficult to separate and distinguish between the natural and human factors in ecological change.

3. Alongside biophysical properties and processes that may have been transformed by human action — for example, the flow of a river and the species composition of a forest, there are other ecological elements around us that are more obviously human-made.

4. An agricultural farm with its soil and water conservation works, its cultivated plants and domesticated animals, its inputs of synthetic fertilisers and pesticides, is clearly a human transformation of nature.

5. The built environment of a city, made from concrete, cement, brick, stone, glass and tar, uses natural resources but is very much a human artefact.