Human beings can alter the balance of ecosystems in two ways: direct alteration and indirect alteration.
The direct alteration is the elimination of certain plants or animals. Humans usually have a direct effect on ecosystems by doing activities that involue natural resources, such as hunting, fishing and logging. It changes the structure and function of natural systems and these changes are affecting human health in a variety of important ways. For example: when a forest is burning, we get less oxigen and breathe the smoke.
Humans have changed many natural ecosystems, such as forests, into artificial ecosystems, such as farmland or towns. These ecosystems often suffer problems such as soil erosion or desertification.
Elena Arrieta, Carlota MartíneZ, Hugo Alberti, Denis Boitiu.
Quinto de Primaria