Changes in one ecosystem ripple through others with varying degrees of impact. As self-regulating open systems that maintain flows of energy and matter, they naturally move toward maturity, stability, and balance in the absence of major disturbances. In ecological terms, the physical environment can be seen as an interdependent web of production and consumption cycles. Through evapotranspiration the atmosphere and plants help to purify water. Plants provide the energy to keep animals alive either directly through consumption or indirectly through their death and decay into the soil, where the resultant chemicals are taken up by new plants.
Soils keep plants and animals alive and work to cleanse water.
The root systems of plants and the mechanical and chemical effects of water percolating through bedrock create new soil layers. Ecosystems therefore help to recycle chemicals needed by living things to survive, redistribute waste products, control many of the pests that cause disease in both humans and plants, and offer a huge pool of resources for humans and other living creatures. However, the stability and balance of ecosystems can be altered by large-scale natural events such as El Ni o, volcanic eruptions, fire, or drought. But ecosystems are more drastically transformed by human activities. The web of ecological interdependency is fragile.