Biodiversity maintains the air we breathe and the water we drink. Green plants purify our air and our water by taking in carbon dioxide, regulating water vapour, releasing oxygen, and cycling nutrients. Through photosynthesis, trees and other plants give off oxygen that helps maintain atmosphere. As a result of these processes, plants play a crucial role in maintaining the planet's water cycle. Wetlands and the vast array of bacteria and other microscopic species they house also act as water filters.

The activities of microbial and animal species - including bacteria, algae, fungi, mites, millipedes and worms - condition soils, bring organic matter, and release essential nutrients to plants. These processes play a key role in the cycling of such crucial elements e.g. nitrogen, carbon and phosphorous between the living and non -living parts of the biosphere.

Wetland ecosystems (swamps, marshes, etc.) absorb and recycle essential nutrients, treat sewage, and cleanse wastes. In estuaries molluscs remove nutrients from the water, helping to prevent over-enrichment and its attendant problems, such as eutrophication arising from fertilizer run-off. Trees and forest soils purify water that flows through forest ecosystems. In preventing soils from being washed away, soil protection by forests also prevent the harmful siltation of rivers from erosion and landsli des.