Biogeochemical cycles are essential to long-term, sustainable life on Earth for several reasons.
First, living things require many chemical elements, and these must be available at the right time, in the right amounts, and in the right concentrations relative to each other. This is the essence of, and the importance of, biogeochemical cycles.
Second, sustained life on Earth is a function of ecosystems, and a primary ecosystem process is the cycling of chemicals necessary for life. On a larger scale, chemicals, nutrients, and trace elements necessary for life are made available from Earth through various parts of biogeochemical cycles.
For example, soil and rock release nutrients to plants through weathering and biochemical processes; water infiltrates rock and soil to emerge as springs and streams necessary for life. In the ocean, single-cell algae release a sulfide compound that oxidizes in the atmosphere, producing condensation nuclei that are necessary to form clouds that transport water and sulfur to the land.
Third, chemical reactions in biogeochemical cycles determine whether chemical elements and necessary compounds’ are available to living things. Photosynthesis involves the availability of carbon dioxide in the carbon cycle.
Green plants use the carbon dioxide with sunlight and water to produce sugar. A by-product is oxygen, which is why we have free oxygen in the atmosphere. Without the carbon and water cycle, none of this would happen and life as we know it wouldn’t be possible.
In general, life on earth depends on the recycling of critical elements (Fig. 5.16). Both physical and biological processes are involved in the creation of active pool of elements. There is continuous transformation of elements from storage pool to active pool, or vice versa.