Figure 8-1: Climate is
controlled by geochemical processes and cycles resulting from the interplay among
the environment's components involved, as affected by human action. The
scheme shows some of these issues. For simplicity, the single double-ended arrows
between issues represent some of the linkages involved. For example, biological
and ecological processes play an important role in modulating the Earth's
climate at both regional and global scale by controlling the amounts of water
vapor and other greenhouse gases that enter into or are depleted from the atmosphere.
Changes in climate affect the boundaries, composition, and functioning of ecological
systems, such as forests, and changes in the structure and functioning of forests
affect the Earth's climate system through changes in the biogeochemical cycles,
particularly cycles of carbon, nitrogen, and water. There are other linkages such
as the connection between air quality and forestry, directly or through acid precipitation,
which for simplicity are not shown here.