Global change and photosynthesis

The phrase global change is generally associated with alterations of climate (temperatures, fluctuations in precipitation, etc) that stem from changes in atmospheric composition. In reality, global change also encompasses more than changes in climate or atmospheric composition; any global-scale change that influences biota directly, or indirectly, can be considered global change. Global change has influenced the biosphere throughout geological time, with changes occurring over periods that allow for either species to evolve to these changes when they occur over long periods, to adapt or acclimate to the changes, or to perish when neither of the previous two responses is effective. While we are currently in the midst of abrupt global change, it certainly is not the first. What differentiates the current changes to our planet from all other global change events is that these abrupt changes are brought about through anthropogenic influences and that they are occurring more rapidly than in previous occasions.