Assignment task: Life has profoundly changed planet Earth in various ways. We will discuss throughout this class many ways in which life modifies its own environment, including planetary chemistry and climate. We will show via a theoretical example how vegetation cover can change the reflective characteristics of the land surface, i.e. the planetary albedo. Since life itself is influenced by climate, and it influences climate, this sets up a feedback. You will gain better understanding of climate feedbacks due to living organisms on a planet (i.e. the biosphere).
Imagine a very simplified model of a planet uniformly covered by land, with a stable uniform temperature everywhere, fixed at, say 15oC. Two species of daisies are the only life form on the planet: a white daisy, which is very reflective of solar radiation and has competitive advantage (grows better) in climates warmer than 15 oC, and a black daisy, which is very absorptive of solar radiation and has a competitive advantage (grows better) in climates colder than 15 oC. These are covering half of the planet's area each at the start of this thought experiment.
Since the daisies respond to temperature changes, but their response influences temperatures itself via the albedo, there is a daisy-albedo feedback set up. Is the daisies' response and effect on temperature acting in the same or opposite direction as the original temperature change? Does this imply that this feedback is a negative or a positive one? Does it have a stabilizing or destabilizing effect on the planet's climate/temperature?