More Environmental Astronomy

Even though we don't understand the Earth and its ecosphere as a being, in many respects, it acts like on, and the assumption that it does, called the Gaia hypothesis, is a reliable way to make good predictions about how the global ecosystem will respond to stress factors, including extraterrestrial impacts. This hypothesis predicts that Earth is robust in the long term and that life will find a way to stabilize things in the long run even though that are factors that could screw it up. 

Of course, on these time scales, the "long term" may be too long to be relevant to humans.

The Gaia hypothesis postulates that life regulates its environment to be favorable for its own survival. Most planets experience numerous perturbations throughout their lifetimes such as asteroid impacts, volcanism, and the evolution of a star's luminosity. For the Gaia hypothesis to be viable, life must be able to keep the conditions of its host planet habitable, even in the face of these challenges. 

ExoGaia, a model created to investigate the Gaia hypothesis, has been previously used to demonstrate that a randomly mutating biosphere is in some cases capable of maintaining planetary habitability. However, those model scenarios assumed that all non-biological planetary parameters were static, neglecting the inevitable perturbations that real planets would experience. To see how life responds to climate perturbations to its host planet, we created three climate perturbations in ExoGaia: one rapid cooling of a planet and two heating events, one rapid and one gradual. The planets on which Gaian feedbacks emerge without climate perturbations are the same planets on which life is most likely to survive each of our perturbation scenarios. Biospheres experiencing gradual changes to the environment are able to survive changes of larger magnitude than those experiencing rapid perturbations, and the magnitude of change matters more than the sign. 

These findings suggest that if the Gaia hypothesis is correct, then typical perturbations that a planet would experience may be unlikely to disrupt it.

Olivia D. N. Alcabes, Stephanie Olson, Dorian S. Abbot, "Typical Climate Perturbations Unlikely to Disrupt Gaia Hypothesis" submitted for publication to MNRAS (June 3, 2019).