Sack Lunch Seminar (SLS)

Enhanced Overall Stability with Biodiversity Under Stochastic
Perturbation of Solar Radiation in Model Food Webs







Classical theory, based on asymptotic resilience, predicts that the stability of
ecosystems decreases with biodiversity. However, this seems to contradict many
empirical observations. Here we analyze three stability properties -resilience,
resistance, overall stability- of several model ecosystems which conserve mass
and resolve varying degrees of biodiversity. We define overall stability as the
temporal variability of the individual populations present in the food web,
relative to their reference state. It reflects the balance between its
resistance to displacement and its resilience to return back to its reference
state. We find that more biodiverse model ecosystems are more overall stable
under stochastic perturbations of solar radiation, due to transient dynamics.
Although the long-term asymptotic resilience of these model ecosystems does
decrease with biodiversity, their overall stability increases due to an
increase of their short-term transient resilience and resistance. The model
ecosystems resistance and transient resilience are related to measurable
ecosystem processes. Resistance is inversely related to total primary
production, and the transient resilience is inversely related to the turnover
time of nutrients. Both relationships follow a power-law equation. Both primary
production and turnover time tend to decrease with biodiversity, the former most
robustly. Therefore, biodiversity tends to enhance both the resistance and the
transient resilience of the model ecosystems, although the link is stronger for
resistance. As a consequence, there is a robust positive correlation between the
model ecosystems biodiversity and their overall stability. Our results
suggest that the loss of biodiversity could weaken the overall stability of
closed ecosystems to environmental changes.