A balanced nature: biodiversity, feasibility and stability in competitive ecosystems

How species interact and how ecosystems persist and maintain biodiversity is key to ecology. Paradoxically, ecological theory predicts that biodiversity inherently leads to instability, whereas in experiments typically increased biodiversity is associated with increased ecosystem stability. Resolving this paradox requires quantifying the probability that a community of species is feasible and stable. Here, we quantify how competition bounds and regulates biodiversity and use this to accurately estimate the probability that a random competitive community persists. Increased competition leads to reduced diversity, but without affecting the ecosystem’s resilience. Experimental results bear out our theoretical prediction that biodiversity is regulated and balanced. We conclude that the loss of biodiversity does not inherently lead to tipping points or a catastrophic collapse of ecosystems.