How can species diversity affect ecosystem stability?

Note that while there is a simple correlation between increased species diversity and stability, this is not a comprehensive explanation.

Increased alpha diversity, or the number of species present, generally leads to greater stability, meaning an ecosystem with a greater number of species is more likely to withstand a disturbance than an ecosystem of the same size with a lower number of species. This is the basis of the diversity-stability hypothesis, which claims that ecosystems with greater species diversity are more stable.

Although there is still much to learn about the subtleties and complexity of diversity, which can be measured in a variety of ways, and stability, which can also be measured in a variety of ways, this hypothesis was controversial for a while because it had not been empirically tested. Currently, however, it is generally accepted.

It has been suggested that biodiversity is not the primary driver of stability but rather a secondary driver and that biodiversity and stability have a bi-directional relationship (Worm and Duffy, 2003). A 2007 review of over 50 empirical studies on diversity-stability concluded that we cannot expect to reach a general conclusion about diversity and stability (Ives and Carpenter, 2007).

According to recent studies on coral reefs, increased stability is a result of beta diversity, or the ratio between regional and local diversity (Mellin et al., 2014).

In conclusion, the diversity-stability hypothesis is no longer untested, but there is still a great deal that needs to be understood. Studies that support the hypothesis outnumber those that refute it, but the balance still lies in understanding much of what is still unknown.

For those interested in further information, there is a good review article in Nature, though it is a little out of date because a lot of new research has been published since then.

Species diversity can affect ecosystem stability by increasing resilience to disturbances and enhancing ecosystem functioning. A diverse ecosystem is more likely to contain species with a variety of traits, which can provide redundancy in ecological functions. This redundancy helps to maintain ecosystem processes even if some species are lost due to disturbances. Additionally, diverse ecosystems are better able to utilize available resources efficiently, which can lead to increased productivity and stability over time. Conversely, ecosystems with low species diversity are more vulnerable to disturbances and may experience declines in stability and functioning if key species are lost.