Communities with more fish species are more productive and more resilient to rising temperatures and temperature swings, according to a new study from the Smithsonian’s Tennenbaum Marine Observatories Network and other international institutions.
The question of whether biodiversity offers practical value (for humans and ecosystems) is controversial, but the new study, published in the Proceedings of the National Academy of Sciences, offers “the most thorough proof yet” that preserving marine biodiversity can benefit people as much as it benefits the oceans.
The discovery came out of the Reef Life Survey, a comprehensive program that has conducted surveys of more than 3,000 fish species in 44 countries around the world.
Armed with the most comprehensive global dataset on marine biodiversity involving standardised counts, the researchers tracked how 11 different environmental factors influenced total fish biomass on coral and rocky reefs around the world. Surprisingly, one of the strongest influences was biodiversity: The number of species (species richness) and the variety in how they use their environment (functional diversity) enhanced fish biomass. The boost in fish resources provided by biodiversity was second only to that of warm temperatures.
Temperature had a more complex relationship with fish biomass: Warmer ocean temperatures tended to boost fish biomass on average, while wider temperature fluctuations hindered it. But biodiversity made fish communities more resilient against changing climate. In communities with only a few species, fish biomass tended to increase with rising temperatures until seas warmed above 20 degrees Celsius (68 degrees Fahrenheit) - at which point biomass started to fall. But communities with many species remained stable at these higher temperatures.
The researchers found a similar buffering effect of diversity against temperature swings. While both high- and low-diversity communities were less productive under fluctuating temperatures, high-diversity communities suffered only half as much as low-diversity ones. The researchers suspect communities with more species are better equipped to handle temperature changes because they have more of their bases covered. When temperatures fluctuate, a community with numerous species has better odds that at least a few species can thrive in the new normal.
“Preserving local biodiversity is not only an ethical directive with aesthetical and genetic insurance value,” said co-author Sergio Navarrete of the Pontifical Catholic University of Chile. “It is an imperative for human life because of the critical role it plays in providing an essential ecosystem function.”
