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Biodiversity makes reef fish more resilient in the face of climate change, research confirms

  • After analyzing data from more than 4,500 fish surveys of reefs around the world to compare the effects of biodiversity and other environmental factors on global reef fish biomass, the authors of the study found that biodiversity was one of the strongest predictors of fish biomass, second only to mean sea-surface temperature.
  • Temperature actually has a more complex relationship with fish biomass — while warmer ocean temperatures tend to boost fish biomass, wider temperature fluctuations have the exact opposite effect.
  • Biodiversity, on the other hand, only makes fish communities more resilient against the changing climate, the researchers found. The researchers found biodiversity can even help buffer against temperature swings.

New research confirms that biodiversity can help reef fish weather the impacts of global warming.

Reef systems with greater numbers of fish species are not just more productive but also more resilient to rising sea-surface temperatures and the temperature swings associated with climate change, according to a new study led by researchers with the Smithsonian’s Tennenbaum Marine Observatories Network.

After analyzing data from more than 4,500 fish surveys of reefs around the world to compare the effects of biodiversity and other environmental factors on global reef fish biomass, the authors of the study found that biodiversity, measured by the number of species (species diversity) and the variety of functional traits (functional diversity) within a reef system, was one of the strongest predictors of fish biomass, second only to mean sea-surface temperature.

A direct impact of the carbon emissions that continue to concentrate in Earth’s atmosphere is warmer, more acidic ocean waters, which has contributed to the bleaching of reefs around the world. Just last month, scientists announced that 99 percent of coral reefs surveyed in Australia’s Great Barrier Reef have been hit by the global bleaching event that has already taken a toll on reefs at the Pacific islands of Hawaii, Vanuatu, American Samoa, and Fiji, as well as parts of the Caribbean, the Florida Keys, and the Indian Ocean.

More than a quarter of coral reefs worldwide are in decline due to overfishing, sediment runoff, and other manmade pressures such as climate change, according to another recent study.

Reef fish in the global center of fish diversity, Raja Ampat, West Papua. Photo by Rick Stuart-Smith.

This has led to accelerated loss of reef fish species all over the globe, which has long troubled scientists. But there was still a question as to whether biodiversity really provided any kind of buffer against these impacts and could help preserve fisheries that are relied on by millions of people around the globe who rely on the bounties of the sea as a staple of their diet.

The present study, published today 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 oceans and marine life, according to lead author Emmett Duffy, director of the Tennenbaum Marine Observatories Network and senior scientist at the Smithsonian Environmental Research Center.

“Biodiversity is more than a pretty face,” Duffy said in a statement. “Preserving biodiversity is not just an aesthetic or spiritual issue—it’s critical to the healthy functioning of ecosystems and the important services they provide to humans, like seafood.”

Duffy and team looked at 11 different environmental factors to determine how they influenced total fish biomass on coral and rocky reefs around the world. They found that species richness and functional diversity enhanced fish biomass more than any other factor save warm temperatures.

But temperature actually has a more complex relationship with fish biomass. While warmer ocean temperatures tend to boost fish biomass, wider temperature fluctuations have the exact opposite effect.

Potato cod (Epinephelus tudula) in no-fishing zone, northern Great Barrier Reef. Photo by Graham J. Edgar.

Biodiversity, on the other hand, only makes fish communities more resilient against the changing climate, the researchers found. In communities with few fish species, biomass tended to increase with rising temperatures until seas warmed above 20 degrees Celsius (68 degrees Fahrenheit), at which point biomass started to decline. But communities with a greater number of species remained stable even at higher temperatures.

“This work is a critical step forward,” co-author Jonathan Lefcheck, of the Virginia Institute of Marine Science, said in a statement. “It shows that experimental ecologists have in fact been on the right track for 20 years, and that biodiversity is paramount to how natural systems work.”

The researchers found biodiversity can even help buffer against temperature swings. While both high- and low-diversity communities were found to be less productive under fluctuating temperatures, they said, high-diversity communities suffered about half as much.

According to the authors, these findings suggest that high biodiversity can help buffer reef communities against the effects of climate change — and that conserving biodiversity could support increased productivity and resilience of reef fisheries.

“Preserving local biodiversity is not only an ethical directive with aesthetical and genetic insurance value,” co-author Sergio Navarrete, of the Pontifical Catholic University of Chile, said in a statement. “It is an imperative for human life because of the critical role it plays in providing an essential ecosystem function.”

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