An international team of palaeontologists and marine ecologists has revealed that studying marine organisms that died out over the past 23 million years can help identify which animals and marine ecosystems are at most risk of extinction today. Their study is published today in the journal Science.

The study focuses on the past 23 million years as the climatic conditions during this period were generally most similar to their current patterns, and the fossil record is dominated by major taxonomic groups that still exist today. Researchers can use this as a baseline to predict which existing species and habitats are most vulnerable to extinction in the future by identifying extinct species with characteristics similar to today’s species.

Left: Giant clam, Tridacna sp. found in Kiritimati, Northern Line Islands. Photo copyright Erin Dillon. Right: Tridacna sp.from the Miocene period, found in East Kalimantan. Photo copyright Jon Todd. 

As the baseline only considers natural, or ‘intrinsic’ extinction risk, an important step in the study was to factor in the risk introduced by human activities such as habitat destruction, overfishing, pollution and ocean acidification in order to predict where extinctions are most likely occur in the future.

“Our goal was to diagnose which species are vulnerable in the modern world, using the past as a guide,” said lead author Seth Finnegan, an assistant professor of integrative biology at University of California, Berkeley. “We believe the past can inform the way we plan our conservation efforts. However, there is a lot more work that needs to be done to understand the causes underlying these patterns and their policy implications.”

Derek Tittensor, the Senior Marine Biodiversity Scientist at UNEP-WCMC and Adjunct Professor at Dalhousie University was part of the group of researchers, who come from a number of organizations. Dr Tittensor’s role was to interpret extinction patterns in the modern day ocean, gather data on modern species and examine the overlap with present day human impacts on the ocean.

“For me, a surprising result was the disproportionate concentration of areas of high natural extinction risk in the tropics,” said Dr Tittensor. “We often think of high-latitude temperate environments as harsh, and tropical environments as benign, but we found the tropics contain more species that are inherently vulnerable to extinction, including many with small range sizes. Combined with high levels of human impacts in many of these areas, they are clear targets for conservation efforts.”

Animals with small geographic ranges were found to be at most risk of extinction. The fossil record also revealed that whales, dolphins and seals show a higher risk of extinction than sharks or scleractinian (hard) corals. Bivalves, such as clams and mussels, had about one-tenth the extinction risk of mammals.

Hotspots of human impact and velocity of climate change overlaid on mean intrinsic risk. From Finnegan et al., 2015, Science

“It’s very difficult to detect extinctions in the modern oceans, but fossils can help fill in the gaps,” added co-author and conservation biologist Sean Anderson, a postdoctoral researcher at Simon Fraser University in Burnaby, British Columbia. “Our findings can help prioritize areas and species that might be at greater risk of extinction and that might require extra attention, conservation or management.”

Derek Tittensor concludes, “Extinction rates in the present day are estimated to be around 1,000 times higher than background rates, due to the severity of human impacts on global ecosystems. Extinctions are forever – they represent the complete loss of a species – so efforts to protect marine environments must be scaled up and enforced, especially in those areas which have been identified as being particularly vulnerable.”

Publication information

Finnegan S, Anderson SC, Harnik PG, et al. (2015) Paleontological baselines for evaluating extinction risk in the modern oceans. Science, 348(6234): 567-570. [DOI:10.1126/science.aaa6635]

Top left: Staghorn Coral (Acropora cervicornis) from the Holocene period found in Enriquillo basin, Dominican Republic. Photo copyright Aaron O’Dea. Top right: Modern Staghorn Coral (Acropora cervicornis) pictured at Bocas del Toro, Panama. Photo copyright Aaron O’Dea. Bottom left: extinct Balaenopteridae from the Late Miocene period, found in Cerro Ballena, Atacama Region, Chile. Photo copyright Nicholas D. Pyenson et al. / Smithsonian Institution. Bottom right: Humpback whale (Megaptera novaeangliae) pictured at Tennakee Inlet, Alaska. Photo copyright Ari S. Friedlaender.