Study from Oregon State University, The Nature Conservancy, and partner institutions found that a marine wildlife epidemic, believed to be largest on record, killed over 90% of sunflower sea stars.
A groundbreaking study from Oregon State University, The Nature Conservancy and over 60 partner institutions led the International Union for Conservation of Nature (IUCN) to list the sunflower sea star (Pycnopodia helianthoides) as Critically Endangered today. The designation comes following a marine wildlife epidemic that decimated the animal’s global population and indicates that the sunflower sea star, which plays an important role in maintaining the West Coast’s rapidly vanishing kelp forests, is one step away from extinction.
Populations of the sunflower sea star (Pycnopodia helianthoides), an animal once abundant throughout its range in marine waters from Alaska to Baja California, Mexico, experienced dramatic crashes in response to a marine wildlife epidemic event – referred to as sea star wasting syndrome – that began in 2013. Using over 61,000 surveys from 31 datasets, The Nature Conservancy and expert ecologists at Oregon State University calculated a 90.6% decline in the global population of sunflower sea stars due to the outbreak and estimated that as many as 5.75 billion animals died from the disease. Their analysis – a collaborative and international undertaking with over 60 partner institutions spanning the entire west coast of North America, from Alaska to Baja California – shows no signs of population recovery in any region in the 5-7 years since the outbreak began.
“The rapid decline of this giant sea star, and of the sea kelp forests that it helps preserve, highlights the importance of every single species on the IUCN Red List of Threatened SpeciesTM. Its entry into the IUCN Red List in the highest threatened category emphasizes the need for urgent action to understand and combat the wasting disease that is sweeping through the population. We hope that this listing leads to positive action and recovery for this species and its ecosystem,” said Caroline Pollock, Programme Officer for the IUCN Red List Unit.
Sunflower sea stars are now nearly absent in the contiguous United States and Mexico. No stars have been observed in Mexico since 2016, none in California since 2018, and only a handful in the outer coasts of Oregon and Washington since 2018. They are still present in Puget Sound, British Columbia, and Alaska, but only at a fraction of their former population in most places.
“These sea stars used to be easy to find, and they were a hit with students and SCUBA divers because they are unforgettable. They can be as big as a trash bin lid with twenty slimy arms covered in suction cups. Unfortunately, your chances of finding one now are next to nothing in most of the contiguous U.S,” said Dr. Sarah Gravem, Research Associate at Oregon State University and lead author on the study that prompted to the sunflower sea star’s Critically Endangered status update. “I don’t think they’re coming back without our help.”
Sunflower sea stars are an important predator of sea urchins and, with the significant loss of these sea stars and other predators throughout their range, purple urchin populations have now exploded in many regions. This overabundance of urchin is linked to a significant decline in kelp forests in multiple regions in recent years. Kelp forests are already facing increased pressure from marine heatwave events and, taken together, these threats contribute to an uncertain future for kelp forest ecosystems which provide critical habitat for thousands of marine animals and support coastal economies.
“The loss of this important predator has left an explosion of purple urchins unchecked and has contributed to devasted kelp forests along the West Coast, making this ecosystem more vulnerable and less resilient to the stressors it’s already facing,” said Norah Eddy, Associate Director of The Nature Conservancy’s California Oceans Program.
Because there is little chance of recovery in the contiguous United States without intervention, The Nature Conservancy and partners are preparing for the many steps necessary for the recovery of this species. “This IUCN listing was the first step in our roadmap to recovery,” said Dr. Walter Heady, Senior Scientist at The Nature Conservancy. As a key element of this plan, The Nature Conservancy in partnership with the University of Washington and others are spearheading the first captive breeding of the species and the potential for a pathway to re-introduction if that is determined needed and appropriate.
“While many of us were concerned about local extinction of the sunflower sea star, results of this study highlight the truly devastating extent of loss of this important marine species. This work provides the foundation for conservation of the species. We are coupling knowledge and momentum gained from this study and listing to inform the roadmap needed to recover sunflower sea star populations,” Dr. Heady concluded.
“Because most people aren’t out in the ocean every day, we don’t realize how much it's being changed and impacted by humans. We need to think creatively about how to keep our oceans healthy. While drawing down carbon emissions is the most pressing need, rebuilding key predator populations, like the sunflower sea star, can be an important piece of the puzzle too,” said Sara Hamilton, PhD Candidate at Oregon State University and seminal author on the study.
The Nature Conservancy is a global conservation organization dedicated to conserving the lands and waters on which all life depends. Guided by science, we create innovative, on-the-ground solutions to our world’s toughest challenges so that nature and people can thrive together. We are tackling climate change, conserving lands, waters and oceans at an unprecedented scale, providing food and water sustainably and helping make cities more sustainable. Working in 76 countries and territories—37 by direct conservation impact and 39 through partners—we use a collaborative approach that engages local communities, governments, the private sector, and other partners. To learn more, visit www.nature.org or follow @nature_press on Twitter.