Study from Oregon State University, The Nature Conservancy, and partner institutions found that active recovery strategies will likely be necessary to save the sunflower sea star from extinction across much of its range.
New research documenting the population crash of the iconic sunflower sea star (Pycnopodia helianthoides), and complete absence of population recovery since the 2013 outbreak of the marine wildlife epidemic sea star wasting disease, was published today in the prestigious journal Proceedings of the Royal Society B. The study calls for new strategies for protecting species impacted by increasingly frequent marine epidemics associated with changing ocean conditions.
The analysis was a collaborative and international undertaking between scientists at Oregon State University, The Nature Conservancy and over 60 partner institutions ranging from First Nations, academia, NGOs, state and federal agencies, and community-based monitoring programs spanning the entire west coast of North America. The study used nearly 50,000 surveys from long-term ecological monitoring efforts to quantify regional differences in how sea star wasting disease devastated local populations, an important area of research as scientists brace for more frequent and intense marine disease outbreak events as climate change intensifies. Researchers found that sunflower sea stars are functionally extinct (> 99% declines) in most of the southern half of its range from Baja California, Mexico to Cape Flattery, Washington, USA. The sea stars also exhibited severe declines (> 87%) from the Salish Sea to the Gulf of Alaska.
The researchers found that the disease started earlier, moved faster, and caused more severe declines in warmer regions than colder ones, though a causal link to climate change has not been established. The analysis shows no sign of population recovery in any region since the outbreak began nearly a decade ago, indicating that assisted recovery will likely be required in the southern half of the species’ range. “In most of the contiguous US and Mexico, the species was essentially wiped out, and is now in real risk of disappearing permanently. From the Puget Sound north though, you can still find pockets with lots of sunflower sea stars even though they also got hammered by the disease,” said Sara Hamilton, PhD candidate at Oregon State University and the lead author of the study.
Sunflower sea stars may play an important role in maintaining healthy kelp forests, and were once abundant throughout their range in marine waters from Alaska to Baja California, Mexico. These animals can be important predators of sea urchins and the loss of sunflower sea stars along with other predators has been associated with explosions of purple urchin populations in some parts of the West Coast. 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 sheer magnitude of the continental-scale loss of this iconic animal and the cascading effects on kelp forest ecosystems is staggering. Billions of animals perished, and we still do not know the causative agent(s) of the disease,” said Vienna Saccomanno, a scientist at The Nature Conservancy and an author on the study. “It’s like the house burnt down almost a decade ago, but we haven’t figured out what caused the fire in the first place or how to stop a similar catastrophe from happening in the future. In this era of rapidly changing ocean conditions, we need to develop better, more nimble strategies to respond to future sudden marine die-off events and ecosystem declines.”
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.
"Species recovery can take a long time and be challenging,” said The Nature Conservancy scientist Walter Heady and author on this study. “Yet, given the speed and magnitude of loss of this species, time is of the essence. We are developing a ‘roadmap to recovery’ for the sunflower sea star to identify information gaps and challenges that will need to be overcome, and key actions necessary to expedite the recovery of this important marine species.”
“Surprisingly little is known about this magnificent creature. This study highlights the importance of long-term monitoring that made this study possible,” states Heady. “We need continued long-term monitoring and more scientific studies to better understand the many species in our oceans, the web of interactions among species and the environment, and how changing ocean conditions may affect ecosystem function and resilience.”
The study’s findings that the sunflower sea star is functionally extinct in most of the southern half of its range points to the urgent need for conservation measures and cross border collaborations.“ The crash of the sea stars due to disease was a warning, and the subsequent collapse of kelp forests is yet another. We have been consistently degrading our marine ecosystems for decades, and if we cannot pivot to a more active approach to marine conservation, it will not get better,” said Sarah Gravem, a postdoctoral scholar at Oregon State University and an author on the study. She continued, “The ocean seems like a big place. But we are bigger, and it’s our responsibility to start cleaning up our mess. Our health and the ocean’s health are inextricably linked, so caring for our oceans is the same as caring for ourselves.”
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.