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The kelps are alright: Studies reveal resilience in kelp forests

  • Nearly half a century since they were first formally surveyed (in 1973), the kelp forests of Tierra del Fuego remain relatively unchanged.
  • Like many marine ecosystems, kelp forests are sensitive to local human stressors such as overfishing, pollution and coastal development, as well as sedimentation, overfishing and marine heatwaves.
  • Re-examining the remote kelp forests of Tierra del Fuego, where there is a distinct lack of direct human impact, gives us a better understanding of the processes accounting for their resilience.
  • Another recently published study, drawing upon 35 years of Landsat data, also supports the idea that kelps are more resilient than previously thought.

As the Beagle traversed the frigid waters of Tierra del Fuego on its famed voyage, Charles Darwin noted the diversity of life teeming in the dense foliage below. Now, nearly half a century since they were first formally surveyed (in 1973), the kelp forests beyond the southernmost tip of South America remain relatively unchanged.

A survey of 11 locations in the easternmost region of the Tierra del Fuego archipelago revealed no significant differences in the abundance of giant kelp (Macrocystis pyrifera) or the sizes of the kelp holdfasts (the part that anchors it to the rocky bottom) since they were first surveyed more than 45 years ago. According to a study published in the journal PLOS ONE, the diversity and amounts of sea urchins also remained relatively unchanged between the two time periods.

Kelps thrive near the shore in Tierra del Fuego.  Image courtesy of Enric Sala/National Geographic.

“Dangerous seas with strong waves, winds, and currents, along with persistent fog made this island a graveyard for early sailing ships,” Alan Friedlander, chief scientist for the National Geographic Society’s Pristine Seas Project and first author of the study, told Mongabay. These harsh conditions have limited the number of scientific studies and, therefore, our understanding of kelp forests in this remote location.

“We experienced all four seasons in a single day and were constantly running from the weather,” Friedlander said, “but at the end of the day it was all worth it when we finally got in the water and were able to experience some of the last pristine kelp forests on earth.”

A kelp forest in Tierra del Fuego. Kelp can grow up to 80 meters (260 feet) in length. Image courtesy of Enric Sala/National Geographic.

Kelps are large seaweeds that can grow up to 80 meters (260 feet) in length and live near the shore in cold-water marine habitats throughout the world. Kelp forests are among the world’s most productive ecosystems, are foundational to many fish and marine communities, and help to protect coasts from wave damage.

Like many marine ecosystems, kelp forests are sensitive to local human stressors such as overfishing, pollution and coastal development, as well as sedimentation and marine heatwaves.

Climate change is also a problem for these fundamentally cold-water species, and losses of kelp forests have been reported worldwide. In 2019, the California Department of Fish and Wildlife reported that kelp forests off the state’s coast had declined by 93% over a five-year period after a marine heatwave in 2014 appeared to have increased the numbers of purple sea urchins, an animal that grazes on kelp.

Sea urchins graze on kelp. An overabundance of urchins can devastate a kelp population. Image courtesy of Enric Sala/National Geographic.

Re-examining the remote kelp forests of Tierra del Fuego, where there is a distinct lack of direct human impact, gives us a better understanding of the processes accounting for their resilience, Friedlander said. And this understanding can help us in managing kelp ecosystems elsewhere.

“In this case, we identified an ecosystem that is resilient in the face of the global biodiversity crisis,” Friedlander said. “It is surprising and encouraging to see a place that has remained virtually unchanged in the 45 years since it was last studied.”

The observational data collected from scuba expeditions for this study were supplemented by Landsat satellite images. The Landsat program, a joint effort of U.S. Geological Survey and NASA, has been gathering data on the Earth’s surface since 1975. Now, researchers are using this tool for kelp monitoring.

“The area we were working in was so remote that there was not adequate satellite coverage prior to 1998,” Friedlander said. “No one cared before that!”

King crabs live among the kelp and help to keep the sea urchin populations in check. Image courtesy of Enric Sala/National Geographic.

Landsat satellite images did not reveal any long-term trends in the Tierra del Fuego kelp forests, but they did reveal that kelp forest cover seemed to follow four-year cycles mirroring sea surface temperature and El Niño rainfall patterns.

Another recently published study, drawing upon 35 years of Landsat data, also supports the idea that kelp are more resilient than scientists suspected.

Decades of Landsat imagery over the coast of Oregon show that the area covered by an annual kelp, Nereocystis luetkeana, can vary quite a bit from year to year, and from reef to reef. One reef had a greater population of kelp in 2018 than at any other time in the last 35 years.

The Landsat data also revealed that the massive kelp loss observed in California over the past five years was not seen in neighboring Oregon. Additionally, a summer with very warm water or large winter waves isn’t always automatically bad news for kelp, as previously thought.

A kelp forest in Tierra del Fuego. Image courtesy of Enric Sala/National Geographic.

“Our findings challenge the picture that’s been making the rounds in the news and points to the need for more research because we really don’t understand kelp very well,” Sara Hamilton, a marine biologist pursuing her Ph.D. at Oregon State University and corresponding author of the paper, said in a statement. Hamilton’s work underscored the need for long-term data to understand kelp populations and how they respond to climate change.

“There are still places that are, at present, resilient and resistant to current threats,” Friedlander said, “but this can only go so far before we reach the tipping point, which, unfortunately, has already happened in many places.

“Overall, this should be a clarion call to address climate change, because it’s not too late.”

Kelps thrive in the shallow sea where light can penetrate. Image courtesy of Enric Sala/National Geographic.

Friedlander, A. M., Ballesteros, E., Bell, T. W., Caselle, J. E., Campagna, C., Goodell, W., … Dayton, P. K. (2020). Kelp forests at the end of the earth: 45 years later. PLOS ONE, 15(3), e0229259. doi:10.1371/journal.pone.0229259

Hamilton, S., Bell, T., Watson, J., Grorud‐Colvert, K., & Menge, B. (2020). Remote sensing: Generation of long‐term kelp bed data sets for evaluation of impacts of climatic variation. Ecology, e03031. doi:10.1002/ecy.3031

Banner image of a kelp forest in Tierra del Fuego courtesy of Enric Sala / National Geographic.

Liz Kimbrough is a staff writer for Mongabay. Find her on Twitter @lizkimbrough_

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