Kelp Me Out

A remote ecosystem is a living time capsule to 50 years ago

South American forests are still talking about Watergate.

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Humans’ environmental impact seems to extend into every corner of the globe, but it may have missed a spot.

In a new study, researchers describe a remote part of Southern Patagonia so undisturbed it seems the scenery hasn’t changed for decades.

Tierra del Fuego, an area of ocean at the southern tip of South America, is like a living, thriving time capsule to 50 years ago. The area's rich forests of kelp appear to be relatively unchanged since it was last thoroughly evaluated, back in 1973.

In the new mission, scuba-diving scientists assessed the number of kelp, sea urchins, and star fish living in Tierra del Fuego's dense, green neighborhoods. What they found suggests that, in complete contrast to the rest of the world, things appear very much the same as they were, all those years ago.

That is welcome news. Kelp forests are some of the most biodiverse ecosystems on the planet. But not all kelp forests are so lucky. these unique ecosystems are among those most threatened by climate change, and as effects like warming sea water spread worldwide, even this remote locale may start to shift.

A. Friedlander et al, PLOS One (2020)

The findings were published Wednesday in the journal PLOS ONE.

Changes over time

Not only are Tierra del Fuego's populations of plants and animals thriving, they appear to have hit a sweet spot in terms of numbers. In the new survey, the researchers didn't come across signs of destructive overpopulation, which in the ocean kelp forests often comes in the form of urchin “barrens,” or areas that the animals graze to the point of decimation.

This image shows how the same species of kelp — and its tenant bivalve — still thrive in Tierra del Fuego.A. Friedlander et al, PLOS One (2020)

However, there was a cyclical change in the forest area. The size of the forest grew and shrunk in approximately four-year cycles, reflecting patterns in both water temperature and El Niño-driven rainfall.

As global temperatures continue to rise through the next decade, this delicate cycle could shift — and that could spell the end of this pristine environment's strange stasis.

Starfish, sea urchin, and kelp populations are relatively stable in Tierra del Fuego.Brent Durand/Moment/Getty Images

"The kelp forest of the extreme tip of South America are some of the most pristine on earth and have not changed substantially since the early 1970s, when they were first surveyed, " Alan Friedlander, lead author of the study and a researcher at the University of Hawai‘i at Mānoa, said in a statement.

The natural world as a whole, however, has changed — and we are already seeing the signs of a major shift in the globe's climate patterns. Studying such relatively untouched havens as the kelp forests of Southern Patagonia could offer insights into how similar regions have shifted over time — and may help predict how they may yet change and evolve.

"Re-examination of this remote region is incredibly valuable in this age of climate change and gives us a better understanding of how these ecosystems function in the absence of direct human impacts," Friedlander said.

Abstract: The kelp forests of southern South America are some of the least disturbed on the planet. The remoteness of this region has, until recently, spared it from many of the direct anthropogenic stressors that have negatively affected these ecosystems elsewhere. Re-surveys of 11 locations at the easternmost extent of Tierra del Fuego originally conducted in 1973 showed no significant differences in the densities of adult and juvenile Macrocystis pyrifera kelp or kelp holdfast diameter between the two survey periods. Additionally, sea urchin assemblage structure at the same sites were not significantly different between the two time periods, with the dominant species Loxechinus albus accounting for 66.3% of total sea urchin abundance in 2018 and 61.1% in 1973. Time series of Landsat imagery of the region from 1998 to 2018 showed no long-term trends in kelp canopy over the past 20 years. However, ~ 4-year oscillations in canopy fraction were observed and were strongly and negatively correlated with the NOAA Multivariate ENSO index and sea surface temperature. More extensive surveying in 2018 showed significant differences in benthic community structure between exposed and sheltered locations. Fish species endemic to the Magellanic Province accounted for 73% of all nearshore species observed and from 98–100% of the numerical abundance enumerated at sites. Fish assemblage structure varied significantly among locations and wave exposures. The recent creation of the Yaganes Marine Park is an important step in protecting this unique and biologically rich region; however, the nearshore waters of the region are currently not included in this protection. There is a general lack of information on changes in kelp forests over long time periods, making a global assessment difficult. A complete picture of how these ecosystems are responding to human pressures must also include remote locations and locations with little to no impact.
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