Giant map of giant kelp forests

A paper published in Communications Earth & Environment has tracked 35 years of satellite data to create a comprehensive map of underwater giant kelp forests.

“Kelp is one of the most productive and important marine ecosystems in the world,” says Nur Arafeh-Dalmau, a PhD candidate at the University of Queensland and lead author on the paper. “It’s comparable to terrestrial rainforests.”

As well as being valuable for fishing and recreational purposes, kelp forests are powerful ecosystems for coastal protection and carbon sequestration.

Arafeh-Dalmau says he initially became interested in mapping kelp after seeing conservation pushes for other marine ecosystems. “I was shocked to see that kelp was never mentioned in these papers.”

He has sought to rectify this by collaborating with a group of Australian, US and Mexican researchers to trace giant kelp forests along the western coast of North America.

The team examined satellite imagery from the past 35 years to map the distribution and ‘persistence’ of giant kelp along thousands of kilometres of coastline, from the US to Mexico.

Arafeh-Dalmau explains that kelp is a very dynamic ecosystem: “They can grow very quickly, but they can also decrease their coverage very quickly.”

Areas where kelp persists are of the most interest to scientists, he says. “There are certain areas where kelp is almost always there, and those areas have higher conservation value.”

It is these persistent regions that Arafeh-Dalmau says should be legally protected, as their resilience makes them good climate refugia.

“It’s important to have these persistent areas because this region has been subject to many El Niño events during this time. And the last one was an extreme event. Also, some of the regions are highly populated.

“Despite all these changes – human population and activity, and climate change – they’re still persisting over time.”

The researchers found areas in Baja California, Mexico, that they say should be prioritised highly for legal protection. Currently, less than one per cent of the Baja California coast is fully protected.

Next, they hope to examine changes in kelp forests over time, as well as other species of kelp and kelp from other regions.

“North of our region, bull kelp becomes the dominant species, so we’re trying to replicate this work over there,” says Arafeh-Dalmau.

After that, the next priority area will be Tasmania.

“The ultimate goal is to go to a global scale. Giant kelp is found in many other places like the southern coast of mainland Australia, Tasmania, areas of South Africa, New Zealand, and also Chile – our idea is to map this globally.”

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