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Some invasive plant species help store more blue carbon

A new study has revealed that some invasive plant species are helping ecosystems absorb more “blue carbon,” which is carbon that is stored in salt marshes, mangroves, and seagrasses along the coast. The introduction of invasive animal species, on the other hand, can have the exact opposite effect.

While blue carbon has been discussed in terms of climate change, the subject has not been explored much regarding invasive species. Study lead author Ian Davidson is a marine invasions biologist at the Smithsonian Environmental Research Center (SERC).

“We were aware of the effects of invasions on other facets of these habitats, but this was the first time we really delved into blue carbon storage,” said Davidson.

The research is the first of its kind to look exclusively at marine habitats when addressing the issue of invasions and carbon storage. Previous studies on carbon storage have focused primarily on terrestrial environments such as forests.

However, marshes and mangroves can store carbon at a rate that is up to 40 times faster than forests. Biologists estimate that the world has lost anywhere from 25 to 50 percent of its blue carbon habitats in the last century, with an additional 8,000 square kilometers vanishing every year.

As policymakers work to mitigate both climate change and the impacts of invasive species, a better understanding of blue carbon ecosystems has become urgent.

“It’s now part of global climate change solutions to get carbon credits in forests,” said study co-author and SERC marine biologist Christina Simkanin. “But for blue-carbon habitats, the marine version, that has been slower to materialize.”

The research team gathered data from 104 different studies, involving 345 comparisons around the world. Each study compared an invaded blue-carbon ecosystem to a similar uninvaded one.

The scientists used the data to calculate how much plant-based biomass or soil carbon changed at each site in the presence of an invasive species.

The study revealed that when the most powerful plants invaded, biomass skyrocketed. These invaders more than doubled an ecosystem’s biomass and potential to store carbon.

“When you have these essentially ‘ecosystem engineers’ come into the system, not only are they helping build habitat, they seem to be doing it more aggressively and more efficiently,” said Davidson.

On the other hand, when plants like algae invaded and took over, biomass fell by more than a third. In addition, invasive animal species cut biomass nearly in half, leaving ecosystems much less effective as blue-carbon sinks.

“Introduced animals are essentially going in there eating, trampling, cutting and destroying biomass,” Davidson explained.

Salt marshes were found to get the biggest biomass boost from their invaders – by an average of about 91 percent. The study authors pointed out that they found very limited research available on seagrasses and mangroves, and that salt marshes made up a huge portion of the data they were able to analyze.

Study co-author Grace Cott concluded: “Ecosystem managers will be faced with a decision to eradicate or control invasive species. The information contained in this study can help managers make decisions if carbon storage is a function they want to enhance.”

The study is published in the journal Global Change Biology.

By Chrissy Sexton, Staff Writer

Image Credit: Gary Peresta/Smithsonian Environmental Research Center

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