Blue Carbon: Invasive Plants Help Prevent Climate Change by Becoming Ecosystem Engineers

Certain invasive species could be helping combat climate change by storing "blue carbon," a study has found. These "ecosystem engineers" were found to boost a given ecosystem's potential to store carbon by growing bigger and faster than the native species they usurped. In some cases, ecosystems experienced a 117 percent boost in biomass and potential to store carbon.

A lot of research into carbon storage has focused on land-based biomass such as forests. However, the potential of coastal environments—like mangroves and salt marshes—is increasingly being looked at in relation to its role in climate change. "It has been established for some time that forests are excellent for carbon storage, but it is only in the last decade that coastal wetlands have been recognised as particularly good for carbon storage and sequestration," study author Grace Cott told Newsweek.

These marine ecosystems have the potential to store carbon around 40 times faster than forests, but they are disappearing fast. An estimated 3,000 square miles are lost every year.

According to the Blue Carbon Initiative, humans are largely responsible for the destruction of these ecosystems. This includes aquaculture, agriculture, the exploitation of mangrove forests and pollution. When blue carbon ecosystems are damaged, carbon is emitted back into the atmosphere, potentially adding to climate change.

Understanding carbon storage systems is important for models of future climate change—knowing how much is being soaked up by different ecosystems on Earth will allow scientists to better forecast how the planet will adapt to the greenhouse gas emissions we are producing.

The latest research paper, published in Global Change Biology, is a meta-analysis including data from 104 studies. These compared blue carbon ecosystems where there had been invasive species introduced to those where there had been no invasion. As a result, the team was able to establish how much plant-based biomass there was and the carbon-storage potential.

Results produced a mixed bag. They found where invasive animal species were introduced, biomass was almost halved. "Introduced animals are essentially going in there eating, trampling, cutting and destroying biomass," lead author Ian Davidson, from the Smithsonian Environmental Research Center, said in a statement.

Invasive plants told a different story. When the newly introduced plant was very dissimilar to the flora already present—such as algae invading a seagrass bed—biomass dropped by around a third. But where an invasive plant was similar to what was already there, biomass increased significantly.

"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," Davidson said. Examples of this include a new type of mangrove tree invading a mangrove forest, or a reed species growing in a salt marsh. Compared with the native species, the invaders grew much faster and larger—upping the potential for blue carbon storage.

The scientists do not advocate introducing invasive species to marine environments as a way of boosting the blue carbon storage potential. Instead, they say the findings can be used in conservation strategies in order to balance the management of invasive species, carbon storage and the function of the ecosystem.

Cott said: "To try to mitigate the effects of climate change we need ecosystems to be able to store carbon. If some invasive species enhance this function then that is a plus. When coastal ecosystems are destroyed (drained, filled-in) they release the stored carbon back to the atmosphere. It is essential that these habitats are not destroyed for global climate change."

This article has been updated to include quotes from Grace Cott