Healthy mangroves can protect against climate change

Mangroves' ability to absorb carbon emissions has been mostly ignored by climate scientists, according to authors of the new paper, published this week in the journal Global Change Biology.

To quantify the carbon absorption and sequestration abilities of Indonesia's Segara Anakan Lagoon, located on the island of Java, scientists radio carbon dated and analyzed the biogeochemical composition of layers in sediment cores pulled from the tropical wetlands.

Specifically, scientists looked at the relationships between a variety of factors, including societal developments, land-use changes, coastal dynamics and climate shifts on the lagoon's carbon reserves. The analysis showed carbon accumulation was influenced most heavily by climate oscillations and human activity.

"The interaction of these two factors changed the lagoon's sediment supply and salinity, which consequently altered the organic matter composition and deposition in the lagoon," researchers wrote in their paper.

The sediment cores sampled from the lagoon were deep enough to reveal 400 years of changing sedimentation patterns within the ecosystem. As the sediment layers showed, the primary source of carbon compounds during the early parts of the 400-year time span were provided by materials eroded and washed downstream from natural mixed forests found inland. During the later phases, more and more carbon-carrying sediments were sourced from agricultural land.

Shifts in climate affected carbon accumulation in the lagoon as a result of precipitation changes. As precipitation levels increased, rivers delivered more carbon-carrying sediment.

Today, mangrove forests like Segara Anakan Lagoon are increasingly threatened by rising sea levels and deforestation. Mangrove forests and other wetlands not only serve as important habitat for threatened species, but also protect against coastal erosion and extreme flooding.

As mangrove health declines, less carbon will be sequestered, and coastal regions will become more vulnerable to the effects of global warming and extreme weather.

"Our research shows that people need to prioritize mangrove ecosystems for conservation and restoration because mangroves absorb carbon efficiently," study author Kartika Anggi Hapsari, climate scientist at Göttingen University in Germany, said in a news release. "It is not enough just to focus on cutting carbon emissions. Society needs to also identify efficient and natural ecosystems, like those dominated by mangrove vegetation, to remove carbon.