Mangroves’ message from the grave

Mangroves help fight climate change but they’re at serious risk from its effects. That’s one of the findings from a study of a massive mangrove dieback that occurred in late 2015.

Local fishermen reported mangroves were dying along hundreds of kilometres along the Gulf of Carpentaria coastline, an area known for its barramundi fishing and high value commercial fisheries.

This caught the attention of Dr Damien Maher of Southern Cross University, who is interested in the chemistry of mangroves—how they store carbon in their soils, remove planet-warming nitrous oxides from the atmosphere, and neutralise ocean acidification by releasing alkaline chemicals into nearby waters.

Damien and his colleagues studied the dead zones, as well as adjacent areas that survived.

“The dead areas were emitting carbon dioxide to the atmosphere straight from the soils. The carbon cycle had shut down because the trees weren’t locking up carbon anymore.”

And the dead areas were no longer exporting alkalinity, a loss of the buffering benefits for marine life nearby that are vulnerable to ocean acidification, such as coral and shellfish.

Damien says this event is a warning of how increasing climate-linked stressors might affect these important ecosystems in coastal zones world-wide.

“Mangroves are valuable habitat that supports fisheries, and provide a natural defence against storm damage during tropical cyclones,” Damien says.

“We think a perfect storm of factors led to this dieback: monsoon seasons with very low rainfall, record high temperatures, and a strong El Niño event with lower sea levels, which prevented toxicity being flushed from soils.”

For more information:

Southern Cross University
Sharlene King
+61 429 661349

Scientists had a rare opportunity to study the chemistry of mangrove dieback in the field. Credit: Damien Maher