Monitoring mangroves as sea levels rise

7 Feb 2019

MangrovesAn international team of scientists are working to understand how mangrove islands in the Pacific-ocean respond to rising sea levels.

In February 2017 the team, including University of Queensland’s Professor Catherine Lovelock, travelled to the island Ouvea in New Caledonia, to study an exceptional mangrove ecosystem.

The Njimec mangrove system in Ouvea is one of the world’s best-preserved mangrove system and for centuries the local people have relied on, and lived in, harmony with the mangrove forest.

However, the Njimec mangrove, like the islands around it, is in danger of becoming submerged due to climate change and the rising level of the ocean.

“Conserving the Njimec mangroves is an issue that goes beyond maintaining biodiversity,” Professor Lovelock said.

“This ecosystem plays an important ecological, social and especially economic role for the local people.”

The island is unique in that it is a completely isolated system, with no external sources of sediment from rivers.

The mangrove’s landmass is maintained by self-replenishing sediment production, meaning that the level of the land is increased through biological sediment production.

The team is worried that the rising ocean levels will outpace the Njimec’s mangroves capacity to keep up with sea level rise, meaning the system will become stressed and eventually submerged.

Over the next few years the team will monitor the fragile relationship that exists between the sea and the land.

The project has two aims, one is to track the rate of sediment production over the mangrove ecosystem and the other is to monitor how the growth of the island’s mangrove forest contributes to this sediment production.

In order to measure the current rate of soil elevation the scientists have set up a series of soil surface elevation tables, which measure how the soil volume of the mangrove changes over time.

MangrovesOver the next couple of years, Ouvea’s soil surface elevation will be analysed as it changes in response to sediment supply and growth of the vegetation.

Electronic dendrometer bands have been placed around the trunks of the mangrove trees and every hour the trees’ girth is recorded.

By recording how the trees grow under fluctuating environmental conditions the team hopes to identify which conditions promote growth and which cause stress.  

“The research gained from the Njimec mangrove project will help us understand how adaptable an ecosystem like this is in response to environmental changes,” Professor Lovelock said.

A wider understanding of this topic will strengthen the coastal communities resilience to climate change and foster ongoing conversations about how the Pacific Islands are going to fare with increasing sea levels.