ABU DHABI // The sandy mud of Abu Dhabi’s eastern mangroves is protected – to an extent.
But this threatened habitat could be a more valuable reserve than anyone thought, according to researchers studying the area.
As tiny crabs wander near semi-submerged mangrove roots, Ibrahim Bugla lays out a 20-metre transect line, taking a soil sample every 5m.
He is the head of marine assessment and monitoring at the Environment Agency–Abu Dhabi, and the samples are evidence of the high carbon content of the soil.
“The more grey and black areas show carbon deposits,” said Dr Himansu Das, the agency’s head of marine endangered species and habitat.
The exact location of each sample is recorded using GPS and the samples – mud, stones and pieces of mangrove root – are taken to be dried, weighed and sent to the United States for carbon analysis using a spectrometer. The holes where each sample was taken quickly fill with water and the team measures the acidity and salinity.
“We want to see what kind of correlation exists between this habitat’s parameters and carbon storage,” he said. “This test allows us to find out how much carbon is locked up in the sediment.”
Nearby, they lay a 100m transect line, marking a 14m circle every 20m. Fifteen sites have been assessed so far, each taking up to four hours.
“We sample all the vegetation within the 7m radius from the centre of the plot,” said Edwin Grandcourt, the agency’s manager of marine assessment and conservation.
A 2m circle is then outlined inside the larger plot. “In that, I count how many saplings there are,” he said. “For any plants above 1.3m, we measure the diameter of the branch at chest height.”
After that, they record everything in the 14m circle.
“We mark trees with a piece of chalk and then we only count plants above 1.3m and measure their diameter,” Mr Grandcourt said.
The team measures from trees’ trunks to the furthest leaves, with the results used to estimate the tree’s biomass, and from that its carbon content.
“We completed the sampling of mangroves, sabkhas and salt marshes in January and we will start with the underwater seagrass beds next month,” Mr Grandcourt said.
The tests are part of the Blue Carbon project launched by the agency last year. The initiative studies how mangroves, seagrass beds and salt marshes isolate carbon from the atmosphere into the sediments.
“We’re interested in that process because it’s very important goods and services that these ecosystems give us,” said Mr Grandcourt. “It will help us understand what the stock of carbon we have here in the UAE is, in association with these habitats, and at what rates they isolate it.”
Dr Das added: “The benefit of storing carbon in the ground is that there is no limit. We can get it after years – trees can store an unlimited amount because they pump it into the sediment, not in their body.”
Once analysed, the results will help decide how best to conserve critical coastal habitats.
“If any developments have a negative impact on them, whether loss or damage, they have to implement a compensation plan,” said Mr Grandcourt. “This will help us determine how much compensation is required.”
Developments that destroy mangroves are required to make up for it by replanting twice the amount destroyed. But some mangroves are thousands of years old – and hold far more carbon than younger trees. This, said Dr Das, means they must be preserved at any cost.
