Destroyed with stem and stalk

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Mangroves in Indonesia

Mangroves are complex wonders of nature. The trees, which are mainly found in tropical coastal areas, have cleverly adapted to their environment and thus survive the changing tides in salty water.

The mud that surrounds their roots not only offers a unique habitat for animal species. Mangrove forests also make an important contribution to coastal protection. And perhaps the most important aspect: The trees store an extraordinary amount of carbon dioxide, and that is good for the climate.

An estimated one third of the world's mangrove forests have been destroyed since the 1980s. A study by NASA has for the first time recorded the status of stocks and the reasons for the decline in a global map. For this purpose, data from the "Landsat" earth observation satellites were evaluated.

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The map shows the loss of mangroves from 2000 to 2016 in kilometers. The researchers differentiate between natural and human factors

Overall, the mangrove decline slowed down between 2000 and 2016, according to the study, which was published in the specialist journal "Global Change Biology". However, the team led by scientist Liza Goldberg found that more than 2000 square kilometers of mangrove forests were lost during the study period. That corresponds to about two percent of the global mangrove area.

In 2010 there were 53,000 square kilometers of mangrove forests on the world's coasts. Mangrove populations disappeared especially in Southeast Asia, where the largest areas are also located. In countries like Indonesia and Bangladesh, areas are cleared for shrimp farming or rice cultivation, but also for firewood.

The researchers distinguished between two factors in the study: Loss due to natural causes such as erosion and storm surges. And the decline due to man-made causes such as agriculture, deforestation and aquaculture. They estimate that 62 percent of the space lost is due to the human factor.

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Regional distribution of losses (information in time and square kilometers)

After all, according to the observations of the researchers, the influence of the human factor has decreased. "On the one hand, that's great," said Liza Goldberg, lead author of the study. "It shows that the effectiveness of environmental protection efforts at the local level is increasing, as is awareness of the importance of mangroves." On the other hand, the data also revealed that in some regions of Southeast Asia the destruction has apparently progressed so far that in many areas no more mangrove loss is possible - because there are no more stands.

Lola Fatoyinbo Agueh, environmental scientist at NASA's Goddard Space Flight Center in Greenbelt, Maryland and co-author of the study, emphasizes the role of mangroves in climate protection. The trees are very efficient carbon sinks and can store up to five times more greenhouse gases than other trees. They only make up three percent of the global forest area, but if they were all cut down, they could release up to ten percent of the carbon emissions stored in trees.

Soil as a carbon store

The leaves of mangroves fall to the ground and, for example, decompose very slowly, creating carbon-rich peat that binds CO₂. However, due to the destruction of the mangrove forests, this carbon escapes into the atmosphere, where it contributes to climate change as a greenhouse gas.

Fatoyinbo Agueh explains how important it is to differentiate between the factors of destruction with regard to climate change. "The nature of the carbon emissions from mangroves depends on the type of land conversion taking place," she said. If you cut down the trees and excavate the ground, for example to create a shrimp pond, this releases much more greenhouse gas than damage caused by natural causes such as storms. Because most of the carbon is stored in the soil.