Why are mangrove forests priceless?

How big is the mangrove forest that the people of Wanduruppa suffered in December 2004: The tsunami after the earthquake of that year swept the sea from 5,000 to 6,000 inhabitants of the village. Small in Sri Lanka.

But Kapuhenwala village escaped danger. Although located next to Wanduruppa but only 2 people died: The power of the tsunami was stopped by 200 ha of mangrove forests, only a few small waves entered the village and almost did not cause much damage.

A place to dump garbage instead of a place where the fry live

Mangrove forest in Mexico.Photo: Octavio Aburto.

Only the use of this protection is enough to preserve primitive forests that are flooded - but the reality is completely different: Sri Lanka has lost half of the mangrove forest, and according to IUCN's vertical information. According to Thailand's Andaman coast, only 100 hectares remain at the time of the tsunami. In the last 25 years, one-fifth of mangrove forests around the world have disappeared: They are cut down to make room for shrimp farms or harbors, to build timber or burn coal, to build guests. hotels often used as cheap garbage dumps.

While profits from these jobs are often carried away, people living directly on the spot suffer the consequences not only of a tsunami, according to Octavio Aburto-Oropeza and the Institute's expert team. Scripps Oceanography in California. They calculated in a typical example and published it in "Proceedings of the National Academy of Sciences". Where researchers are most interested in is the coast of the Baja California peninsula and the surrounding mainland, the region of the northern Pacific mangrove forests. Although the population density here is low, the area of ​​the ecosystem is still reduced by 2% annually, in some areas more than a quarter of mangroves have been destroyed.

The mangrove tree borders the sea and the mainland not only protects the coast. They are also home to many commercially caught fish. So Mr. Aburto-Oropeza and his colleagues learned about the correlation between the size of a mangrove forest and the amount of fish caught by nearby villages.

One third of fish originates from mangrove forest

The more and more the mangrove forest becomes, the more protection the fry and some species of shrimp will have, and the more fish they catch: Nearly a third of the fish grow in these flooded forests. 11,600 tons of seafood sold annually has brought to surrounding villages income of 19 million USD. On every hectare of mangroves, the local people's income is 200 times more than the previous estimate of the Mexican government, giving them between $ 25,000 and $ 50,000, while a shrimp farm has the same area. only earns 1,000 USD.

Mangrove forest under water.Tree roots are a safe haven for fry and many crustaceans.Photo: Octavio Aburto.

Now, this ecological and economic value is also recognized in many other places - for example in Southeast Asia, where many forest regeneration projects are carried out after the tsunami disaster to protect the coast in a way. less money. But according to Maricar Samson and Rene Rollon of the Philippines University in Quezon City, this good intention often fails.

Good intentions, big mistakes

According to scientists, ignorance is the main cause: Operators often do not understand the ecological requirements of mangrove species and therefore have chosen the wrong place to plant. Lack of nutrients, excessive flow of water and storms have greatly damaged new crops. Worse, they often unintentionally destroy many of the active ecosystems, such as areas with seagrass beds, where fish lay eggs or flooded fields, which stop migratory birds. Instead, two ecologists recommend choosing gentle areas and only submerged during a third of the tide cycle.

Before going to search for suitable places, Samson and Rollon also advised to renovate the former places of shrimp farms because they were often in the area of ​​previous mangroves.