Science - October 6, 2010

Tropical species in new Dutch territories

Dutch biodiversity is on the brink of a massive expansion. From 10 October, it will include tropical flora and fauna. Dolfi Debrot has been doing research for Imares and the ministry of LNV on what it will take to manage the sea, the mangrove swamps and the coral reefs of Bonaire, St. Eustatius and Saba.

Mangrove seegrass field serves as a delivery room
Dolfi Debrot is waiting with bated breath to find out how the Washington-Slagbaai National Park on Bonaire has survived the fire at oil storage company Bopac, which went on for weeks. 'Rumour has it that a great deal of soot has descended on the surrounding nature areas. Research is being done on that now', says Debrot, for whom the fire demonstrates that environmental management on the island is behind the times, and that the oil industry carries high risks. 'A good emergency plan is needed. The Dutch Antilles, of which Bonaire is still a part, have not got round to that because of a general shortage of capacity.'
From 10 October, this will be the Netherlands' problem. Due to constitutional reform, on that date the Dutch Antilles - currently an autonomous country within the kingdom - will break up.  Bonaire, St. Eustatius and Saba (known as the BES islands) will become part of the Netherlands. This means the Netherlands taking responsibility for the welfare of 20,000 new citizens, 15,000 of them on Bonaire, as well as for thousands of new species of plants and animals. These are species of a totally different kind than people are used to in the Netherlands: mangroves rather than pines, the clear tropical ocean rather than the murky North Sea.
Destressing coral
'The coral reefs on Bonaire are the most beautiful in the whole of the Caribbean', Debrot declares. 'Sadly though, the corals there are also affected by coral bleaching, probably caused by a combination of water pollution, warming, and acidification of seawater. But if coral reefs can be saved anywhere, it is on Bonaire', Debrot believes. 'Of course we cannot do much on the spot about things like rising temperatures, but the Netherlands must remove the local stress factors for the coral as far as possible. And people are working on that. There is a sewage treatment plant under construction, there are fish reserves and there is going to be an area with restrictions on the anchoring of ships. Their anchors tear the reef apart.'
Tropical marine biologist Dolfi Debrot (51) lived for years on the Antilles as director of the Caribbean Research and Management of Biodiversity foundation. Last spring he moved on to Imares in Den Helder in the Netherlands. He is also a member of a workgroup that has been asked by the ministry of Agriculture, Nature and Food Quality (LNV) to study the coastal waters around the BES islands. This area is known as the Exclusive Economic Zone, an expanse of sea, extending to about 370 kilometres from the coast, in which the Netherlands has exclusive fishing and mineral rights.
Together with the tropical team at Imares, the workgroup is inventorying what needs to happen on the BES island and which laws, treaties and protocols apply there. 'We are also looking at issues such as rising temperatures and sea levels, which have consequences both for the ecosystems on land and for the coral reefs, and therefore also for tourism and coastal defense.'
Spreading forest threatens seagrass
One good example is Lac Bay on Bonaire, a lagoon of eight square kilometers of seagrass and mangrove forest. The area is facing problems, explains Debrot. One problem is the growing numbers of tourists, but another is the vitality of the mangrove trees, which  leaves a lot to be desired. It is a natural process in such coastal forests for the mangroves on the landward side of the forest to die out, since most of the sediments sinks down so that the mangroves end up hardly standing in water and they give up the ghost. By way of compensation, though, the mangroves on the seaward side gradually expand into the lagoon. But on Bonaire there is a problem with both these processes. Erosion is causing a lot of the island's soil to be drained into the forest, accelerating the deterioration of the trees' habitat. That process is reinforced by the manure and the grazing from illegally roaming donkeys, goats and sheep. And on the seaward side, the forest is threatening the seagrass, which is essential for the island's turtles. 'If it goes on like this, the trees will eventually be at the mouth of the bay, and they cannot grow beyond that because of the rougher waters. And in the end, both the seagrass and the mangroves will disappear. At the ministry of LNV's request, Imares and the Bonaire National Marine Park are working out what should be done. One of the things we have decided is to carry out a pilot project in which we will dredge up sediment at two places to regenerate the forest. And a fence is going to be put up to keep livestock out.'

Useful for people
Within the workgroup, Debrot's efforts are directed at improving policy on nature and biodiversity. 'Of course, everyone has heard of the sea turtles, but these islands and the waters around them are home to very many rare species. The Caribbean region has a large number of endemic life forms, species which are exclusive to one of the islands. These include not just several species of snail, but also the well-known Bonaire bananaquit (coereba flaviola), for example, which is a separate sub-species of a bird that is common throughout the Caribbean.'
Conserving rare plant and animal species is crucial not just from the biodiversity angle, says Debrot, but also because of their potential for human beings. 'Many organisms on the reef have grown onto it. To protect themselves from predators, some of them emit poisons. Medical science is increasingly interested in these bioactive substances. An antibiotic that was discovered in one of the ascidians from the sea around Bonaire is now big business - to the tune of millions of dollars a year.

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