Mangroves are often seen as smelly, mosquito infested areas close to the crystal clear blue ocean. So why not chop down the trees and build a resort from which you can directly walk into the sea as has happened at so many tropical beaches? Not the smartest idea in hindsight, since those same mangroves actually make sure that the ocean remains so blue.
Mangroves function as a first barrier or buffer, both for storms and typhoons but also for mud, nutrients and pollutants that rivers bring down from the mountains. There’s a good article in the Science and Environment section of the BBC website on how effective mangroves are at providing security. Mangroves function as a nursery ground for part of the fish species. Rabbitfish, snappers and trevallies grow up in the mangroves protected from predators and migrate to the reef at a later stage, as documented in a report published by Dirkje Verhoeven at MCP. Because the ecosystems of the mangroves, seagrass and coral reef are interdependent, resorts make it very hard for themselves by removing an important ecosystem since the reef in front of the resort will slowly degrade. Mangroves frequently occur in the same area where coral reefs and seagrass occur.
Mangroves have some very special adaptations that make them grow in areas where no other trees can grow, namely in intertidal areas with very salty conditions. They need to remove their excess of salt to survive. Mangroves do that by excreting the salt through their leaves. If you look closely at the leaves you’ll often see salt crystals. The soil is muddy, compact and not very stable which makes it hard for mangroves to develop roots in the mud. The species that are almost permanently in the water have developed a more stable root structure with roots sticking out of the trunk that is very well visible. Because the mud is so dense, the mangroves have developed a special kind of roots sticking out of the ground called pneumatophores to ‘breathe’ oxygen. The seeds already germinate on the parent plant, so when the seedling falls down from the tree in the water, it actually has a chance of surviving the hostile salty environment.
Although it is now illegal in the Philippines to cut mangroves, it has already happened on a huge scale and mangroves have gone down from 5000 square km to roughly half this amount. In our area we have two extensive mangrove areas of which one is practically our backyard. The Coastal Resource Manager of Zamboanguita has already been replanting mangroves in old fish ponds and MCP volunteers are helping as much as we can. Besides replantinmg we now conduct frequent tours in the mangroves with our volunteers but also teach local school and church groups as we show them around and xplain why mangroves are so important. Additionally MCP started a mangrove nursery at our base a few months ago with as many different mangrove species as possible to be able to plant back a mix of species that comes closest to the original diverse ecosystem.