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Mangroves - are salt-tolerant, woody, seed-bearing plants that are found in tropical and subtropical areas where they are subject to periodic tidal inundation. The Philippines has over 40 species of mangroves and is one of the most biodiverse regions in the world as there are only about 70 species of mangroves worldwide. The mangrove ecosystem is a very diverse one and is home to many birds, fish, mammals, crustaceans and other animals.


Mangroves are very specialized plants and have adapted to survive in a very harsh environment where other plants cannot survive. An example of an interesting adaptation is the root system of mangroves. Since mangroves often live in muddy environments where gas exchange is difficult, the root systems of many mangrove species are highly specialized. One example of this is pneumatophores or breathing roots which look like fingers sticking out of the ground which are seen on Avicennia spp. (api-api) and Sonneratia spp. (pagatpat) trees. Other roots which grow out from branches and the trunk of mangrove trees such as those on Rhizophora spp. (bakaun) are called stilt or prop roots. These roots contain lenticels or breathing holes which allow gas exchange above the ground. These stilt roots also provide support and anchorage during high winds and wave action as well as serving as an attachment substrate for many marine organisms. Other species have knee or knob roots above the ground such as seen in Busain.


Mangroves must also deal with the saltwater environment that they live in. While many mangrove trees grow best in a mixture of saltwater, an excessive amount of salt would certainly kill them. In order to deal with this mangrove species have developed a number of different adaptations. Certain trees such as api-api are excreters and they expel salt crystals from their leaves which is then washed away by the rain. Others are excluders and block salt from entering through their roots. They accomplish this by having a high innate concentration of salt in their roots which prevents water from entering against the osmotic gradient. Other plants are secluders which concentrate salt in certain leaves which turn yellow and die and expel the salt when these leaves die.


Mangroves also have adapted certain reproductive mechanisms to deal with the harsh salt water environment. One of these is the viviparous propagule or tungki found on bakuan. This propagule is already germinated on the tree and has a basic stem structure and can therefore easily be implanted in the substrate and quickly begin to grow. If the propagule does however fall in the water it has the ability to float for up to one year which aids greatly in dispersal of mangrove species.


Mangroves provide an important nursery for fish, shellfish and other organisms. It is estimated that each hectare of mangrove produces 3,600 kg of litterfall which provides food for 1,000 kg of marine organisms. With the abundance of food for fish present in the mangroves, each year one hectare of forest yields 283.5 metric tons of fish per year. Mangroves also provide other important functions such as preventing soil erosion and protecting shoreline from typhoons and strong waves. Mangroves provide many other products and services such as medicines, alcohol, housing materials and are an area for research and tourism.


Even with all of these known benefits the state of mangroves within the Philippines is very dim. In the early 1900’s there were approximately 500,000 hectares of mangroves but today there are only about 120,000 hectares. Many of the mangrove areas were destroyed to make way for fishponds and reclamation areas. They were used indiscriminately for housing materials and were disturbed by siltation and pollution.

Now that the true benefit of these ecosystems is known there is protection and rehabilitation of these important ecosystems. It is now illegal to cut down mangroves for any purpose and local governments and community organizations have taken active roles in planting and managing mangrove plantations. There is hope that in the future mangroves will return to the healthy status that they once held in the past.

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