Mangrove Basics 

  1. Mangroves are some of the most important ecosystems on Earth
  2. Mangrove forests grow in intertidal zones and estuary mouths between land and sea. They anchor and protect coastal ecosystems, and make up a transitional zone between land and ocean, connecting and supporting both
  3. Most mangroves live on muddy soils, but they also can grow on sand, peat, and coral rock
  4. Mangroves vary in height from small shrubs to 40-metre-tall trees
  5. Mangrove forests are comprised of salt-tolerant plant species that are highly adapted to their environment of highly saline water and soil. Mangroves have specially adapted aerial and salt-filtering roots and salt-excreting leaves which enable them to occupy saline wetlands where other plant life cannot survive
  6. Some mangroves have unique “breathing roots”, called “pneumataphores”. They contain pores called “lenticles” through which the plants absorb oxygen. They are not active during high tide, when they are submerged. These delicate lenticels are highly susceptible to clogging by pollutants (such as oil), damage from parasites, and prolonged flooding. Over time, environmental stress can kill large swathes of mangrove forest
  7. The largest remaining tract of mangrove forest in the world is found in the Sundarbans on the edge of the Bay of Bengal
  8. There are 54 to 75 species of mangroves worldwide, with the greatest mangrove diversity found in Southeast Asia
  9. Mangrove forests are essential nursery grounds for all kinds of marine life including fish, rays, and invertebrates
  10. They also provide critical habitat for a number of threatened and endangered species including manatees, tigers, and hundreds of species of birds
mangroves basics

Threats

More than one in six mangrove species worldwide are in danger of extinction as a result of a number of factors, including coastal development, climate change, logging and agriculture.

We have already lost over half of the world’s original mangrove forest area, estimated at 32 million hectares (approx. 80 million acres).

About half of mangrove loss has occurred in the last 50 years, mostly in the last two decades, due to:

  • Shrimp farming
  • Tourism
  • Urbanisation
  • Expansion of agriculture
  • Roadways
  • Marinas and ports
  • Other coastal development

The current rate of mangrove loss is approximately 1% per annum (according to the Food and Agriculture Organization – FAO), or roughly 150,000 hectares (approx. 370,000 acres) of mangrove wetlands lost each year

Reproduction 

  • Mangroves reproduce through a process known as “viviparity”
  • During this process, the “embryos” will germinate on the trees themselves. These are called “propagules”. During this phase, these propagules gain essential nutrients from the parent tree that prepare them for the next phase of their growth
  • The propagules will then drop into the water beneath the tree, and may take root there, or they may float for a period of time, dispersing to another area

Essential Services 

  • Recent research shows that mangroves are incredible carbon sinks, sequestering more carbon than any of their terrestrial counterparts. Mangrove forests sequester approximately 1.5 metric tons/hectare/year of carbon
  • Mangroves protect coasts from erosion and from violent storms, and provide a host of economic benefits and ecosystem services to human communities

Distribution 

  • Mangrove forests are found between the latitudes of 32°N and 38°S, along the tropical and subtropical coasts of Africa, Australia, Asia, and the Americas
  • The distribution of mangrove forests is mostly determined by sea level and its fluctuations. Other factors are air temperature, salinity, currents, weather patterns, shore slope, and soil substrate
scuba diver cover 2/2017

For more on mangroves, check out the article “Mighty Mangroves” in Scuba Diver AustraliaAsia + Oceanplanet “Blue Green Edition” Issue 2/2017. The article follows the story of how an “accidental forest” (mangroves!) saved a village in the Philippines from a super-typhoon, and has helped revitalise the local fishery. The issue itself is dedicated to conservation and honours the winners of the Bluegreen360 Awards 2017, presented to those businesses that are committed to eco-friendly practices and marine conservation.

 

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