Mangroves

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Mangroves

What are Mangroves?

Mangroves are groups of trees and shrubs that inhabit coastal intertidal zones in the tropics. There a more than 80 extant species, some growing as high as 200 feet. The slow moving waters in mangrove forests allow for the accumulation of fine sediments, creating a muddy benthic area. Some mangroves have dense tangles of prop roots or buttresses that enable the trees to cope with rising and falling tides; others have snorkel-life roots called pnuematophores that stick out of the mud to help them take in air.[1]

Where are They Found?

Mangroves only grow at tropical and subtropical latitudes near the equator. Mangroves also require an environment containing low-oxygen soil to grow. Most of the world's mangroves are found in Southeast Asia, with many also being found in Florida.[1]

What Benefits Do They Offer?

Mangroves stabilize the coastline, reducing erosion from storm surges, currents, waves, and tides. This means that mangroves act as a great buffer against hurricanes and tropical storms[1]. Their intricate root system is attractive to fish and other organisms seeking food and shelter. They also serve as habitats for many juvenile fish, oysters, crabs, shrimp, and birds. Mangroves help decrease the effects of global warming through carbon sequestration and storage. Mangrove growth helps to intercept pollutants and land derived nutrients before they contaminate deeper water. This is important because nutrient transport from land to estuaries is one of the main agents of ecological change in coastal areas[2].

What are the Stressors of Deforestation?

  • Estimated that at least half of the world’s mangroves have been lost and continue to be destroyed at a rate of about one percent per year[1]
  • Stressors
  1. Coastal development driven by tourism and growing populations[1]
  2. Aquaculture, particularly shrimp farming[3]
    • Mariculture has been reported as responsible for 50% loss of mangroves in the Philippines and 50-80% in Southeast Asia
    • These ponds often have short life spans due to toxin accumulation and sulfide acidification, causing these pond owners to move to a new section of mangrove, furthering the destruction of mangrove forests[2]
  3. Agriculture run-off carrying pesticides and herbicides
  4. Man-made changes in tidal or river flow that starve the system of sediment input
  5. Sea level rise[1]

What are the Side Effects of Deforestation?

  • Loss of mangroves reduces the amount of carbon sequestration possible and releases carbon stored in the soils, worsening the greenhouse effect
  • Coastal communities left unprotected from storms and hurricanes
  • Deforested shorelines are subject to greater rates of erosion and are unable to keep pace with sea level rise[1]
  • One of the world’s most threatened tropical ecosystems with global loss exceeding 35%
    • There is a pattern of reduced mangrove forest area for nearly all countries containing them, especially countries with large mangrove areas[2]
    • In Americas, mangrove deforestation is 2,251 km2 per year, which is higher rate than tropical rainforest deforestation[4]

What lives in the Mangroves?

A scrawled cowfish swimming near manatee grass in a mangrove forest.
  • Birds roost in the canopy
  • Shellfish and organisms attach themselves to the roots, such as barnacles, oysters, crabs, sponges, anemones
  • Snakes and crocodiles hunt there
  • Nectar source for bats and honeybees
  • Juvenile fish find shelter there during there vulnerable first weeks[3]

What are the Common Types of Mangroves?

Red Mangrove[5]

Grows along the edge of the shoreline where conditions are harshest
Tangled, reddish prop roots and gray bark over a dark red wood
Grows to heights of 80 feet
Clusters of white flowers bloom during the spring months

Black Mangrove[5]

Long horizontal roots with pneumatophores
Bark is dark and scaly
Grows to heights of 65 feet
White flowers blossom in spring

White Mangrove[5]

Occupying higher land than the Red and Black Mangroves
No visible aerial roots, but can develop peg roots
The least cold tolerant
Grows to heights of 50 feet
Produce greenish-white flowers in spikes in spring

Buttonwood Mangrove[5]

Found in the upland transitional zone
Sensitivity to frost
Button-like appearance of the flower heads that grow in branched clusters, forming cone-like fruit

How Are They Linked to Coral Reefs?

  • Provide nutrients to neighboring ecosystems such as coral reefs and sea grass beds
  • Nearby coral reefs suffer further pressure from sedimentation when mangroves are removed and can no longer filter the water[1]
  • Mangroves in the Caribbean have a strong influence on the fish populations in reefs near them
    • The largest herbivorous fish in Atlantic, Scarus guacamaia (rainbow parrotfish), is dependent on mangroves and has become locally extinct when they are gone[4]
      • Decreased amount of herbivores will cause reefs to become less resilient to algal overgrowth
    • Fisheries productivities are likely to decrease without mangroves
  • In a study in Belize comparing mangrove-scarce reefs to mangrove-rich reefs, the biomass of nearly every fish studied was much greater in the mangrove-rich areas
    • Biomass of the blue striped grunt on patch reefs in the mangrove-rich area increased by 2667%
    • Biomass of all 6 species studied in the patch reefs increased from 191% to 2667% in mangrove-rich areas[4]
  • Mangroves act as intermediate nursery between seagrass beds and patch reefs[4]

References

  1. 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 http://www.habitat.noaa.gov/abouthabitat/mangroves.html
  2. 2.0 2.1 2.2 http://vb3lk7eb4t.search.serialssolutions.com.libproxy.lib.unc.edu/?&url_ver=Z39.88-2004&url_ctx_fmt=info:ofi/fmt:kev:mtx:ctx&rft_val_fmt=info:ofi/fmt:kev:mtx:journal&rft.atitle=Mangrove%20forests%3A%20One%20of%20the%20world%27s%20threatened%20major%20tropical%20environments&rft.aulast=Valiela&rft.date=2001&rft.epage=815&rft.genre=article&rft.issn=0006-3568&rft.issue=10&rft.jtitle=BIOSCIENCE&rft.pages=807-815&rft.spage=807&rft.stitle=BIOSCIENCE&rft.volume=51&rfr_id=info:sid/www.isinet.com:WoK:UA&rft.au=Bowen%2C%20JL&rft.au=York%2C%20JK&rft_id=info:doi/10.1641%2F0006-3568%282001%29051
  3. 3.0 3.1 http://ngm.nationalgeographic.com/2007/02/mangroves/warne-text/6
  4. 4.0 4.1 4.2 4.3 http://vb3lk7eb4t.search.serialssolutions.com.libproxy.lib.unc.edu/?ctx_ver=Z39.88-2004&ctx_enc=info:ofi/enc:UTF-8&rfr_id=info:sid/ProQ%3Apqdiearthsci&rft_val_fmt=info:ofi/fmt:kev:mtx:journal&rft.genre=article&rft.jtitle=Nature&rft.atitle=Mangroves+enhance+the+biomass+of+coral+reef+fish+communities+in+the+Caribbean&rft.au=Mumby%2C+P+J%3BEdwards%2C+A+J%3BArias-Gonzalez%2C+JE%3BLindeman%2C+K+C%3BBlackwell%2C+P+G%3BGall%2C+A%3BGorczynska%2C+MI%3BHarborne%2C+A+R%3BPescod%2C+CL%3BRenken%2C+H%3BWabnitz%2C+CCC%3BLlewellyn%2C+G&rft.aulast=Mumby&rft.aufirst=P&rft.date=2004-02-05&rft.volume=427&rft.issue=6974&rft.spage=533&rft.isbn=&rft.btitle=&rft.title=Nature&rft.issn=00280836
  5. 5.0 5.1 5.2 5.3 http://www.flmnh.ufl.edu/fish/southflorida/mangrove/profiles.html