BATS, MANGROVE TREES, PINK SHRIMP and FIREFLIES

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I KNOW SOME THINGS ABOUT MANGROVE SWAMPS.

• THE MUD THE TREES GROW IN REALLY STINKS.
• IF YOU GO INTO A MANGROVE SWAMP YOU WILL DEFINITELY BE EATEN ALIVE BY
  • MOSQUITOES
  • MIDGES (JAWS WITH WINGS)
  • BITING ANTS

AND YOU MIGHT BE KILLED BY A POISONOUS WATERSNAKE OR A 23 FOOT CROCODILE.

You do know a few things about mangrove swamps, but if that is all you know, then there is a lot that you don't know.

ALL RIGHT, ENLIGHTEN ME. BEGIN WITH THE BATS.

Fruit bats eat the nectar and pollen of mangrove tree flowers. The Asiatic long-tongued fruit bat and the dawn bat help to ensure the survival of mangrove trees by pollinating their flowers.(1)

Dawn bat, Eonycteris spelaea; mangrove flower pollinator

Other fruit bats eat the young shoots and fruit of mangrove trees and find a safe daytime roost in the tangled swamp. Also, many insect-eating bats are attracted by the hordes of different kinds of insects that live in mangrove swamps.(2)

WHY SHOULD WE CARE WHETHER MANGROVE TREES SURVIVE?

• Mangrove trees grow on tropical coasts. They create land by trapping silt and debris in their tangled prop roots. The trees protect coastal land by acting as a strong bulwark against the powerful eroding action of the sea. (2,3)

  Following the Asian tsunami on 26 December, 2004, M.S. Swaminathan, a leading agriculturist in India, was widely quoted in world newspapers. He said that coastal areas of India where mangroves exist and have been restored were protected from the devastation wreaked by the tsunami. M.S. Swaminathan chairs a l4 year old research organization dedicated to restoration of mangroves on India's eastern coast in anticipation of the future tidal effects of global warming. Environment groups in Jakarta and Sri Lanka reported similar protection from intact mangrove swamps in their areas.

The world range of mangrove trees is outlined in green. The red dots are the locations of the world's largest concentration of mangroves; between India and Bangladesh where the Ganges River enters the sea, and the delta of the Niger River in Africa.(2)

• Mangrove tree leaves are the starting point of an elaborate, valuable food chain that begins with nourishing microbes and ends with nourishing people and providing them with jobs.
  • Fallen mangrove leaves are eaten by microscopic marine microbes such as
    • fungi
    • amoebas
    • bacteria
    • roundworms

(To us these microscopic creatures look like a brown slime on the mangrove leaf.)

• Tiny marine worms find the brown microbe slime a delicious, nourishing meal.
• The tiny worms and the microbe-enriched leaves become food for small crabs, shrimp, mollusks, sandhoppers, and many other sea creatures.
• Small fish feed on the crabs, shrimp and mollusks.
• Bigger fish, harvested commercially and for home use, feed on the small fish.

Some large fish that are important in commercial catches bypass the small fish meals and filter nourishing mangrove leaf fragments directly from the mud floor of the bays and estuaries.

• The mangrove swamp is a rich protective habitat for young sea creatures that will eventually become important in human nutrition and commerce. Pink shrimp eggs are laid in the Dry Tortugas, about 100 miles from the Florida coast. Millions of speck sized larvae travel back to the Florida mangrove nurseries where they mature. Young pink shrimp emerge from that safe haven and begin a journey back to the Dry Tortugas where as adults they lay eggs and also become a multi-million dollar catch for shrimpers. Many human beings profit from this pink shrimp harvest that is dependent in part on the nurturing environment of the mangrove nurseries. (3)

• Mangrove tree wood is an important source of charcoal and wood chips. Some mangrove tree harvesting is well-managed and young trees replace the cut trees. Many other mangrove swamps are permanently destroyed by logging that is not managed on a sustainable basis.

• Another source of income for people from mangrove swamps is tourism.

DO YOU MEAN THERE ARE PEOPLE WHO WANT TO GO INTO THOSE TANGLED DANGEROUS SWAMPS? WHATEVER FOR?

The front rank trees of a mangrove swamp live in two worlds. At high tide they are sea trees, at low tide they are land trees. The creatures that live in mangrove swamps are both marine and land animals, so there is a more varied population in the swamps than in any other habitat.

People want to see mudskippers, the fish that can walk on land and climb trees. People want to see the archer fish that can swim beneath a tree, let fly a stream of water from its mouth and dislodge a resting insect from a leaf. When darkness falls, people want to see hundreds of mangrove trees ablaze with the synchronized flashing of countless fireflies.(4)

People want to see the proboscis monkey, found only in Borneo, whose primary food is mangrove leaves. Those leaves are from one of the species of mangroves that is known to be bat-pollinated.

People may want to see a 25 foot long crocodile or a 3 foot long monitor lizard.

To accommodate these people, the mangrove swamps in some countries have elevated boardwalks, kayak and canoe channels, viewing hides and guided boat trips.

The Brown Pelican roosts in mangrove trees and lines its nest with mangrove leaves (from another island)

WELL, HMMM, I SUPPOSE I WOULD FIND IT INTERESTING; WALKING FISH, TREES ABLAZE WITH FIREFLIES, PROBOSCIS MONKEYS, EXOTIC BIRDS . . . IF I WRAP UP REALLY WELL AGAINST THE MOSQUITOES, MIDGES AND ANTS . . .

Don't delay in making your travel plans. Mangrove trees and everything associated with them are in peril. Poor logging practices, housing, tourist and shrimp farm development, pollution from pesticides, sewage and oil spills, hurricanes and typhoons are all taking a toll. The long-term effects of global warming and a rise in sea levels are still unclear, but they are considered as potential threats to mangrove swamps. The effects of the Asian tsunami on 26 December 2004 makes a very strong case for the protective effects of undisturbed mangrove swamps.

YOU'RE RIGHT, I DIDN'T KNOW MUCH ABOUT MANGROVES. DO BATS PLANT THE SEEDS?

No, mangrove trees do their own planting and it is always in water. Instead of dropping a fruit or a seed or relying on animals or birds for seed dispersal, some kinds of mangroves release a fully formed seedling. It drops into the water, floats away, sometimes for hundreds of miles, until it encounters an oyster bed, a coral reef or a sandbar. Depending on the length of time at sea, a young tree may arrive at its destination equipped with roots and leaves. Once in place, it grows quickly, reaches a height of 2 feet in a year, and is able to flower and donate its own offspring to the sea in 6 years. The tree may eventually reach a height of 80 feet.(2)

The miniature Asiatic Long-tongued Fruit Bat, a mangrove flower pollinator, roosting with red mangrove flowers, fruit and a seedling

SO, THE CONTRIBUTIONS OF THE MANGROVE TREES ARE COASTAL PROTECTION, HABITAT FOR JUNIOR FISH AND SHRIMP WHO BECOME COMMERCIAL CATCHES AS ADULTS, WOOD CHIPS, CHARCOAL, NEWSPRINT, AND UNIQUE NATURE EXPERIENCES. ANYTHING ELSE?

Food for animals, food for people, glue, oil for dressing hair, fibres for textiles, tool handles, cosmetics, matchsticks, incense, musical instruments, tannin for preserving leather, dyes,fish traps, fish poison, fishing boats, fishing poles,thatch for roofing, scaffolding, mining props, dock pilings, railway sleepers, matting, sugar, alcohol, cooking oil, vinegar, honey, medicines, paper, and other local uses that are unknown.(5)

THAT IS A VERY DIVERSE LIST OF PRODUCTS, FROM HAIR OIL TO RAILWAY SLEEPERS. WHAT ORDER OF PLANTS DO MANGROVES BELONG TO?

Mangroves are unique among bat-plants in that they belong to 9 orders and 16 families. In contrast, all bananas belong to one order, Zingiberales, and one family, Musaceae. The majority of mangroves, 35 of the 50 to 60 species, are found in the order of Myrtales, and most of those 35 species are in the Rhizophoraceae family.

Mangroves are halophytes which means they are salt-loving. They are grouped together by their ability to live in salty conditions more than by their botanical similarities. For example, there is a mangrove in the palm family, a mangrove in the family with baobab, durian and balsa trees and a mangrove in the cocoa family.(2)

WHERE CAN I LEARN MORE ABOUT MANGROVES?

From books and websites. Here they are.

Stafford-Deitsch, J. (l996) Mangrove. The forgotten habitat. Immel, London

Hogarth, Peter J. (l999) The biology of mangroves. Oxford University Press.

Hutchings, P. and Saenger, P. (l987) Ecology of mangroves. University of Queensland Press,

St. Lucia

Tomlinson, P.B. (l986) The botany of mangroves. Cambridge University Press, Cambridge.

http://www.kenyanmangroves.com

http://www.earthisland.org/map This is the Mangrove Action Project website, an excellent way to learn more about mangroves, their benefits and the efforts to protect, regenerate and conserve the swamps.

Other References:

(1)Fujita, M.S. 1991. Flying Fox (Chiroptera:Pteropodidae) Pollination, Seed Dispersal, and Economic Importance: A Tabular Summary of Current Knowledge, Resource Publication No. 2, Bat Conservation International.

(2)Hogarth, Peter J. (l999) The biology of mangroves. Oxford University Press.

(3)Wild Nursery of the Mangroves, National Geographic, Vol. 151, No. 5, May 1977, Pages 669-688

(4)MacKinnon, John, Borneo, The World's Wild Places/Time-Life Books/Amsterdam, 1975

(5)Mangroves:a fascinating eco-system;http://www.papuaweb.org/dlib/tema//kamoro/muller-sda/07a.rtf

Text and illustrations by Mary Louise Alley-Crosby who thanks Dr. Merlin D. Tuttle, Founder and President, Bat Conservation International, Austin, Texas, for permission to use his photograph of a dawn bat as source material.

Links checked 8 March 2006

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