What’s all the fuss about Cayman’s mangroves?

Know your islands

Grand Cayman’s Central Mangrove Wetland is the ecological heart of Grand Cayman.

It is critical to so many important natural processes that the National Trust for the Cayman Islands considers its long term protection to be one of the fundamental requirements for the well-being of future generations in the Cayman Islands.

Approximately 1,500 acres of the Central Mangrove Wetland is protected through the Marine Parks Law, forming part of the Environmental Zone, which has been in effect for Little Sound and its fringing mangroves since 1986. Efforts are now underway to increase the area of the Wetland under protection, through conservation land purchase.

The Central Mangrove Wetland is part of a large scale water flow system, filtering and conditioning the surface water and shallow ground water which flows into North Sound. Both by constant tidal flushing of the mangrove fringes and by occasional massive overflows of accumulated rainwater from the entire Central Mangrove basin, the Wetland provide a flow of nutrients into North Sound.

These nutrients form the base of a complex food chain from the Turtle Grass and shrimp mounds in Little Sound, through to the snappers and lobsters which move from the mangroves to the reef. The entire living system of North Sound is inextricably linked to the Central Mangroves, and would collapse if the Wetland were ever destroyed.

The Wetland covers a total of about 8,500 acres, still almost entirely in its natural state. Except for areas of open water, it is covered by a canopy of trees, which absorb sunlight and radiate part of that energy as heat, warming the air near the leaves.

The same air also becomes saturated with water vapour, evaporating from the leaves’ breathing pores and from the ponds below. Warm air is less dense than cooler air, and rises in a complex pattern of convection currents. Saturated air rising above the Central Mangrove Wetland in this way forms rapidly developing clouds, which are carried west by the prevailing winds and dump rain over the central and western districts of Grand Cayman.

This process is believed to contribute a large part of western Grand Cayman’s rainfall, which is 40% greater than in the eastern districts. Without the Central Mangroves, George Town and West Bay could be almost as dry as East End, but without the benefit of an unspoiled ground water lens to keep the trees healthy and the well water fresh.

The Central Mangrove Wetland is surrounded by some of Grand Cayman’s best agricultural land, and also by a system of fresh water lenses. The Wetland helps to hold back rainwater flowing towards the sea from higher land, and so maintains the fresh water lenses and holds up high fresh water tables in agricultural land.

Mangrove canalisation and development in western Grand Cayman has already shown how vulnerable our agriculture and groundwater supplies are to the destruction of neighbouring wetlands.

West Indian Whistling Duck, Grand Cayman Parrots, Snowy Egrets and many other native birds depend on the Central Mangrove Wetland for food, shelter and as a place to breed. Various crab species, smaller crustaceans – some of which have only recently been described by scientists – and countless species of insects and other invertebrates inhabit the Wetland, along with fish, Hickatees, Agouti and many other animal life forms.

The Red, Black and White Mangroves are joined by Buttonwoods, and a variety of dry land trees like Mahogany and Wild Fig have also gained a foothold in the more remote areas of the Wetland, where fresh rainwater sometimes floats on top of the salty groundwater.

Join the National Trust for a mangrove boat tour. Cayman Kayaks also conducts up-close-and-personal tours of the mangroves, day, sunset or night cruises. Explore the mangroves to truly understand its value.

Grow Cayman Plants and encourage Cayman Wildlife. For more information, to share knowledge or to get involved with the many activities in the National Trust’s Know Your Islands Program, visit www.nationaltrust.org.ky, www.caymanwildlife.org or call 949-0121.

Last week’s answer: The Red-Footed Booby of Little Cayman flies out to sea at dawn and spends the day diving for fish.

Trivia question: Name one of Cayman’s rarest trees that have leaves somewhat similar to the cultivated ‘Jasmine’ shrub.

Look for the answer in next week’s feature.

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