“Forest of the roots”
August 15, 2005
There is no shortage of untested theory concerning the processes that structure mangrove forests. Wayne Sousa uses his pattern data gathered from long-term monitoring of natural stands on Galeta, to refine these ideas into testable hypotheses relevant to his study forests. With replicated field manipulations, he tests hypotheses that zonation is controlled by: selective predation on mangrove propagules by crabs; differential dispersal and establishment of propagules; hierarchical, but spatially contingent, interspecific competition among juvenile mangroves; or selective herbivory, especially by caterpillars and stem-boring beetles.
The photo shows Sousa measuring a Laguncularia sapling planted in 1999 experiment that tests for potentially interactive effects of insect herbivory and plant competition on patterns of gap regeneration.
Unfortunately, the persistence of these important and distinctive coastal ecosystems is gravely threatened by a plethora of human-caused environmental perturbations. In recent decades, mangrove habitats have suffered dramatic declines in area due to coastal development, non-renewable resource exploitation (e.g. clear cutting, mining, and aquiculture), pollution, high rates of sedimentation, and alterations of hydrology. It has been estimated that as much as a third of the world’s mangrove forest have been lost in the past 50 years.
In the Caribbean, the rate of mainland mangrove deforestation is 1.4-1.7% annually, comparable to rates for threatened tropical rainforests. The information Sousa and colleagues collect on natural patterns of mangrove regeneration is critical to management and conservation of these unique habitats.