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E  C O S Y S T E M ST R U C T U R E I  N D I C AT O R S

H  A B I TAT E  X T E N T

Conservation Objective

Determine the extent and condition of coral reef, mangrove and seagrass habitat; develop methods for

tracking change; develop a target for the limits of acceptable change; and minimize losses due to direct

human actions.

Threats

The main threats to coral reef habitat are coral disease, coral bleaching, competition from macroalgae

and sponges, hurricanes, effects of overfishing, pollution (including sedimentation and nutrification),

direct removal or damage, and global climate change. The greatest threats to mangrove and seagrass

habitat are direct losses associated with coastal development or other land alteration, plus freshwater

flow alterations that adversely impact water quality.

Management Actions

· Develop a regional GIS database of habitat maps; develop refined remote-sensing techniques to

monitor habitat extent regularly.

· Prohibit direct removal of coral reef, mangrove or seagrass habitat during coastal development

projects.

· Reduce sediment and contaminant runoff associated with agricultural practices or coastal

development.

· Investigate opportunities to restore or enhance habitat extent or quality (e.g., replanting

mangroves or restoring linked habitats).

· Develop regional program to survey regulatory compliance of coastal development projects (i.e.,

aerial surveys).

· Investigate and map historical habitat distributions.

Seagrass beds and mangrove forests also provide

Habitat extent refers to how much area a given

critical habitat for the juvenile life stages of many

habitat, such as a mangrove forest, covers. If there

commercially important reef fish and invertebrates

is too little of a particular habitat (or if it is divided

(e.g., lobsters). The rainbow parrotfish, a key reef

up into too-small pieces or is too far removed from

herbivore, depends on nearby mangroves and

other, functionally related habitats), the existence of

seagrass meadows for nursery habitat, as do grunts,

some coastal organisms or even other habitats may

barracuda and several snapper species.

be threatened.

These critical linkages among habitats can be broken

Coral reefs, seagrass beds and mangrove forests

by direct habitat destruction or by more subtle coastal

form a complex and dynamic mosaic that provides

degradation, and the ecological consequences may

critical foraging areas and nurseries, plus physical

not be immediately evident. It is important to monitor

and chemical buffering. Proximity and connectivity

regularly the extent and connectivity of key coastal

among these environments facilitates energy and

habitats.

material flows, creates corridors for transient species

and provides critical habitat for many reef species at

Indicators selected to track habitat extent are:

a variety of developmental stages.

S11 - Coral Reef Areal Extent

Coral reefs dissipate wave energy, thus providing

environments suitable for seagrass and mangrove

S12 - Mangrove Areal Extent

colonization. Seagrasses and mangroves stabilize

sediments and take up nutrients, helping to sustain

S13 - Seagrass Areal Extent

the clear, low-nutrient waters in which corals thrive.

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