Mangroves: Trouble in the Tropics

Reddish egrets, pictured at right perched on a mangrove tree, are restricted to a narrow fringe of mangrove forest along the coastlines of the southeastern United States, Mexico, Central America, and the West Indies. They depend on mangroves for nesting and foraging habitat—but mangroves are not doing well.

Worldwide, their range declined 2% a year from the early 1980s to 2001. At that rate, mangroves could be gone within 100 years, and so would the animals that depend on them.

Mangroves grow around the world in the salty waters of the tropics and subtropics. They help stabilize the coastline and provide protection from hurricanes. Many species of fish, shrimp, and other marine animals use the tidally flooded mangrove forests as nurseries and foraging areas.

Less well known is the fact that many species of animals make their homes in the mangrove canopy. Around the world, 69 species and subspecies of animals live almost their entire lives in mangroves.

48 kinds of birds are restricted to mangroves

• Striated heron (Northern Australia)
• Great-billed heron (Papua New Guinea and Australia)
• Reddish egret (Florida, Caribbean and Central America)
• Madagascar Teal (Madagascar)
• Rufous crab-hawk (Venezuela to Brazil)
• Common black-hawk (Cuba)
• Mangrove black-hawk (Pacific Coast of Central America)
• Grey-necked wood-rail (São Paulo to Santa Catarina, Brazil)
• Rufous-necked wood-rail (Central America)
• Chestnut rail (Papua New Guinea and Australia)
• Plain-flanked rail (Venezuela)
• Clapper rail (Central and South America)
• Mangrove hummingbird (Pacific Coast of Costa Rica)
• Saphire-bellied hummingbird (Colombia)
• Brown-winged kingfisher (East India to Malaysia)
• Ruddy kingfisher (Malaysia)
• Collared kingfisher (Australia)
• Greater flameback (Malaysia to Bali)
• Laced woodpecker (Western Thailand)
• Mangrove pitta (India to Southeast Asia)
• Straight-billed woodcreeper (western coast of Central America)
• Mangrove blue flycatcher (Thailand to Papua New Guinea)
• Magpie robin (Malaysia)
• Mangrove grey fantail (Papua New Guinea and Australia)
• Rufous fantail (Kimberley, western Australia, and West Queensland)
• Shiny flycatcher (Kimberley, western Australia, and West Queensland)
• Broad-billed flycatcher (West Queensland)
• Mangrove whistler (India to Southeast Asia)
• White-breasted whistler (Australia)
• Mangrove golden whistler (Northern Territory, Australia)
• Ashy tailorbird (Java)
• Mangrove gerygone (Papua New Guinea and Australia)
• Dusky gerygone (Western Australia)
• Large-billed gerygone (Papua New Guinea and Australia)
• Great tit (Malaysia)
• Mouse-brown sunbird (Western Africa)
• Copper-throated sunbird (Thailand to Papua New Guinea)
• Red-headed myzomela (Papua New Guinea and Australia)
• Yellow whiteeye (Australia)
• Mangrove honeyeater (Papua New Guinea and Australia)
• Varied honeyeater (Northwestern Queensland, Australia)
• Mangrove vireo (Pacific Coast of Mexico)
• Prairie warbler (Southern Florida, North America)
• Yellow “mangrove” warbler (Central America and the Caribbean)
• Lemon-breasted flycatcher (Kimberley, western Australia)
• Mangrove robin (Australia)
• Black butcherbird (Northern Territory, Australia)
• Mangrove finch (Galápagos Islands, Ecuador)

14 kinds of reptiles

• Mangrove Terrapin (Southern Florida and Keys, North America)
• Water Monitor (Phillipine Islands)
• Mangrove Monitor (Papua New Guinea and Australia)
• Little File Snake (India to Australia)
• Mangrove Snake (Southeast Asia to the Phillipines)
• Yellow-banded Water Snake (Andaman Islands)
• Dog-faced Water Snake (India to Southeast Asia)
• Australian Bockdam (Northern Australia)
• Crab-eating Snake (India to Australia)
• Glossy Marsh Snake (Inidia to Thailand)
• Red-tailed Green Rat Snake (Southeast Asia to the Phillipines)
• Richardson's Mangrove Snake (Northern Australia)
• Mangrove Water Snake (Southern Florida, North America)
• Mangrove Pit-Viper (India to Singapore)

6 kinds of mammals

• Pygmy three-toed sloth (Bocas del Toro, Panama)
• Vordermann's Pipistrelle (Borneo)
• Northern Pipistrelle (Northern Australia)
• Proboscis Monkey (Borneo)
• Garrido's Hutia (Cuba)
• Carrera's Hutia (Cuba)

1 amphibian

Mangroves occur in 2 distinct biogeographical regions:

• North and South America and the west coast of Africa
• the east coast of Africa, southeast Asia, and Australia

The latter region has more species of mangroves and more species of mangrove specialists. The reason for the disparity between regions is unknown but the explanation may be recent ice ages, when mangroves retreated to equatorial regions and may have expanded in Asia because lower water levels exposed more land.

Living in mangroves is not easy. Animals must cope with regular tidal floods, storms, and a salty environment. Nevertheless, food can be abundant and many specialize on eating crabs.

According to a recently published paper by Russ Greenberg and David Luther,

“Mangroves are threatened by development, pollution, mariculture, and changes in sea level and salinity. The global impact of such threats on mangrove taxa remains poorly understood, as mangrove ecology and conservation are usually approached at a local rather than a global scale.”

This article summarizes the information in this publication:

Mangroves: A Global Perspective on the Evolution and Conservation of their Terrestrial Vertebrates. 2009. Luther, David A. and Greenberg, Russell. Bioscience, 59(7): 602-612.

View abstract

Mangrove ecosystems are found globally along tropical and subtropical coastlines. They exhibit a steep environmental gradient between inland and marine systems, providing a unique, selective environment that shapes local morphological, physiological, and behavioral adaptations. In the first global assessment of terrestrial vertebrate species that are restricted to mangrove ecosystems, we found 48 bird, 14 reptile, 1 amphibian, and 6 mammal species endemic to mangroves, the majority of which are found in Asia and Australia. We also found that more than 40% of assessed mangrove-endemic vertebrates are globally threatened. Clearly, additional research is needed to better understand mangrove-endemic vertebrates in order to conserve them. Future research should focus on global inventories, intercontinental comparative work, and the ecology of mangroveendemic vertebrates.

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