The Loss of Species: Mangrove Extinction Risk and Geographic Areas of Global Concern

Beth Polidoro ,Joanna C Ellison,Toyohiko Miyagi,Jurgenne H Primavera,Elizabeth J Farnsworth,Gregg E Moore,Lorna Collins,Edwino S Fernando,Suzanne R Livingstone,Norman C Duke,Jonnell C Sanciangco,Vien Ngoc Nam,Yamin Wang,Severino G Salmo,Sukristijono Sukardjo,Jean Wan Hong Yong,Aaron M Ellison,Kent E Carpenter,Jin Eong Ong,Nico Koedam ,K Kathiresan

doi:10.1371/journal.pone.0010095

Abstract

Mangrove species are uniquely adapted to tropical and subtropical coasts, and although relatively low in number of species, mangrove forests provide at least US $1.6 billion each year in ecosystem services and support coastal livelihoods worldwide. Globally, mangrove areas are declining rapidly as they are cleared for coastal development and aquaculture and logged for timber and fuel production. Little is known about the effects of mangrove area loss on individual mangrove species and local or regional populations. To address this gap, species-specific information on global distribution, population status, life history traits, and major threats were compiled for each of the 70 known species of mangroves. Each species' probability of extinction was assessed under the Categories and Criteria of the IUCN Red List of Threatened Species. Eleven of the 70 mangrove species (16%) are at elevated threat of extinction. Particular areas of geographical concern include the Atlantic and Pacific coasts of Central America, where as many as 40% of mangroves species present are threatened with extinction. Across the globe, mangrove species found primarily in the high intertidal and upstream estuarine zones, which often have specific freshwater requirements and patchy distributions, are the most threatened because they are often the first cleared for development of aquaculture and agriculture. The loss of mangrove species will have devastating economic and environmental consequences for coastal communities, especially in those areas with low mangrove diversity and high mangrove area or species loss. Several species at high risk of extinction may disappear well before the next decade if existing protective measures are not enforced.

Highlights

The importance of mangroves for humans and a variety of coastal organisms has been well documented [1,2,3,4,5,6,7]
These include viviparous or cryptoviviparous seeds adapted to hydrochory; pneumatophores or aerial roots that allow oxygenation of roots in hypoxic soils; and salt exclusion or salt excretion to cope with high salt concentrations in the peat and pore water in which mangroves grow
For the International Union for the Conservation of Nature (IUCN) Red List assessments, we defined a mangrove species based on Tomlinson’s list of major and minor mangroves, supplemented by a few additional species supported by the expanded definition provided by Duke [33]

Summary

Introduction

The importance of mangroves for humans and a variety of coastal organisms has been well documented [1,2,3,4,5,6,7]. Mangrove forests are comprised of unique plant species that form the critical interface between terrestrial, estuarine, and near-shore marine ecosystems in tropical and subtropical regions. They protect inland human communities from damage caused by coastal erosion and storms [8,9,10,11], provide critical habitat for a variety of terrestrial, estuarine and marine species [5,12,13,14], and serve as both a source and sink for nutrients and sediments for other inshore marine habitats including seagrass beds and coral reefs [2,15]. The economic value of mangroves can be difficult to quantify, the relatively small number of mangrove species worldwide collectively provide a wealth of services and goods while occupying only 0.12% of the world’s total land area [22]

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Results

Conclusion