A World Without Mangroves?

Mangrove forests once covered more than 200,000 km² of sheltered tropical and subtropical coastlines (1). They are disappearing worldwide by 1 to 2% per year, a rate greater than or equal to declines in adjacent coral reefs or tropical rainforests (2-5). Losses are occurring in almost every country that has mangroves, and rates continue to rise more rapidly in developing countries, where >90% of the world's mangroves are located. The veracity and detail of the UN Food and Agriculture Organization data (2) on which these observations are based may be arguable, but mangrove losses during the last quarter century range consistently between 35 and 86%. As mangrove areas are becoming smaller or fragmented, their long-term survival is at great risk, and essential ecosystem services may be lost.

Emerging from the embrace of a mangrove tree-lined channel in northern Brazil, these pescadores, like coastal fishers worldwide, know that healthy mangroves mean good fishing and a secure livelihood. CREDIT: N. C. DUKE

Deforestation of mangrove forests, which have extraordinarly high rates of primary productivity (3), reduces their dual capacity to be both an atmospheric CO₂ sink (10) and an essential source of oceanic carbon. The support that mangrove ecosystems provide for terrestrial as well as marine food webs would be lost, adversely affecting, for example, fisheries (11). The decline further imperils mangrove-dependent fauna with their complex habitat linkages, as well as physical benefits like the buffering of seagrass beds and coral reefs against the impacts of river-borne siltation, or protection of coastal communities from sea-level rise, storm surges, and tsunamis (12, 13). Human communities living in or near mangroves would lose access to sources of essential food, fibers, timber, chemicals, and medicines (14).

We are greatly concerned that the full implications of mangrove loss for humankind are not fully appreciated. Growing pressures of urban and industrial developments along coastlines, combined with climate change and sea-level rise, urge the need to conserve, protect, and restore tidal wetlands (11, 13). Effective governance structures, socioeconomic risk policies, and education strategies (15) are needed now to enable societies around the world to reverse the trend of mangrove loss and ensure that future generations enjoy the ecosystem services provided by such valuable natural ecosystems.

N. C. Duke^*
Centre for Marine Studies
University of Queensland
St Lucia
Qld 4072, Australia

^*To whom correspondence should be addressed. E-mail: n.duke{at}uq.edu.au

J.-O. Meynecke
Australian Rivers Institute and School of Environment
PMB 50 GCMC, Griffith University
Qld 9726, Australia

S. Dittmann
School of Biological Sciences
Flinders University
GPO Box 2100
Adelaide, SA 5001, Australia

A. M. Ellison
Harvard University
Harvard Forest
324 North Main Street
Petersham, MA 01366, USA

K. Anger
Alfred-Wegener-Institut für Polar-und Meeresforschung
Kurpromenade
D-27498 Helgoland, Germany

U. Berger
Technical University Dresden
Institut für Waldwachstum und Forstliche Informatik
Postfach 1117 01735 Tharandt, Germany

S. Cannicci
Dipartimento di Biologia Animale e Genetica "Leo Pardi," Università degli Studi di Firenze
Via Romana
17, I-50125 Firenze, Italy

K. Diele
Center for Tropical Marine Ecology
Fahrenheitstrasse 6
28359 Bremen, Germany

K. C. Ewel
U.S. Department of Agriculture Forest Service
2126 NW 7th Lane
Gainesville, FL 32603, USA

C. D. Field
Faculty of Science (Gore Hill)
University of Technology
Sydney
Post Office Box 123
Broadway NSW 2007, Australia

N. Koedam
Laboratory of General Botany and Nature Management
Mangrove Management Group
Vrije Universiteit Brussel
Pleinlaan 2
B-1050 Brussels, Belgium

S. Y. Lee
Australian Rivers Institute and School of Environment
PMB 50 GCMC
Griffith University
Qld 9726, Australia

C. Marchand
LGPMC, EA 3325
University of New Caledonia
Noumea, New Caledonia, and
R 103, Institut de Recherche pour le Développement (IRD)
Marseille, France

I. Nordhaus
Center for Tropical Marine Ecology
Fahrenheitstrasse 6
28359 Bremen, Germany

F. Dahdouh-Guebas
Biocomplexity Research Focus
c/o Laboratory of General Botany and Nature Management
Mangrove Management Group
Vrije Universiteit Brussel
Pleinlaan 2
B-1050 Brussels, Belgium

References and Notes

1. M. D. Spalding, F. Blasco, C. D. Field, World Mangrove Atlas(International Society for Mangrove Ecosystems, Okinawa, Japan, 1997).
2. FAO, "Status and trends in mangrove area extent worldwide" (Forest Resources Division, FAO, Paris, 2003).
3. D. M. Alongi, Environ. Conserv. 29, 331 (2002).
4. I. Valiela, J. L. Bowen, J. K. York, Bioscience 51, 807 (2001).
5. R. Stone, Science 316, 678 (2007).
6. N. C. Duke, M. C. Ball, J. C. Ellison, Glob. Ecol. Biogeogr. Lett. 7, 27 (1998).
7. A. M. Ellison, Trees Struct. Funct. 16, 181 (2002).
8. O. L. Petchey, K. J. Gaston, Proc. R. Soc. London B 69, 1721 (2002).
9. Global Marine Species Assessment: www.sci.odu.edu/gmsa/index.shtml.
10. D. R. Cahoon et al., J. Ecol. 91, 1093 (2003).
11. E. B. Barbier, Econ. Policy 22, 177 (2007).
12. F. Dahdouh-Guebas et al., Curr. Biol. 15, 443 (2005).
13. E. McLeod, R. V. Salm, Managing Mangroves for Resilience to Climate Change (IUCN, 2006).
14. K. C. Ewel, R. R. Twilley, J. E. Ong, Glob. Ecol. Biogeogr. Lett. 7, 83 (1998).
15. Mangroves Future Project (IUCN), www.iucn.org/tsunami/.
16. The 2006 Australian mangrove meetings (MMM) at the Gold Coast and Daintree were sponsored by the University of Queensland, Griffith University, James Cook University, Queensland Department of Primary Industries and Fisheries, and the Ian Potter Foundation. We thank our funding sources for their support of our research on mangroves. F.D.G. is a Postdoctoral Research Scientist from the Research Foundation-Flanders (FWO-Vlaanderen). S.C.'s research is funded by the PUMPSEA project (EU 6th FP). A.M.E.'s research is supported by the Harvard Forest and by the U.S. NSF.