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www.sciencemag.org SCIENCE VOL 317 6 JULY 2007
41
LETTERS I BOOKS I POLICY FORUM I EDUCATION FORUM I PERSPECTIVES
44
Donating
frozen embryos
Donath
46
53
Hippocampus
in depth
LETTERS
edited by Etta Kavanagh
A World Without Mangroves?
AT A MEETING OF WORLD MANGROVE EXPERTS HELD LAST YEAR IN
Australia, it was unanimously agreed that we face the prospect of a
world deprived of the services offered by mangrove ecosystems, per-
haps within the next 100 years.
Mangrove forests once covered more than 200,000 km
2
of shel-
tered 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 occur-
ring 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.
Where mangrove forests are cleared for aquaculture, urbanization,
or coastal landfill or deteriorate due to indirect effects of pollution and
upstream land use (3, 4), their species richness is expected to decline
precipitously, because the number of mangrove plant species is directly
correlated with forest size (6, 7). Examples from other ecosystems
have shown that species extinctions can be followed by loss in func-
tional diversity, particularly in species-poor systems like mangroves,
which have low redundancy per se (8). Therefore, any further decline
in mangrove area is likely to be followed by accelerated functional
losses. Mangroves are already critically endangered or approaching
extinction in 26 out of the 120 countries having mangroves (2, 9).
Deforestation of mangrove forests, which have extraordinarly high
rates of primary productivity (3), reduces their dual capacity to be both
an atmospheric CO
2
sink (10) and an essential source of oceanic car-
bon. The support that mangrove ecosystems provide for terrestrial as
well as marine food webs would be lost, adversely affecting, for exam-
ple, fisheries (11). The decline further imperils mangrove-dependent
fauna with their complex habitat linkages, as well as phys-
ical benefits like the buffering of seagrass beds and coral
reefs against the impacts of river-borne siltation, or protec-
tion 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 essen-
tial 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,
1
* J.-O. MEYNECKE,
2
S. DITTMANN,
3
A. M. ELLISON,
4
K. ANGER,
5
U. BERGER,
6
S. CANNICCI,
7
K. DIELE,
8
K. C. EWEL,
9
C. D. FIELD,
10
N. KOEDAM,
11
S. Y. LEE,
2
C. MARCHAND,
12
I. NORDHAUS,
8
F. DAHDOUH-GUEBAS
13
1
Centre for Marine Studies, University of Queensland, St Lucia, Qld 4072, Australia.
2
Australian Rivers Institute and School of Environment, PMB 50 GCMC, Griffith University,
Qld 9726, Australia.
3
School of Biological Sciences, Flinders University, GPO Box 2100,
Adelaide, SA 5001, Australia.
4
Harvard University, Harvard Forest, 324 North Main Street,
Petersham, MA 01366, USA.
5
Alfred-Wegener-Institut für Polar- und Meeresforschung,
Kurpromenade, D-27498 Helgoland, Germany.
6
Technical University Dresden, Institut für
Waldwachstum und Forstliche Informatik, Postfach 1117 01735 Tharandt, Germany.
7
Dipartimento di Biologia Animale e Genetica “Leo Pardi,” Università degli Studi di Firenze,
Via Romana, 17, I-50125 Firenze, Italy.
8
Center for Tropical Marine Ecology,
Fahrenheitstrasse 6, 28359 Bremen, Germany.
9
U.S. Department of Agriculture Forest
Service, 2126 NW 7th Lane, Gainesville, FL 32603, USA.
10
Faculty of Science (Gore Hill),
University of Technology, Sydney, Post Office Box 123, Broadway NSW 2007, Australia.
11
Laboratory of General Botany and Nature Management, Mangrove Management Group,
Vrije Universiteit Brussel, Pleinlaan 2, B-1050 Brussels, Belgium.
12
LGPMC, EA 3325,
University of New Caledonia, Noumea, New Caledonia, and UR 103, Institut de Recherche
pour le Développement (IRD), Marseille, France.
13
Biocomplexity Research Focus, c/o
Laboratory of General Botany and Nature Management, Mangrove Management Group,
Vrije Universiteit Brussel, Pleinlaan 2, B-1050 Brussels, Belgium.
COMMENTARY
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
Published by AAAS
on July 12, 2007 www.sciencemag.orgDownloaded from
6 JULY 2007 VOL 317 SCIENCE www.sciencemag.org
42
LETTERS
*To whom correspondence should be addressed. E-mail:
n.duke@uq.edu.au
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 world-
wide” (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.
Supporting Undergraduate
Research
THE FINDINGS OF THE EDUCATION FORUM
“Benefits of undergraduate research experi-
ences” by S. H. Russell and colleagues (27
April, p. 548) confirm the widely held belief
that undergraduate research increases interest
in scientific and related research careers.
Indeed, as student researchers and editors with
an international undergraduate journal,
the Journal of Young Investigators (JYI;
www.jyi.org), we have experienced first-hand
several of the points that the authors raised.
We at JYI, however, believe that under-
graduate research programs should place
more emphasis on the art of scientific com-
munication. The benefits include the opportu-
nity to communicate undergraduate research
work to a broader audience. Such an experi-
ence also develops skills necessary for the
fluid but logical nature of scientific writing.
These skills are otherwise missed when
engrossed in wet lab work or not developed
fully when merely writing final lab reports. A
culture of responsibility and integrity is also
developed as student authors face rigorous
demands of scientific review and editing (data
integrity, plagiarism, etc.).
Most importantly, the undergraduate pub-
lication experience gives students an early
introduction to the world of peer review, a cor-
nerstone of science. For JYI, a student-led
journal, this benefit is doubly advantageous.
Not only do student authors benefit from peer
review, our JYI student reviewers are also
trained in the art of reviewing, a skill not given
much emphasis in undergraduate research.
JYI has been at the forefront of such under-
graduate peer review and publication for 10
years since its inception in 1997. From over
500 submissions, we have published 120
undergraduate research articles. Our high-
lights for the past year include 10 special issues
devoted to publishing research articles of vari-
ous universities’ Research Experiences for
Undergraduates program, and participation in
the recent 2007 AAAS Meeting, during which
we hosted a workshop for science writing.
Our aim is to see science writing and
communication play a central role in the
undergraduate research experience.
FARHAN ALI,
1
NAFISA M. JADAVJI,
2
WILLIE CHUIN
HONG ONG,
3
KAUSHAL RAJ PANDEY,
4
ALEXANDER
NIKOLICH PATANANAN,
5
HARSHA KIRAN
PRABHALA,
6
CHRISTINE HONG-TING YANG
7
1
Department of Psychology, National University of
Singapore, Singapore.
2
Department of Neuroscience,
Canadian Center for Behavioural Neuroscience, Lethbridge,
AC T1K 3M4, Canada.
3
Optical Materials and Systems
Division, DSI Building, Data Storage Institute, 5
Engineering Drive 1, Singapore, 117608.
4
Department of
Medicine, Tribhuvan University, Kathmandu, POB No 1524,
Nepal.
5
Department of Microbiology, Immunology, and
Molecular Genetics, University of California at Los Angeles,
Los Angeles, CA 90095, USA.
6
Department of Biomedical
Engineering, Johns Hopkins University, Baltimore, MD
21218, USA.
7
Department of Human Biology, Stanford
University, Stanford, CA 94305, USA.
Isoprene, Cloud Droplets,
and Phytoplankton
THERE IS AN ERROR THAT MAY INVALIDATE
the main conclusion of the Research Article
“Phytoplankton and cloudiness in the South-
ern Ocean” by N. Meskhidze and A. Nenes
(1 Dec. 2006, p. 1419). The authors report an
increase in cloud reflectivity resulting from a
30% decrease in cloud droplet effective radius
and a doubling of cloud droplet number con-
centration over a large phytoplankton bloom
in the Southern Ocean, resulting in an extra 15
W m
2
of energy reflected back to space. They
attribute these changes to enhanced isoprene
produced in the bloom. Our measurements
made during the Southern Ocean Iron Ex-
periments (SOFeX) (1) were used by Mesk-
hidze and Nenes to scale seawater isoprene
values based on measured chlorophyll-a con-
centrations. Unfortunately, they converted our
isoprene concentrations incorrectly, result-
ing in a three-order-of-magnitude overesti-
mation and hence a much greater calculated
isoprene flux.
During SOFeX, we measured climate-
relevant organic gases in the dynamic head-
space of an equilibrator (2) in contact with
seawater (1). We reported isoprene concen-
trations to be on average 560 pptv (parts per
trillion by volume or picomoles mole
1
of
air) inside of the SOFeX North Patch (NP),
which is the mixing ratio that the air above
the water would have if the headspace were
static. To convert from mixing ratio of static
headspace to seawater concentration, we use
Henry’s Law:
C
g
× K
H
= C
a
(Eq. 1)
where C
g
is the mixing ratio of a gas in equi-
librium with the dissolved gas in the aqueous
phase, C
a
. An average Henry’s law constant
(K
H
) for isoprene of 0.0130 M atm
1
was used
(3). Therefore, the average seawater isoprene
concentration in the NP was ~7.3 picomoles
L
1
(pM). Listed in the authors’ Table 2 is an
average isoprene concentration of 31.4
nanomoles L
1
(nM) in the NP. This leads me
to believe that isoprene is not the reason for
their observed extra cloud albedo.
OLIVER W. WINGENTER
New Mexico Institute of Mining and Technology, Socorro,
NM 87801, USA.
References
1. O. W. Wingenter et al., Proc. Natl. Acad. Sci. U.S.A. 101,
8537 (2004) (doi:10.1073).
2. J. E. Johnson, Anal. Chim. Acta 395, 119 (1999).
3. R. Sander, http://www.mpch-mainz.mpg.de/~sander/res/
henry.html.
Response
WE THANK WINGENTER FOR HIS LETTER.
Indeed, we misinterpreted some of the data
in Wingenter et al. (1). We were unaware
that “concentration of dissolved gases
measured in and around the fertilized
patch” in (1) referred not to seawater con-
Letters to the Editor
Letters (~300 words) discuss material published
in Science in the previous 3 months or issues of
general interest. They can be submitted through
the Web (www.submit2science.org) or by regular
mail (1200 New York Ave., NW, Washington, DC
20005, USA). Letters are not acknowledged upon
receipt, nor are authors generally consulted before
publication. Whether published in full or in part,
letters are subject to editing for clarity and space.
Published by AAAS
on July 12, 2007 www.sciencemag.orgDownloaded from
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