Magazine
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substrates depend on binding at
                      Essay
this site, there are probably
additional substrate recognition
sites. Another contribution to
                      How effective were mangroves as a
substrate selection is made by
scaffold proteins, e.g. AKAP79,
                      defence against the recent tsunami?
which target the phosphatase to
neuronal synapses or other
cellular sites. Calcineurin also      Whether or not mangroves function as buffers against tsunamis is the
delegates work to protein         subject of in-depth research, the importance of which has been
phosphatase 1 (PP1) through a       neglected or underestimated before the recent killer tsunami struck. Our
phosphatase cascade, in which       preliminary post-tsunami surveys of Sri Lankan mangrove sites with
dephosphorylation of the PP1        different degrees of degradation indicate that human activity
antagonists DARPP-32 or          exacerbated the damage inflicted on the coastal zone by the tsunami.
inhibitor-1 by calcineurin relieves
their inhibitory effect on PP1, and
                      F. Dahdouh-Guebas1*,
allows PP1 to act on its own                                    their large above-ground aerial
                      L.P. Jayatissa3*, D. Di Nitto1,
preferred substrates.                                       root systems and standing crop.
                      J.O. Bosire4, D. Lo Seen5 and              Like many habitats, mangrove
                      N. Koedam2
What are its inhibitors?                                      forests have been degraded and
Cyclosporin A (CsA) and FK506                                   destroyed by humans, and their
bind tightly to the abundant        Mangrove forests have iconic              loss is a source of global concern.
                                                  In the second half of the 20th
intracellular proteins cyclophilin A    status as natural ecosystems that
and FKBP12, respectively, and       provide services to humans. They            century, 50% of the world’s
the resulting ligand–protein        function as breeding, spawning,             mangrove forests have been
complex binds to calcineurin and      hatching and nursing grounds for            destroyed, and current annual
impedes access of protein         marine and pelagic species, and             loss rates vary from 1 to 20% [1].
substrates to the active site.       are important in the daily               Ironically, the great human
Blockade of a biological process      livelihood of local human                tragedy of the recent December
                                                  26th tsunami may provide the
by CsA and independently by        subsistence communities.
FK506 is diagnostic for          Mangrove representatives such as            stimulus for a better
calcineurin involvement. Other       Rhizophora spp. also function as a           understanding of what mangrove
inhibitors that find frequent       physical barrier against tidal and           forests can and cannot do for
experimental use are the          ocean influences by means of              human well-being.
autoinhibitory peptide from
calcineurin and fragments of the                                      6.  Walawey Ganga E.
                                                      8.  Kahandamodara L.
regulatory proteins                       Relatively good pre-tsunami         9.  Rekawa L.
                                   mangrove status            11.  Dickwella
DSCR1/MCIP/calcipressin/Rcn1p,                                       12.  Talalla L.
                          Cryptic
Cabin1/cain, and AKAP79.                                          20.  Akurala
                         ecological
                                                      18.  Galle-Unawatuna
                         degradation
                                                      17.  Koggala L.
Does it have any medical                                          21.  Balapitiya E.
                                                      1.  Batticaloa L.
relevance? Calcineurin signalling                                      7.  Kalametiya L.
is prominent in transplant                                         13.  Devinuwara L.
                                   Bad pre-tsunami            14.  Nilwala Ganga E.
rejection and autoimmune                       mangrove status            15.  Polwatumodara
                                                      16.  Kapparatota
disease, where the inhibitors CsA
                                                      19.  Ginganga E.
and FK506 are used clinically, and                                     4.  Palatupana L.
                                                      5.  Kirinda L.
is being studied for its               No                          9.  Kirama Oya mouth
contribution to myocardial             cryptic                         22.  Kosgoda
                          ecological                        23.  Bentota Ganga E.
hypertrophy and to virulence in          degradation
                                                      24.  Kaluwamodara
fungal pathogens.                                              2.  Komari L.
                      Relatively good pre-tsunami
                                                      3.  Pottuvil L.
                         mangrove status
                                                     100
                                               90
                                       80
                              70
                      60
Where can I find out more?                        Similarity                      Current Biology
Aramburu, J., Rao, A., and Klee, C.B.
  (2000). Calcineurin: from structure
                      Figure 1. Dendrogram generated by a cluster analysis of the 24 mangrove sites
  to function. Curr. Top. Cell. Regul.
                      investigated, indicating their characteristics and the impact of the tsunami (big wave,
  36, 237–295.
                      severely impacted; small wave, little impacted).
Rusnak, F., and Mertz, P. (2000).
  Calcineurin: form and function.    The ‘mangrove status’ is a combination of pre-tsunami aerial extent of the front man-
  Physiol. Rev. 80, 1483–1521.      grove and pre-tsunami mangrove destruction (see text). The tsunami had only a small
                      impact on lagoons that show no cryptic ecological degradation (sites 2, 3, 23 and 24)
                      or that are protected by the distance from the shore and by frontal Rhizophora spp.
                      fringes (sites 17, 18 and 21). The lagoons are numbered clockwise from East to West,
The CBR Institute for Biomedical
                      to emphasize that damage was not linked to geographic position in view of tsunami
Research and Department of Pathology,
                      wave energy. A map overview of all lagoons can be found in Jayatissa et al. [18], with
Harvard Medical School, Boston,
                      the exception of Batticaloa, Komari and Potuvil, which are located at the easternmost
Massachusetts 02115, USA.
                      extremity of the island. L, Lagoon; E, Estuary.
E-mail: hogan@cbr.med.harvard.edu
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                          Figure 2. Nypa fruticans at   provide — for construction and
                          Talalla (A) and young mixed   fire wood, ethnomedicinal
                          mangrove    fringes  at
                                          products, fishing habitat, coastal
                          Rekawa (B) show damage
                                          protection and so on.
                          caused by the tsunami,
                                            In late 2001, we interviewed
                          whereas interior mangrove
                                          local inhabitants on the Indian
                          zones and land areas were
                          largely unaffected. Young    subcontinent — the region
                          N. fruticans shoots are now   second-hardest hit by last
                          regenerating (LPJ).
                                          December’s tsunami — asking
                                          about the extent to which
                                          mangroves protected their
                                          homesteads against disastrous
                                          ‘water-related’ events: cyclones
                                          and wave action, but also
                                          tsunamis and sea level increases.
                                          They substantiated their view
                                          well; one interviewee noted:
                                          “during the recent devastation by
                                          tropical cyclone 07B (November
                                          6th, 1996) areas where
                                          mangroves were in relatively
                                          good condition were saved from
                                          the fury of the cyclone and its
                                          associated flooding events as
                                          opposed to adjacent places
                                          where mangroves had been
                                          converted to shrimp farms”.
                                          Similarly, in the Philippines, such
                                          traditional ecological knowledge
  In the aftermath of the Indian    from socio-economic and           of fisherfolk indicated that
Ocean tsunami, which killed over    ethnobiological surveys that        mangroves have a protective
a quarter million people and left    focus on the services of          buffering function [6,7].
millions homeless, experts and     mangrove forests. Over the last        In January 2005, we conducted
the media wondered how many       several years, our teams have        preliminary post-tsunami surveys
lives might have been saved if     conducted interviews with local       in 24 mangrove lagoons and
only we had not destroyed our      people in Mexico, Gambia,          estuaries in Sri Lanka’s coastal
mangrove forests. Others,        Cameroon, Tanzania, Kenya,         zones along the South-West,
however, were more skeptical,      India, Sri Lanka and Vietnam, and      South and South-East coasts of
countering: “fear of big waves is    inquired about their relationships     the island. The districts visited
no reason to plant mangroves”      with mangrove forests, and about      were heavily hit and counted at
[2]. What, then, is the role of     the services that these forests       least 23,558 deaths, more than
mangroves, and how many lives
might they have saved?
                     Box 1
  Despite the popular and widely
accepted view that mangroves act     Are all plants in the mangrove environment true mangrove species?
as living dykes [3], there is
surprisingly little data available to
test that hypothesis. The        Mangrove plants are commonly subdivided into major components (true, strict or
important question is what future    exclusive mangrove species), minor components (non-exclusive mangrove
role should mangrove forests play    species) and mangrove associates. The major components feature a complete
                     fidelity to the mangrove environment, pure stands, morphological and
in coastal zone management and
                     physiological adaptations and taxonomic isolation [19]. An additional distinction
protection? The answer will not be
                     should be made between mangroves that are disturbance-resistant (for example
simple, as there are a lot of
                     Excoecaria agallocha), euryhaline (for example Avicennia marina) or fairly well
different types of mangrove forest
                     adapted to freshwater (for example Sonneratia caseolaris), on the one hand, and
in a wide variety of settings, and
                     those that are most ecologically vulnerable, most valuable and impacted from an
in some places mangroves are
                     ethnobotanical point of view, and those considered most characteristic of mature
simply absent from the natural
                     natural mangroves from an aesthetical point of view (for example
environment.
                     Rhizophoraceae), on the other hand [9,18]. This distinction is required to help
  Apart from occasional
                     detect ‘cryptic ecological degradation’, in which introgressive mangrove-
observations and photographic
                     associated vegetation or minor mangrove species slowly start to dominate a
evidence of uprooted terrestrial
                     forest of true mangrove species (qualitative degradation) without loss of spatial
trees [4,5], the closest scientific
                     extent (no change or an increase in area) [9].
evidence for the buffering
function of mangroves comes
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                    Figure 3. Two forest areas
80% of the total Sri Lankan death
                    near  Talalla  (A)  and
toll [8]. Aided by previous field
                    Kahandamodara (B), which
knowledge, we assessed the
                    had   become    largely
following five characteristics     dominated by mangrove
semi-quantitatively: (A) the pre-   associates   —   cryptic
tsunami extent of the front      ecological degradation —
                    have been destroyed by
mangrove (the first 500m fringe,
                    the tsunami. It is very
taking into account that this is a
                    unlikely that these areas
conservative width able to
                    have the potential to be
provide protection against a      recolonized by original true
tsunami); (B) the extent of      mangrove representatives,
mangroves already destroyed      because less than a month
                    after   the   tsunami,
before the tsunami; (C) the
                    Acrostichum aureum was
‘naturalness’ of the mangrove, in
                    showing signs of strong
terms of the presence or absence
                    regeneration (C) (LPJ).
of cutting activities and of cryptic
ecological degradation [9]; (D)
tsunami damage to the front
mangrove; and (E) tsunami
damage to lives and properties in
the back mangrove and behind
the mangrove. These
characteristics were compiled
into the pre-tsunami mangrove
status (A+B), the presence of
cryptic ecological degradation
(C), and the destruction by the
tsunami (D+E), and a cluster
analysis (group average), using
PRIMER version 5.2.8, was
performed based on Bray-Curtis
similarity (Figure 1).
  Our results show that, where
mangroves occur in the districts
visited, they did in fact offer
protection. Apart from some
isolated trees of Excoecaria
agallocha L., there were no
records of uprooted adult
mangrove trees. At most,
mangrove fringes near the water
edge took all the energy and were
damaged (Figure 2). Creek-
fringing Nypa fruticans (Mangrove   splits indicate whether ‘cryptic    A more in-depth ‘crime-scene
palm) had its leaves bent or torn   ecological degradation’ occurred   investigation’ is urgently needed,
off, but anchoring protection of    (Figure 1). Mangrove sites with no  but at present our conclusions
this plant by its rhizomatous stem   cryptic ecological degradation, or  are that three factors can
allowed new young leaves to      those well protected by distance   undermine the ability of
emerge less than a month after     inland and by Rhizophora spp.    mangroves to protect coastal
the tsunami impact. Other true     fringes, all experienced a low    villages: first, complete clearance;
mangrove representatives (Box 1)    destructive impact from the     second, insufficient regrowth
such as Sonneratia spp., the stem   tsunami. The key feature of those  following a previous clearing; and
of which can measure several      forests that were damaged      third, infusion of adult mangroves
meters in circumference, or      appears to be a prominence of    (where present) with excess of
Rhizophora spp. or Bruguiera      vegetative associates not typical  non-mangrove vegetation
spp., which has wide prop or knee   of natural mangrove forests (Box   components.
roots, also stood firm against the   1). The important lesson is that,    It is important to recognize that
ocean surge.              even though a coastal area might   any compromising of mangrove
  Forests dominated by less      superficially seem to be       ‘protective function’ is relevant to
typical mangrove associates      protected by a mangrove forest,   a wide variety of storm events,
(Box 1), however, were severely    that habitat could be cryptically  and not just tsunamis. Whereas
damaged (Figure 3A,B). This is     degraded and not offer the      the Indian Ocean area counted
also evident from the         desired storm protection (see    ‘only’ 63 tsunami events between
dendrogram, where the major      also [9,10]).            1750 and 2004, there were more
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                        Figure 4. Sand dune       tremendous ecosystem services,
                        vegetation and Casuarina     including protection against
                        equisetifolia   plantations
                                         extreme weather events and
                        may   contribute  to  a
                                         natural catastrophes [17]. When
                        reduced impact by ocean
                                         we fail to raise awareness about
                        surges.
                                         these functions, and we destroy
                        However, it should also be
                                         or degrade the world’s natural
                        investigated to which extent
                        negative ecological influ-    ecosystems too much, we do so
                        ences occur from such arti-   at our own peril.
                        ficially planted barriers. (A)
                        Hambantota, (B) Tissamara-
                                         Acknowledgments
                        hama, S. Sri Lanka coast
                                         The first author is a Postdoctoral
                        (LPJ).
                                         Researcher of the Fund for Scientific
                                         Research (FWO-Vlaanderen). This
                                         research is within the objectives of the
                                         International Geosphere-Biosphere
                                         Programme (IGBP), Past Global
                                         Changes (PAGES) Focus 5: Past
                                         Ecosystem Processes and Human-
                                         Environment Interactions. We thank T.
                                         Jayasingam (Eastern University, Sri
                                         Lanka) for fieldwork logistics and Peter
                                         Kareiva (The Nature Conservancy, USA)
                                         for comments on our manuscript drafts.


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Magazine
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   in Sri Lanka affect biota and human                         entice bees to switch from a
                       Correspondences
   populations in and around coastal                          familiar species to sample a new
   lagoons. Curr. Biol. 15, 579–586.
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10.  Kairo, J.G., Dahdouh-Guebas, F.,
                                               We examined the behavior of
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                       Lars Chittka                 this article online), all providing
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   Restoration and management of
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   Afr. J. Bot. 67, 383–389.
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1Biocomplexity  Research Team, c/o
2General  Botany and Nature
Management, Mangrove Management
                                                           Nestbox
Group, Vrije Universiteit Brussel,
Pleinlaan 2, B-1050 Brussels, Belgium.
1E-mail: fdahdouh@vub.ac.be
3Department of Botany, University of                                         Current Biology
Ruhuna, Matara, Sri Lanka. 4Kenya
Marine and Fisheries Research Institute,
                       Figure 1. Choice array.
PO Box 81651, Mombasa, Kenya.
5Institut Français de Pondichéry, Rue     Eight equally and highly rewarding inflorescences, each containing three flowers, were
St. Louis 11, BP 33, 605 001         presented to the observer bee in a 105 x 70 x 30 cm flight arena connected to the
Pondicherry, India.              nestbox.