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Marine vegetated habitats (seagrasses, salt-marshes, macroalgae and mangroves) occupy 0.2% of the ocean surface, but contribute 50% of carbon burial in marine sediments. Their canopies dissipate wave energy and high burial rates raise the seafloor, buffering the impacts of rising sea level and wave action that are associated with climate change. The loss of a third of the global cover of these ecosystems involves a loss of CO2 sinks and the emission of 1 Pg CO2 annually. The conservation, restoration and use of vegetated coastal habitats in eco-engineering solutions for coastal protection provide a promising strategy, delivering significant capacity for climate change mitigation and adaption.
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The loss of natural CO2 sinks and reservoirs results in about
12–20% of anthropogenic greenhouse gas emissions1. Strategies
to mitigate climate change that are based on actions to prevent
this loss have focused on the conservation of terrestrial sinks, pri-
marily tropical forests2. Reports that vegetated coastal habitats rank
among the most intense carbon sinks in the biosphere3 lead to so-
called blue carbon strategies4 to explore their potential for mitigating
climate change, stimulating an increase in papers on the topic from
30 studies published in 2005 to 110 papers in 2012. In parallel, the
role of vegetated marine ecosystems in ghting climate change can
be developed beyond conservation of CO2 sink capacity
4–6 by con-
sidering their contribution to both mitigation of CO2 emissions and
adaption to sea-level rise, increasing wave energy and storm surges.
Here we present the scientic basis and opportunities for a com-
prehensive strategy to use vegetated coastal habitats to mitigate
and adapt to climate change. We focus specically on two aspects:
the capacity of these habitats to act as CO2 sinks, referring to recent
reviews for further detail, and their ability to protect the coast against
erosion from sea-level rise and increasing wave action (as well as pro-
viding sources of biodiesel). ese are roles that hold considerable
potential for climate change adaptation and mitigation strategies but
that have not yet received sucient attention.
Vegetated coastal habitats in the biosphere
Characterized by the presence of macrophytes, both submerged (sea-
grass and macroalgae) and partially emerged (mangroves and salt-
marshes), these habitats occupy a narrow fringe— from the upper
intertidal zone to about 40m depth — along the shores of all conti-
nents. Globally, they extend over approximately 2.3–7.0millionkm2,
with macroalgae being the largest contributors and mangroves
accounting for the smallest area (Table1). e global area and trends
in area change of mangrove forests are reasonably well estimated,
whereas those for seagrass meadows, which cannot be retrieved from
remote sensing products, have much greater uncertainty. However,
global estimates for salt marshes suer from severe, 20-fold uncer-
tainties (Table1). is is surprising as salt marshes can be easily
assessed by remote sensing, and these uncertainties probably derive
from the amalgamation of salt marshes in the broader and ambigu-
ous category of wetlands in the Ramsar Convention (Convention
on Wetlands of International Importance)7. Specically, category H
The role of coastal plant communities for climate
change mitigation and adaptation
Carlos M. Duarte1,2,3,*, Iñigo J. Losada4, Iris E. Hendriks2, Inés Mazarrasa2 and Núria Marbà2
Marine vegetated habitats (seagrasses, salt-marshes, macroalgae and mangroves) occupy 0.2% of the ocean surface, but
contribute 50% of carbon burial in marine sediments. Their canopies dissipate wave energy and high burial rates raise the
seafloor, buering the impacts of rising sea level and wave action that are associated with climate change. The loss of a third
of the global cover of these ecosystems involves a loss of CO2 sinks and the emission of 1PgCO2 annually. The conservation,
restoration and use of vegetated coastal habitats in eco-engineering solutions for coastal protection provide a promising
strategy, delivering significant capacity for climate change mitigation and adaption.
(Intertidal marshes) in the Ramsar Classication System for Wetland
Type combines freshwater and salt marshes (Recommendation 4.7
as amended by Resolution VI.5 of the Ramsar Conference of the
Contracting Parties), which are reported jointly providing an imped-
iment to assessments of the area occupied by salt marshes alone.
About 25% to 50% of the area covered by vegetated coastal
habitats has been lost in the past 50years (Table1). Losses of sea-
grass, which are accelerating globally8, have been mostly caused
by increased nutrient inputs and coastal transformation9, and salt-
marshes and mangroves have been lost due to changes in land use,
coastal transformation and reclamation10,11. Losses of seagrass12,13 and
kelps14 associated with heat waves indicates that climate change may
lead to loss of seagrass in some areas, such as the Mediterranean15.
On the other hand, mangroves have been reported to extend their
range polewards with climate change16.
Submerged canopies reduce ow and turbulence17,18, increase the
bottom shear stress and dampen wave energy19,20 and ow velocity21,
thereby promoting sedimentation and reducing sediment resuspen-
sion22. Partially submerged vegetation, such as salt marshes and man-
grove forests in tidal areas, also aect ow speed23, and reduce wave
action24 and sediment deposition23–26. More specically, mangroves
may trap about 80% of suspended sediment25. rough their high
productivity and capacity to enhance sediment accretion, seagrass,
salt marshes and mangroves build large carbon deposits while rais-
ing the sea oor (Tables2 and 3), acting as important carbon sinks
and mitigating the impacts of sea-level rise on coastline.
e ability of vegetated coastal habitats to engineer their envi-
ronment underpins their remarkable capacity for supplying ecosys-
tems services26. A pioneer survey of ecosystem services across the
biosphere ranked vegetated coastal habitats among the most valu-
able ecosystems on Earth27, primarily for their capacities to regulate
nutrient uxes, provide habitat26 and climatic regulation, and for
their function as CO2 sinks28 and coastal protection26.
Carbon sequestration
Despite the small fraction of the ocean surface occupied by salt
marsh, mangrove and seagrass ecosystems, they account for 46.9%
of the total carbon burial in ocean sediments3,4. Most macroalgal
stands develop on hard, rocky substrates, and despite their high
productivity (Table1) and capacity to trap suspended particles — do
1UWA Oceans Institute, University of Western Australia, 35 Stirling Highway, 6009 Crawley, Western Australia, Australia, 2Department of Global Change
Research, Instituto Mediterráneo de Estudios Avanzados (CSIC-UIB), Miquel Marqués 21, 07190 Esporles, Spain, 3Faculty of Marine Sciences, King
Abdulaziz University, PO Box80207, Jeddah 21589, Saudi Arabia,4Instituto de Hidráulica Ambiental, Universidad de Cantabria, Isabel Torres 15, 39011
Santander, Spain. *e-mail:
© 2013 Macmillan Publishers Limited. All rights reserved
not develop signicant carbon deposits. Community primary
production generally exceeds respiration in vegetated coastal habi-
tats3,28 leading to their capacity for producing excess organic carbon
and acting as CO2 sinks (Fig.1). Carbon sequestration in vegetated
coastal habitats is further enhanced by their unique ability to trap
particles from the water ow and store them in the soil29 (Fig.1).
As a result, burial rates of organic carbon in salt marsh, mangrove
and seagrass ecosystems are exceptionally high (Table2), exceed-
ing those in the soils of terrestrial forests by 30–50 fold5. Globally,
coastal vegetated habitats bury a similar amount of organic carbon
to terrestrial forests annually, despite the extent of coastal marine
vegetation being less than 3% of that of forests.
e carbon buried in coastal vegetated ecosystems can be pre-
served over millennia, as demonstrated by radiocarbon dating of
seagrass30, salt marsh31 and mangrove soils32. e ecient preserva-
tion of the carbon under these habitats is due to: slow decomposi-
tion rates33; low nitrogen and phosphorous concentrations in plant
tissues; low oxygen levels in the sediments; and the allocation of a
large fraction, oen exceeding 50%, of plant biomass production to
roots and rhizomes that are buried into the soil34. In addition, the
entangled network of roots (and rhizomes) and the dense canopy of
coastal vegetation protect soil carbon deposits from erosion (Fig.1).
Indeed, some vegetated coastal habitats can support organic-rich
soils5 that deserve conservation measures.
Seagrass, salt marshes and mangroves accumulate enough carbon
and mineral particles to support characteristic sediment accretion rates
exceeding 10cm per century, with the highest accretion rates found in
salt marshes (Table3, Fig.1). Recent (that is, twentieth century) accre-
tion rates in mangrove forests have been reported to average 28cm per
century35. Moreover, sediment accretion responds to climate change
through feedbacks that involve increased plant growth and produc-
tion, which are conducive to faster accretion rates with increasing CO2
(ref.36) and sea-level rise37. Indeed, recent models indicate that cli-
mate change will increase salt marsh carbon burial and accretion rates
in the rst half of the twenty-rst century38.
e long-term preservation and continuous accretion of carbon in
the soil of coastal habitats with sea-level rise leads to the development
of organic carbon deposits several metres thick30,38. e magnitude of
carbon deposits under the top metre of soil in a salt marsh or seagrass
meadow is similar, on average, to that in the upper 1-m soil in ter-
restrial forests (Table2), whereas the top metre of soil in mangrove
forests stores more than three times the organic carbon contained in
the upper soil under forests on land39. Globally, salt marsh, mangrove
and seagrass ecosystems store about 10PgC each in their top 1-m soil
layer39 (Table2). is is one order of magnitude lower than the soil
carbon stock under terrestrial forests, but still large enough to play a
role in the global carbon cycle.
Protection against coastal flooding and erosion
e risks of accelerated sea-level rise with climate change are fur-
ther enhanced by associated increases in the frequency of extreme sea
level, waves and the strength of storm surges40, resulting in a higher
intensity and frequency of ooding and erosion of vulnerable coastal
areas. Observations and numerical reanalysis have shown that signi-
cant wave-height variations are clearly linked to climate modes41,42 and
that wave heights have increased in the North Pacic, North Atlantic
and Southern Ocean during the past century43–45. Sea level has been
rising globally at an average rate of 1.6±0.2mmyr–1 since 190146, and
Ta b l e 1 | E x t e n s i o n , p r o d u c t i o n a n d l o s s e s o f v e g e t a t e d c o a s t a l e c o s y s t e m s .
Global extension
Local net primary
production (g C m2 yr1)
Global net primary
production (Pg C yr1)
Global loss rate
(% yr1)
Percentage of area lost since
the Second World War
Salt marshes 22,000–400,0005
44029 0.01–0.18 1–261
Mangroves 137,760–152,3615
40029 0.06 1–361
Seagrasses 177,000–600,000527829 0.05–0.17 0.98308
Macroalgae 2,000,000100–6,800,00029 9429 0.19–0.64 – –
Sup ersc ript numb ers i ndic ate t he re fere nce s ource s of data . For s ome p aram eter s and habi tat s more tha n one esti mate (or ra nge o f es tima tes) i s ava ilab le.
Ta b l e 2 | C a r b o n b u r i a l a n d s o i l s t o c k s i n v e g e t a t e d c o a s t a l e c o s y s t e m s .
Local C burial rate
(g C m2 yr1)
Local C stock in soil
(Mg C ha1)
Global C burial rate
(Tg C yr1)
Global C stock in soil
(Pg C)
Salt marshes 218±245162 (259)65 4.8–87.350.4–6.5
Mangroves 16335 25564 (683 .4)38 22.5–24.935 9.4–10.4
Seagrasses 138±385139.7 (372)39 48.0–11254.2–8.439
Mean and, when available, standard error of the mean (±s.e.m.) of organic carbon (C) burial and stock within the top 1 m of soil. Maximum local C stock is provided in brackets. Global C stocks are estimated from
local C stocks and ecosystem extension (Table 1) unless indicated. Superscript numbers indicate the reference sources of data.
Ta b l e 3 | S e d i m e n t a c c r e t i o n a n d e l e v a t i o n r a t e s i n v e g e t a t e d c o a s t a l e c o s y s t e m s .
Ecosystem Accretion rates (mm yr1) Elevation rates (mm yr1)
Range Average Median s.d. nRange Average Median s.d. n
Salt marshes 0.39–61.1 6.73 5.5 0.7 98 –6.92–25 3.76 2.01 1.33 22
Mangroves 0.34–20.8 5.47 4.5 0.38 123 –9.5–11.3 1.87 1.4 0.53 58
Seagrasses 0.61–6 2.02 1.48 0.44 12 –5.2–10.2 –0.08 –5.17 5.14 3
Range, average, median, standard deviation (s.d.) and number of observations (n) for a compilation of representative values of sediment accretion and elevation rates compiled from the published literature101.
© 2013 Macmillan Publishers Limited. All rights reserved
moderate emission scenarios project a future global mean sea-level
rise of 0.21–0.48m by 2100 (Intergovernmental Panel on Climate
Change scenario SRES A1B for 2090–2099)47, with some recent pro-
jections exceeding a global mean sea-level rise of 1m (ref.48). Even
if wave projections carry substantial uncertainty, the direct connec-
tion between wind and storminess indicates that climate change is
likely to have a signicant impact on wave heights and other wave
parameters49. As a result, coastal ooding and erosion will be, and
are already becoming, a major threat to coastal areas, demanding the
introduction of sustainable measures to cope with this problem.
Coastal protection measures against wave action are purely based
on the principle that the incident wave energy ux — dened as the
wave energy multiplied by the velocity of a wave group — has to be
balanced by the total energy reected, transmitted and dissipated
at the protection element50. Formulated in a simple way, the wave
energy ux that is not reected oshore or dissipated is transmitted
onshore, thereby inducing ooding, erosion or damages to infra-
structure, goods and services, or loss of lives. Vegetated coastal hab-
itats, through their capacity to provide coastal protection26, could
assist in mitigating the impacts of sea-level rise and the associated
increase in wave action.
e function of vegetated coastal habitats for coastal protec-
tion involves the attenuation of wave transmission onshore (Fig.1),
which can be achieved by: (1) inducing wave breaking as the main
damping mechanism19; (2) dissipating energy through ow separa-
tion51; (3) dissipating energy through friction on rough surfaces;
(4) dissipating energy through porous friction52,53; (5) producing a
barrier eect that reects energy in the oshore direction — and a
combination of the above mechanisms.
e capacity of vegetated coastal habitats for protecting the coast
against the dierent dynamics considered (waves, storm surges, tsu-
namis and currents) is highly dependent on both the large- and small-
scale characteristics of these ecosystems (Supplementary Table1).
e relevant elements of natural ecosystems are their location and
geometry with respect to the incoming dynamics, which may aect
shoaling, refraction, diraction, blocking or breaking. Wave atten-
uation will be dependent on the freeboard of the vegetated eld,
namely the relationship between the submergence and total water
depth (h); the relative wave height (H/h, where H is wave height), the
width (b) of the eld with respect to the incoming wavelength (L) (the
longer the wave, the wider the domain needs be to achieve damping),
the vegetation density, the nature of the substrate and the quality and
abundance of the aboveground biomass. e geometry of each indi-
vidual plant (roots, stems and canopies), its buoyancy, stiness and
degrees of freedom also aect wave attenuation50,54.
Wave breaking is closely controlled by the relationship between
H and h, the ratio of which increases as waves propagate towards
the shore by the combined eect of wave shoaling and shallower
depths. Breaking takes place when a certain threshold of H/h has
been reached. erefore, changes in the bathymetry may contrib-
ute to dissipation. Hence, the capacity of vegetated coastal habitats
to raise the sea oor at speeds that can match or exceed current
sea-level rise (Table3), thereby counterbalancing the eect of sea-
level rise on h, allows them to remain eective in breaking waves
with moderate to high scenarios of sea-level rise, in areas where
subsidence and other processes that lower the elevation of the
shore are not important.
Flow separation occurs at the edges of large structures, or
on the lee side of small structures. e turbulent wake gener-
ated is a sink of energy. Flow separation is controlled by the
Reynolds number (ratiobetween inertial and viscous forces),
the Keulegan–Carpenter number (ratio between drag and iner-
tiaforces) and the relative roughness of the body surface. e
parameters considered to dene the contribution of each of the
forces depend on the process considered. Fields of slender, verti-
cal rigid or exible elements such as seagrass, kelp, salt-marshes
or mangroves are typical sources of this kind of dissipation55.
Vegetated coastal habitats can thus dissipate wave energy through
ow separation.
Opportunity for
expansion/conservation Sediment stabilization
Sediment accretion
Carbon burial
Energy dissipation/wave attentuation
CO2 uptake
Opportunity for
CO2 uptake
Particle trapping
Carbon deposition
Carbon burial
Energy dissipation/wave attentuation
Opportunity for
Particle trapping
Carbon deposition
CO2 uptake
Carbon burial
Sediment stabilization
Energy dissipation/wave attentuation
Figure 1 | Key processes of vegetated coastal habitats for climate change
mitigation and adaptation. Processes that aect the capacity for climate
change mitigation (CO2 sinks) and adaptation (shore line protection from
rising sea level) are shown for seagrass meadows (upper panel), salt
marshes (middle panel) and mangrove forests (lower panel). Blue arrows
indicate transport of atmospheric or dissolved material, red arrows show
transport of particulates and purple arrows indicate vegetative growth.
Images reproduced with permission: Top, Posidonia meadow, water colour
by Miquel Alcaraz; middle, Spartina in Rattekaai salt marsh, photo by
Iris Hendriks; bottom, Mangrove Forest, photo by Rohan Arthur.
© 2013 Macmillan Publishers Limited. All rights reserved
Seagrass and other vegetated coastal habitats also provide
protection by the dissipation of wave energy thanks to friction result-
ing from their presence increasing the bottom roughness, reducing
near-bed ow velocity and elevating the bottom boundary layer56.
Vegetated coastal habitats with their particular stem density and ex-
ibility also provide a porous medium with a large energy dissipation
capacity57. Turbulent and laminar ow inside porous structures is
an important sink of wave energy that is controlled by the Reynolds
number, the size of the porous elements and the porosity58.
Hence, vegetated coastal habitats act on all of the mechanisms
that dissipate wave energy (Supplementary Table1). However, their
contribution to bathymetric changes through sediment accumu-
lation (Supplementary Table1 and ref.59) and shoreline accretion
is key to shoreline protection, aside from direct damping of the
incoming waves.
Climate change mitigation
e conservation and protection of ecosystems that act as carbon
sinks are among the cheapest, safest and easiest solutions to reduce
greenhouse gas emissions and promote adaptation to climate
change6,60. High loss rates of vegetated coastal habitats (Table2), ten
times faster than those of tropical forests61, represent a major loss
of natural CO2 sink capacity and coastal protection and therefore
contribute to the component of increased greenhouse gas emis-
sions that is termed land-use change1. Specically, by combining
specic loss rates (Table1) with estimates of global CO2 sink capac-
ity (Table2), the loss of vegetated coastal habitats is found to repre-
sent a loss of CO2 sink capacity of approximately 7–20TgCO2yr–1.
e fate of soil carbon stored in tidal wetlands that are submerged
when vegetation is lost is an open question that requires research.
However, there is evidence that soil carbon stores can be destabi-
lized when mangroves and salt marsh cover is removed, leaving
soils exposed to the atmosphere — the unvegetated habitats act as
sources of CO2 and CH4 to the atmosphere62–64. Pendleton etal.65
estimated that 0.15–1.02PgCO2 are being released annually from
loss or conversion of vegetated coastal habitats, assuming that all
of the organic carbon in biomass and the top metre of soils is lost.
is estimate, which carries considerable uncertainty, is equiva-
lent to 3–19% of that from deforestation globally, and results in
economic damages of US$6–42billion annually from loss of CO2
sequestration alone65, not accounting for the damages associated
with the loss of coastal protection capacity. e uncertainty in the
loss of carbon sink capacity and in emissions released by habitat
losses is dominated by uncertainties in the global extent and loss
rates of these habitats, with the rough estimates available (Table1),
which are particularly coarse in the case of salt marshes, propagat-
ing unveried across citation networks. Improved estimates of the
global extent and loss rates of vegetated coastal habitats are urgently
needed to assess the potential of conservation and restoration of
these habitats as an element of climate change mitigation strategies.
e use of vegetated coastal ecosystems to protect and restore
lost CO2 sink capacity and prevent the loss of deposits to mitigate
climate change — Blue Carbon initiatives — was proposed in 20094.
One aim is to encourage various carbon trading programmes to
credit activities in tidal wetland and seagrass ecosystems. For exam-
ple, there is interest in extending the REDD+ (Reducing Emissions
from Deforestation and Forest Degradation), including conserva-
tion, sustainable management of forests and enhancement of for-
est carbon stocks) programme — a UN programme drawing from
voluntary payments and market CO2 taxes to pay land-owners to
conserve forests66 — to the coastal ocean. Avoidance of losses in
vegetated coastal habitats that are threatened by local human activ-
ity (for example, aquaculture, waste-water discharges to coastal
water, coastal tourism developments and reclamation) could help
to maintain CO2 sinks and therefore be considered within the
REDD+ mechanism.
Blue Carbon initiatives could broaden the participation in the
current REDD+ scheme, as small island states — who are eager to
mitigate the climate change that threatens their livelihoods through
sea-level rise — have reduced opportunities at present to partici-
pate in REDD+ due to limited land space. However, island states
oen have extensive shallow platforms (for example, the Bahamas,
the Maldives and Cuba) that support vegetated coastal habitats,
where conservation initiatives funded by a Blue Carbon extension
of REDD+ could be successfully deployed and contribute to cli-
mate change mitigation. As vegetated coastal habitats are intense
carbon sinks (Table2), even conservation and revegetation projects
that involve relatively limited areas can be signicant.
Unlike lost forests, which were largely transformed to cropland
and pastures, most lost coastal habitats have not been transformed
to other uses and generally lack property rights. ey are there-
fore available for recolonization by coastal vegetation. Indeed,
vegetated coastal habitats can be restored at a large scale. e best
demonstration is the complete reforestation of the Mekong Delta
mangrove forests (which were completely destroyed by the US
Air Force in the war 40years ago) through the initiative of the
Vietnamese government, arguably the largest ecosystem restora-
tion ever undertaken67. Likewise, large-scale mangrove aoresta-
tion programmes have been successful in ailand and — more
recently India; and large-scale salt marsh restoration schemes
are in place in China68 and the USA
69. Seagrass transplants can,
because of their clonal nature, return several million shoots per site
aer a few years70, even at a typical success rate of 30%. No carbon
burial estimates are available for seagrass revegetation projects, but
one study found that sediment carbon accumulation by a revege-
tated seagrass meadow doubled that in bare sediments 9years aer
planting71. However, studies conducted over the past decade have
shown that carbon burial rates in restored mangrove forests72 and
salt marshes73 are similar to those in undisturbed habitats, despite
sediment carbon pools in revegetated mangroves, salt marshes
and seagrass meadows being lower than in undisturbed habitats
9 (ref.71), 20 (ref.72) and 28 (ref.73) years aer planting. Hence,
restoration of coastal vegetation has been proposed to be a sound
strategy to mitigate climate change74.
However, extending the REDD+ programme to encompass
coastal vegetation is not without challenges. Current REDD+
accountings only consider the carbon stored as aboveground bio-
mass, where much of carbon capture by forest is bound. In contrast,
coastal habitats store most of the carbon that is sequestered in sedi-
ments (for example, 68% for mangroves and 95% for seagrasses39).
Accounting for soil carbon within REDD+ also requires knowledge
of the origin of the carbon stored in sediments. Although this is
possible through stable isotope analysis of sediment carbon in sea-
grass meadows28, apportioning carbon between allochthonous and
autochthonous sources in salt marsh and mangrove sediments is not
as straightforward.
Expanding REDD+ to vegetated coastal habitats requires the
development and acceptance of protocols for measuring, report-
ing, verifying and monitoring the carbon stored in sediments.
Revegetation programmess, which are an option for coastal wet-
lands, are not currently considered in REDD+, which focuses on
conservation. Revegetation projects require that suitable conditions
be re-established and, in the case of seagrass, can be met with mixed
success. e need for monetary compensation may also preclude
revegetation programmes where habitats have been converted to
other uses (for example, aquaculture farms, coastal infrastructure
or reclaimed areas). Finally, although payments under REDD+ con-
servation approaches can be immediate, revegetation methods may
require decades before carbon credits can be collected. An extended
REDD+ programme may not be applicable to coastal habitats that
are particularly vulnerable to sea-level rise, as losses of the associated
carbon sinks cannot be avoided through conservation. Specically,
© 2013 Macmillan Publishers Limited. All rights reserved
although carbon accumulation in salt-marshes increases with
sea-level rise, it does so until a critical rate is reached, beyond which
the marsh vegetation is drowned, halting carbon accumulation75.
e fate of carbon deposits lost to submergence is not known, but
the question is important for understanding the full impact of tidal
wetland feedbacks on climate.
Blue biofuels. Macroalgal beds dominate the global area and pro-
duction of vegetated coastal habitats (Table1), but most macroalgal
communities grow on hard substrates and do not contribute to car-
bon sequestration except for the biomass that may be exported to
the deep sea76. Yet macroalgae can play a role in mitigating climate
change if either wild or aquaculture crops are used to derive biofuels.
e development of biofuels from mass aquaculture of macroalgae is
a new, vibrant area of research77,78, which has the potential to contrib-
ute to climate change mitigation. e production of ‘blue biofuels’
has many advantages over that based on land crops (green biofuels),
generating multiple environmental and societal impacts79,80. Blue
biofuels do not compete for arable land and water with food crops,
whereas green biofuels have co-opted both essential resources from
agriculture, becoming a threat to food security81. Moreover, blue
biofuels are not currently staples of global signicance, and so the
production does not negatively aect food prices in the global mar-
ket. In contrast, the development of green biofuels has diverted crops
otherwise used as staples (corn or palm oil) away from the food mar-
ket into fuel production, becoming an element in the recent global
rise of food prices81. Moreover, neither pesticides nor fertilizers are
used in most seaweed farms, which remove nutrients oen found in
excess in coastal waters, generating environmental benets in coastal
areas aected by eutrophication. In areas where nutrient availabil-
ity is insucient for macroalgae farming, such as in the Yellow Sea
(China), large kelp production is supported by multi-species polycul-
tures, where kelps benet from nutrients released by scallops, oysters
and/or mussels. Fertilizer production and application are a signi-
cant component of greenhouse gas emissions, as the Haber–Bosch
reaction — used to produce ammonia for fertilizers — is an energy-
intensive process and excess fertilizer application is a major source
of N2O (ref.82), a major greenhouse gas. Finally, phosphorus res-
ervoirs are being depleted, so replacing land with marine biofuels
without fertilizer application will allow more phosphorus to be used
to produce food. Hence there is a potential for wild and cultured
macroalgae to help mitigate climate change, while generating signi-
cant additional benets.
Climate change adaptation
Vegetated coastal ecosystems are important in protecting the coast
against ooding and erosion due to waves and storm surges
under mean and extreme conditions, including hurricanes
(Supplementary Table1 and ref.59). Seagrasses have a particularly
high capacity to dissipate wave energy, whereas salt marshes and
mangroves have a high capacity to protect from surges. Moreover,
these ecosystems oen occur in juxtaposition with seagrass in
subtidal areas and salt marshes or mangroves (depending on lati-
tude) in the intertidal zone, thereby increasing their combined
eectiveness in protecting from waves and surges.
Benets of ecosystem-based coastline protection. Articial
coastal protection structures are constructed with an expected
service life spanning several decades. Whereas extreme events are
considered in their design, the statistics of extreme events is now
aected by climate change and may alter during their operational
life. As climate change was not generally considered in the design
of most coastal defences that are now in place, an intense upgrade
of coastal defence structures during the coming decades will be
needed worldwide, requiring a huge investment to provide adap-
tation to an uncertain level of climate change83. Unlike articial
structures, vegetated ecosystems can naturally adapt to changes in
sea levels and wave storminess if they are not severely aected by
human action, as demonstrated by their capacity to adjust accretion
rates to sea-level rise37. Hence, the adaptive capacity of vegetated
coastal habitats helps maintain their capacity for coastal protection
at a negligible cost, while conserving the ecosystems and maintain-
ing their services84,85. e potential of a coastal ecosystem to pro-
tect the coastline does not increase linearly with its size, but varies
nonlinearly19,86. e eectiveness of sediment accretion by vegetated
coastal habitats in adapting to sea-level rise is dependent, however,
on both the rates of accretion, which vary 10-fold within habitat
types (Table3), and local processes such as compaction, subsidence
and local rates of sea-level rise. Indeed, reported elevation rates for
vegetated coastal habitats tend to be lower than accretion rates, and
the two available estimates that report elevation rates for seagrass
meadows indicate net subsidence (Table3 and ref.59).
Adaptation strategies that include the conservation, restoration or
introduction of vegetated coastal ecosystems provide a cost-eective
option for addressing the increased risk from ooding and ero-
sion under climate change in vulnerable areas. Moreover, produc-
ing vegetated coastal protections, unlike cement-based structures,
generates limited CO2 emissions and in fact removes atmospheric
CO2. However, CO2 emissions may be generated where machinery
is involved in preparing the terrain and revegetating the coast. In
addition, salt marshes and mangrove forests, particularly newly
created ones, can release CH4 and N2O that may partially oset
the carbon sequestered87. Accordingly, best practices to minimize
greenhouse gas emissions from eco-engineering projects need be
developed. e adaptation of vegetated coastal habitats to increased
CO2 and higher sea level involves an increase in sediment accretion,
also enhancing their capacity to act as carbon sinks. Lastly, vege-
tated coastal habitats have a high capacity to produce carbonates
and other materials that contribute to sediment accretion, beach
nourishment and to dune formation on land54,88, further preventing
coastal erosion.
Coastal vegetation may not always oer sucient protection, as
the capacity of natural ecosystems for shoreline protection varies
due to seasonal and interannual variations in the development of
the vegetation. In addition, the requirements for successful devel-
opment of coastal vegetation — such as elevation, currents and
wave exposure85,89 — are not met everywhere, restricting the areas
where protection based on coastal vegetation can be successful.
Finally, the particular circumstances of an event (that is, tidal con-
ditions and the track of a storm) can also aect the eectiveness of
coastal vegetations in shoreline protection.
Costs. Conserving and restoring vegetated coastal habitats is also
relatively inexpensive and is aordable to all countries, includ-
ing developing ones. According to the International Federation of
the Red Cross and Red Crescent (ref.90), replanting mangroves
in Vietnam has helped to reduce the cost of dyke maintenance by
US$7.3million a year for an investment of US$1.1million over the
period 1998–2002. Indeed, existing coastal wetlands in the USA have
been estimated to provide a value of US$23.2billion a year at present
in storm protection services91 at only the (minor) cost of conserving
these habitats.
Articial coastal structures provide limited or no extra benets
beyond the function for which they were built, and may generate
negative impacts — possibly including a role in promoting jellysh
blooms92. In contrast, vegetated coastal habitats add benets such as
nutrient cycling, food provision and biodiversity regulation to their
capacity for coastal protection26, thereby further increasing the value
and positive externalities of defence strategies that involve these habi-
tats. For instance, mangrove expansion has been shown to improve
the yield of sheries93. In turn, conserving vegetated habitats for their
capacity to sequester CO2 or their role in enhancing biodiversity will
© 2013 Macmillan Publishers Limited. All rights reserved
increase coastal protection as a side benet. erefore, the restoration
and preservation of these ecosystems can be considered a cost-
eective strategy due to the combined services provided for climate
change mitigation and adaptation.
For decades vegetated coastal ecosystems have remained the poor
relations of biological conservation61. However, recent ndings on
their remarkable capacity for CO2 sequestration and storage, and
their capacity for sediment accretion and coastal protection, have
converged to identify these habitats as essential elements of a strat-
egy that combines both climate change adaptation and mitigation.
Unfortunately, the role of vegetated coastal habitats as a valid
alternative in the portfolio of measures for climate change mitiga-
tion and adaptation has not been suciently considered by coastal
managers, who still opt for hard adaptation measures and on-land
mitigation options. Strategies that involve vegetated coastal habi-
tats are now being included in an eco-engineering approach to
climate change. Eco-engineering emerged in the early 1960s94, but
it has only recently gained broad recognition as a new paradigm.
e original starting point to use natural energy sources as the pre-
dominant input to manipulate and control environmental systems
was broadened by Mitsch and Jørgensen95 to ‘the design of sus-
tainable ecosystems that integrate human society with its natural
environmental to promote both’. Examples of experiments and suc-
cessful implementations of eco-engineering in coastal protection
projects89,96 can be found for example in the Netherlands, a country
challenged by sea-level rise (Table 4). e preceding discussion
points at a huge opportunity to develop projects and training cur-
ricula in coastal eco-engineering through options that are based on
vegetated coastal habitats to mitigate and adapt to the impacts of
climate change.
A comprehensive coastal eco-engineering programme could
strike a rational balance between mitigation and adaptation instru-
ments based on protecting and restoring or introducing dierent
vegetated coastal ecosystems to maximize the potential synergies
between them. Indeed, the separation between adaptation and miti-
gation strategies may lead to lost opportunities and to underestimate
the value of conservation, as is clearly the case for a REDD+ exten-
sion focused on vegetated coastal ecosystems, which would need
to account for their role in coastal protection, with a value likely
to exceed that of CO2 sequestration by at least an order of magni-
tude. Moreover, cost–benet analyses should not focus on benets
that are associated with climate change mitigation and adaptation
alone, but should encompass the broad suite of services that veg-
etated coastal habitats provide26. Eco-engineering approaches that
involve wetland creation can provide habitat for threatened species,
as exemplied by the refugia that mangrove forest oers to critically
endangered felids and primates in Africa and Asia97, thereby deliv-
ering conservation benets beyond those associated with coastal
protection or carbon stocks. e eco-engineering approach could
become societally and economically ecient and may oer greater
opportunities for countries — especially developing ones — to
achieve sustainable targets even under limited nancial resources
and capacity.
Coastal eco-engineering through vegetated coastal ecosystems
represents a new paradigm, whose signicance can be best under-
stood by drawing a parallel with material science. Coastal engineer-
ing has introduced a new material whose production, unlike that of
cement, does not lead to CO2 emissions, but rather CO2 removal. It
can achieve comparable eciency for coastal protection to cement-
based solutions; can repair itself; can grow; and can adapt to shi-
ing conditions. is newly discovered material is none other than
marine plants.
Ta b l e 4 | E c o - e n g i n e e r i n g s o l u t i o n s f o r c o a s t a l a r e a s i n t h e N e t h e r l a n d s .
Environment Problem Eco-dynamic design Area
Tidal Erosion of the
intertidal area
Surplus Sand nourishmenta
Shellfish reefsb
Circle-shaped nourishmentc
Eastern Scheldt
Eastern Scheldt
Coastal erosion Sand dunes
Wet lands
Flooding (waves) Optimizing texture of dykes by
ecological growth
North Sea c
Non-tidal Flooding (storms) Semi-natural floodplains
Willow flo odplainsd
a–d refer to the photographic examples of eco-dynamic design shown on the right. Eco-dynamic designs are based on the dynamics of the natural environment: developing hydraulic engineering infrastructure and
at the same time creating opportunities for nature and the environment. Sand nourishment is a technique where extra sand is deposited in an (intertidal) area to counter losses from erosion. In the Delfland Sand
Engine experiment, a larger than normal (surplus) nourishment of 21.5 million m3 of sand was introduced, rising up to 7m above mean sea level. The sand is gradually redistributed by natural processes over the
shoreface beach and dunes102. Images courtesy of: 1, Joop van Houdt/Rijkswaterstaat; 2–4 Ecoshape.
© 2013 Macmillan Publishers Limited. All rights reserved
Received 20 October 2012; accepted 4 July 2013;
published online 29 October 2013.
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is study was funded by the Spanish Ministry of Economy and Competitiveness
(projects MEDEICG, CTM2009-07013and ESTRESX, CTM2012-32603), the EU FP7
projects Opera (contract number 308393) and MedSEA (contract number -265103)
and the CSIRO Coastal Carbon Cluster. N.M. was supported by a Gledden Fellowship
from the Institute of Advanced Studies of the University of Western Australia, I.H. was
supported by a Posdoctoral contract of the JAE programme of CSIC and I.M. by a PhD
scholarship of the Government of the Balearic Islands (Spain).
Additional information
Supplementary information is available in the online version of the paper. Reprints
and permissions information is available online at
Correspondence should be addressed to C.M.D.
Competing financial interests
e authors declare no competing nancial interests.
© 2013 Macmillan Publishers Limited. All rights reserved
... This figure is in line with all the other BC ecosystems combined (Duarte et al., 2013;Nellemann & Corcoran, 2009). In Scotland therefore, BC sequestration by macroalgae can be tentatively estimated at 0.19 Mt C yr -1 (Figure 1.2). ...
... Early estimates of production of seaweeds alone range between 400-1,900 g C m -2 yr -1 (Mann, 1982), are still considered relatively accurate but ranges tend to be large. Duarte et al., (2013) estimate annual primary production by macroalgae lies between 0.19-0.64 Pg C yr -1 over a global range of 2-6.8 million km 2 . ...
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The ecological and biological importance as well as economic, and cultural value of macroalgae is becoming more prominent. Introduction of the term ‘blue carbon’ (BC) has drawn attention to natural coastal ecosystems, the habitats they provide, and their capacity to fix CO2. The overall aim of this thesis was to place the importance of carbon sequestration within the already essential services that macroalgae provide to the biosphere. This thesis focused on: 1) Quantifying the amount of detritus produced by species in Scottish macroalgae habitats and providing annual figures of total carbon leaving kelp forests in fluxes, 2) understanding the processes of degradation of detritus from three dominant kelp species and estimating the pathways of carbon loss of the detritus, and 3) identifying the sources of sediment carbon using biomarkers and environmental DNA primers specific to the class Phaeophyceae. Macroalgae in the North-East Atlantic: 1) fix significant amounts of CO2 through photosynthesis thus removing it from the atmosphere, 2) release the carbon fixed through photosynthesis as detritus which accumulates and is buried, broken down by bacteria, and contributes to food webs, and 3) contributes carbon to sediment stores in Scotland and the wider North-East Atlantic shelf. These three criteria are fundamental blue carbon habitat characteristics. It is thereby recommended that macroalgae are henceforth included in blue carbon frameworks and directives, particularly in Scotland, where the contribution to long-term carbon stores in fjord and shelf systems is potentially greater than any other BC habitat in the region. It is estimated that 0.2 Mt C yr-1 is transferred to sediments from macroalgae in Scotland, the equivalent of 0.04 g C m-2 of kelp forest.
... However, the aforementioned processes greatly contribute to the potential of the natural greenhouse gas effect that is global warming through increased amount of these gases. Over the past years the entire world has been warmer at a rate never seen in human history, (Duarte et al., 2013) all because of the human-induced and/or amplified greenhouse gases emissions. This effect is what raises environmental concerns globally. ...
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Global climate change has negative effects, on impoverished individuals and poor countries are more severely affected than others. They are particularly at risk due to their heavy reliance on natural resources and poor ability to adapt to climatic change upshots. However, by lowering carbon emissions, carbon trading systems should enhance the environment's air quality and sustenance. The amount of greenhouse gases in the atmosphere is more dependent on human activity, making it easier to govern and control. The main organic sources of greenhouse gases are biomass decomposition, natural fires, and biological respiration. Anthropogenic greenhouse gas emissions increase the Earth's natural greenhouse effect and cause global warming by trapping outgoing infrared radiation within the atmosphere due to the formed pseudo blanket. Global warming impacts humans, plants and animals via a variety of mechanisms with varying levels of complexity, directness, and timing. The negative effects of climate change may be mitigated through adaptation, but this option must be carefully considered given that developing nations are clearly at a disadvantage in terms of technology, resources, and institutional capacity. The capacity to adapt is particularly related to socioeconomic characteristics.
... The potential importance of mangroves in the global carbon cycle and in offsetting global climate change is highlighted by scientists around the globe (Suratman, 2008). The disproportionally large role of coastal vegetated ecosystems as efficient natural carbon sinks has been highlighted (Mcleod et al., 2011;Duarte et al., 2013). The term "blue carbon" was coined to describe carbon burial in vegetated coastal ecosystems such as mangrove forests, seagrass beds, and salt marshes. ...
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A study was undertaken at Lothian Wild Life Sanctuary of Indian Sundarbans to estimate the stored carbon in the mangrove vegetation of the island. 34 true mangrove species were documented from the island, but on the basis of criterion DBH > 5 cm, only 26 species were selected for the estimation. We focused on the stem biomass and the carbon locked in this compartment as the other above ground structures (like leaves, twigs and branches) are converted into litter and act as relatively temporary sink of carbon. Stem carbon exhibited direct proportionality with stem biomass in all the species. The total biomass of the documented species (except those whose DBH values are less than 5-1 cm) was 164.24 t ha. The stored carbon in the stem region of these-1 species was 74.18 t ha , which is equivalent to 272.25 tonnes of carbon dioxide. This study concludes the carbon sequestration potential of blue carbon ecosystems such as Mangroves are humongous and can be a potential answer to climate change mitigation.
... In addition, in Vietnam, industrialization and tourism are concentrated in coastal areas that increases the vulnerability of these areas (Sekhar, 2005). Since seagrass meadows significantly reduce flow velocity, dissipate wave energy and stabilize the sediments thereby influencing the hydrodynamic environment, they are capable of diminishing erosion risks and storm surges, which are crucial in coastal zone management (Duarte et al., 2013). In the case of Vietnam, there have been suggestions that seagrass restoration has the potential to limit the impacts of hydrometeorological hazards along the coastline as many are in a poor condition (except Khanh Hoa province) although without the removal of existing pressures these are unlikely to be successful. ...
Seagrass communities in Vietnam are important primary producers in the coastal environment and play a key role in shoreline protection as a bioshield in the country. In the past two decades, seagrass research in Vietnam has advanced in many aspects, including distribution mapping, plant genetics and biophysical characteristics, sustainable use of seagrass beds, restoration and protection of seagrass meadows, establishment of marine protected areas (MPAs), and collaborative research with international institutions. In this paper, we presented a state-of-the-art review of recent seagrass research conducted in Vietnam. Despite the recent increase in the number of seagrass studies conducted in Vietnam, these coastal ecosystems continue to be poorly mapped and managed in some areas. Although a number of recent studies highlighted the use of seagrass ecosystems as a coastal bioshield in Vietnam, they have undergone degradation in recent years due to pollution, sedimentation and turbidity, eutrophication and habitat loss. Remote sensing is considered as an effective tool for mapping seagrasses in recent studies, particularly due to the ability to accurately map, model and assess the condition of some hard to access sites. Collaboration among regional authorities, NGOs and research institutions can provide an appropriate basis for understanding these complex systems at a national scale and afford an important scientific reference for supporting management and conservation decisions in Vietnam. Sustainable use of seagrass ecosystems can bring economic benefits as well as environmental protection along the coastal areas of Vietnam.
... It is becoming increasingly common for soils to become salinized worldwide, negatively influencing plant growth (Parmar et al., 2020). The use of salt-tolerant plants reduces seawater erosion on the coast by creating an environment that facilitates plant growth, aids in the development of a bioreactor system, and assists in the bioremediation process (Duarte et al., 2013;Fariña et al., 2018). The herb S. portulacastrum can tolerate high salt levels without salt glands and bladders in its succulent leaves, indicating the existence of a specialized salt tolerance mechanism (Yi et al., 2014). ...
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Sesuvium portulacastrum has a strong salt tolerance and can grow in saline and alkaline coastal and inland habitats. This study investigated the physiological and molecular responses of S. portulacastrum to high salinity by analyzing the changes in plant phytohormones and antioxidant activity, including their differentially expressed genes (DEGs) under similar high-salinity conditions. High salinity significantly affected proline (Pro) and hydrogen peroxide (H2O2) in S. portulacastrum seedlings, increasing Pro and H2O2 contents by 290.56 and 83.36%, respectively, compared to the control. Antioxidant activities, including superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), significantly increased by 83.05, 205.14, and 751.87%, respectively, under high salinity. Meanwhile, abscisic acid (ABA) and gibberellic acid (GA3) contents showed the reverse trend of high salt treatment. De novo transcriptome analysis showed that 36,676 unigenes were matched, and 3,622 salt stress-induced DEGs were identified as being associated with the metabolic and biological regulation processes of antioxidant activity and plant phytohormones. POD and SOD were upregulated under high-salinity conditions. In addition, the transcription levels of genes involved in auxin (SAURs and GH3), ethylene (ERF1, ERF3, ERF114, and ABR1), ABA (PP2C), and GA3 (PIF3) transport or signaling were altered. This study identified key metabolic and biological processes and putative genes involved in the high salt tolerance of S. portulacastrum and it is of great significance for identifying new salt-tolerant genes to promote ecological restoration of the coastal strand.
... Despite their importance in providing ecosystem services, salt marshes have been destroyed for centuries (Duarte et al., 2013). ...
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Blue carbon ecosystems are recognized as carbon sinks and therefore for their potential for climate mitigation. While carbon stocks and burial rates have been quantified and estimated regionally and globally, there are still many knowledge gaps on carbon fluxes exchanged particularly at the interface vegetation-atmosphere. In this study we measured the atmospheric CO 2 concentrations in a salt marsh located in the Patos Lagoon Estuary, southern Brazil. Eddy correlation techniques were applied to account for the CO 2 exchange fluxes between the vegetation and the atmosphere. Our dataset refers to two sampling periods spanning from July up to November 2016 and from January to April 2017. By using time series analysis techniques including wavelet and cross-wavelet analysis, our results show the natural cycles of the CO 2 exchanges variability and the relationship of these cycles with other environmental variables. We also present the amplitudes of the salt marsh-atmosphere CO 2 fluxes’ diurnal cycle for both study periods and demonstrate that the CO 2 fluxes are modulated by the passage of transient atmospheric systems and by the level variation of surrounding waters. During daytime, our site was as a CO 2 sink. Fluxes were measured as -6.71 ± 5.55 μmol m ⁻² s ⁻¹ and -7.95 ± 6.44 μmol m ⁻² s ⁻¹ for the winter-spring and summer-fall periods, respectively. During nighttime, the CO 2 fluxes were reversed and our site behaved as a CO 2 source. Beside the seasonal changes in sunlight and air temperature, differences between the two periods were marked by the level of marsh inundation, winds and plant biomass (higher in summer). The net CO 2 balance showed the predominance of the photosynthetic activity over community respiration, indicating the role of the salt marsh as a CO 2 sink. When considering the yearly-averaged net fluxes integrated to the whole area of the Patos Lagoon Estuary marshes, the total CO 2 sink was estimated as -87.6 Mg C yr ⁻¹ . This paper is the first to measure and study the vegetation-atmosphere CO 2 fluxes of a salt marsh environment of Brazil. The results will contribute to the knowledge on the global carbon budget and for marsh conservation and management plans, including climate change policies.
... There are however knowledge gaps of estimates on carbon storage and greenhouse gas fluxes following restoration that likely hinder the inclusion of blue carbon ecosystems into carbon accounting and crediting schemes. There is also large variability in carbon storage among and within blue carbon habitats at local scales (Thomas 2014;Green, Alix et al. 2018;Lewis et al. 2018) that hampers obtaining robust estimates of carbon storage at national to global scales (Duarte et al. 2013;Serrano et al. 2019b;Costa et al. 2021a). ...
Technical Report
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Te Tauihu (Top of the South Island, NZ) Councils (MLDC, NLCC, TLDC) sought advice on options for activities or actions to reverse the decline in state of coastal and marine habitats to build resilience in these habitats likely to be impacted by climate change. An Envirolink medium advice grant was used to review local reasons for restoration, summarise existing relevant marine restoration techniques and identify methods or species relevant for Te Tauihu highlighting ‘shovel-ready’ projects. Shellfish restoration was considered the top priority because of the areal extent of historic degradation. Restoration of such habitats are very likely to produce additional benefits to fisheries production (shellfisheries, fishes), and contribute to reducing climate change risks (through carbon sequestration and through the greater resilience provided by healthy ecosystems). Successful restoration of shellfish and seaweeds/grasses is more likely if soft sediment habitats can also be protected from benthic disturbance and if terrestrial sediment discharge into coastal marine areas is reduced. Recent restoration successes (e.g., green-lipped mussels, saltmarsh) and increasing knowledge of climate change risks provide encouragement and impetus to continue broadening the scope and scale of marine restoration efforts in Te Tauihu.
... The potential importance of mangroves in the global carbon cycle and in offsetting global climate change is highlighted by scientists around the globe (Suratman, 2008). The disproportionally large role of coastal vegetated ecosystems as efficient natural carbon sinks has been highlighted (Mcleod et al., 2011;Duarte et al., 2013). The term "blue carbon" was coined to describe carbon burial in vegetated coastal ecosystems such as mangrove forests, seagrass beds, and salt marshes. ...
Full-text available
A study was undertaken at Lothian Wild Life Sanctuary of Indian Sundarbans to estimate the stored carbon in the mangrove vegetation of the island. 34 true mangrove species were documented from the island, but on the basis of criterion DBH > 5 cm, only 26 species were selected for the estimation. We focused on the stem biomass and the carbon locked in this compartment as the other above ground structures (like leaves, twigs and branches) are converted into litter and act as relatively temporary sink of carbon. Stem carbon exhibited direct proportionality with stem biomass in all the species. The total biomass of the documented species (except those whose DBH values are less than 5-1 cm) was 164.24 t ha. The stored carbon in the stem region of these-1 species was 74.18 t ha , which is equivalent to 272.25 tonnes of carbon dioxide. This study concludes the carbon sequestration potential of blue carbon ecosystems such as Mangroves are humongous and can be a potential answer to climate change mitigation.
Coastal nature-based solutions (NbS) are increasingly recognized for their multiple benefits to socio-ecological systems, including climate mitigation and adaptation (e.g. conservation, restoration and sustainable management of coastal ecosystems for climate). National climate plans, such as the Nationally Determined Contributions (NDCs) developed under the Paris Agreement, include coastal NbS as a practical and effective action to help countries achieve their climate and biodiversity targets. However, the absence of a standardized NDC structure and the lack of guidance about how NbS should be included in NDCs can hinder access to external funding for developing countries and prevent transparent reporting on progress at the international level. In this context, our aim is to understand how coastal NbS are currently included in NDCs by evaluating their alignment with the IUCN Global Standard for NbS. Our analysis focuses on the description of coastal NbS in the NDCs of Pacific Small Island Developing States (PSIDS), as they are among the most vulnerable countries to the impacts of climate change. Overall, we find that, for the 22 coastal NbS examined in the NDCs of PSIDS, the degree of alignment with the eight criteria of the IUCN Global Standard is insufficient or partial, with slightly better alignment with the standard in revised NDCs than in original NDCs. We discuss opportunities provided by the standardization of the description of coastal NbS in NDCs, in terms of access to funding and stock taking to monitor the effectiveness of implementation and progress towards long-term goals. We also discuss the relevance of using the IUCN Global Standard for reporting on NbS in NDCs for PSIDS.
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Fluid dynamics is the study of the movement of fluids. Among other things, it addresses velocity, acceleration, and the forces exerted by or upon fluids in motion (Daugherty et al., 1985; White, 1999; Kundu and Cohen, 2002). Fluid dynamics affects every aspect of the existence of seagrasses from the smallest to the largest scale: from the nutrients they obtain to the sediment they colonize; from the pollination of their flowers to the import/export of organic matter to adjacent systems; from the light that reaches their leaves to the organisms that live in the seagrass habitats. Therefore, fluid dynamics is of major importance in seagrass biology, ecology, and ecophysiology. Unfortunately, fluid dynamics is often overlooked in seagrass systems (Koch, 2001).
Sedimentologic and stratigraphic characteristics of five tidal marshes in Great Bay Estuary, New Hampshire, which is located on the western boundary of the Gulf of Maine, were assessed from 20 vibracores, detailed descriptions of surficial environments, pollen analyses, and radiocarbon dating. Modern marsh sequences in Great Bay Estuary initiated with a time-transgressive basal peat that formed at the upland-brackish marsh boundary. The oldest basal peat deposit sampled during this study was dated at ~ 4560 cal yr B.P. (based on an age of 4060 ± 40 14C yr B.P.). The original tidal marshes that formed in Great Bay Estuary apparently were unable to accrete at a high enough rate to allow seaward expansion, resulting in a transgressive sequence of low marsh or mudflat sediments overlying the basal peat. The transgressive tidal marsh sequence is capped by high marsh sediments that corresponded to a slowing of relative sea-level (RSL) rise in the region and regressive seaward expansion of the tidal marshes. However, significant variations from these transgressive-regressive sequences occur in the Great Bay tidal marshes as a result of more recent marsh expansion and tidal channel migrations.
The wave-induced kinematics and dynamics of a submerged or emerged vegetation field is analyzed. Using potential flow and an eigenfunction expansion, the problem is solved considering regular as well as irregular incident waves. The model takes into account the vegetation motion and solves for the complete wave system on the vegetation field and in its vicinity. The model is validated against experimental laboratory data obtained by other authors, showing a much better agreement than previous theoretical models. In this paper the model is used to evaluate wave height evolution (damping), vegetation and fluid motion, and forces and moments on the vegetation. Furthermore, the inclusion of irregular waves provides force and moment distributions on the vegetation field depending on the wave climate statistics.