ArticlePDF Available

Mangroves among the most carbon-rich forests in the tropics

Authors:
  • Washington Department of Natural Resources & University of Washington
  • Oregon State University and Illhaee Sciences International
  • Center for International Forestry Research Bogor Indonesia & Department of Geophysics and Meteorology IPB University Bogor

Abstract and Figures

Mangrove forests occur along ocean coastlines throughout the tropics, and support numerous ecosystem services, including fisheries production and nutrient cycling. However, the areal extent of mangrove forests has declined by 30-50% over the past half century as a result of coastal development, aquaculture expansion and over-harvesting. Carbon emissions resulting from mangrove loss are uncertain, owing in part to a lack of broad-scale data on the amount of carbon stored in these ecosystems, particularly below ground. Here, we quantified whole-ecosystem carbon storage by measuring tree and dead wood biomass, soil carbon content, and soil depth in 25 mangrove forests across a broad area of the Indo-Pacific region--spanning 30° of latitude and 73° of longitude--where mangrove area and diversity are greatest. These data indicate that mangroves are among the most carbon-rich forests in the tropics, containing on average 1,023Mg carbon per hectare. Organic-rich soils ranged from 0.5m to more than 3m in depth and accounted for 49-98% of carbon storage in these systems. Combining our data with other published information, we estimate that mangrove deforestation generates emissions of 0.02-0.12Pg carbon per year--as much as around 10% of emissions from deforestation globally, despite accounting for just 0.7% of tropical forest area.
Content may be subject to copyright.
LETTERS
PUBLISHED ONLINE: 3 APRIL 2011 | DOI: 10.1038/NGEO1123
Mangroves among the most carbon-rich forests in
the tropics
Daniel C. Donato1*, J. Boone Kauffman2, Daniel Murdiyarso3, Sofyan Kurnianto3, Melanie Stidham4
and Markku Kanninen5
Mangrove forests occur along ocean coastlines throughout the
tropics, and support numerous ecosystem services, including
fisheries production and nutrient cycling. However, the areal
extent of mangrove forests has declined by 30–50% over the
past half century as a result of coastal development, aqua-
culture expansion and over-harvesting1–4. Carbon emissions
resulting from mangrove loss are uncertain, owing in part to
a lack of broad-scale data on the amount of carbon stored
in these ecosystems, particularly below ground5. Here, we
quantified whole-ecosystem carbon storage by measuring tree
and dead wood biomass, soil carbon content, and soil depth in
25 mangrove forests across a broad area of the Indo-Pacific
region—spanning 30of latitude and 73of longitude—where
mangrove area and diversity are greatest4,6. These data indi-
cate that mangroves are among the most carbon-rich forests
in the tropics, containing on average 1,023 Mg carbon per
hectare. Organic-rich soils ranged from 0.5m to more than 3 m
in depth and accounted for 49–98% of carbon storage in these
systems. Combining our data with other published information,
we estimate that mangrove deforestation generates emissions
of 0.02–0.12 Pg carbon per year—as much as around 10% of
emissions from deforestation globally, despite accounting for
just 0.7% of tropical forest area6,7.
Deforestation and land-use change currently account for 8–20%
of global anthropogenic carbon dioxide (CO2) emissions, second
only to fossil fuel combustion7,8. Recent international climate
agreements highlight Reduced Emissions from Deforestation and
Degradation (REDD+) as a key and relatively cost-effective option
for mitigating climate change; the strategy aims to maintain
terrestrial carbon (C) stores through financial incentives for forest
conservation (for example, carbon credits). REDD+and similar
programs require rigorous monitoring of C pools and emissions8,9,
underscoring the importance of robust C storage estimates for
various forest types, particularly those with a combination of high
C density and widespread land-use change10.
Tropical wetland forests (for example, peatlands) contain
organic soils up to several metres deep and are among the largest
organic C reserves in the terrestrial biosphere11–13. Peatlands’
disproportionate importance in the link between land use and
climate change has received significant attention since 1997, when
peat fires associated with land clearing in Indonesia increased
atmospheric CO2enrichment by 13–40% over global annual
fossil fuel emissions11. This importance has prompted calls to
specifically address tropical peatlands in international climate
change mitigation strategies7,13.
1USDA Forest Service, Pacific Southwest Research Station, 60 Nowelo St., Hilo, Hawaii 96720, USA, 2USDA Forest Service, Northern Research Station, 271
Mast Rd., Durham, New Hampshire 03824, USA, 3Center for International Forestry Research (CIFOR), PO Box 0113 BOCBD, Bogor 16000, Indonesia,
4USDA Forest Service, International Programs, 1099 14th street NW, Suite 5500W, Washington, District of Columbia 20005, USA, 5Viikki Tropical
Resources Institute (VITRI), University of Helsinki, PO Box 27, FIN-00014, Finland. *e-mail:ddonato@wisc.edu.
Overlooked in this discussion are mangrove forests, which occur
along the coasts of most major oceans in 118 countries, adding
30–35% to the global area of tropical wetland forest over peat
swamps alone4,6,12. Renowned for an array of ecosystem services,
including fisheries and fibre production, sediment regulation, and
storm/tsunami protection2–4, mangroves are nevertheless declining
rapidly as a result of land clearing, aquaculture expansion,
overharvesting, and development2–6. A 30–50% areal decline over
the past half-century1,3 has prompted estimates that mangroves
may functionally disappear in as little as 100 years (refs 1,2). Rapid
twenty-first century sea-level rise has also been cited as a primary
threat to mangroves14, which have responded to past sea-level
changes by migrating landward or upward15.
Although mangroves are well known for high C assimilation
and flux rates16–22, data are surprisingly lacking on whole-ecosystem
carbon storage—the amount which stands to be released with
land-use conversion. Limited components of C storage have been
reported, most notably tree biomass17,18, but evidence of deep
organic-rich soils22–25 suggests these estimates miss the vast majority
of total ecosystem carbon. Mangrove soils consist of a variably
thick, tidally submerged suboxic layer (variously called ‘peat’ or
‘muck’) supporting anaerobic decomposition pathways and having
moderate to high C concentration16,20,21. Below-ground C storage
in mangrove soils is difficult to quantify5,21 and is not a simple
function of measured flux rates—it also integrates thousands of
years of variable deposition, transformation, and erosion dynamics
associated with fluctuating sea levels and episodic disturbances15.
No studies so far have integrated the necessary measurements for
total mangrove C storage across broad geographic domains.
In this study we quantified whole-ecosystem C storage in
mangroves across a broad tract of the Indo-Pacific region, the
geographic core of mangrove area (40% globally) and diversity4,6.
Study sites comprised wide variation in stand composition
and stature (Fig. 1, Supplementary Table S1), spanning 30
of latitude (8S–22N), 73of longitude (90–163E), and
including eastern Micronesia (Kosrae); western Micronesia
(Yap and Palau); Sulawesi, Java, Borneo (Indonesia); and the
Sundarbans (Ganges-Brahmaputra Delta, Bangladesh). Along
transects running inland from the seaward edge, we combined
established biometric techniques with soil coring to assess variations
in above- and below-ground C pools as a function of distance
from the seaward edge in two major geomorphic settings:
estuarine/river-delta and oceanic/fringe. Estuarine mangroves
(n=10) were situated on large alluvial deltas, often with a
protected lagoon; oceanic mangroves (n=15) were situated in
NATURE GEOSCIENCE |ADVANCE ONLINE PUBLICATION |www.nature.com/naturegeoscience 1
© 2011 Macmillan Publishers Limited. All rights reserved.
LETTERS NATURE GEOSCIENCE DOI: 10.1038/NGEO1123
a
b
Figure 1 |Examples of Indo-Pacific mangroves. The sample included a
broad range of stand stature, composition, and soil depth. a, Exemplary
large-stature, high-density mangrove dominated by Bruguiera, Borneo,
Indonesia (canopy height >15 m, canopy closure >90%, soil depth >3 m).
b, Exemplary small-stature, low-density mangrove dominated by
Rhizophora, Sulawesi, Indonesia (canopy height <4m, canopy closure
<60%, soil depth 0.35–0.78m). Both estuarine and oceanic mangroves
can exhibit both conditions (see Supplementary Table S1).
marine-edge settings, often the coasts of islands with fringing
coral reefs. Seaward distance and geomorphic setting may
influence C dynamics through differences in tidal flushing and
relative importance of allochthonous (river sediment) versus
autochthonous (in situ litter and root production) controls on soil
C accumulation5,16.
We found that mangroves are among the most C-dense forests
in the tropics (sample-wide mean: 1,023 Mg C ha1±88 s.e.m.),
and exceptionally high compared to mean C storage of the
world’s major forest domains (Fig. 2). Estuarine sites contained
a mean of 1,074 Mg C ha1(±171 s.e.m.); oceanic sites contained
990 ±96 Mg C ha1. Above-ground C pools were sizeable (mean
159 Mg C ha1, maximum 435 Mg C ha1), but below-ground
storage in soils dominated, accounting for 71–98% and 49–90%
of total storage in estuarine and oceanic sites, respectively (Figs 2
and 3). Below-ground C storage was positively but weakly
correlated to above-ground storage (R2=0.21 and 0.50 in estuarine
and oceanic sites, respectively). Although soil C pools increased
slightly with distance from the seaward edge in oceanic sites
(because of increasing soil depth), changes in both above- and
Boreal Temperate Tropical
upland
Mangrove
Indo-Pacific
0
200
400
600
800
1,000
1,200
1,400
Ecosystem C storage (Mg ha¬1)
Above-ground live + dead
Soils 0¬30 cm depth + roots
Soils below 30 cm depth
Figure 2 |Comparison of mangrove C storage (mean ±95% confidence
interval) with that of major global forest domains. Mean C storage by
domain was derived from ref. 9, including default values for tree, litter, dead
wood, root:shoot ratios, and soils, with the assumption that the top 30cm
of soil contains 50% of all C residing in soil9, except for boreal forests
(25%). Domain means are presented for context; however some forest
types within each contain substantially higher or lower C stores9,10. In
general, the top 30 cm of soil C are considered the most vulnerable to
land-use change9; however in suboxic peat/muck soils, drainage,
excavation, and oxidation may influence deeper layers29.
below-ground C storage over this distance gradient were highly
variable and not statistically significant (Fig. 3).
So far, quantification of below-ground C storage in man-
groves has been impeded by a lack of concurrent data on soil
carbon concentration, bulk density, and depth, and how these
vary spatially5,21. We found high C concentration (% dry mass)
throughout the top metre of the soil profile, with a decrease
below 1 m (Fig. 4a). Carbon concentration was lower in es-
tuarine (mean =7.9%) versus oceanic (mean =14.6%) sites.
Soil bulk density (BD) did not differ significantly by setting or
distance from the seaward edge (generally 0.35–0.55 g cm3),
but did increase with depth (Fig. 4b). Combining C concentra-
tion and BD yielded mean C densities of 0.038 g C cm3and
0.061 g C cm3in estuarine and oceanic soils, respectively. The
total depth of the peat/muck layer differed between estuarine
and oceanic sites (Fig. 4c) and was the main driver of varia-
tions in below-ground C storage (Fig. 3). Estuarine stands over-
lie deep alluvial sediment deposits, usually exceeding 3 m depth;
oceanic stands contained a distinct organic-rich layer overlying
hard coral sand or rock, with peat/muck thickness increasing
from a mean of 1.2 m (±0.2 s.e.m.) near the seaward edge to
1.7 m (±0.2 s.e.m.) 135 m inland (Fig. 4c). In terms of total
below-ground C storage, the shallower soil depth in oceanic man-
groves was compensated in part by higher soil organic C con-
centration (Fig. 4a,c).
These data indicate that high productivity and C flux rates
in mangroves16–22 are indeed accompanied by high C storage,
especially below ground. High per-hectare C storage coupled with
a pan-tropical distribution (total area 14 million ha; refs 4,6)
suggests mangroves are a globally important surface C reserve.
Although our sample is not intended to represent all mangrove
types (precluding simple scaling up), some constraints on global
storage can be derived by combining an uncertainty range from
our empirical data (5th to 95th percentile C storage values) with
additional global data on soil C concentration, depth, and standing
biomass16,17,21,23,24 (see Methods in Supplementary Information).
This approach yields an estimate of 4.0–20 Pg C globally. This
estimate will undoubtedly be refined, but suggests mangroves add
significantly to tropical wetland forest C storage (for example,
tropical peatlands: 82–92 Pg C; ref. 12).
2NATURE GEOSCIENCE |ADVANCE ONLINE PUBLICATION |www.nature.com/naturegeoscience
© 2011 Macmillan Publishers Limited. All rights reserved.
NATURE GEOSCIENCE DOI: 10.1038/NGEO1123 LETTERS
400
200
0
200
400
600
800
1,000
1,200
1,400
Below-ground Above-ground
C storage (Mg ha¬1)
400
200
0
200
400
600
800
1,000
1,200
1,400
Below-ground Above-ground
C storage (Mg ha¬1)
0 10 35 60 85 110 135
Distance from seaward edge (m)
0 10 35 60 85 110 135
Distance from seaward edge (m)
Estuarine mangroves Oceanic mangroves
Trees
Down wood
Roots
Soil
ab
Figure 3 |Above- and below-ground C pools in Indo-Pacific mangroves, assessed by distance from the seaward edge. a, Estuarine mangroves situated on
large alluvial deltas. b, Oceanic mangroves situated in marine edge environments—for example, island coasts. Below-ground C comprised 71–98% and
49–90% of ecosystem C in estuarine and oceanic sites, respectively. Overall carbon storage did not vary significantly with distance from the seaward edge
in either setting over the range sampled (P>0.10 for above-ground, below-ground, and total C storage by functional data analysis (FDA, see Methods);
95% CIs for rates-of-change all overlapped zero and were between 1.2 and 3.9 Mg C ha1per metre of distance from edge).
Carbon emissions from land-use change in mangroves are
not well understood. Our data suggest a potential for large
emissions owing to perturbation of large C stocks. The fate of
below-ground pools is particularly understudied, but available
evidence suggests that clearing, drainage, and/or conversion
to aquaculture—aside from affecting vegetation biomass—also
decreases mangrove soil C significantly16,22,26–28. In upland forests,
the top 30 cm of soil are generally considered the most susceptible
to land-use change9; however in wetland forests, drainage and
oxidation of formerly suboxic soils may also influence deeper
layers29. To provide some constraints on estimated emissions,
we used a similar uncertainty propagation technique, combining
our C storage values with other global data16,17 and applying
a range of assumptions regarding land-use effects on above-
and below-ground pools (see Supplementary Information). This
approach yields a plausible estimate of 112–392 Mg C released
per hectare cleared, depending in large part on how deeply soil
C is affected by different land uses. Coupled with published
ranges of mangrove deforestation rate (1–2%; refs 1,4) and global
area (13.7–15.2 million ha; refs 4,6), this estimate leads to global
emissions on the order of 0.02–0.12 Pg C yr1. This rate adds
significantly to oft-cited peatland emissions (0.30 Pg C yr1) and
global deforestation emissions (1.2 Pg C yr1; ref. 7) despite
accounting only for loss of standing stocks but not other known
mangrove-conversion influences, such as decreased C sequestration
rate, burial efficiency, and export to ocean16,18, nor increases in
normally-low methanogenesis in some disturbed soils16,27.
In addition to direct losses of forest cover, land-use activities
will also impact mangrove responses to sea-level rise14,15. Man-
groves have been remarkably persistent through rapid sea-level rises
(5–15 mm yr1) during the late Quaternary Period (0–18,000 yr bp)
because of (1) landward migration, and (2) autogenic changes
in soil-surface elevation through below-ground organic matter
production and/or sedimentation15. Under current climate trends,
sea level is projected to rise 18–79 cm from 1999–2099 (higher
if ice-sheet melting continues accelerating)8,30, implying a period-
averaged rate of 1.8–7.9 mm yr1, notwithstanding local varia-
tions and temporal nonlinearities. Although this rate is not unprece-
dented, it is unclear yet whether mangroves are currently keeping
pace with sea levels14,15. Anthropogenic influences could constrain
future resilience to sea-level rise through coastal developments
that impede inland migration (for example, roads, infrastructure),
upland land uses that alter sediment and water inputs (for example,
dams, land clearing), and mangrove degradation that reduces
below-ground productivity14. This synergy of land use and climate
change impacts presents additional uncertainties for the fate and
management of coastal C stores.
Critical uncertainties remain before estimates of mangrove C
storage and land-use emissions can be improved. Among these are
geographic variations in soil depth, a key but unknown parameter
in most regions5,21. Similarly, empirical data on land-use change
impacts on soil C is strongly lacking, especially for deep layers
(but see refs 26–28). Quantitative estimates are also needed of
the relative area occupied by estuarine/delta and oceanic/fringe
mangroves, which is not addressed in most analyses of mangrove
area4,6. Because these two systems store below-ground C differently,
improved spatial data will greatly refine estimates of global C storage
and emissions owing to disturbance.
Our data show that discussion of the key role of tropical wetland
forests in climate change could be broadened significantly to include
mangroves. Southeast Asian peatlands are currently being advanced
as an essential component of climate change mitigation strategies
such as REDD+(refs 7,13), and mangroves share many of the
same relevant characteristics: deep organic-rich soils, exceptionally
high C storage, and extensive deforestation/degradation resulting in
potentially large greenhouse gas emissions. The well-known ecosys-
tem services and geographic distribution of mangroves1–4 suggest
these mitigation strategies could be effective in providing ancillary
benefits as well as potential REDD+ opportunities in many tropical
countries. Because land use in mangroves affects not only standing
stocks but also ecosystem response to sea-level rise, maintaining
these C stores will require both in situ mitigation (for example,
reducing conversion rates) as well as facilitating adaptation to
rising seas. The latter challenge is largely unique to management
NATURE GEOSCIENCE |ADVANCE ONLINE PUBLICATION |www.nature.com/naturegeoscience 3
© 2011 Macmillan Publishers Limited. All rights reserved.
LETTERS NATURE GEOSCIENCE DOI: 10.1038/NGEO1123
0 10 35 60 85 110 135
Distance from seaward edge (m)
0 10 35 60 85 110 135
Distance from seaward edge (m)
Organic C content (%)
0
0
1
2
10 20
Depth (m)
0 10 20 0 10 20 0 10 20 0 10 20 0 10 20
Estuarine Oceanic
Bulk density (g cm¬3)
0.3 0.6 0.3 0.6 0.3 0.6 0.3 0.6 0.3 0.6 0.3 0.6
Estuarine/oceanic combined
Soil depth (m)
Estuarine (88% >3 m)
Oceanic
0
1
2
Depth (m)
Soil depth (m)
3
2
1
0
a
b
c
Figure 4 |Soil properties determining below-ground carbon storage in
Indo-Pacific mangroves. a, Soil C concentration was greater in oceanic
(mean =14.6%) versus estuarine (mean =7.9%) sites (P=0.001), and
decreased with depth (P<0.0001; effect stronger in oceanic sites).
Change in C concentration with seaward distance was biologically
insignificant. b, Soil bulk density did not differ significantly with setting
(P=0.79); hence one line is shown combining both settings. Bulk density
increased with depth (P<0.0001) but not seaward distance (P=0.20),
and a distance*depth interaction term was not significant (P=0.47). c, Soil
depth increased with distance from the seaward edge in oceanic stands
(FDA result: P=0.002, 95% CI for rate-of-change =21–65 cm increase
per 100 m distance).
of coastal forests, calling for watershed-scale approaches, such
as landscape buffers for accommodating inland migration where
possible, maintenance of critical upstream sediment inputs, and
addressing degradation of mangrove productivity from pollution
and other exogenous impacts14,15.
Methods
We sampled 25 mangrove sites (n=10 estuarine, n=15 oceanic) across the
Indo-Pacific (8S–22N, 90–163E) using a transect starting from, and running
perpendicular to, the seaward edge. To maximize scope and representativeness,
we stratified the sample across a broad range of stand conditions—including
small-stature stands and shallow soils (<4 m canopy height, <10 cm mean tree
diameter, <0.5 m soil depth) to large-stature stands and deep soils (>15 m canopy
height, >20 cm mean tree diameter, soil depth >3m) (Supplementary Table S1).
These structural characteristics of forest stature and soil depth are primary
determinants of C storage, probably more so than environmental gradients or
geographic variation per se. Specific transect starts were determined randomly
a priori from aerial imagery, notwithstanding constraints of access and land
ownership. Within six circular sample plots spaced at 25-m intervals along each
transect, we measured standing tree and down wood (dead wood on forest floor)
biomass using standard biometric techniques (stem surveys, planar intercept
transects), then applying region-specific or common allometric equations and
C:biomass conversions for both above-ground and below-ground biomass. We
measured soil depths at three systematic locations in each plot using a graduated
aluminium probe (inference limit 3 m). We extracted a soil core from each plot
using a 6.4-cm open-face peat auger to minimize sample disturbance/compaction,
systematically divided the soil profile into depth intervals, and collected subsamples
from each interval. Subsamples were dried to constant mass and weighed for
bulk density determination, then analysed for C concentration using the dry
combustion method (induction furnace). Standard error in total ecosystem C
storage was computed by propagating standard errors of component pools. For
estuarine and oceanic sites separately, we analysed changes in soil depth and C
pools with distance from the seaward edge using functional data analysis (site-level
regressions for rate-of-change with distance, followed by a one-sample parametric
test on all rates-of-change for strength of positive or negative relationship). We
analysed spatial variations in soil C concentration and bulk density using linear
mixed-effects regression models, assessing fixed effects of depth, distance from
the seaward edge, and geomorphic setting, with a random effect of site to account
for within-site dependence. Ranges for global C storage and emission rates were
obtained using 5th percentile, mean, or 95th percentile estimates from this study
(which accounts for the possibility that biomass and soil C pools differ globally
from our mean values—higher or lower), with an adjusted soil C density based
on a recent global analysis16, combined with recently published low to high
estimates of global mangrove area and deforestation rate1,4,6. See full Methods in
Supplementary Information.
Received 30 September 2010; accepted 23 February 2011;
published online 3 April 2011
References
1. Duke, N. C. et al. A world without mangroves? Science 317, 41–42 (2007).
2. Polidoro, B. A. et al. The loss of species: Mangrove extinction risk and
geographic areas of global concern. PLoS ONE 5, e10095 (2010).
3. Alongi, D. M. Present state and future of the world’s mangrove forests.
Environ. Conserv. 29, 331–349 (2002).
4. Food and Agriculture Organization of the United Nations (FAO). The World’s
Mangroves 1980–2005 (FAO Forestry Paper 153. FAO, 2007).
5. Bouillon, S., Rivera-Monroy, V. H., Twilley, R. R., Kairo, J. G. & Mangroves,
in The Management of Natural Coastal Carbon Sinks (eds Laffoley, D. &
Grimsditch) (IUCN, 2009).
6. Giri, C. et al. Status and distribution of mangrove forests of the world using
earth observation satellite data. Glob. Ecol. Biogeogr. 20, 154–159 (2011).
7. van der Werf, G. R. et al. CO2emissions from forest loss. Nature Geosci. 2,
737–738 (2009).
8. IPCC in The Fourth Assessment Report Climate Change 2007 (eds Pachauri, R.
K. & Reisinger, A.) (IPCC, 2007).
9. Intergovernmental Panel on Climate Change (IPCC) in Good Practice Guidance
for Land use, Land-use Change, and Forestry (eds Penman, J. et al.) (Institute
for Global Environmental Strategies, 2003).
10. Keith, H., Mackey, B. G. & Lindenmayer, D. B. Re-evaluation of forest biomass
carbon stocks and lessons from the world’s most carbon-dense forests.
Proc. Natl Acad. Sci. USA 106, 11635–11640 (2009).
11. Page, S. E. et al. The amount of carbon released from peat and forest fires in
Indonesia during 1997. Nature 420, 61–65 (2002).
12. Page, S. E., Rieley, J. O. & Banks, C. J. Global and regional importance of the
tropical peatland carbon pool. Glob. Change Biol. 17, 798–818 (2011).
13. Murdiyarso, D. M., Hergoualc’h, K. & Verchot, L. V. Opportunities for
reducing greenhouse gas emissions in tropical peatlands. Proc. Natl Acad.
Sci. USA 107, 19655–19660 (2010).
14. Gilman, E. L., Ellison, J., Duke, N. C. & Field, C. Threats to mangroves from
climate change and adaptation options. Aquat. Bot. 89, 237–250 (2008).
15. Alongi, D. M. Mangrove forests: Resilience, protection from tsunamis, and
responses to global climate change. Estuar. Coast Shelf Sci. 76, 1–13 (2008).
16. Kristensen, E., Bouillon, S., Dittmar, T. & Marchand, C. Organic carbon
dynamics in mangrove ecosystems. Aquat. Bot. 89, 201–219 (2008).
17. Komiyama, A., Ong, J. E. & Poungparn, S. Allometry, biomass, and productivity
of mangrove forests. Aquat. Bot. 89, 128–137 (2008).
18. Twilley, R. R., Chen, R. H. & Hargis, T. Carbon sinks in mangroves and
their implications to carbon budget of tropical coastal ecosystems. Water Air
Soil Pollut. 64, 265–288 (1992).
19. Bouillon, S. et al. Mangrove production and carbon sinks: A revision of global
budget estimates. Glob. Biogeochem. Cycles 22, GB2013 (2008).
20. Alongi, D. M. et al. Sediment accumulation and organic material flux in a
managed mangrove ecosystem: Estimates of land–ocean–atmosphere exchange
in peninsular Malaysia. Mar. Geol. 208, 383–402 (2004).
21. Chmura, G. L., Anisfeld, S. C., Cahoon, D. R. & Lynch, J. C. Global carbon
sequestration in tidal, saline wetland soils. Glob. Biogeochem. Cycles 17,
1111 (2003).
22. Eong, O. J. Mangroves—a carbon source and sink. Chemosphere 27,
1097–1107 (1993).
23. Golley, F., Odum, H. T. & Wilson, R. F. The structure and metabolism of a
Puerto Rican red mangrove forest in May. Ecology 43, 9–19 (1962).
24. Fujimoto, K. et al. Belowground carbon storage of Micronesian mangrove
forests. Ecol. Res. 14, 409–413 (1999).
25. Matsui, N. Estimated stocks of organic carbon in mangrove roots and
sediments in Hinchinbrook Channel, Australia. Mangr. Salt Marsh. 2,
199–204 (1998).
26. Sjöling, S., Mohammed, S. M., Lyimo, T. J. & Kyaruzi, J. J. Benthic bacterial
diversity and nutrient processes in mangroves: Impact of deforestation.
Estuar. Coast Shelf Sci. 63, 397–406 (2005).
4NATURE GEOSCIENCE |ADVANCE ONLINE PUBLICATION |www.nature.com/naturegeoscience
© 2011 Macmillan Publishers Limited. All rights reserved.
NATURE GEOSCIENCE DOI: 10.1038/NGEO1123 LETTERS
27. Strangmann, A., Bashan, Y. & Giani, L. Methane in pristine and impaired
mangrove soils and its possible effects on establishment of mangrove seedlings.
Biol. Fertil. Soils 44, 511–519 (2008).
28. Granek, E. & Ruttenberg, B. I. Changes in biotic and abiotic processes following
mangrove clearing. Estuar. Coast Shelf Sci. 80, 555–562 (2008).
29. Hooijer, A., Silvius, M., Wösten, H. & Page, S. PEAT-CO2:Assessment of
CO2Emissions from Drained Peatlands in SE Asia. Delft Hydraulics Report
Q3943 (2006).
30. Church, J. A. et al. Understanding global sea levels: Past, present and future.
Sustain. Sci. 3, 9–22 (2008).
Acknowledgements
We thank our many international partners and field personnel for assistance with
logistics and data collection: Kosrae Island Resource Management Authority; Yap
State Forestry; Orangutan Foundation International; Indonesian Directorate General
for Forest Protection and Nature Conservation; University of Manado and Bogor
Agricultural University, Indonesia; Bangladesh Forest Department; and KPSKSA
(Cilacap, Indonesia). We thank K. Gerow for statistical assistance, and R. Mackenzie,
C. Kryss and J. Bonham for assistance compiling site data. Funding was provided by
USDA Forest Service International Programs and the Australian Agency for International
Development (AusAID).
Author contributions
D.C.D. co-designed the study, collected field data, performed data analyses, and led the
writing of the paper. J.B.K. conceived and co-designed the study, and contributed to data
collection and writing. D.M. co-conceived the study, arranged for and contributed to data
collection, and contributed to writing. S.K. contributed to data collection, data analysis,
and writing. M.S. collected field data and contributed to writing. M.K. co-conceived the
study and contributed to writing.
Additional information
The authors declare no competing financial interests. Supplementary information
accompanies this paper on www.nature.com/naturegeoscience. Reprints and permissions
information is available online at http://npg.nature.com/reprintsandpermissions.
Correspondence and requests for materials should be addressed to D.C.D.
NATURE GEOSCIENCE |ADVANCE ONLINE PUBLICATION |www.nature.com/naturegeoscience 5
© 2011 Macmillan Publishers Limited. All rights reserved.
... Os manguezais atuam como importantes produtores primários do ambiente marinho, transformando nutrientes minerais em matéria orgânica vegetal (fitomassa), que além de prover sustento para a base de teias alimentares costeiras, geram bens e serviços ecossistêmicos sem custos para os usuários ribeirinhos(SCHAEFFER-NOVELLI et al., 2012). Adicionalmente, os manguezais são componentes chave no ciclo do carbono atmosférico, sendo considerados, dentre as florestas tropicais, como a mais rica em carbono(DONATO et al., 2011), tanto na estrutura arbórea quanto no sedimento, atuando como reservatório desse elemento. ...
... Cabe ainda destacar que os manguezais também sustentam inúmeras atividades extrativistas artesanais. Embora a importância desse ecossistema seja indiscutível, observa-se em todo o mundo uma clara tendência de degradação dos manguezais, sendo reportada uma perda de 30-50% da sua área nos últimos 50 anos, o que resulta no grande risco de extinção de aproximadamente 40% das espécies de animais restritas aos manguezais(Luther e Greenburg, 2009;Donato et al., 2011). Corroborando essa observação,Duke et al. (2007) afirmam que, nesse ritmo, em cem anos, os manguezais serão reduzidos a áreas tão pequenas que sua funcionalidade será perdida.O Brasil possui a terceira maior área de manguezal do mundo, com aproximadamente 25.000 km²; no entanto, a forte pressão antrópica, fruto principalmente da carcinicultura, expansão imobiliária e a extração de sal marinho, propiciou uma taxa de degradação dos manguezais de até 0,3% no período compreendido entre 1980 a 2005 (FERNANDES, 2012). ...
... Os manguezais atuam como importantes produtores primários do ambiente marinho, transformando nutrientes minerais em matéria orgânica vegetal (fitomassa), que além de prover sustento para a base de teias alimentares costeiras, geram bens e serviços ecossistêmicos sem custos para os usuários ribeirinhos(SCHAEFFER-NOVELLI et al., 2012). Adicionalmente, os manguezais são componentes chave no ciclo do carbono atmosférico, sendo considerados, dentre as florestas tropicais, como a mais rica em carbono(DONATO et al., 2011), tanto na estrutura arbórea quanto no sedimento, atuando como reservatório desse elemento. ...
... Cabe ainda destacar que os manguezais também sustentam inúmeras atividades extrativistas artesanais. Embora a importância desse ecossistema seja indiscutível, observa-se em todo o mundo uma clara tendência de degradação dos manguezais, sendo reportada uma perda de 30-50% da sua área nos últimos 50 anos, o que resulta no grande risco de extinção de aproximadamente 40% das espécies de animais restritas aos manguezais(Luther e Greenburg, 2009;Donato et al., 2011). Corroborando essa observação,Duke et al. (2007) afirmam que, nesse ritmo, em cem anos, os manguezais serão reduzidos a áreas tão pequenas que sua funcionalidade será perdida.O Brasil possui a terceira maior área de manguezal do mundo, com aproximadamente 25.000 km²; no entanto, a forte pressão antrópica, fruto principalmente da carcinicultura, expansão imobiliária e a extração de sal marinho, propiciou uma taxa de degradação dos manguezais de até 0,3% no período compreendido entre 1980 a 2005 (FERNANDES, 2012). ...
... The tropics also contain two particularly important ecosystems for carbon storage: tropical mangroves, which line the coasts of more than 110 tropical nations (FAO and UNEP 2020b), and forested peatlands, which are especially prevalent in Southeast Asia and have been subject to conversion to palm oil plantations in recent decades (Cazzolla Gatti et al. 2019). These forests store vast amounts of carbon, which is vulnerable to loss (Donato et al. 2011;Goldstein et al. 2020). Tropical forests are being cleared at much higher rates than boreal and temperate forests, emitting vast amounts of carbon. ...
Article
Full-text available
Better Forests, Better Cities evaluates how forests both inside and outside city boundaries benefit cities and their residents, and what actions cities can take to conserve, restore and sustainably manage those forests. This report is the first of its kind comprehensive resource on the connection between cities and forests, synthesizing hundreds of research papers and reports to show how all forest types can deliver a diverse suite of benefits to cities.
... Coastal ecosystems consisting of mangrove forests, tidal salt marshes, and seagrass have a high potential for the carbon stored in living biomass (above and below ground), non-living biomass and soil, known as blue carbon (Howard et al. 2014). According to Murdiyarso et al. (2015) and Donato et al. (2011), mangrove forests can store 3-5 times higher carbon than lowland tropical forests. Based on the estimation of Alongi et al. (2015), mangrove and seagrass areas in Indonesia have carbon potential as much as 3.4 Pg or contribute about 17 % of the total blue carbon potential in the world. ...
Article
Full-text available
Mangrove area is a transitional area with abundant natural resources, providing environmental services for coastal communities in regulating water systems, preventing seawater intrusion, as well as providing oxygen and carbon stock (C-stock). Comprehensive data of mangrove forests in Sambas Regency, West Kalimantan province is very limited. This study aims to monitor the condition of mangrove forests and estimate their potential carbon stocks in Sambas Regency. There are six dominant mangrove species in Sambas Regency, namely Avicennia alba, A. marina , Bruguiera cylindrica, B. gymnorrhiza, Lumnitzera littorea, and Rhizophora apiculata. Vegetation density varies from sparse to dense, ranging from 800-4700 trees per ha with a canopy cover of 55.00-86.63 %. The range of mangrove species diameter values is from 4.39 ±0.69-27.45 ±21.14 cm. Potential C-stock ranged from 7.17 ±0.32-546.67 ±70.83 Mg C•ha-1 with an average of 130.62 ±166.34 Mg C•ha-1. The highest potential of mangrove C-stock was found at the Sebubus location. Mangrove vegetation in this study has a high potential of carbon stock, the potential value close to Kubu Raya Regency, West Kalimantan province, and higher than several mangrove ecosystems in Indonesia. In general, the condition of mangrove vegetation in this area is still good and has great potential for carbon stock. However, protection and sustainable use are needed in conserving the mangrove ecosystem in this area.
... This was also the case for the data set presented in Figures 1b and 1c (Rovai et al., , 2021. However, studies quantifying carbon at deeper depths reported greater carbon stocks (Donato et al., 2011;Sanderman et al., 2018;Sanders et al., 2016). When only looking at the first meter of soil, it makes sense that higher carbon densities are reported in lagoons and carbonate settings (Figure 1) since the SOC they store is not being "diluted" by allochthonous inorganic sediment deposition as reported in terrigenous delta and estuaries. ...
Article
Full-text available
Plain Language Summary Mangrove forests are intertidal ecosystems efficient at trapping carbon in their sediments. While this ecological process is well recognized, the quantity of carbon being deposited is still uncertain. Considering the growing number of studies that have collected samples to estimate carbon burial rates, Breithaupt and Steinmuller (2022, https://doi.org/10.1029/2022GL100177) recently published a meta‐analysis to compile and compare carbon burial between mangrove types. Their study reported great variability between mangrove types based on their sediment supply and geomorphological configuration. Their results are interesting because they go against previous estimates of mangrove carbon stocks distribution. Also, the approach used has the potential to be applied to other components of the mangrove carbon budget. Doing so would improve our fundamental understanding of carbon cycling in mangrove ecosystems. It would also help refine carbon storage estimates for future conservation projects interested in generating carbon credits.
... and Acanthus spp.) species . Mangroves serve as highly productive areas and provide spawning and nursery grounds for migratory species, play a significant role in the global carbon cycle (Donato et al., 2011;Cooray et al., 2021), promote sustainability of fishing communities (Madarasinghe et al., 2020a;Madarasinghe et al., 2020b;zu Ermgassen et al., 2021) with high primary productivity, and protect the coastal zone, preventing erosion and reducing the impact of natural hazards such as tsunamis (Dahdouh-Guebas et al., 2005). ...
Article
1. Among the several threats to the conservation of mangrove ecosystems in most South Asian countries, shrimp farming is predominant. Since the introduction of shrimp farming in Sri Lanka in the 1980s, mangroves on the island’s north-western coast have been continually cleared to create new shrimp farms, leading to a decline in the social-ecological services provided by the mangrove ecosystems. 2. Using aerial (1973) and satellite (1996–2020) images, this study assessed areal changes in mangroves and shrimp farms in the Pambala-Chilaw lagoon complex and Ihala Mahawewa, as well as the ecological footprint of shrimp farming in the study area. 3. Mangroves around the Chilaw lagoon had decreased in areal extent by 45% from 1973 to 2020 of which 92% of this change was attributed to shrimp farming. There was, however, a decrease in the areal extent of shrimp farms from 2001 to 2020, and a corresponding increase in mangroves from 2006 to 2020. 4. The ecological footprint of shrimp farming was assessed by comparing the expected surface ratios with those recorded for shrimp farms with mangroves and surface water bodies in the study area from 1973 to 2020. The results showed that the current shrimp farming was unsustainable (i.e. high ecological footprint). 5. While the results support the current view that there is cause for cautious optimism with mangrove conservation (as evidenced by an increase in mangrove areal extent), it also reveals that semi-intensive shrimp farming in Sri Lanka and probably other similar tropical countries is unsustainable. 6. If immediate actions such as effective regulation of shrimp farming activities and mangrove restoration are not taken, the mangrove ecosystem will continue to decline.
Article
Mangrove forests are reported to be invaded by invasive alien species (IAS). This study was therefore aimed at studying the level of distribution of the IAS, Acacia auriculiformis A. Cunn. ex Benth. in mangrove ecosystems in the southern coast of Sri Lanka and assessing the risk to periphery of mangrove forest by considering the Rekawa mangrove forest as a model site. Growth performances of two mangrove species; Rhizophora mucronata and Avicennia marina in the presence of Acacia plants were also tested under three different competition levels; low, moderate and high. According to the results, infestation of Acacia plants was significant in the southern coast of Sri Lanka, particularly in Matara and Hambantota districts (p<0.05). Species diversity determined as the Simpson diversity index was high (0.77) in the periphery of the Rekawa mangrove forest. Four true mangroves and two associates co-occurring with A. auriculiformis in the periphery could be observed during the field validation experiment. The highest seedling (15.4±2.2 m) and sapling (11.2±2.8 m) densities were reported for A. auriculiformis plants. Dominance, calculated as the importance value index of different species in the mangrove periphery varied from 18.0-120.6 and the latter highest was recorded for Acacia which has the highest relative density (42.1%) and the relative dominance (52.5%). The total leaf area of the Rhizophora plants grown in the high-competition level was significantly lower than that of the control plants while the dry weights at three different competition levels; were significantly higher (p<0.05) than the control. This could be due to the higher root biomass allocation. In Avicennia plants, cumulative shoot height, total leaf area and dry weight of the plants grown at the high-competition level were significantly lower than that of the control plants (p<0.05). A. auriculiformis plants grown with these true mangrove species better performed and did not show any significant deviation from the respective control plants. The level of survival of Acacia was significantly reduced at 25 psu (p<0.05). Early intervention and serious scrutiny are much needed to reverse the possible impacts of IAS on mangrove forests and the need for forest conservation is emphasized.
Article
Three bacterial strains, designated as AS18 T , AS27 and AS39, were obtained from mangrove sediment sampled in Futian district, Shenzhen, PR China. Cells of these strains were Gram-negative rods with no flagella. They were able to grow at 10–42 °C (optimum, 37 °C), at pH 5–9 (optimum, pH 6) and in 1–11 % (w/v) NaCl (optimum, 2 %). Phylogenetic analysis based on 16S rRNA gene sequences indicated that the new isolates were clustered within the genus Mangrovimonas , closely related to Mangrovimonas yunxiaonensis (95.1 % similarity) and Mangrovimonas spongiae (94.7 % similarity). Phylogenomic analysis based on multiple core genes revealed that the three strains were located in a different cluster from other closely related strains of the genus Mangrovimonas . Digital DNA–DNA hybridization, average nucleotide identity and average amino acid identity values calculated from genome sequences between isolates and type strains were lower than 25, 75 and 72 %, respectively. The dominant fatty acids were iso-C 15 : 0 and iso-C 15 : 1 G. The main respiratory quinone was identified as MK-6. The major polar lipids contained phosphatidylethanolamine, two unidentified aminolipids and five unidentified lipids. The results of multiphase taxonomy suggested that the three strains should be assigned to a novel species of the genus Mangrovimonas , for which the name Mangrovimonas futianensis sp. nov. is proposed, with the type strain AS18 T (=GDMCC 1.2739 T =JCM 34871 T ).
Article
Full-text available
Mangrove distribution maps are used for a variety of applications, ranging from estimates of mangrove extent, deforestation rates, quantify carbon stocks, to modelling response to climate change. There are multiple mangrove distribution datasets, which were derived from different remote sensing data and classification methods, and so there are some discrepancies among these datasets, especially with respect to the locations of their range limits. We investigate the latitudinal discrepancies in poleward mangrove range limits represented by these datasets and how these differences translate climatologically considering factors known to control mangrove distributions. We compare four widely used global mangrove distribution maps - the World Atlas of Mangroves, the World Atlas of Mangroves 2, the Global Distribution of Mangroves, the Global Mangrove Watch. We examine differences in climate among 21 range limit positions by analysing a set of bioclimatic variables that have been commonly related to the distribution of mangroves. Global mangrove maps show important discrepancies in the position of poleward range limits. Latitudinal differences between mangrove range limits in the datasets exceed 5°, 7° and 10° in western North America, western Australia and northern West Africa, respectively. In some range limit areas, such as Japan, discrepancies in the position of mangrove range limits in different datasets correspond to differences exceeding 600 mm in annual precipitation and > 10 °C in the minimum temperature of the coldest month. We conclude that dissimilarities in mapping mangrove range limits in different parts of the world can jeopardise inferences of climatic thresholds. We expect that global mapping efforts should prioritise the position of range limits with greater accuracy, ideally combining data from field-based surveys and very high-resolution remote sensing data. An accurate representation of range limits will contribute to better predicting mangrove range dynamics and shifts in response to climate change.
Article
Indonesia is the largest archipelagic country in the world and has vast natural resources. In the maritime sector, efforts to realize the sustainability of natural resources in coastal ecosystems have focused on mangroves and seagrass meadows, also known as blue carbon ecosystems, that have an important role in regulating the Earth's climate. The need for ecosystem-based climate change mitigation combined with economic recovery and improved environment conditions has shifted the motivation and escalated mangrove restoration efforts in Indonesia. As the richest mangrove nation with the greatest mangrove carbon stocks in the world, recently Indonesia has taken significant steps in the land use sector to reduce emissions by acknowledging the ‘true’ value of mangrove carbon and setting priorities for mangrove conservation and restoration within Indonesia’s climate actions. This paper reviews opportunities and challenges in mainstreaming mangrove blue carbon into policy in Indonesia. We evaluate the gaps in regulations and policies and propose pathways for the national blue carbon action. As mangroves are embedded in both forestry and marine sectors and the responsibilities for management lies within several government ministries, an integrated framework is suggested to support the national blue carbon strategy. The Indonesia Blue Carbon Strategy Framework (IBCSF) encompasses three main elements that should be considered in order to address challenges and seize opportunities in blue carbon: coordination, policy and funding.
Article
Full-text available
Mangrove ecosystems are threatened by climate change. We review the state of knowledge of mangrove vulnerability and responses to predicted climate change and consider adaptation options. Based on available evidence, of all the climate change outcomes, relative sea-level rise may be the greatest threat to mangroves. Most mangrove sediment surface elevations are not keeping pace with sea-level rise, although longer term studies from a larger number of regions are needed. Rising sea-level will have the greatest impact on mangroves experiencing net lowering in sediment elevation, where there is limited area for landward migration. The Pacific Islands mangroves have been demonstrated to be at high risk of substantial reductions. There is less certainty over other climate change outcomes and mangrove responses. More research is needed on assessment methods and standard indicators of change in response to effects from climate change, while regional monitoring networks are needed to observe these responses to enable educated adaptation. Adaptation measures can offset anticipated mangrove losses and improve resistance and resilience to climate change. Coastal planning can adapt to facilitate mangrove migration with sea-level rise. Management of activities within the catchment that affect long-term trends in the mangrove sediment elevation, better management of other stressors on mangroves, rehabilitation of degraded mangrove areas, and increases in systems of strategically designed protected area networks that include mangroves and functionally linked ecosystems through representation, replication and refugia, are additional adaptation options.
Article
Full-text available
Mangroves, the only woody halophytes living at the confluence of land and sea, have been heavily used traditionally for food, timber, fuel and medicine, and presently occupy about 181 000 km2 of tropical and subtropical coastline. Over the past 50 years, approximately one-third of the world's mangrove forests have been lost, but most data show very variable loss rates and there is considerable margin of error in most estimates. Mangroves are a valuable ecological and economic resource, being important nursery grounds and breeding sites for birds, fish, crustaceans, shellfish, reptiles and mammals; a renewable source of wood; accumulation sites for sediment, contaminants, carbon and nutrients; and offer protection against coastal erosion. The destruction of mangroves is usually positively related to human population density. Major reasons for destruction are urban development, aquaculture, mining and overexploitation for timber, fish, crustaceans and shellfish. Over the next 25 years, unrestricted clear felling, aquaculture, and overexploitation of fisheries will be the greatest threats, with lesser problems being alteration of hydrology, pollution and global warming. Loss of biodiversity is, and will continue to be, a severe problem as even pristine mangroves are species-poor compared with other tropical ecosystems. The future is not entirely bleak. The number of rehabilitation and restoration projects is increasing worldwide with some countries showing increases in mangrove area. The intensity of coastal aquaculture appears to have levelled off in some parts of the world. Some commercial projects and economic models indicate that mangroves can be used as a sustainable resource, especially for wood. The brightest note is that the rate of population growth is projected to slow during the next 50 years, with a gradual decline thereafter to the end of the century. Mangrove forests will continue to be exploited at current rates to 2025, unless they are seen as a valuable resource to be managed on a sustainable basis. After 2025, the future of mangroves will depend on technological and ecological advances in multi-species silviculture, genetics, and forestry modelling, but the greatest hope for their future is for a reduction in human population growth.
Article
Full-text available
1] Wetlands represent the largest component of the terrestrial biological carbon pool and thus play an important role in global carbon cycles. Most global carbon budgets, however, have focused on dry land ecosystems that extend over large areas and have not accounted for the many small, scattered carbon-storing ecosystems such as tidal saline wetlands. We compiled data for 154 sites in mangroves and salt marshes from the western and eastern Atlantic and Pacific coasts, as well as the Indian Ocean, Mediterranean Ocean, and Gulf of Mexico. The set of sites spans a latitudinal range from 22.4°S in the Indian Ocean to 55.5°N in the northeastern Atlantic. The average soil carbon density of mangrove swamps (0.055 ± 0.004 g cm À3) is significantly higher than the salt marsh average (0.039 ± 0.003 g cm À3). Soil carbon density in mangrove swamps and Spartina patens marshes declines with increasing average annual temperature, probably due to increased decay rates at higher temperatures. In contrast, carbon sequestration rates were not significantly different between mangrove swamps and salt marshes. Variability in sediment accumulation rates within marshes is a major control of carbon sequestration rates masking any relationship with climatic parameters. Globally, these combined wetlands store at least 44.6 Tg C yr À1 and probably more, as detailed areal inventories are not available for salt marshes in China and South America. Much attention has been given to the role of freshwater wetlands, particularly northern peatlands, as carbon sinks. In contrast to peatlands, salt marshes and mangroves release negligible amounts of greenhouse gases and store more carbon per unit area.
Article
Full-text available
Aim Our scientific understanding of the extent and distribution of mangrove forests of the world is inadequate. The available global mangrove databases, compiled using disparate geospatial data sources and national statistics, need to be improved. Here, we mapped the status and distributions of global mangroves using recently available Global Land Survey (GLS) data and the Landsat archive. Methods We interpreted approximately 1000 Landsat scenes using hybrid supervised and unsupervised digital image classification techniques. Each image was normalized for variation in solar angle and earth–sun distance by converting the digital number values to the top-of-the-atmosphere reflectance. Ground truth data and existing maps and databases were used to select training samples and also for iterative labelling. Results were validated using existing GIS data and the published literature to map ‘true mangroves’. Results The total area of mangroves in the year 2000 was 137,760 km2 in 118 countries and territories in the tropical and subtropical regions of the world. Approximately 75% of world's mangroves are found in just 15 countries, and only 6.9% are protected under the existing protected areas network (IUCN I-IV). Our study confirms earlier findings that the biogeographic distribution of mangroves is generally confined to the tropical and subtropical regions and the largest percentage of mangroves is found between 5° N and 5° S latitude. Main conclusions We report that the remaining area of mangrove forest in the world is less than previously thought. Our estimate is 12.3% smaller than the most recent estimate by the Food and Agriculture Organization (FAO) of the United Nations. We present the most comprehensive, globally consistent and highest resolution (30 m) global mangrove database ever created. We developed and used better mapping techniques and data sources and mapped mangroves with better spatial and thematic details than previous studies.
Article
Full-text available
Nearly 50% of terrigenous materials delivered to the world's oceans are delivered through just twenty-one major river systems. These river-dominated coastal margins (including estuarine and shelf ecosystems) are thus important both to the regional enhancement of productivity and to the global flux of C that is observed in land-margin ecosystems. The tropical regions of the biosphere are the most biogeochemically active coastal regions and represent potentially important sinks of C in the biosphere. Rates of net primary productivity and biomass accumulation depend on a combination of global factors such as latitude and local factors such as hydrology. The global storage of C in mangrove biomass is estimated at 4.03 Pg C; and 70% of this C occurs in coastal margins from 0 to 10 latitude. The average rate of wood production is 12.08 Mg ha–1 yr–1, which is equivalent to a global estimate of 0.16 Pg C/yr stored in mangrove biomass. Together with carbon accumulation in mangrove sediments (0.02 Pg C/yr), the net ecosystem production in mangroves is about 0.18 Pg C/yr. Global estimates of export from coastal wetlands is about 0.08 Pg C/yr compared to input of 0.36 Pg C/yr from rivers to coastal ecosystems. Total allochthonous input of 0.44 Pg C/yr is lower than in situ production of 6.65 Pg C/yr. The trophic condition of coastal ecosystems depends on the fate of this total supply of 7.09 Pg C/yr as either contributing to system respiration, or becoming permanently stored in sediments. Accumulation of carbon in coastal sediments is only 0.41 Pg C/yr; about 6% of the total input. The NEP of coastal wetlands also contribute to the C sink of coastal margins, but the source of this C is part of the terrestrial C exchange with the atmosphere. Accumulation of C in wood and sediments of coastal wetlands is 0.205 Pg C/yr, half the estimate for sequestering of C in coastal sediments. Burial of C in shelf sediments is probably underestimated, particularly in tropical river-dominated coastal margins. Better estimates of these two C sinks in the tropics, coastal wetlands and shelf sediments, is needed to better understand the contribution of coastal ecosystems to the global carbon budget.
Article
Full-text available
The coastal zone has changed profoundly during the 20th century and, as a result, society is becoming increasingly vulnerable to the impact of sea-level rise and variability. This demands improved understanding to facilitate appropriate planning to minimise potential losses. With this in mind, the World Climate Research Programme organised a workshop (held in June 2006) to document current understanding and to identify research and observations required to reduce current uncertainties associated with sea-level rise and variability. While sea levels have varied by over 120m during glacial/interglacial cycles, there has been little net rise over the past several millennia until the 19th century and early 20th century, when geological and tide-gauge data indicate an increase in the rate of sea-level rise. Recent satellite-altimeter data and tide-gauge data have indicated that sea levels are now rising at over 3mmyear−1. The major contributions to 20th and 21st century sea-level rise are thought to be a result of ocean thermal expansion and the melting of glaciers and ice caps. Ice sheets are thought to have been a minor contributor to 20th century sea-level rise, but are potentially the largest contributor in the longer term. Sea levels are currently rising at the upper limit of the projections of the Third Assessment Report of the Intergovernmental Panel on Climate Change (TAR IPCC), and there is increasing concern of potentially large ice-sheet contributions during the 21st century and beyond, particularly if greenhouse gas emissions continue unabated. A suite of ongoing satellite and in situ observational activities need to be sustained and new activities supported. To the extent that we are able to sustain these observations, research programmes utilising the resulting data should be able to significantly improve our understanding and narrow projections of future sea-level rise and variability.
Article
Accurate inventory of tropical peatland is important in order to (a) determine the magnitude of the carbon pool; (b) estimate the scale of transfers of peat-derived greenhouse gases to the atmosphere resulting from land use change; and (c) support carbon emissions reduction policies. We review available information on tropical peatland area and thickness and calculate peat volume and carbon content in order to determine their best estimates and ranges of variation. Our best estimate of tropical peatland area is 441 025 km 2 ($11% of global peatland area) of which 247 778 km 2 (56%) is in Southeast Asia. We estimate the volume of tropical peat to be 1758 Gm 3 ($ 18–25% of global peat volume) with 1359 Gm 3 in Southeast Asia (77% of all tropical peat). This new assessment reveals a larger tropical peatland carbon pool than previous estimates, with a best estimate of 88.6 Gt (range 81.7–91.9 Gt) equal to 15–19% of the global peat carbon pool. Of this, 68.5 Gt (77%) is in Southeast Asia, equal to 11–14% of global peat carbon. A single country, Indonesia, has the largest share of tropical peat carbon (57.4 Gt, 65%), followed by Malaysia (9.1 Gt, 10%). These data are used to provide revised estimates for Indonesian and Malaysian forest soil carbon pools of 77 and 15 Gt, respectively, and total forest carbon pools (biomass plus soil) of 97 and 19 Gt. Peat carbon contributes 60% to the total forest soil carbon pool in Malaysia and 74% in Indonesia. These results emphasize the prominent global and regional roles played by the tropical peat carbon pool and the importance of including this pool in national and regional assessments of terrestrial carbon stocks and the prediction of peat-derived greenhouse gas emissions.
Article
Accurate inventory of tropical peatland is important in order to (a) determine the magnitude of the carbon pool; (b) estimate the scale of transfers of peat-derived greenhouse gases to the atmosphere resulting from land use change; and (c) support carbon emissions reduction policies. We review available information on tropical peatland area and thickness and calculate peat volume and carbon content in order to determine their best estimates and ranges of variation. Our best estimate of tropical peatland area is 441 025 km2 (∼11% of global peatland area) of which 247 778 km2 (56%) is in Southeast Asia. We estimate the volume of tropical peat to be 1758 Gm3 (∼18–25% of global peat volume) with 1359 Gm3 in Southeast Asia (77% of all tropical peat). This new assessment reveals a larger tropical peatland carbon pool than previous estimates, with a best estimate of 88.6 Gt (range 81.7–91.9 Gt) equal to 15–19% of the global peat carbon pool. Of this, 68.5 Gt (77%) is in Southeast Asia, equal to 11–14% of global peat carbon. A single country, Indonesia, has the largest share of tropical peat carbon (57.4 Gt, 65%), followed by Malaysia (9.1 Gt, 10%). These data are used to provide revised estimates for Indonesian and Malaysian forest soil carbon pools of 77 and 15 Gt, respectively, and total forest carbon pools (biomass plus soil) of 97 and 19 Gt. Peat carbon contributes 60% to the total forest soil carbon pool in Malaysia and 74% in Indonesia. These results emphasize the prominent global and regional roles played by the tropical peat carbon pool and the importance of including this pool in national and regional assessments of terrestrial carbon stocks and the prediction of peat-derived greenhouse gas emissions.