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Global peatland dynamics since the Last Glacial Maximum
Zicheng Yu,
1
Julie Loisel,
1
Daniel P. Brosseau,
1
David W. Beilman,
2
and Stephanie J. Hunt
1
Received 11 April 2010; revised 26 May 2010; accepted 7 June 2010; published 9 July 2010.
[1] Here we present a new data synthesis of global peatland
ages, area changes, and carbon (C) pool changes since the
Last Glacial Maximum, along with a new peatland map and
total C pool estimates. The data show different controls of
peatland expansion and C accumulation in different regions.
We estimate that northern peatlands have accumulated
547 (473–621) GtC, showing maximum accumulation in
the early Holocene in response to high summer insolation
and strong summer – winter climate seasonality. Tropical
peatlands have accumulated 50 (44–55) GtC, with rapid
rates about 8000–4000 years ago affected by a high and
more stable sea level, a strong summer monsoon, and
before the intensification of El Niño. Southern peatlands,
mostly in Patagonia, South America, have accumulated
15 (13–18) GtC, with rapid accumulation during the
Antarctic Thermal Maximum in the late glacial, and during
the midHolocene thermal maximum. This is the first
comparison of peatland dynamics among these global
regions. Our analysis shows that a diversity of drivers at
different times have significantly impacted the global C
cycle, through the contribution of peatlands to atmospheric
CH
4
budgets and the history of peatland CO
2
exchange
with the atmosphere. Citation: Yu, Z., J. Loisel, D. P. Brosseau,
D. W. Beilman, and S. J. Hunt (2010), Global peatland dynamics
since the Last Glacial Maximum, Geophys. Res. Lett., 37, L13402,
doi:10.1029/2010GL043584.
1. Introduction
[2] Peatlands worldwide, in particular northern (boreal
and subarctic) peatlands, have been shown to be important
players in the global carbon (C) cycle in the recent past. Their
possible trajectories in a changing climate have become a
focus of global C cycle research, and a number of modeling
groups have started to incorporate peatlands into global
models [Frolking et al., 2009;Kleinen et al., 2010]. However,
we still lack a fundamental understanding of broadscale
controls over peatland expansion and C accumulation in
different regions. Also, basic estimates of the size of the
peat C pool are variable. For example, for northern peatlands,
by far the beststudied region, estimates range from 270 to
450 GtC [Gorham, 1991; Clymo et al., 1998; Turunen et al.,
2002]. Further, although progress has been made for wet-
lands in general [Matthews and Fung, 1987] and for northern
peatlands [MacDonald et al., 2006], an ecosystembased
digital map of global peatland regions is still lacking at a
scale useful for modeling and synthesis. The need for syn-
thesized data at a global scale, and the need for a better
understanding of processes and controls, currently limit
efforts to incorporate peatlands into global models to better
constrain potential carboncycle – climate interactions and
feedbacks [Joos et al., 2004; Friedlingstein et al., 2006].
[3] Here we present the first results of our synthesis of
global peatland inception age and C accumulation data, and
we discuss the broadscale controls of peatland dynamics in
different regions since the Last Glacial Maximum (LGM).
The objectives of this paper are (1) to present a new global
scale map of major peatland regions; (2) to present the first
global peatbased database of peatland initiation and area
change since the LGM; (3) to document C accumulation var-
iations and associated broadscale controls in different regions
(northern, tropical and southern); and (4) to discuss the roles
and implications of peatlands for the global C cycle. The
presented map and database will provide a valuable founda-
tion for global C cycle modeling and synthesis activities.
2. Data Sources and Data Analysis
[4] Data sources for the peatland map (Figure 1) were
based on the most uptodate information available from
individual countries or regions in major peatland regions
of the world (see Table S1 of Text S1 in the auxiliary
material).
3
Some of these peatland data sets are available
in shapefile or raster digital formats, including those from
Canada, Tasmania and part of Russia. For other regions, we
mapped peatlands either as histosols and/or gleysols layers
as in the Harmonized World Soil Database V1.1 or from
digitized paper sources. The peatland areas we used in the
peat C pool calculations were derived from the literature
(see Table 1 and the auxiliary material), rather than directly
from the new peatland map presented. This is necessary
because the peatland map shows peatlandabundant regions
where peatlands cover at least 5% of the landmass, but
accurate true peatland coverage and distribution is not avail-
able for many mapped regions.
[5] The radiocarbondated (
14
C) ages of basal peat, indi-
cating the onset of peataccumulating conditions, were
taken from original published sources for tropical peatlands
and southern peatlands (see Table S2 of Text S1) and from
a previous synthesis for northern peatlands (Figure 2)
[MacDonald et al., 2006]. All
14
C dates were calibrated to
calendar years with the IntCal04 dataset [Reimer et al.,
2004]. The frequency histograms were constructed by add-
ing the number of dates within 2s range (95% probability)
of calibrated ages at 10year intervals. The frequencies were
1
Department of Earth and Environmental Sciences, Lehigh
University, Bethlehem, Pennsylvania, USA.
2
Department of Geography, University of Hawai’iatMānoa,
Honolulu, Hawaii, USA.
Copyright 2010 by the American Geophysical Union.
00948276/10/2010GL043584
3
Auxiliary materials are available in the HTML. doi:10.1029/
2010GL043584.
GEOPHYSICAL RESEARCH LETTERS, VOL. 37, L13402, doi:10.1029/2010GL043584, 2010
L13402 1of5

then added to calculate cumulative percentages. We inter-
pret the frequency of basal dates as reflecting changes in
peatland area over time, under the assumption that individual
peatlands expanded linearly in their area since their initial
formation. Detailed lateral expansion studies of individual
peatlands, and especially a better processlevel understanding
of peatland expansion, would help us refine the temporal
patterns of regional peatland area increase [Korhola et al.,
2010]. For example, the higher rates of peatland initiation
and peat carbon accumulation we observe during the early
Holocene [Yu et al., 2009] would likely have also caused
much higher rate of peatland area expansion of individual
peatlands at that time, but it is clear that more basinscale
studies are needed.
[6] To estimate regional averages of apparent C accu-
mulation rates, we calculated timeweighted rates for each
available site in 1000year bins, either from raw data includ-
ing multiple calibrated ages and bulk density measurements/
estimates or from published C accumulation rates. We then
averaged the rates in each 1000year bin for each region
(northern, tropical and southern peatlands). These recon-
structed rates of peat C accumulation from peat cores are
apparent rates in that they have been affected by total deep
C decomposition since peat formation, often spanning
thousands of years, and therefore underestimate by some
degree the true rate of past C uptake (but see Z. C. Yu
(Holocene carbon flux histories of the world’s peatlands:
Global carboncycle implications, submitted to Holocene,
2010)).
[7] Changes in peat C pools at 1000year intervals in
different regions were calculated as the product of the
peatland area at that time, as inferred from cumulative basal
age frequency and peatland total area at the present, and
C accumulation rates for each 1000year bin. These Cpool
intervals were added to generate cumulative C pools. The
C pool ranges were estimated on the basis of standard
errors of the mean C accumulation rates, which represent a
minimum estimate of error, as other uncertainties in basal
ages, possible nonlinear peatland expansion, and peatland
areas are not included.
3. Results
[8] The peatland initiation patterns for northern peatlands
show a peak in the early Holocene around 119ka(1ka=
1000 cal year BP) (Figure 2b) [MacDonald et al., 2006]
(n = 1516). The C accumulation rates in many northern
peatlands also show a peak in the early Holocene (Figure 2c),
with a rate of about 25 g C m
−2
yr
−1
. The overall time
weighted average rate is 18.6 g C m
−2
yr
−1
during the
Holocene based on 33 sites from northern peatlands [Yu et al.,
2009].
Figure 1. Global map of peatland regions and peatland study sites with basal peat ages (small dots; colors showing the
ages of peatland initiation: black <8 ka, red 812 ka, and blue >12 ka) and detailed carbon accumulation rates (large open
triangles). The peatland map was compiled based on the most uptodate and detailed information available from individual
countries and regions (see Text S1 for detailed sources). Three main peatland regions are northern peatlands, tropical
peatlands and southern peatlands, delineated at 30° N/S latitudes. Two insets show details of peatland areas and study sites
in Southeast Asia and Patagonia.
Table 1. Summary Results From Northern, Tropical and Southern
Peatlands
a
Area
(km
2
)
C Pool (GtC)
(Range)
Holocene C Rate
(gC m
−2
yr
−1
)
Northern peatlands 4,000,000 547 (473–621) 18.6
Tropical peatlands 368,500 50 (44–55) 12.8
Southern peatlands
(Patagonia)
45,000 15 (13–18) 22.0
a
References for peatland area data are in Text S1, available online.
YU ET AL.: GLOBAL PEATLANDS SINCE THE LGM L13402L13402
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