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Journal ArticleDOI

Holocene carbon emissions as a result of anthropogenic land cover change

TL;DR: In this article, the authors developed a new, annually resolved inventory of anthropogenic land cover change from 8000 years ago to the beginning of large-scale industrialization (ad 1850), which is based on a simple relationship between population and land use observed in several European countries over preindustrial time.
Abstract: Humans have altered the Earth’s land surface since the Paleolithic mainly by clearing woody vegetation first to improve hunting and gathering opportunities, and later to provide agricultural cropland. In the Holocene, agriculture was established on nearly all continents and led to widespread modification of terrestrial ecosystems. To quantify the role that humans played in the global carbon cycle over the Holocene, we developed a new, annually resolved inventory of anthropogenic land cover change from 8000 years ago to the beginning of large-scale industrialization (ad 1850). This inventory is based on a simple relationship between population and land use observed in several European countries over preindustrial time. Using this data set, and an alternative scenario based on the HYDE 3.1 land use data base, we forced the LPJ DGVM in a series of continuous simulations to evaluate the impacts of ALCC on terrestrial carbon storage during the preindustrial Holocene. Our model setup allowed us to quantify the importance of land degradation caused by repeated episodes of land use followed by abandonment. By 3 ka BP, cumulative carbon emissions caused by anthropogenic land cover change in our new scenario ranged between 84 and 102 Pg, translating to c. 7 ppm of atmospheric CO2. By ad 1850, emissions were 325–357 Pg in the new scenario, in contrast to 137–189 Pg when driven by HYDE. Regional events that resulted in local emissions or uptake of carbon were often balanced by contrasting patterns in other parts of the world. While we cannot close the carbon budget in the current study, simulated cumulative anthropogenic emissions over the preindustrial Holocene are consistent with the ice core record of atmospheric d13CO2 and support the hypothesis that anthropogenic activities led to the stabilization of atmospheric CO2 concentrations at a level that made the world substantially warmer than it otherwise would be.

Summary (3 min read)

Introduction

  • Because most countries lack reliable land use surveys prior to the middle of the twentieth century, these reconstructions rely on hindcasting techniques based on estimated historical populations and assumptions about how people used the land.
  • This finding has led to the conclusion that forest clearance by humans could not have played a significant role in the gradual rise of CO 2 concentrations that began during the mid- dle Holocene about 8 ka (cal. BP; 8000 yr before ad 1950).
  • The assumption that land use per capita has remained constant over time is not supported by published evidence or by widely accepted land use theory.

Holocene Special Issue

  • At Helmholtz-Zentrum Geesthacht, Zentrum für Material- und Küstenforschung GmbH on July 2, 2013hol.sagepub.comDownloaded from 776 The Holocene 21(5) and labor-intensive methods of extracting more food per unit area farmed, so that land use per capita decreases as population density increases.
  • In the earliest and least populated phase of the Holocene, most humans were hunter-gatherers, and practiced a nomadic or semi-sedentary lifestyle (e.g. Bellwood, 2005; Mazoyer and Roudart, 2006; Richerson et al., 2001).
  • Rather, simulations of preindustrial land use should take into account existing scientific knowledge and theory on how humans are known to have cleared land in the past.
  • Here the authors reconstruct carbon emissions caused by ALCC over the Holocene based on contrasting scenarios of population and anthropogenic land use over time, including a new empirical model in which per capita ALCC declines over time and a conventional model that holds per capita ALCC roughly constant over time.

Materials and methods

  • To extend their population time series for each region from 3 ka back to 8 ka, the authors used a time series of global population simulated by the Global Land Use and Technological Evolution Simulator (GLUES; Lemmen, 2009; Wirtz and Lemmen, 2003).
  • The authors simulated ALCC based on population data, maps of land suitability for agriculture and pasture, and a simple relationship between population density and preindustrial land use (Kaplan et al., 2009).
  • The LPJ DGVM is driven by spatially and temporally explicit data sets of climate, soil properties and atmospheric CO 2 concen- trations (Sitch et al., 2003).
  • For the simulations with the HYDE land use data, if the fraction of land under anthropogenic land use becomes greater than the calculated usable fraction, then the unusable fraction is reduced to reflect the remaining unused portion.

Scenarios of ALCC

  • The two ALCC scenarios used in this study differ substantially .
  • The slight increase in per capita land use with time seen in HYDE reflects the country-level trends in per capita land use observed during the late twentieth century upon which this data.

Land use simulation Pre-1850

  • B Based on conversion of vegetation reconstructions of Matthews (1983) and Leemans and Cramer (1991). at Helmholtz-Zentrum Geesthacht, Zentrum für Material- und Küstenforschung GmbH on July 2, 2013hol.sagepub.comDownloaded from 786 The Holocene 21(5) for this time period .
  • During the last 200 years of their model runs (ad 1650 to 1850) carbon emissions reach similar rates for both ALCC data sets , as total emissions reach 166 Pg C for the HYDE scenario and 343 Pg C for the KK10 scenario.
  • Table 4 presents preindustrial emissions from ALCC from a number of other studies.
  • The carbon emission numbers derived in this analysis are substantially higher than those from most previous simulations.
  • For the preindustrial era, previous estimates have ranged between 48 and 153 Pg C, whereas their simulations based on the KK10 and HYDE data sets indicate that releases of 325– 357 Pg C and 137–189 Pg C could have occurred, respectively.

Discussion

  • Large differences between the two ALCC data sets in this study highlight the remarkable amount of uncertainty in estimating the magnitude and overall trend of Holocene ALCC.
  • In the following sections, the authors discuss their results in the context of previous attempts to quantify Holocene ALCC carbon emissions, both from modeling and topdown estimates and they provide evidence to support their model simulations based on the ice core record of atmospheric CO 2 con- centrations and d13CO 2 .
  • In general, previous estimates of preindustrial carbon emissions from ALCC appear to be substantial underestimates resulting from the assumption that per capita land use has remained constant for the past 8000 years, an assumption not in agreement with observations (Boserup, 1965, 1981; Chao, 1986; Ellis and Wang, 1997; Ruddiman and Ellis, 2009; Ruddiman et al., forthcoming).
  • Of the few ‘natural’ forest patches that remain, most have survived because they were in terrain too remote, steep, or otherwise uneconomical to be cut, and their carbon density would thus be lower than in the more productive lowland soils used first for agriculture and pasture (Ellis and Ramankutty, 2008).

Evaluation of the ALCC scenarios

  • The lack of continental- to global-scale syntheses of evidence for human impact on the Earth’s land surface makes it difficult at this point to perform anything more than a superficial, qualitative evaluation of their ALCC scenario results.
  • Developing a continuous synthesis of global human impact at the regional level is currently a major focus of interdisciplinary research coordination, e.g. through the AIMES/PAGES IHOPE program.
  • These ongoing efforts should be combined with existing surveys of human impact over the Holocene using multiple proxies (e.g. Dearing, 2006; Gaillard et al., 2010; Hellman et al., 2008; Sugita, 2007a, b), and with archaeological data syntheses (e.g. Weninger et al., 2006; Zimmermann et al., 2004) that have traditionally been overlooked by the natural science community.
  • At the site scale, there is considerable paleoecological and archaeological evidence for early extensive human land use in, e.g. Andes (ChepstowLustry and Winfield, 2000), Mesoamerica (Pohl et al., 1996), Europe (Tinner et al., 2007), and China (Ren, 2000).
  • While syntheses of charcoal records from remote areas of the globe attribute Holocene trends in biomass burning to climatic changes rather than ALCC (Marlon et al., 2008; Power et al., 2008), other regional syntheses (e.g. McWethy et al., 2009; Nevle and Bird, 2008) show that biomass burning correlates strongly with the rise and fall of human societies.

Future perspectives and conclusions

  • Holocene carbon cycle modeling can be improved in multiple ways to achieve more accurate quantification of carbon balances throughout history.
  • Finally, a number of efforts are currently underway to improve the functionality of DGVMs to more accurately model global carbon exchanges, e.g. by including a representation of peatland dynamics or using more plant functional types.
  • Carbon emissions as a result of anthropogenic land use over the preindustrial Holocene could have had a very substantial impact on the global carbon cycle.
  • Their results favor far larger early anthropogenic carbon emissions than previous estimates (which are a factor of 3–7 smaller).

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Original
Kaplan, J.O.; Krumhardt, K.; Ellis, E.C.; Ruddiman, W.F.; Lemmen, C.;
Klein Goldewijk, K.:
Holocene carbon emissions as a result of anthropogenic land cover
change
In: The Holocene (2010) SAGE Publications
DOI: 10.1177/0959683610386983

http://hol.sagepub.com/
The Holocene
http://hol.sagepub.com/content/21/5/775
The online version of this article can be found at:
DOI: 10.1177/0959683610386983
2011 21: 775 originally published online 30 December 2010The Holocene
Jed O. Kaplan, Kristen M. Krumhardt, Erle C. Ellis, William F. Ruddiman, Carsten Lemmen and Kees Klein Goldewijk
Holocene carbon emissions as a result of anthropogenic land cover change
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- Dec 30, 2010 OnlineFirst Version of Record
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Holocene carbon emissions as a result
of anthropogenic land cover change
Jed O. Kaplan,
1
Kristen M. Krumhardt,
1
Erle C. Ellis,
2
William
F. Ruddiman,
3
Carsten Lemmen
4
and Kees Klein Goldewijk
5
Abstract
Humans have altered the Earth’s land surface since the Paleolithic mainly by clearing woody vegetation first to improve hunting and gathering opportunities,
and later to provide agricultural cropland. In the Holocene, agriculture was established on nearly all continents and led to widespread modification of
terrestrial ecosystems. To quantify the role that humans played in the global carbon cycle over the Holocene, we developed a new, annually resolved
inventory of anthropogenic land cover change from 8000 years ago to the beginning of large-scale industrialization (ad 1850). This inventory is based on a
simple relationship between population and land use observed in several European countries over preindustrial time. Using this data set, and an alternative
scenario based on the HYDE 3.1 land use data base, we forced the LPJ dynamic global vegetation model in a series of continuous simulations to evaluate
the impacts of humans on terrestrial carbon storage during the preindustrial Holocene. Our model setup allowed us to quantify the importance of land
degradation caused by repeated episodes of land use followed by abandonment. By 3 ka BP, cumulative carbon emissions caused by anthropogenic land
cover change in our new scenario ranged between 84 and 102 Pg, translating to c. 7 ppm of atmospheric CO
2
. By ad 1850, emissions were 325–357
Pg in the new scenario, in contrast to 137–189 Pg when driven by HYDE. Regional events that resulted in local emissions or uptake of carbon were
often balanced by contrasting patterns in other parts of the world. While we cannot close the carbon budget in the current study, simulated cumulative
anthropogenic emissions over the preindustrial Holocene are consistent with the ice core record of atmospheric d
13
CO
2
and support the hypothesis that
anthropogenic activities led to the stabilization of atmospheric CO
2
concentrations at a level that made the world substantially warmer than it otherwise
would be.
Keywords
agricultural intensification, anthropogenic land cover change, dynamic global vegetation model, global carbon cycle, Holocene CO
2
, prehistory
The Holocene
21(5) 775
–791
© The Author(s) 2010
Reprints and permission:
sagepub.co.uk/journalsPermissions.nav
DOI: 10.1177/0959683610386983
hol.sagepub.com
Introduction
Several attempts have been made to reconstruct the history of
anthropogenically induced land cover change (ALCC), and in
some cases the resulting CO
2
emissions, both in the industrial
era and in preceding centuries ( Houghton, 2003; Houghton
et al., 1999; Klein Goldewijk, 2001; Pongratz et al., 2008;
Ramankutty and Foley, 1998, 1999; Strassmann et al., 2008).
Because most countries lack reliable land use surveys prior to
the middle of the twentieth century, these reconstructions rely
on hindcasting techniques based on estimated historical popu-
lations and assumptions about how people used the land.
A common hindcasting method, linear scaling, first estab-
lishes the quantitative link between modern populations and
land use data (typically within the interval 1960–2005) and
then uses prior (historical) population data to estimate past
land use by assuming near-constant land use per person (Klein
Goldewijk, 2001; Klein Goldewijk et al., 2010a, b; Pongratz
et al., 2008).
Land use estimates based on this assumption inevitably show
little human land use prior to the exponential population explo-
sion that began near
ad 1500 and accelerated through the present
day (Figure 1). This finding has led to the conclusion that forest
clearance by humans could not have played a significant role in
the gradual rise of CO
2
concentrations that began during the mid-
dle Holocene about 8 ka (cal. BP; 8000 yr before ad 1950). Atmo-
spheric CO
2
increased by ~22 ppm from the 8 ka minimum to the
start of the industrial era (Ruddiman, 2007).
The assumption that land use per capita has remained con-
stant over time is not supported by published evidence or by
widely accepted land use theory. Archeologists, paleoecologists,
paleobotanists, anthropologists, and other field-based research-
ers have repeatedly shown that from the late Paleolithic to the
beginning of widespread industrialization, the first human resi-
dents and especially farmers in any region used far more land per
person than those after them, and that land use per capita has
decreased over time as populations increase, land availability per
capita declines, technologies improve, and land use intensifies
(e.g. Johnston, 2003; for reviews see, e.g. Kaplan et al., 2009;
Ruddiman and Ellis, 2009). Indeed, Boserup (1965, 1981) syn-
thesized evidence across field studies to develop the most widely
used general model of land use intensification, in which popula-
tion pressure drives farmers to implement ever-more innovative
1
Ecole Polytechnique Fédérale de Lausanne, Switzerland
2
University of Maryland Baltimore County, USA
3
University of Virginia, USA
4
Institut für Küstenforschung, Germany
5
Netherlands Environmental Assessment Agency, The Netherlands
Received 7 June 2010; revised manuscript accepted 27 July 2010
Corresponding author:
Jed O. Kaplan, ARVE Group, Environmental Engineering Institute, Ecole
Polytechnique Fédérale de Lausanne, Station 2, 1015 Lausanne, Switzerland
Email: jed.kaplan@epfl.ch
Holocene Special Issue
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776 The Holocene 21(5)
and labor-intensive methods of extracting more food per unit
area farmed, so that land use per capita decreases as population
density increases.
Regional historical observations from Europe and China sup-
port the theory that land cover change per capita fell sharply over
at least the last 2000 years (Chao, 1986; Ellis and Wang, 1997;
Ervynck et al., 2007; Hermy and Verheyen, 2007; Kaplan et al.,
2009; McEvedy and Jones, 1978; Ruddiman, 2003; Ruddiman
and Ellis, 2009; Ruddiman et al., forthcoming; Verheyen
et al., 1999). In the earliest and least populated phase of the
Holocene, most humans were hunter-gatherers, and practiced a
nomadic or semi-sedentary lifestyle (e.g. Bellwood, 2005;
Mazoyer and Roudart, 2006; Richerson et al., 2001). Under these
conditions, forest clearing by fire was extensive, both from fires
set intentionally to improve foraging conditions, and by the mere
presence of humans with anthropogenic fire and livestock (for a
review see Williams, 2008). Once agriculture was established, per
capita land use decreased steadily. Ruddiman and Ellis (2009)
summarized evidence on population and land clearing to suggest
that per capita land use has decreased ten-fold since the mid
Holocene. Likewise, in Lemmen’s (2009) model of prehistoric
technical and societal changes, per capita land use decreased by a
factor of seven from the emergence of agriculture at 11 ka to 3 ka.
In short, the assumption of constant land use per capita in pre-
industrial times is unjustified. Given that early farmers could have
been using more than ten times as much land per capita as later
ones, it is premature to conclude that human activities have played
little or no role in the preindustrial (before ad 1850) CO
2
increase
(Figure 1). Rather, simulations of preindustrial land use should
take into account existing scientific knowledge and theory on
how humans are known to have cleared land in the past. Such
studies may then provide meaningful tests of the hypothesis that
early agriculture caused the unprecedented interglacial CO
2
increases observed 8000 years ago (Ruddiman, 2003; see also
Ruddiman et al., forthcoming). Olofsson and Hickler (2008)
made a first attempt in this direction, but their study assumed con-
stant per capita land use after 1700, and it lumped earlier clear-
ance into two categories: 90% clearance for ‘states and empires’,
and very little clearance for all other ‘agricultural groups’.
Here we reconstruct carbon emissions caused by ALCC over
the Holocene based on contrasting scenarios of population and
anthropogenic land use over time, including a new empirical
model in which per capita ALCC declines over time and a con-
ventional model that holds per capita ALCC roughly constant
over time. These scenarios are used to drive a dynamic global
vegetation model to estimate regional and global patterns of
changes in terrestrial carbon storage through the last 8000
years. The resulting differences in global and regional patterns of
ALCC and carbon emissions are then contrasted to highlight the
global importance of assuming constant land use per capita versus
2900
100
200
300
400
500
600
700
800
900
1000
1100
1200
1300
200040006000 15001000
BC
year
500 1000
AD
100
200
300
400
500
600
700
800
900
1000
1100
1200
1300
Human population (millions)
1250 15001750
250
260
270
280
Atmospheric CO
2
concentration (ppm)
400060008000 10001500200025003000
cal. yr BP
250
260
270
280
2900
250500750
Population from HYDE
Population from KK10
Population range from literature
Spline regression through CO2 data
Dome Fuji
EPICA DML
EPICA Dome C (Flückiger)
EPICA Dome C (Monin)
EPICA South Pole
Law Dome firn and ice cores
Taylor Dome
Vostok
1850
100
Figure 1. Human population history and record of atmospheric CO
2
concentrations from 8 ka to ad 1850. Time series of population data
from 209 regions was used to produce the KK10 ALCC data set. The gray area around the population estimates represents the range of
population estimates in literature. The smoothed spline fit to ice core and firn CO
2
records (see Krumhardt and Kaplan, 2010) was used to
drive the LPJ DGVM
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Kaplan et al. 777
models that incorporate changes in per capita land use with popu-
lation density. Finally, we discuss how the ALCC emission esti-
mates derived here relate to independent constraints on the global
carbon cycle during the Holocene.
Materials and methods
In order to quantify ALCC emissions over the Holocene we
(1) developed a new scenario of global ALCC from 8 ka bp
(calendar years before ad 1950) to ad 1850 based on existing
methodology, (2) assembled climate, soils and CO
2
data used to
drive a Dynamic Global Vegetation Model (DGVM), (3) modified
the LPJ DGVM to handle ALCC and made several other small
improvements to the model, and (4) ran the model in a number of
experiments to characterize the range of possible emissions sce-
narios. Development of the new ALCC time series involved prepa-
ration of a new data base of estimates of prehistoric and historical
global population. We assembled new driver data sets of CO
2
con-
centrations and meteorology based on the latest available data sets.
The modifications to the LPJ DGVM included a novel mechanism
to simulate transient land use and shifting cultivation and an
improved geographic distribution of soil organic matter based on
compilation of observations. Methods specifically concerning our
treatment of ALCC in the DGVM are described below. A detailed
description of the rest of our methodology is contained in the sup-
plementary material to this article, available online.
Anthropogenic land cover change (ALCC)
The primary driver of Holocene CO
2
emissions in this study was
a gridded time series of global ALCC. We used two ALCC data
sets to drive LPJ DGVM, (1) the HYDE 3.1 data base (Klein
Goldewijk et al., 2010b) and (2) a new data set developed for this
study, hereinafter called the Kaplan and Krumhardt 2010 (KK10)
data set. The KK10 scenario makes the central assumption that
humans use land more intensively in all regions of the world with
increasing population density and land scarceness (Boserup,
1965). In contrast, the standard version of the Historical Data base
of the Global Environment (HYDE; Klein Goldewijk et al.,
2010b), is based on a nearly linear relationship between popula-
tion and area of land under agriculture, and shows very little vari-
ation in per capita land use. Here, we use the HYDE 3.1 data set
of ALCC (crop + pasture fractions) to provide a comparison to
our results with the KK10 scenario and in order to compare our
results with those from other carbon cycle studies that used the
HYDE data set (e.g. Strassmann et al., 2008). In using HYDE as
input to LPJ, we added the crop and pasture fractions of each
gridcell and linearly interpolated between each timeslice. As the
development and evaluation of the HYDE data base is described
in detail in another publication (Klein Goldewijk et al., 2010b),
here we focus the rest of this section on the description of the new
KK10 data set.
An empirical model for simulating past ALCC was recently
developed by Kaplan et al. (2009) and applied to Europe for the
past 3000 years. We expanded on this method in the current study
by expanding the geographic scope to global and the entire time
period from 8000 years ago to ad 1850, when the Industrial Revo-
lution began to profoundly alter relationships between population
and land use (Ellis and Ramankutty, 2008). Uniquely, the Kaplan
et al. (2009) method is based on a non-linear relationship between
population density and land use, which generally translates to a
decrease in per capita land use with time, as population densities
increase and land use intensification occurs.
Human population is the main input for estimating ALCC
using the KK10 model. We assembled a new, annually resolved
data base of population from 1000 bc to ad 1850 for 209 regions
of the world (Figures 1 and S1). A complete description of the
methods used to assemble our historical population data base may
be found in Krumhardt (2010). In summary, our population esti-
mates are based primarily on McEvedy and Jones (1978), replaced
or adjusted wherever better data were available. Adjustments to
population estimates for Europe are discussed in Kaplan et al.
(2009). For the Western Hemisphere before fifteenth-century con-
tact with Europeans, we used updated values from a number of
sources, all of which indicated that the McEvedy and Jones (1978)
figures were generally at the very low range of estimates (Denevan,
1992; Krumhardt, 2010). Our data set therefore presents substan-
tially increased population numbers for the pre-Columbian West-
ern Hemisphere over those of McEvedy and Jones (1978). To
capture spatial patterns in population changes across China, pro-
vincial data from 221 bc to ad 1850 was used (Zhao and Xie,
1988), allowing detailed improvements in population patterns
and dynamics without changing total values significantly from
McEvedy and Jones (1978). To extend our population time series
for each region from 3 ka back to 8 ka, we used a time series of
global population simulated by the Global Land Use and Techno-
logical Evolution Simulator (GLUES; Lemmen, 2009; Wirtz and
Lemmen, 2003).
We simulated ALCC based on population data, maps of land
suitability for agriculture and pasture, and a simple relationship
between population density and preindustrial land use (Kaplan
et al., 2009). Time series of population estimates for each population
region were transformed into the fraction of land used by people
by first calculating population density on arable land within each
region and then applying this value to a sigmoidal function that
relates population density to the estimated area of land under
deforestation. The amount of arable land in any population region
is constrained by observationally based estimates of land suitabil-
ity for cultivation and pasture at the present day (Ramankutty
et al., 2002). In this sense, a limitation of our methodology is that
we do not account for the way improvements in technology (e.g.
irrigation, terracing, or the development of the steel plow) pro-
gressively opened up land to agricultural activities through time
(Kaplan et al., 2009). While suitability for cultivation is a function
of both climate and soil quality (Ramankutty et al., 2002), pasture
suitability is determined only by climate, and accounts for areas
suitable for grazing livestock as well as for wood harvest for con-
struction or fuel (Kaplan et al., 2009). The spatial distribution of
land use is determined by the total amount of land required for
any region and time multiplied by the land suitability factor. This
method results in maps of land use that display the most suitable
land being cleared first, followed by use of increasingly marginal
land as population pressure, and thus land required, increases.
The population density–forest clearance relationship deteriorates
with industrialization, urbanization and trade, and therefore the
KK10 data set covers only the time period from 8 ka to ad 1850.
A detailed discussion of the methodology used to simulate ALCC
is contained in Kaplan et al. (2009).
Because the original population density–ALCC relationship
was developed using observations in Europe, and the potential
productivity of land for agriculture and pasture is much higher in
tropical regions and lower in boreal regions, it was necessary to
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Citations
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TL;DR: Myhre et al. as discussed by the authors presented the contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC) 2013: Anthropogenic and Natural Radiative forcing.
Abstract: This chapter should be cited as: Myhre, G., D. Shindell, F.-M. Bréon, W. Collins, J. Fuglestvedt, J. Huang, D. Koch, J.-F. Lamarque, D. Lee, B. Mendoza, T. Nakajima, A. Robock, G. Stephens, T. Takemura and H. Zhang, 2013: Anthropogenic and Natural Radiative Forcing. In: Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Stocker, T.F., D. Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex and P.M. Midgley (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA. Coordinating Lead Authors: Gunnar Myhre (Norway), Drew Shindell (USA)

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Abstract: Human use of land has transformed ecosystem pattern and process across most of the terrestrial biosphere, a global change often described as historically recent and potentially catastrophic for both humanity and the biosphere. Interdisciplinary paleoecological, archaeological, and historical studies challenge this view, indicating that land use has been extensive and sustained for millennia in some regions and that recent trends may represent as much a recovery as an acceleration. Here we synthesize recent scientific evidence and theory on the emergence, history, and future of land use as a process transforming the Earth System and use this to explain why relatively small human populations likely caused widespread and profound ecological changes more than 3,000 y ago, whereas the largest and wealthiest human populations in history are using less arable land per person every decade. Contrasting two spatially explicit global reconstructions of land-use history shows that reconstructions incorporating adaptive changes in land-use systems over time, including land-use intensification, offer a more spatially detailed and plausible assessment of our planet's history, with a biosphere and perhaps even climate long ago affected by humans. Although land-use processes are now shifting rapidly from historical patterns in both type and scale, integrative global land-use models that incorporate dynamic adaptations in human-environment relationships help to advance our understanding of both past and future land-use changes, including their sustainability and potential global effects.

608 citations

Journal ArticleDOI
TL;DR: The current global extent, duration, type and intensity of human transformation of ecosystems have already irreversibly altered the terrestrial biosphere at levels sufficient to leave an unambiguous geological record differing substantially from that of the Holocene or any prior epoch.
Abstract: Human populations and their use of land have transformed most of the terrestrial biosphere into anthropogenic biomes (anthromes), causing a variety of novel ecological patterns and processes to emerge. To assess whether human populations and their use of land have directly altered the terrestrial biosphere sufficiently to indicate that the Earth system has entered a new geological epoch, spatially explicit global estimates of human populations and their use of land were analysed across the Holocene for their potential to induce irreversible novel transformation of the terrestrial biosphere. Human alteration of the terrestrial biosphere has been significant for more than 8000 years. However, only in the past century has the majority of the terrestrial biosphere been transformed into intensively used anthromes with predominantly novel anthropogenic ecological processes. At present, even were human populations to decline substantially or use of land become far more efficient, the current global extent, duration, type and intensity of human transformation of ecosystems have already irreversibly altered the terrestrial biosphere at levels sufficient to leave an unambiguous geological record differing substantially from that of the Holocene or any prior epoch. It remains to be seen whether the anthropogenic biosphere will be sustained and continue to evolve.

601 citations

References
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Book
01 Jan 1965
TL;DR: In this paper, Boserup argues that changes and improvements occur from within agricultural communities, and that improvements are governed not simply by external interference, but by those communities themselves using extensive analyses of the costs and productivity of the main systems of traditional agriculture.
Abstract: This book sets out to investigate the process of agrarian change from new angles and with new results. It starts on firm ground rather than from abstract economic theory. Upon its initial appearance, it was heralded as "a small masterpiece, which economic historians should read--and not simply quote"--Giovanni Frederico, Economic History Services. The Conditions of Agricultural Growth remains a breakthrough in the theory of agricultural development. In linking ethnography with economy, developmental studies reached new heights. Whereas "development" had been seen previously as the transformation of traditional communities by the introduction (or imposition) of new technologies, Ester Boserup argues that changes and improvements occur from within agricultural communities, and that improvements are governed not simply by external interference, but by those communities themselves Using extensive analyses of the costs and productivity of the main systems of traditional agriculture, Ester Boserup concludes that technical, economic, and social changes are unlikely to take place unless the community concerned is exposed to the pressure of population growth.

3,639 citations


"Holocene carbon emissions as a resu..." refers background or methods or result in this paper

  • ...The KK10 scenario makes the central assumption that humans use land more intensively in all regions of the world with increasing population density and land scarceness (Boserup, 1965)....

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  • ...…to be substantial underestimates resulting from the assumption that per capita land use has remained constant for the past 8000 years, an assumption not in agreement with observations (Boserup, 1965, 1981; Chao, 1986; Ellis and Wang, 1997; Ruddiman and Ellis, 2009; Ruddiman et al., forthcoming)....

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  • ...Indeed, Boserup (1965, 1981) synthesized evidence across field studies to develop the most widely used general model of land use intensification, in which population pressure drives farmers to implement ever-more innovative 1Ecole Polytechnique Fédérale de Lausanne, Switzerland 2University of…...

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Journal ArticleDOI
TL;DR: Satellite-monitoring of the abundance of open water in the peatlands of the West Siberian Plain and the Hudson/James Bay Lowland is suggested as a likely method of detecting early effects of climatic warming upon boreal and subarctic peatland environments.
Abstract: Boreal and subarctic peatlands comprise a carbon pool of 455 Pg that has accumulated during the postglacial period at an average net rate of 0.096 Pg/yr (1 Pg = 1015g). Using Clymo's (1984) model, the current rate is estimated at 0.076 Pg/yr. Longterm drainage of these peatlands is estimated to be causing the oxidation to CO2 of a little more than 0.0085 Pg/yr, with conbustion of fuel peat adding °0.026 Pg/yr. Emissions of CH4 are estimated to release ° 0.046 Pg of carbon annually. Uncertainties beset estimates of both stocks and fluxes, particularly with regard to Soviet peatlands. The influence of water table alterations upon fluxes of both CO2 and CH4 is in great need of investigation over a wide range of peatland environments, especially in regions where permafrost melting, thermokarst erosion, and the development of thaw lakes are likely results of climatic warming. The role of fire in the carbon cycle of peatlands also deserves increased attention. Finally, satellite—monitoring of the abundance of open water in the peatlands of the West Siberian Plain and the Hudson/James Bay Lowland is suggested as a likely method of detecting early effects of climatic warming upon boreal and subarctic peatlands.

3,546 citations


"Holocene carbon emissions as a resu..." refers background or methods in this paper

  • ...Bottom-up attempts to estimate the amount of carbon sequestered in peats over the Holocene result in a published range of 250–450 Pg C (Frolking and Roulet, 2007; Gajewski et al., 2001; Gorham, 1991; MacDonald et al., 2006; Yu, forthcoming)....

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  • ...Yu (forthcoming) estimated that ~270 Pg C were stored in boreal peatlands during the last 7000 years, consistent with estimates by Gorham (1991) and Gajewski et al. (2001)....

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Journal ArticleDOI
TL;DR: The LPJ model as mentioned in this paper combines process-based, large-scale representations of terrestrial vegetation dynamics and land-atmosphere carbon and water exchanges in a modular framework, including feedback through canopy conductance between photosynthesis and transpiration and interactive coupling between these 'fast' processes and other ecosystem processes.
Abstract: The Lund-Potsdam-Jena Dynamic Global Vegetation Model (LPJ) combines process-based, large-scale representations of terrestrial vegetation dynamics and land-atmosphere carbon and water exchanges in a modular framework. Features include feedback through canopy conductance between photosynthesis and transpiration and interactive coupling between these 'fast' processes and other ecosystem processes including resource competition, tissue turnover, population dynamics, soil organic matter and litter dynamics and fire disturbance. Ten plants functional types (PFTs) are differentiated by physiological, morphological, phenological, bioclimatic and fire-response attributes. Resource competition and differential responses to fire between PFTs influence their relative fractional cover from year to year. Photosynthesis, evapotranspiration and soil water dynamics are modelled on a daily time step, while vegetation structure and PFT population densities are updated annually. Simulations have been made over the industrial period both for specific sites where field measurements were available for model evaluation, and globally on a 0.5degrees x 0.5degrees grid. Modelled vegetation patterns are consistent with observations, including remotely sensed vegetation structure and phenology. Seasonal cycles of net ecosystem exchange and soil moisture compare well with local measurements. Global carbon exchange fields used as input to an atmospheric tracer transport model (TM2) provided a good fit to observed seasonal cycles of CO2 concentration at all latitudes. Simulated inter-annual variability of the global terrestrial carbon balance is in phase with and comparable in amplitude to observed variability in the growth rate of atmospheric CO2 . Global terrestrial carbon and water cycle parameters (pool sizes and fluxes) lie within their accepted ranges. The model is being used to study past, present and future terrestrial ecosystem dynamics, biochemical and biophysical interactions between ecosystems and the atmosphere, and as a component of coupled Earth system models.

2,735 citations

Journal ArticleDOI
TL;DR: In this paper, the possible responses of ecosystem processes to rising atmospheric CO2 concentration and climate change are illustrated using six dynamic global vegetation models that explicitly represent the interactions of ecosystem carbon and water exchanges with vegetation dynamics.
Abstract: The possible responses of ecosystem processes to rising atmospheric CO2 concentration and climate change are illustrated using six dynamic global vegetation models that explicitly represent the interactions of ecosystem carbon and water exchanges with vegetation dynamics. The models are driven by the IPCC IS92a scenario of rising CO2 (Wigley et al. 1991), and by climate changes resulting from effective CO2 concentrations corresponding to IS92a, simulated by the coupled ocean atmosphere model HadCM2-SUL. Simulations with changing CO2 alone show a widely distributed terrestrial carbon sink of 1.4‐3.8 Pg C y ‐1 during the 1990s, rising to 3.7‐8.6 Pg C y ‐1 a century later. Simulations including climate change show a reduced sink both today (0.6‐ 3.0 Pg C y ‐1 ) and a century later (0.3‐6.6 Pg C y ‐1 ) as a result of the impacts of climate change on NEP of tropical and southern hemisphere ecosystems. In all models, the rate of increase of NEP begins to level off around 2030 as a consequence of the ‘diminishing return’ of physiological CO2 effects at high CO2 concentrations. Four out of the six models show a further, climate-induced decline in NEP resulting from increased heterotrophic respiration and declining tropical NPP after 2050. Changes in vegetation structure influence the magnitude and spatial pattern of the carbon sink and, in combination with changing climate, also freshwater availability (runoff). It is shown that these changes, once set in motion, would continue to evolve for at least a century even if atmospheric CO2 concentration and climate could be instantaneously stabilized. The results should be considered illustrative in the sense that the choice of CO2 concentration scenario was arbitrary and only one climate model scenario was used. However, the results serve to indicate a range of possible biospheric responses to CO2 and climate change. They reveal major uncertainties about the response of NEP to climate

1,982 citations


"Holocene carbon emissions as a resu..." refers background in this paper

  • ...…modeling studies that ignore preindustrial ALCC resulted in simulations of peak Holocene terrestrial C storage (plants and surface soils) of 1600–2500 Pg (Cramer et al., 2001; Kaplan et al., 2002; McGuire et al., 2001; Sitch et al., 2003), with about one-third of total C stored in living biomass....

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  • ...A number of more recent modeling studies that ignore preindustrial ALCC resulted in simulations of peak Holocene terrestrial C storage (plants and surface soils) of 1600–2500 Pg (Cramer et al., 2001; Kaplan et al., 2002; McGuire et al., 2001; Sitch et al., 2003), with about one-third of total C stored in living biomass....

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Journal ArticleDOI
TL;DR: In this paper, the authors presented a simple approach to derive geographically explicit changes in global croplands from 1700 to 1992, by calibrating a remotely sensed land cover classification data set against cropland inventory data.
Abstract: Human activities over the last three centuries have significantly transformed the Earth's environment, primarily through the conversion of natural ecosystems to agriculture. This study presents a simple approach to derive geographically explicit changes in global croplands from 1700 to 1992. By calibrating a remotely sensed land cover classification data set against cropland inventory data, we derived a global representation of permanent croplands in 1992, at 5 min spatial resolution [Ramankutty and Foley, 1998]. To reconstruct historical croplands, we first compile an extensive database of historical cropland inventory data, at the national and subnational level, from a variety of sources. Then we use our 1992 cropland data within a simple land cover change model, along with the historical inventory data, to reconstruct global 5 min resolution data on permanent cropland areas from 1992 back to 1700. The reconstructed changes in historical croplands are consistent with the history of human settlement and patterns of economic development. By overlaying our historical cropland data set over a newly derived potential vegetation data set, we analyze our results in terms of the extent to which different natural vegetation types have been converted for agriculture. We further examine the extent to which croplands have been abandoned in different parts of the world. Our data sets could be used within global climate models and global ecosystem models to understand the impacts of land cover change on climate and on the cycling of carbon and water. Such an analysis is a crucial aid to sharpen our thinking about a sustainable future.

1,765 citations


"Holocene carbon emissions as a resu..." refers background in this paper

  • ...…induced land cover change (ALCC), and in some cases the resulting CO 2 emissions, both in the industrial era and in preceding centuries ( Houghton, 2003; Houghton et al., 1999; Klein Goldewijk, 2001; Pongratz et al., 2008; Ramankutty and Foley, 1998, 1999; Strassmann et al., 2008)....

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Frequently Asked Questions (17)
Q1. What are the contributions in "Holocene carbon emissions as a result of anthropogenic land cover change" ?

Humans have altered the Earth ’ s land surface since the Paleolithic mainly by clearing woody vegetation first to improve hunting and gathering opportunities, and later to provide agricultural cropland. Their model setup allowed us to quantify the importance of land degradation caused by repeated episodes of land use followed by abandonment. While the authors can not close the carbon budget in the current study, simulated cumulative anthropogenic emissions over the preindustrial Holocene are consistent with the ice core record of atmospheric dCO 2 and support the hypothesis that anthropogenic activities led to the stabilization of atmospheric CO 2 concentrations at a level that made the world substantially warmer than it otherwise would be. 

The carbon-isotope (d13C) composition of CO 2 in ice-core air bubbles can be used to assess net emissions/storage of terrestrial carbon during previous millennia. 

accounting for improvements in technology (e.g. the development of irrigation or heavy steel plows) by having a spatially and temporally dynamic agricultural land suitability data set would allow us to better simulate the spatial distributions of land use over time. 

By 3 ka BP, cumulative carbon emissions caused by anthropogenic land cover change in their new scenario ranged between 84 and 102 Pg, translating to c. 7 ppm of atmospheric CO2 . 

A substantial reason for the range of global carbon change estimates is uncertainty in assessing how much carbon is stored in ‘natural’ vegetation (Olson et al., 1983). 

Much of the uncertainty around the extent of past land use comes from the lack of knowledge about the magnitude and distribution of the global human population and the time course of technological evolution and intensification. 

To incorporate shifting land use practices in their ALCC model, the authors further created a scheme for modeling the turnover of agricultural land that simulates progressive use, abandonment, and conversion of unused land, e.g. shifting cultivation. 

the updated soil and climate data sets (supplementary methods) used in this study could lead to differences in natural carbon compared with other studies, though these effects are likely to be small over the long timescales considered here (Jung et al., 2007). 

Allowing for the effects of other natural factors (CO2 fertilization, monsoon-related releasesand storage of carbon, and carbon storage in peat), Elsig et al. (2009) estimated Holocene ALCC emissions of ~50 Pg C. 

Between 3 ka and about ad 300 (1.65 ka) ALCC emissions continue to rise steadily and at a higher rate compared with the earlier Holocene (Figure 5), while very little variability is observed in atmospheric CO2 (Figure 1). 

the KK10 scenario shows that parts of Mesoamerica, the Andes, Europe and China were nearly 60% cleared and some parts of sub-Saharan Africa were up to 50% cleared at ad 1. 

Because the original population density–ALCC relationship was developed using observations in Europe, and the potential productivity of land for agriculture and pasture is much higher in tropical regions and lower in boreal regions, it was necessary toat Helmholtz-Zentrum Geesthacht, Zentrum für Material- und Küstenforschung GmbH on July 2, 2013hol.sagepub.comDownloaded from778 

in Lemmen’s (2009) model of prehistoric technical and societal changes, per capita land use decreased by a factor of seven from the emergence of agriculture at 11 ka to 3 ka. 

The authors expanded on this method in the current study by expanding the geographic scope to global and the entire time period from 8000 years ago to ad 1850, when the Industrial Revolution began to profoundly alter relationships between population and land use (Ellis and Ramankutty, 2008). 

To model the effects of ALCC terrestrial vegetation in LPJ, the authors followed the approach of Strassmann et al. (2008), where managed and unmanaged land is represented on separate sub-grid scale tiles. 

More dramatic is the up to 10 ppm drop in CO 2 concentrations between ad 1500 and 1700 (MacFarling Meure et al., 2006); this corresponds closely to the time of maximum carbon uptake as a result of land abandonment in the Western Hemisphere following European contact as discussed in the previous section. 

Differentiating among different types of land use systems (e.g. Ellis and Ramankutty, 2008; Verburg et al., 2009), would improve the quality of their carbon budget simulations by allowing us to simulate a more diverse suite of land use patterns (e.g. managed and unmanaged rangelands, managed forests).