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three decades, for instance, average daily per capitaOne contribution of 17 to a Discussion Meeting Issue ‘Food crops in
a changing climate’.
*Author for correspondence (fisher@iiasa.ac.at).climate change (e.g. Kimball et al. 2002; Jablonski et al.
2002; Ainsworth & Long 2005), the associated impacts
of high temperatures, altered patterns of precipitation
Many interactive processes determine the dynamics
of world food demand and supply: agro-climatic
conditions, land resources and their management are
clearly a key component, but they are critically affected
by distinct socio-economic pressures, including current
and projected trends in population growth, availabilityregional planning and ultimately the welfare of its
people.
Current research confirms that while crops would
respond positively to elevated CO
2
in the absence of
a group of more than 40 ‘least-developed’ countries,
mostly in sub-Saharan Africa, where domestic per
capita food production declined by 10% in the last 20
years (e.g. UN Millennium Project 2005).economic variables within a unified and coherent framework to produce a global assessment of food
production and security under climate change. The results from the study suggest that critical impact
asymmetries due to both climate and socio-economic structures may deepen current production and
consumption gaps between developed and developing world; it is suggested that adaptation of
agricultural techniques will be central to limit potential damages under climate change.
Keywords: agriculture; crop production; climate change; food security; sub-Saharan Africa;
risk of hunger
RODUCTION
is significant concern about the impacts of
e change and its variability on agricultural
tion worldwide. First, issues of food security
prominently in the list of human activities and
tem services under threat of dangerous anthro-
c interference on Earth’s climate (Watson et al.
IPCC 2001a,b; Ecosystem Millennium Assess-
2005; see also article II, UNFCCC). Second,
ountry is naturally concerned with potential
es and benefits that may arise over the coming
s from climate change impacts on its territory as
globally, since these will affect domestic and
tional policies, trading patterns, resource use,
and possibly increased frequency of extreme
such as drought and floods, will probably comb
depress yields and increase production risks in
world regions, widening the gap between rich and
countries (e.g. IPCC 2001a,b). A consensu
emerged that developing countries are more vuln
to climate change than developed countries, beca
the predominance of agriculture in their econo
the scarcity of capital for adaptation measures,
warmer baseline climates and their heigh
exposure to extreme events (Parry et al. 2001).
climate change may have particularly serious
sequences in the developing world, where som
million people are undernourished. Of great concmalnutrition, are computed. This modelling approach connects the relevant bio-physical and socio-Socio-economic and clim
agriculture: an integrated
Gu¨nther Fischer
1,
*
, Mahendra
and Harrij v
1
International Institute for Applied Syste
2
Goddard Institute for Space Stud
A comprehensive assessment of the impacts of clim
developed, up to 2080 and at a global level, alb
integrated ecological–economic modelling frame
agro-ecological zoning information, socio-econo
Specifically, global simulations are performed us
conjunction with IIASAs global food systemmod
circulation models, under four different socio-eco
on climate change. First, impacts of different sc
crop growth determinants of yield are evaluated
the extent of potential agricultural land and rel
detailed bio-physical results are then fed into an
may interact with alternative development pathw2067ate change impacts on
assessment, 1990–2080
ah
1
, Francesco N. Tubiello
1,2
Velhuizen
1
Analysis (IIASA), Laxenburg, Austria
Columbia University, NY, USA
e change on agro-ecosystems over this century is
with significant regional detail. To this end an
rk is employed, encompassing climate scenarios,
c drivers, as well as world food trade dynamics.
the FAO/IIASA agro-ecological zone model, in
using climate variables from five different general
mic scenarios from the intergovernmental panel
rios of climate change on bio-physical soil and
a 5
0
!5
0
latitude/longitude global grid; second,
d potential crop production is computed. The
onomic analysis, to assess how climate impacts
s, and key trends expected over this century for
Phil. Trans. R. Soc. B (2005) 360, 2067–2083
doi:10.1098/rstb.2005.1744
Published online 24 October 2005q 2005 The Royal Society

growth and climate change. In short, the questions
we address herein are as follows: what are the likely
impacts of climate change on the world’s agricultural
resources? How do climate impacts compare to socio-
economic pressures over this century? Where and how
do significant interactions arise? A few previous studies,
notably Rosenzweig & Parry (1994), FAO (2003) and
Parry et al. (2004), have employed various components
of the FAO–IIASA methodology to address these same
questions; we believe, however, that this is the first time
that a fully coherent, unified data and modelling system
has been used.
Specifically, we employ the FAO–IIASA agro-
climatic database and modelling framework known as
the agro-ecological zones or AEZ, model (e.g. Fischer
et al. 2002a,b), in conjunction with four socio-
economic scenarios defined by IPCC and the IIASA
world food system or basic linked system (BLS)
(Fischer et al. 1988, 2002b; Parry et al. 1999)(figure 1).
The main simulation results of the study herein
presented include climate change impacts on agro-
climatic resources, potential arable land and related
changes in crop production patterns. Our economic
analyses assess over this century changes to food
demand, production, trade and prices and the scale
and location of risk of hunger.
2. MATERIAL AND METHODS
The combination of a spatially detailed bio-physical/
agronomic assessment tool and a global food system model
provides an integrated ecological–economic framework for
the assessment of the impacts of climate change and
2068 G. Fischer and others An integrated assessment of agriculture, 1990–2080intake has risen globally from 2400 to 2800 cal (from
10 to 12 MJ), spurred by economic growth, improved
production systems, international trade and globaliza-
tion of food markets. Feedbacks of such growth
patterns on cultures and personal taste, lifestyle and
demographic changes have in turn led to major dietary
changes—mainly in developing countries, where shares
of meat, fat and sugar to total food intake have
increased by about 40% (e.g. Fischer et al. 2002b).
Given the virtual impossibility to test experimen-
tally, or to simply try to sum up in a linear fashion all
relevant agro-climatic and socio-economic factors
involved in determining long-term future trends, it is
no surprise that the scientific literature is replete with
modelling studies attempting to assess at least some of
the aspects likely to characterize the impacts of climate
change on future agricultural production. There is a
wealth of site-specific, regional and/or national short-
and long-term assessments of climate change impacts
performed to date (e.g. Rosenzweig et al. 2002;
Tubiello et al. 2002; Olesen & Bindi 2002; Reilly
et al. 2003). Global assessments of climate change on
food production have been less frequent (i.e. Rosenz-
weig & Parry 1994; Fischer et al. 2002b; Parry et al.
2004), due in part to the difficulties of gathering
comprehensive global agro-climatic datasets, in part to
the need to employ global trade economic models (see
below), as well as due to the significant computer
resources required.
Such assessment studies have focused mainly on
agro-climatic components, including simplified
approaches to simulating adaptation responses, i.e.
changes in agro-technology that enable farmers to
minimize risks and/or maximize profits under changed
climates. Focus of assessment studies with adaptation
has either been on explicit, simple farm-level adap-
tation strategies; or on implicit, market-driven response
functions (see, for discussion, Rosenzweig & Tubiello
in press). The first approach is local, allowing for agro-
technological detail, but lacking key regional market
feedbacks. It includes on-site evaluation of strategies
such as early planting, use of cultivars better adapted to
altered climates or modifications to water and/or
fertilizer levels. The second approach better includes
agro-economic dynamics over a region, but cannot
provide specific technical solutions. It includes gener-
alized strategies such as regional shifting of cropping
systems andmanagement; responses based on pesticide
and/or fertilizer use, etc. Furthermore, local studies
with crop models allow for better calibration and
validation compared to regional approaches.
Clearly, both methodologies are necessary in order
to conduct more realistic regional studies. In addition,
and importantly, local to regional effects of global food
trade would need to be included within either
approach. This is because international trade can
greatly modify the regional dynamics of food demand,
production and supply under present climate, and thus
significantly modulate impacts under climate change
(e.g. Reilly et al. 2001; Tubiello 2005).
This paper presents an integrated ecological–econ-
omic modelling framework for the assessment of the
world food system in the twenty-first century, under
various future scenarios of population, economicPhil. Trans. R. Soc. B (2005)climate
model
SRES
scenario
climate impact
response relations
world market
production
demand
trade
global food system
(basic linked system)
BLS
Figure 1. Graphic description of the AEZ–BLS modelling
framework. Socio-economic SRES scenarios determine both
climatic and market conditions under which AEZ and BLS
are run. Climatic impacts on agricultural production—
computed with AEZ, are passed on to the agricultural
economics and trade model, BLS, to determine overall
impacts on world food systems.ecological–economic analysis
AEZ