Global Consequences of Land Use
Jonathan A. Foley,
1
*
Ruth DeFries,
2
Gregory P. Asner,
3
Carol Barford,
1
Gordon Bonan,
4
Stephen R. Carpenter,
5
F. Stuart Chapin,
6
Michael T. Coe,
1
. Gretchen C. Daily,
7
Holly K. Gibbs,
1
Joseph H. Helkowski,
1
Tracey Holloway,
1
Erica A. Howard,
1
Christopher J. Kucharik,
1
Chad Monfreda,
1
Jonathan A. Patz,
1
I. Colin Prentice,
8
Navin Ramankutty,
1
Peter K. Snyder
9
Land use has generally been considered a local environmental issue, but it is becoming a
force of global importance. Worldwide changes to forests, farmlands, waterways, and
air are being driven by the need to provide food, fiber, water, and shelter to more than
six billion people. Global croplands, pastures, plantations, and urban areas have expanded
in recent decades, accompanied by large increases in energy, water, and fertilizer con-
sumption, along with considerable losses of biodiversity. Such changes in land use have
enabled humans to appropriate an increasing share of the planet’s resources, but they
also potentially undermine the capacity of ecosystems to sustain food production,
maintain freshwater and forest resources, regulate climate and air quality, and amelio-
rate infectious diseases. We face the challenge of managing trade-offs between imme-
diate human needs and maintaining the capacity of the biosphere to provide goods and
services in the long term.
L
and-use activities—whether converting
natural landscapes for human use or
changing management practices on
human-dominated lands—have transformed
a large proportion of the planet_s land sur-
face. By clearing tropical forests, practicing
subsistence agriculture, intensifying farmland
production, or expanding urban centers, hu-
man actions are changing the world_sland-
scapes in pervasive ways (1, 2) (Fig. 1, fig. S1,
and table S1). Although land-use practices
vary greatly across the world, their ultimate
outcome is generally the same: the acquisition
of natural resources for immediate human
needs, often at the expense of degrading en-
vironmental conditions.
Several decades of research have re-
vealed the environmental impacts of land use
throughout the globe, ranging from changes
in atmospheric composition to the extensive
modification of Earth_s ecosystems (3–6). For
example, land-use practices have played a role
in changing the global carbon cycle and, pos-
sibly, the global climate: Since 1850, roughly
35% of anthropogenic CO
2
emissions resulted
directly from land use (7). Land-cover changes
also affect regional climates through changes
in surface energy and water balance (8, 9).
Humans have also transformed the hydrologic
cycle to provide freshwater for irrigation, in-
dustry, and domestic consumption (10, 11).
Furthermore, anthropogenic nutrient inputs to
the biosphere from fertilizers and atmospheric
pollutants now exceed natural sources and have
widespread effects on water quality and coastal
and freshwater ecosystems (4, 12). Land use
has also caused declines in biodiversity through
the loss, modification, and fragmentation of
habitats; degradation of soil and water; and
overexploitation of native species (13) (SOM
Text S1).
Ironically, just as our collective land-use
practices are degrading ecological conditions
across the globe, humanity has become de-
pendent on an ever-increasing share of the
biosphere_s resources. Human activities now
appropriate nearly one-third to one-half of
global ecosystem production (14), and as de-
velopment and population pressures continue
to mount, so could the pressures on the bio-
sphere. As a result, the scientific community is
increasingly concerned about the condition of
global ecosystems and Becosystem services[
(15, 16) (SOM Text S2).
Land use thus presents us with a dilemma.
On one hand, many land-use practices are
absolutely essential for humanity, because they
provide critical natural resources and ecosystem
services, such as food, fiber, shelter, and fresh-
water. On the other hand, some forms of land
use are degrading the ecosystems and services
upon which we depend, so a natural question
arises: Are land-use activities degrading the
global environment in ways that may ultimately
undermine ecosystem services, human welfare,
and the long-term sustainability of human so-
cieties? Here, we examine this question and fo-
cus on a subset of global ecosystem conditions
we consider most affected by land use. We also
consider the challenge of reducing the negative
environmental impacts of land use while main-
taining economic and social benefits.
Food Production
Together, croplands and pastures have become
one of the largest terrestrial biomes on the planet,
rivaling forest cover in extent and occupying
È40% of the land surface (17, 18)(Fig.2).
Changing land-use practices have enabled
world grain harvests to double in the past four
decades, so they now exceed È2 billion tons
per year (19). Some of this increase can be
attributed to a È12% increase in world cropland
area, but most of these production gains resulted
from ‘‘Green Revolution’’ technologies, includ-
ing high-yielding cultivars, chemical fertilizers
and pesticides, and mechanization and irrigation
(4, 20) (fig. S2A). During the past 40 years,
there has been a È700% increase in global
fertilizer use (4, 5)andaÈ70% increase in
irrigated cropland area (21, 22).
Although modern agriculture has been
successful in increasing food production, it
has also caused extensive environmental dam-
age. For example, increasing fertilizer use
has led to the degradation of water quality in
many regions (4, 12, 13) (fig. S2B). In ad-
dition, some irrigated lands have become
heavily salinized, causing the worldwide loss
of È1.5 million hectares of arable land per
year, along with an estimated $11 billion in
lost production (20). Up to È40% of global
croplands may also be experiencing some de-
gree of soil erosion, reduced fertility, or over-
grazing (20). The loss of native habitats also
affects agricultural production by degrading
the services of pollinators, especially bees
(23, 24). In short, modern agricultural land-
use practices may be trading short-term in-
creases in food production for long-term losses
REVIEW
1
Center for Sustainability and the Global Environ-
ment (SAGE), University of Wisconsin, 1710 Univer-
sity Avenue, Madison, WI 53726, USA.
2
Department
of Geography and Earth System Science Interdisci-
plinary Center, University of Maryland, College Park,
College Park, MD 20742, USA.
3
Department of Global
Ecology, Carnegie Institution of Washington, Stanford,
CA 94305, USA.
4
National Center for Atmospheric
Research (NCAR), Post Office Box 3000, Boulder, CO
80307–3000, USA.
5
Center for Limnology, University
of Wisconsin, 680 North Park Street, Madison, WI
53706, USA.
6
Institute of Arctic Biology, University of
Alaska, Fairbanks, AK 99775, USA.
7
Center for Con-
servation Biology, Department of Biological Sciences,
371 Serra Mall, Stanford University, Stanford, CA 94305,
USA.
8
QUEST, Department of Earth Sciences, Uni-
versity of Bristol, Wills Memorial Building, Bristol BS8
1RJ, UK.
9
Department of Atmospheric Sciences, Uni-
versity of Illinois, 105 South Gregory Street, Urbana,
IL 61801, USA.
*To whom correspondence should be addressed:
jfoley@wisc.edu
.Present address: Woods Hole Research Center,
Woods Hole, MA 02543, USA.
22 JULY 2005 VOL 309 SCIENCE www.sciencemag.org570

in ecosystem services, including many that
are important to agriculture.
Freshwater Resources
Land use can disrupt the surface water
balance and the partitioning of precipitation
into evapotranspiration, runoff, and ground-
water flow. Surface runoff and river discharge
generally increase when natural vegetation
(especially forest) is cleared (25, 26). For
instance, the Tocantins River basin in Brazil
showed a È25% increase in river discharge
between 1960 and 1995, coincident with ex-
panding agriculture but no major change in
precipitation (26).
Water demands associated with land-use
practices, especially irrigation, directly affect
freshwater supplies through water withdrawals
and diversions. Global wa-
ter withdrawals now total
È3900 km
3
yr
j1
,orÈ10%
of the total global renew-
able resource, and the con-
sumptive use of water (not
returned to the watershed) is
estimatedtobeÈ1800 to
2300 km
3
yr
j1
(22, 27)(fig.
S3A). Agriculture alone ac-
counts for È85% of global
consumptive use (22). As a
result, many large rivers, es-
pecially in semiarid regions,
have greatly reduced flows,
and some routinely dry up
(21, 28). In addition, the
extraction of groundwater
reserves is almost univer-
sally unsustainable and has
resulted in declining water
tables in many regions
(21, 28)(fig.S2,BandC).
Water quality is often
degraded by land use. In-
tensive agriculture increases
erosion and sediment load,
and leaches nutrients and
agricultural chemicals to
groundwater, streams, and
rivers. In fact, agriculture has become the
largest source of excess nitrogen and phospho-
rus to waterways and coastal zones (12, 29).
Urbanization also substantially degrades water
quality, especially where wastewater treat-
ment is absent. The resulting degradation of
inland and coastal waters impairs water sup-
plies, causes oxygen depletion and fish kills,
increases blooms of cyanobacteria (including
toxic varieties), and contributes to waterborne
disease (12, 30).
Forest Resources
Land-use activities, primarily for agricultural
expansion and timber extraction, have caused a
net loss ofÈ7to11millionkm
2
of forest in the
past 300 years (17, 32, 33). Highly managed
forests, such as timber plantations in North
America and oil-palm plantations in Southeast
Asia, have also replaced many natural forests
and now cover 1.9 million km
2
worldwide (31).
Many land-use practices (e.g., fuel-wood
collection, forest grazing, and road expansion)
can degrade forest ecosystem conditions—in
terms of productivity, biomass, stand struc-
ture, and species composition—even without
changing forest area. Land use can also de-
grade forest conditions indirectly by introduc-
ing pests and pathogens, changing fire-fuel
loads, changing patterns and frequency of ig-
nition sources, and changing local meteoro-
logical conditions (34).
In many parts of the world, especially in
East Asian countries, reforestation and affor-
estation are increasing the area of forested
lands (35). Furthermore, forest management
in many regions is acting to improve forest
conditions. For example, inadvertent nitrogen
fertilization, peatland drainage, and direct man-
agement efforts increased the standing bio-
mass of European forests by È40% between
1950 and 1990, while their area remained
largely unchanged (36, 37). These forests have
become a substantial sink of atmospheric
carbon (È0.14 Pg C yr
j1
in the 1990s) (37),
although other ecosystem services (including
those provided by peatlands) and biodiversity
are likely diminished.
Regional Climate and Air Quality
Land conversion can alter regional climates
through its effects on net radiation, the di-
vision of energy into sensible and latent heat,
and the partitioning of precipitation into soil
water, evapotranspiration, and runoff. Model-
ing studies demonstrate that land-cover changes
in the tropics affect climate largely through
water-balance changes, but changes in temper-
ate and boreal vegetation influence climate
primarily through changes in the surface radi-
ation balance (38). Large-scale clearing of
tropical forests may create a warmer, drier
climate (39), whereas clearing temperate and
boreal forest is generally thought to cool the
climate, primarily through increased albedo
(40) (table S2, A and B).
Urban ‘‘heat islands’’ are an extreme case
of how land use modifies regional climate.
The reduced vegetation cover, impervious
surface area, and morphology of buildings in
cityscapes combine to low-
er evaporative cooling, store
heat, and warm the surface
air (41). A recent analysis
of climate records in the
United States suggests that
a major portion of the tem-
perature increase during the
last several decades resulted
from urbanization and other
land-use changes (9). Land-
cover change has also been
implicated in changing the
regional climate in China;
recent analyses suggest that
the daily diurnal tempera-
ture range has decreased as
a result of urbanization (42).
Land-use practices also
change air quality by alter-
ing emissions and changing
the atmospheric conditions
that affect reaction rates,
transport, and deposition.
For example, tropospheric
ozone (O
3
)isparticularly
sensitive to changes in vege-
tation cover and biogenic
emissions. Land-use prac-
tices often determine dust
sources, biomass burning, vehicle emission
patterns, and other air pollution sources.
Furthermore, the effects of land use on local
meteorological conditions, primarily in urban
heat islands, also affect air quality: Higher
urban temperatures generally cause O
3
to in-
crease (43).
Infectious Disease
Habitat modification, road and dam construc-
tion, irrigation, increased proximity of peo-
ple and livestock, and the concentration or
expansion of urban environments all modify
the transmission of infectious disease and can
lead to outbreaks and emergence episodes
(44). For example, increasing tropical defor-
estation coincides with an upsurge of malaria
100 %



0 %
pre-settlement frontier subsistence intensifying intensive
stage in land use transition
natural
ecosystems
frontier
clearings
subsistence
agriculture
and
small-scale
farms
intensive
agriculture
urban
areas
protected/
recreational lands
p
r
o
p
o
r
t
i
o
n

o
f

l
a
n
d
s
c
a
p
e
?
Fig. 1. Land-use transitions. Transitions in land-use activities that may be experienced
within a given region over time. As with demographic and economic transitions, societies
appear also to follow a sequence of different land-use regimes: from presettlement nat-
ural vegetation to frontier clearing, then to subsistence agriculture and small-scale farms,
and finally to intensive agriculture, urban areas, and protected recreational lands. Dif-
ferent parts of the world are in different transition stages, depending on their history,
social and economic conditions, and ecological context. Furthermore, not all parts of
the world move linearly through these transitions. Rather, some places remain in one
stage for a long period of time, while others move rapidly between stages. [Adapted
from (1) and (2)]
R EVIEW
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