417
type, whether to meet demand or in response to changing regional climates, will
change evapotranspiration, infiltration, and runoff rates, impacting water availability and regional climate. Crop extensification into marginal land will increase the
extent of these impacts.
FEW system models should represent how water availability will drive crop
choice and distribution, and the feedback effects these have on water quantity and
quality. Key questions are: How will the water cycle (along with the coupled carbon
and nitrogen cycles) be altered by changes in agricultural land use? How will this
coupled system respond to progressive climate change and feedback on regional
water supply?
15.3.4 Food–Energy–Water–Climate
The above intersystem connections must be considered in the context of the changing
climate, which both affects and is affected by FEW systems and their interactions,
and FEW system models must, therefore, represent not only the current systems but
also their evolution under changing climate conditions.
Climate change impacts on FEW systems are already visible and projected to
increase. Rising temperatures are altering traditional growing zones, shifting food
and bioenergy crops into nontraditional, formerly unsuitable marginal land, with
new impacts on both of these environments.
Climate change alters the physiological and structural properties of terrestrial
ecosystems, perturbing their soil–plant–atmosphere interactions. Severe weather
events such as heat waves, droughts and floods are projected to increase in frequency and/or intensity, with significant consequences for short- and long-term
food and bioenergy production. For example, critical vegetation losses due to
drought can lead to drastic increases in soil erosion and upland sediments impounding flood control reservoirs. They may remarkably increase evapotranspiration,
amplifying catchment water storage anomalies.
Reduced yield due to environmental change may drive sharp price increases,
with potential effects on future crop choice and land use, and this should be captured by economic component(s) in FEW system models.
The impacts of FEW systems on climate are equally important. For instance, agricultural management practices (e.g., irrigation, fertilization, tillage, crop rotation) can
significantly alter the land surface properties controlling energy and water fluxes.
These feedbacks may alter regional-local climate over seasons to decades, thus
modifying the biophysical environment in which crops grow. Likewise, irrigation,
which changes terrestrial hydrology, may cause much larger evapotranspiration
than its induced local plus recycled remote rainfall, resulting in a net water loss; this
alters surface water and energy budgets. The resultant near-surface cooling tends to
suppress moist convection and reduce rainfall.
By contrast, moistening may enhance or suppress local convection when the
antecedent soil is relatively wet or extremely dry, causing precipitation to increase
over irrigated areas during normal and pluvial years but decrease during drought
15 Modeling
type, whether to meet demand or in response to changing regional climates, will
change evapotranspiration, infiltration, and runoff rates, impacting water availability and regional climate. Crop extensification into marginal land will increase the
extent of these impacts.
FEW system models should represent how water availability will drive crop
choice and distribution, and the feedback effects these have on water quantity and
quality. Key questions are: How will the water cycle (along with the coupled carbon
and nitrogen cycles) be altered by changes in agricultural land use? How will this
coupled system respond to progressive climate change and feedback on regional
water supply?
15.3.4 Food–Energy–Water–Climate
The above intersystem connections must be considered in the context of the changing
climate, which both affects and is affected by FEW systems and their interactions,
and FEW system models must, therefore, represent not only the current systems but
also their evolution under changing climate conditions.
Climate change impacts on FEW systems are already visible and projected to
increase. Rising temperatures are altering traditional growing zones, shifting food
and bioenergy crops into nontraditional, formerly unsuitable marginal land, with
new impacts on both of these environments.
Climate change alters the physiological and structural properties of terrestrial
ecosystems, perturbing their soil–plant–atmosphere interactions. Severe weather
events such as heat waves, droughts and floods are projected to increase in frequency and/or intensity, with significant consequences for short- and long-term
food and bioenergy production. For example, critical vegetation losses due to
drought can lead to drastic increases in soil erosion and upland sediments impounding flood control reservoirs. They may remarkably increase evapotranspiration,
amplifying catchment water storage anomalies.
Reduced yield due to environmental change may drive sharp price increases,
with potential effects on future crop choice and land use, and this should be captured by economic component(s) in FEW system models.
The impacts of FEW systems on climate are equally important. For instance, agricultural management practices (e.g., irrigation, fertilization, tillage, crop rotation) can
significantly alter the land surface properties controlling energy and water fluxes.
These feedbacks may alter regional-local climate over seasons to decades, thus
modifying the biophysical environment in which crops grow. Likewise, irrigation,
which changes terrestrial hydrology, may cause much larger evapotranspiration
than its induced local plus recycled remote rainfall, resulting in a net water loss; this
alters surface water and energy budgets. The resultant near-surface cooling tends to
suppress moist convection and reduce rainfall.
By contrast, moistening may enhance or suppress local convection when the
antecedent soil is relatively wet or extremely dry, causing precipitation to increase
over irrigated areas during normal and pluvial years but decrease during drought
15 Modeling