Land degradation is threatening the world

1
Paper No B33B-0396A
Impact of land use change on wind erosion and
dust emission Scenarios from the central US
John Tatarko, USDA-ARS, Manhattan,
KS (John.Tatarko_at_ars.usda.gov) Gregory S. Okin,
UCLA, Los Angeles, CAJeff Herrick, USDA-ARS, Las
Cruces, NMJunran Li, UCLA, Los Angeles, CA
Methods The Wind Erosion Prediction System
(WEPS), developed by the USDA-Agricultural
Research Service, is a processed-based, daily
time step wind erosion model that simulates
hydrology, plant growth and decomposition, land
management, and soil surface erodibility to
simulate wind erosion soil loss (total,
suspension, and PM10 sizes) as affected by
stochastically simulated local weather. The WEPS
Hydrology submodel can also simulate water use
for land management systems. WEPS was applied to
the following land use scenarios for a 160 acre
loamy fine sand field in Dallam County, TX to
simulate their effects on soil loss by wind and
water use. Tolerable (sustainable) loss for this
soil is 1.1 kg/m2/yr (5 t/ac/yr) .
As expected, the WW-F scenario, similar to that
used during the Dust Bowl shows excessive wind
erosion/dust emission. Changing to native short
grass, as was done in response to the Dust Bowl
significantly reduces soil loss on these soils as
does land planted to tall grass species for the
CRP. However, as CRP contracts expire,
converting these lands to croplands or harvesting
the biomass shows erosion potentials greater than
tolerable amounts if residues removed exceed
certain levels. Water use is also affected by
land use. Evaporation amounts increase with
amounts of plant material (i.e., mulch) removed,
while transpiration is dependent on the amount of
live leaf area. The WW-F scenario is the most
conserving of total water use since every other
year, the fallow period has a high residue mulch
and no transpiring plants. The short and tall
grass scenarios exhibit relative low water use
while irrigated corn requires almost twice that
of other land uses, mostly the result of
irrigation and increased transpiration
demands. Conclusions Conversion of range or CRP
lands to cropland or biomass harvesting run the
risk of excessive erosion/dust emission if
insufficient biomass is left on the soil. The
results indicate that policy and economic forces
shaping land use decisions can have significant
effects on wind erosion and, importantly, dust
emission with local and regional consequences.
In addition, water use results show the potential
effects of land use changes on this precious
resource which is a limiting factor in much of
the central US, particularly in the western Great
Plains states.
Introduction Land degradation is threatening the
worlds food supply. Significant land use
changes are expected throughout the central
United States (US) in the coming years,
particularly resulting from climate change,
changes in US rangeland/farm policy, and
increasing exploitation of land-intensive
sustainable energy sources. These land use
changes have potential to further degrade soil,
air, and water resources. The water limited
central US has historically undergone drought and
land use changes, most notably during and
following the Dust Bowl period of the 1930s when
large areas ravaged by wind erosion were
converted to grasslands in an effort to reduce
soil loss. More recently, additional highly
erodible lands were planted to grass under the
Conservation Reserve Program (CRP) to further
reduce wind erosion. However, farm policy
changes will force much of the current CRP acres
out of the program. In addition, there is
increased interest in the conversion of
traditional crops to production of biofuels such
as cellulosic ethanol. The purpose of this study
was to investigate potential land use change
scenarios on wind erosion, dust emission, and
water use. By simulating various past and future
land use scenarios, the effects of land use
change on wind erosion and dust emissions as well
as water use can be evaluated.
Symbol Scenario
WW-F Winter wheat-fallow crop rotation similar to that used prior and during the Dust Bowl
NSG Native short grass species (e.g., Grama-bouteloua) such as planted post Dust Bowl
TG-CRP Tallgrass species (e.g., Switchgrass-panicum) for Conservation Reserve Program
TG-30 Tallgrass species (e.g., Switchgrass-panicum) harvested for biofuels at 30 cm (12) height
T G-15 Tallgrass species (e.g., Switchgrass-panicum) harvested for biofuels at 15 cm (6) height
ICCT Irrigated Corn, Conventional tillage, harvested for grain with stalks left in the field
ICCT-120 Irrigated Corn, Conventional tillage, harvested for biofuels at 120 cm (48) height
ICNT Irrigated Corn, No-till, harvested for grain with stalks left in the field
ICNT-90 Irrigated Corn, No-till, harvested for biofuels at 90 cm (36) height
ICNT-75 Irrigated Corn, No-till, harvested for biofuels at 75 cm (30) height
Results
Scenario Symbol Soil Loss Soil Loss Soil Loss Water Use Water Use Water Use
Scenario Symbol Total Suspension PM10 Evaporation Transpiration Total
Scenario Symbol kg/m2/yr kg/m2/yr kg/m2/yr mm/yr mm/yr mm/yr
WW-F 17.0 11.7 0.3 173.1  114.2 287.3
NSG 0.005 0.004 0.0001 105.1  257.0 362.1
TG-CRP 0.01 0.007 0.0002 111.0  249.2 360.1
TG-30 0.25 0.18 0.005 128.2   230.9 359.1
TG-15 1.88 1.38 0.037 130.4   228.0 358.4
ICCT 0.114 0.07 0.002 210.8   472.3 683.1
ICCT-120 1.89 1.27 0.034 262.3   393.3 655.6
ICNT 0.0 0.0 0.0 189.3   489.4 678.7
ICNT-90 0.28 0.18 0.005 247.9   406.4 654.3
ICNT-75 1.32 0.8 0.024 249.3   400.9 650.2
Signifies total soil loss greater than the tolerable amount of 1.1 kg/m2/yr or 5 t/ac/yr. Signifies total soil loss greater than the tolerable amount of 1.1 kg/m2/yr or 5 t/ac/yr. Signifies total soil loss greater than the tolerable amount of 1.1 kg/m2/yr or 5 t/ac/yr. Signifies total soil loss greater than the tolerable amount of 1.1 kg/m2/yr or 5 t/ac/yr. Signifies total soil loss greater than the tolerable amount of 1.1 kg/m2/yr or 5 t/ac/yr. Signifies total soil loss greater than the tolerable amount of 1.1 kg/m2/yr or 5 t/ac/yr. Signifies total soil loss greater than the tolerable amount of 1.1 kg/m2/yr or 5 t/ac/yr.