Mary S. McKenney

Agricultural Impacts of and Responses to Climate Change in the Missouri-Iowa-Nebraska-Kansas (MINK) Region

The climate of the 1930s was used as an analog of the climate that might occur in Missouri, Iowa, Nebraska and Kansas (the MINK region) as a consequence of global warming. The analog climate was imposed on the agriculture of the region under technological and economic conditions prevailing in 1984/87 and again under a scenario of conditions that might prevail in 2030. The EPIC model of Williamset al. (1984), modified to allow consideration of the yield enhancing effects of CO2 enrichment, was used to evaluate the impacts of the analog climate on the productivity and water use of some 50 representative farm enterprises. Before farm level adjustments and adaptations to the changed climate, and absent CO2 enrichment (from 350 to 450 ppm), production of corn, sorghum and soybeans was depressed by the analog climate in about the same percent under both current and 2030 conditions. Production of dryland wheat was unaffected. Irrigated wheat production actually increased. Farm level adjustments using low-cost currently available technologies, combined with CO2 enrichment, eliminated about 80% of the negative impact of the analog climate on 1984/87 baseline crop production. The same farm level adjustments, plus new technologies developed in response to the analog climate, when combined with CO2 enrichment, converted the negative impact on 2030 crop production to a small increase. The analog climate would have little direct effect on animal production in MINK. The effect, if any, would be by way of the impact on production of feed-grains and soybeans. Since this impact would be small after on-farm adjustments and CO2 enrichment, animal production in MINK would be little affected by the analog climate.

Sensitivity of some potential evapotranspiration estimation methods to climate change

A simulation approach was used to generate estimates of the sensitivity of potential evapotranspiration (ETp) to climate change using eight alternative ETp estimation methods. The methods, which differ in structure and data requirements, were: Thornthwaite, Blaney-Criddle, Hargreaves, Samani-Hargreaves, Jensen-Haise, Priestley-Taylor, Penman, and Penman-Monteith. The simulations were performed using climate data from five sites in the North American Great Plains. The results indicate that the methods differ, in some cases significantly, in their sensitivities to temperature and other climate inputs. The degree of agreement among the methods is affected, to some extent, by location and by time of year. When two GCM-derived scenarios of climatic change were applied, the predicted response of ETp varied in magnitude and in some cases in sign, according to the estimation method used. The differences among methods can be attributed both to differences in their sensitivities to climate, and to differences in the climatic factors they consider. The implications of these findings for studies of climatic change are discussed.

Preparing the erosion productivity impact calculator (EPIC) model to simulate crop response to climate change and the direct effects of CO2

The adaptation of a crop simulation model to deal with the impacts of rising CO2 and climate change is described in this paper. Algorithms that represent the direct effects of atmospheric CO2 on crop photosynthetic efficiency and water use were developed for use with the erosion productivity impact calculator (EPIC), a mechanistic crop simulation model. Representative farms were designed to reflect the major cropping systems in the MINK (Missouri-Iowa-Nebraska-Kansas) region and data were assembled to simulate them in EPIC. Climate data were compiled to represent conditions under the control (1951–1980) and analog (1931–1940) climates. Actual daily temperature and precipitation data from a number of climatological stations across the MINK region were used in the simulations. Daily values of solar radiation, relative humidity, and wind speed were simulated stochastically from monthly First Order Weather Station records.

Evapotranspiration in a greenhouse-warmed world: A review and a simulation

Abstract The ways in which the greenhouse effect may affect evapotranspiration ( ET ) rates are briefly reviewed. ET may change because of atmospheric warming and because of associated changes in other climatic factors. ET rates may also be altered by the stimulation of plant growth and increase in stomatal resistance that occur in response to CO 2 enrichment of the atmosphere. The Penman-Monteith model of evapotranspiration was employed with data from four different ecosystems to estimate the possible range of changes in ET which may occur in response to the climatic and plant changes mentioned above. The climatic and plant factors were first varied individually to determine model sensitivity. These factors were then varied simultaneously according to scenarios of climatic change to determine their combined impact on ET . Depending on the ecosystem and on climatic conditions, ET can differ by −20 to +40% from the control case (no climate or plant change).

Simulations of crop responses to climate change: effects with present technology and currently available adjustments (the ‘smart farmer’ scenario)

Abstract If climate changes, farmers will have to adapt to a new set of climate constraints. In this paper we examine the efficacy of strategies for dealing with climate change that are currently available to farmers and that are inexpensive to use; we refer to this group of strategies as ‘adjustments’. Adjustment schemes of various kinds were identified for us by agricultural experts in the Missouri-Iowa-Nebraska-Kansas (MINK) states. These can involve changes in land use, changes in variety and crop selection, changes in planting and harvesting practices, and changes in fertility and pest management. Using the erosion productivity impact calculator (EPIC) model on a small set of representative farms, we tested adjustments of these kinds. The simulations show that earlier planting, longer-season cultivars and the use of furrow diking for moisture conservation would offset some of the yield losses induced by climate change in warm-season crops. Longer-season varieties of wheat (a cool-season crop) and shorter-season varieties of the perennials wheatgrass and alfalfa were also effective. The adjustments to climate change diminished yield losses in all crops but irrigated wheat. Despite the positive effects of adjustments, however, yields of all dryland warm-season crops remained lower than control levels. The adjustments also increased demand for irrigation water. Carbon dioxide enrichment had the same incremental effect on crop yields with or without adjustments (see the fourth paper in this issue), except in the case of alfalfa and sorghum, where a CO 2 -adjustment interaction was found. We conclude that currently available techniques would partially offset the yield reductions caused by a 1930s-like climate, but that in most crops the yield reductions would still be substantial.

Validation of EPIC model simulations of crop responses to current climate and CO2 conditions: comparisons with census, expert judgment and experimental plot data

Abstract A crop simulation model must first be capable of representing the actual performance of crops grown in any particular region before it can be applied to the prediction of climate change impacts. Erosion productivity impact calculator (EPIC) simulations of crop productivity in the Missouri-Iowa-Nebraska-Kansas (MINK) region under the 1951–1980 climate were compared with the US Department of Agricultures ‘County Yield Estimates’ data (averaged over 1984–1987), with expert estimates of yields for each ‘representative’ farm and with the results of agronomic experiments reported in the literature. Most EPIC-simulated yields agreed to within ±20% with USDA reported yields and expert estimates, although there were some outliers. EPIC-simulated yields, evapotranspiration and water use efficiency fell well within the range of experimental results. Perfect agreement with observed crop performance was not a requisite nor should it have been expected. We judged the EPIC simulations sufficiently reliable to justify use of the model in simulating the effects of climate change on crops.

Simulations of crop response to climate change: effects with present technology and no adjustments (the ‘dumb farmer’ scenario)

Abstract The climate of the 1930s—our analog of climate change—was imposed on farms representative of agriculture in the Missouri-Iowa-Nebraska-Kansas (MINK) region through the erosion productivity impact calculator (EPIC) model. Two levels of atmospheric CO 2 were considered: 350 and 450 ppm. No attempts to adjust or adapt the farms to the climate change were made. Results from simulations under the analog climate (1931–1940) were compared with results from simulations under the control climate (1951–1980). EPIC-simulated yields of warm-season crops were reduced by the analog climate. Yield reductions ranged from 7% for irrigated corn to 25% for dryland and soybeans. Simulated yields of dryland wheat were, on the whole, unchanged by the analog climate. Crops under irrigation fared better than dryland crops, although irrigation demand increased markedly. The simulated loss of crop yields under the analog climate was due to truncated growing seasons accompanied by reduced evapotranspiration. The higher level of atmospheric CO 2 alleviated simulated yield losses for all crops, although for corn and soybeans, particularly, yield losses remained significant.

The MINK methodology: background and baseline

A four step methodology has been developed for study of the regional impacts of climate change and the possible responses thereto. First the region’s climate sensitive sectors and total economy are described (Task A, current baseline). Next a scenario of climate change is imposed on the current baseline (Task B, current baseline with climate change). A new baseline describing the climate sensitive sectors and total regional economy is projected for some time in the future (Task C, future baseline, year 2030) in the absence of climate change. Finally, the climate change scenario is reimposed on the future baseline (Task D, future baseline with climate change). Impacts of the climate change scenario on the current and future regional economies are determined by means of simulation models and other appropriate techniques. These techniques are also used to assess the impacts of an elevated CO2 concentration (450 ppm) and of various forms of adjustments and adaptations.

Simulation of crop productivity and responses to climate change in the year 2030: the role of future technologies, adjustments and adaptations

Abstract Advances in agricultural technology may affect the response of crop yields to a future climate change induced by greenhouse warming. We illustrate a methodology for simulating these effects by manipulating the parameters of a crop simulation model erosion productivity impact calculator (EPIC) to represent a set of proposed future technologies. Sensitivity analyses were first performed to test the effect of changes in each of the parameters individually. Crop yields were then simulated with a set of these future technologies under the climate of the 1951–1980 period (the ‘control’ climate) and under the climate of the 1930s (used as an analog of climate change), for locations in Missouri, Iowa, Nebraska and Kansas (MINK). The future technologies increased yields by an average of 72% above current levels, but had little effect on the sensitivity of crop yields to climate change. Next, realizing that attempts will probably be made to adjust farming practices to a changed climate, we implemented a set of changes which represent both currently available strategies for coping with the analog climate as well as new techniques which might be developed in response to a hotter, drier climate. With these changes in place, both yields and water use were less affected by the analog climate. If the direct effects of increased CO 2 are also considered, yields of all crops but corn were equal to or greater than those that occur with no climate change. We also considered the economic feasibility of crop substitutions and shifts in the location of irrigated agriculture as adjustments to the analog climate. The final step in this analysis was to scale farm-level results to the regional level.

An introduction to the methodology, the region of study, and a historical analog of climate change

Abstract We introduce a methodology for simulating the impact of climate change induced by greenhouse warming and the direct effects of the rising atmospheric CO 2 concentration on agricultural productivity and for considering the farm-level response to these impacts. The methodology permits the climate change-agriculture question to be viewed in terms of future changes and provides for systematic consideration of the role of adaptation. The methodology has been applied to the four-state Missouri-Iowa-Nebraska-Kansas (MINK) region—a region whose economy is heavily based on natural resources likely to be affected by climate change. In this first application the weather records of the Dust Bowl Era (1931–1940) were used as the basis for a scenario of climate change. That decade was warmer and drier than the current climatic normal in the MINK region. However, the methodology is not dependent specifically on climate analogs for scenario building; general circulation model experiments or other appropriate surrogates can be used, as well. The general structure of the methodology is described in this paper; details are given in the five subsequent papers.