Principal Component Analysis of Crop Yield Response to Climate Change

The objective of this study is to compare the effects of climate change on crop yields across different regions. A Principal Component Regression (PCR) model is developed to estimate the historical relationships between weather and crop yields for corn, soybeans, cotton, and peanuts for several northern and southern U.S. states. Climate change projection data from three climate models are applied to the estimated PCR model to forecast crop yield response. Instead of directly using weather variables as predictor variables, the PCR model uses weather indices transformed from original weather variables by the Principal Component Analysis (PCA) approach. A climate change impact index (CCII) is developed to compare climate change effects across different regions. The key contribution of our study is in identifying a different climate change effects in crop yields in different U.S. states. Specifically, our results indicate that future warmer weather will have a negative impact for southern U.S. counties, while it has insignificant impact for northern U.S. counties in the next four decades.Principal component regression, Crop yield response, Climate change., Crop Production/Industries,

Climate Change and Texas Water Planning: an Economic Analysis of Inter-basin Water Transfers

Panel models with random effects are used to estimate how climate influences in-stream surface water supply, municipal water demand, crop yields and irrigation water use. The results are added into TEXRIVERSIM, a state wide economic, hydrological, environmental and inter-basin water transfer (IBTs) investment model, through the objective function and hydrological constraints. A climate change related scenario analysis from the Global Circulation Models (GCMs)--Hadley, Canadian, BCCR and NCAR with SRES scenarios A1B, B1, and A2 indicates that inter-basin water transfers not only greatly relax water scarcity problems for major cities and industrial counties, but also create growth opportunity for Houston. However, while destination basins receive the benefits, source basins will experience dramatic reduction in in-stream flow and water flows to bays and estuaries. Climate change requires accelerated water development with more IBTs proving economically feasible depending on the GCMs and SRES scenarios.Climate Change, Inter-basin Water Transfers, Water Scarcity, Environmental Stream Flows, Environmental Economics and Policy, Q25, Q54, Q58,

Climate change impacts on hydrologic components and occurrence of drought in an agricultural watershed

The study on potential acceleration of future hydrologic cycle due to change in precipitation and increase in temperature are essential for managing natural resources and setting policy. The impact of future climate change on hydrologic components of Goodwater Creek Experimental Watershed (GCEW) and experimental field (Field1) were assessed using climate datasets from the Coupled Model Intercomparison Project Phase 5 (CMIP5), Soil and Water Assessment Tool (SWAT) and Agricultural Policy Environmental Extender (APEX). SWAT and APEX models were setup and calibrated for watershed and field scale using observed hydrology data at their respective outlets. The study identified future (2016-2075) occurrence of meteorological, hydrological, agricultural droughts, and extreme events based on projections of future climate in the GCEW and SWAT simulations. Standardized Precipitation Index, Standardized Streamflow Index, and Soil Moisture Index were used to represent the three types of drought. CMIP5 data were downscaled to watershed and field scale using quantile mapping for precipitation and delta method for temperature. Historical and future ensembles of downscaled precipitation and temperature, and modeled water yield, surface runoff, and evapotranspiration were compared. At the watershed scale, ensemble SWAT simulated results indicated increased springtime precipitation, water yield, surface runoff and a shift in evapotranspiration peak one month earlier in the future. At field scale, two management system business-As-Usual (BAU) and Aspirational (ASP) management system were compared to access the environmental benefits of improved management system using APEX model. Simulated results indicated that the change in management alone from BAU to ASP during historic period resulted in 25% (162 mm to 120 mm) reduction in surface runoff. The simulated average annual runoff loss was reduced by 16.5% (192 mm to 160 mm) and 18.8% (203 mm to 165 mm) in ASP scenario compared to BAU for ensemble of RCP 8.5 for near and far future respectively. The average ensemble annual soluble nitrogen loss was 8 kg/ha for BAU compared to 3.9 kg/ha for ASP management for baseline historic period. Result indicated the inclusion of no-till and winter cover crop resulted in increased subsurface flow. The result indicates the environmental benefit of crop rotation and cover crop with reduction in runoff and nutrient losses. The ASP management provides surface cover all year round and improves soil quality resulting in lower runoff.Includes bibliographical reference

Improving Agronomic Structure in Econometric Models of Climate Change Impacts

Economists are relying on agronomic concepts to construct weather or climate independent variables and improve the reliability and efficiency of econometric models of climate change impact on U.S. agriculture. The use of cumulative heat measures in agronomy (growing degree-days), has recently served as a basis for the introduction of plurimonthly calendar heat variables in these models. However, season-long weather conditions seem at odds with conventional agronomic wisdom that emphasizes crucial differences in crop stage sensitivity to environmental stress. In this paper I show that weather variables matched to key corn development stages provide an enhanced and more stable fit than their calendar counterparts. More importantly, the proposed season-disaggregated framework yields very different implications for adaptation than its calendar counterparts as it indicates that most of the projected yield damages are accounted during the flowering period, a relatively short period in the crop cycle. This should open the door to more advanced yield models that account for additional possibilities of adaptation and thus provide a more nuanced outlook on the potential impacts of climate change on crop yields.agriculture, climate change, corn, degree-days, phenology, proxy, yield, Production Economics, Research Methods/ Statistical Methods, Resource /Energy Economics and Policy, Q54, C23,

Between heat death and drought stress, the impact of adverse environmental conditions on critical development stages of agricultural production in the North German Plain

Changing boundary conditions through environmental shifts, worldwide as well as regional, challenge well- established agricultural production systems. While the extraordinary impacts on crop development through adverse environmental conditions during critical development stages are frequently considered a risk, they are rarely analysed. This is likely due to the complexity of the problem, with interactions and interdependencies between numerous abiotic and biotic factors entangled on various levels. This thesis investigates these complex interactions between adverse environmental conditions and critical development stages and their impact on agricultural production of the North German Plain. It identifies important, critical development stages, it develops an outlook for the abundance of adverse environmental conditions, and it identifies mitigation strategies for this specific problem by pattern analysis. A literature study identifies prominent critical development stages that help navigate the topic of adverse environmental conditions and critical development stages in agricultural production. Further, it shows that crop simulation models seemingly lack in capacities to model development-stage specific stress responses. A modelling study provides an outlook; it finds a consistent increase in abundance of numerous adverse environmental conditions throughout the North German Plain. The inabilities of crop simulation models (DSSAT) are omitted by neglecting modelled yield response and focusing on the evaluation of the abundance of adverse environmental conditions within phenological development stages. A case study of drought impact on yield variability approaches the problem from another angle. The inventory of drought patterns shows that diversification of production systems is a possible mitigation strategy. Further, it found a starting point for improvements of crop simulation models towards a better assessment of critical development stages in the poorly simulated drought response around flowering. This inventory was derived for various production systems for an example region in the North German Plain.Widrige Witterungsbedingungen während kritischer Wachstumsphasen können eine außergewöhnlich starke Wirkung auf die pflanzliche Entwicklung haben, z.B. Trockenheit während der Blüte. Dabei reichen die Auswirkungen von Ertragsrückgängen über Qualitätseinbußen bis zum Totalausfall. Es ist anzunehmen, dass die etablierten Produktionssysteme künftig nicht mehr an die veränderten Umweltbedingungen angepasst sein werden und sich solche Konsequenzen häufen werden. Damit geht das Risiko einher, dass die Produktion nicht mehr auf dem gewohnt hohen und zuverlässigen Niveau stattfinden kann. Dies gilt für die Landwirtschaft im Norddeutschen Tiefland wie weltweit. Um diese Risiken für das Norddeutsche Tiefland im speziellen einzuschätzen, wurde in dieser Arbeit eine Übersicht zu kritischen Phasen der pflanzlichen Entwicklung und Ertragsbildung erstellt, eine Perspektive für Risiken der Landwirtschaft im Norddeutschen Tiefland entwickelt und ein systematischer Ansatz zur Verbesserung von Analysemethoden und Werkzeugen getestet. Kritische Phasen werden schon lange als Herausforderung wahrgenommen. Die Literaturübersicht zeigt, dass je nach Fragestellung zahlreiche spezifische Definitionen genutzt werden, und dass systematische Ansätze zur Analyse der Wirkung von widrigen Witterungsbedingungen auf kritische Phasen selten sind. Zusätzlich wird gezeigt, dass kritische Phasen als Phänologie-spezifische Reaktionen auf bestimmte Umweltbedingungen in Pflanzenwachstumsmodellen, dem Werkzeug der Wahl zur Analyse von Produktionssystemen, kaum entwickelt sind. Mit dem Pflanzenwachstumsmodell DSSAT (Decision Support System for Agricultural Transfer) konnte, trotz der für Pflanzenwachstumsmodelle typischen Beschränkungen, die Häufigkeit von widrigen Witterungsbedingungen während ausgesuchter Pflanzenwachstumsphasen für drei Zukunftsszenarien abgeleitet werden. Unter der Voraussetzung, dass es zu keinerlei Anpassungen kommt, ergeben sich für das Norddeutsche Tiefland folgende Perspektiven: Die Häufigkeiten für widrige Witterungsbedingungen während ausgewählter Wachstumsphasen nimmt durch alle evaluierten Szenarien durchgängig zu und dies trotz vorteilhafter, phänologischer Entwicklungen wie der Verlängerung der Vegetationsperiode. Darüber hinaus fordert der Klimawandel den etablierten Pflanzenbau im Norddeutschen Tiefland teils auch auf unerwartete Weise heraus, so muss trotz Temperaturerhöhung weiterhin mit Spätfrost gerechnet werden. Häufig treten widrige Umweltbedingungen nicht vollständig willkürlich auf. Eine Auswertung langer Ertragszeitreihen durch eine Musteranalyse zeigt und klassifiziert die Wirkung von Trockenheit auf die Ertragsvariabilität in Niedersachsen. Neben der Klassifizierung der rezenten Produktionssysteme, die Schlüsse über eine Risiken-vermindernde Gestaltung von zukünftigen Produktionssystemen geben kann, identifiziert die Anwendung der Methode auf modellierte Ertragsreihen Ansatzpunkte, an denen das Pflanzenwachstumsmodell gezielt mittels Phänologie-spezifischer Prozesse verbessert werden kann, z. B. der verbesserten Simulation des Übergangs zur reproduktiven Entwicklung

Quantifying the GCM-related uncertainty for climate change impact assessment of rainfed rice production in Cambodia by a combined hydrologic - rice growth model

The effects of climate change on agriculture are a major concern for global food security. In this study, the impacts of climate change on rainfed rice production in the granary of Cambodia were examined on a basin scale by developing and applying a combined model consisting of a crop model and a basin-scale distributed hydrological model. The response of rice production to soil-water availability was simulated for past (1981–2000) and future (2041–2060, 2081–2100) periods. From 34 general circulation models (GCMs) that participated in the Coupled Model Intercomparison Project Phase 5 (CMIP5), 5 GCMs were selected by evaluating monthly rainfall in the past. Although annual rainfall was projected to increase by all five selected GCMs, notable decreases in rainfed rice production were projected with 3 GCMs, while small changes were projected with the other 2 GCMs. The main factor restricting future rice production was soil water availability, brought by the projected change in the seasonal distribution of rainfall and the projected more severe dry spells in the early monsoon season. The results suggest the importance of the selection and bias correction of GCMs to force rice crop models and of the simulation of soil water flow on a basin scale for the assessment of rain-fed rice production. In particular, improvements in projections of rainfall amounts over shorter periods rather than annual or seasonal periods, which fit within the time scales of rice plant growth, were suggested to be important

Hydrology, Soil Erosion and Climate Interactions on Low Compaction Steep-Sloped Reclaimed Sites in the Southern Appalachian Coal Fields, Tennessee

The use of loose spoil on steep slopes for surface coal mining reclamation sites has been promoted by the US Department of Interior, Office of Surface Mining for the establishment of native forest. Although low-compaction spoils improve tree survival and growth, the erodibility and hydrology of steep slopes may change due to this practice. The purpose of this study was to quantify the erodibility (K factor), and the Curve Number (CN) value for low compaction, steep-sloped (\u3e 20%) reclaimed mine lands in the Appalachian region, USA. This study also investigated the performance of the SEDCAD model in estimating erosion and sediment delivery from these slopes, and tried to estimate the potential change in rainfall erosivity due to climate change in the study region. Three active coal mining sites in the Appalachian region of East Tennessee were monitored for rainfall, runoff, and sediment yields. The estimated time-varying K factor ranged between 0.03 and 0.5 t۰ha۰h۰ha-1۰MJ-1۰mm-1, with the highest values immediately following reclamation site construction. Rill development greatly influenced sediment yields. A fining of delivered sediment size was observed from the period of rill development to relatively stable rill morphology, with the D84 changed from 17.3 mm to 1.7 mm. Meanwhile, different methods were used to identify CN values of these new reclaimed surfaces as they are vital for design of runoff and sediment control structures. In contrast to previous studies, CN estimation methods utilized in this study propose a narrower, more practical CN value range of 58.5 ~ 60.0, based on standard asymptotic behavior, for low-compaction steep-sloped reclaimed surfaces. This study also investigated the performance of SEDCAD in estimating erosion and sediment delivery. Model input parameters were assessed with respect their impacts on SEDCAD outputs. In general, SEDCAD appeared to overestimate sediment yield compared to what was measured from study sites, and modeled sediment yields were found to be sensitive to CN selection. Finally, this study showed that for all future greenhouse gas emission scenarios the overall annual rainfall erosivity will increase in the study area, though the distribution of erosivity throughout the year will be similar to the present

Emulating global climate change impacts on crop yields

The potential effects of climate change on the environment and society are many. In order to effectively quantify the uncertainty associated with these effects, highly complex simulation models are run with detailed representations of ecosystem processes. These models are computationally expensive and can involve a computer run of several days. Computationally cheaper models can be obtained from large ensembles of simulations using statistical emulation. The purpose of this paper is to construct a cheaper computational model (emulator) from simulations of the Lund- Potsdam-Jena managed Land (LPJmL), which is a dynamic global vegetation and crop model. This paper focuses on statistical emulation of potential crop yields from LPJmL and an emulator is constructed using a combination of ordinary least squares, principal component analysis and weighted least squares methods. For five climate models, under cross-validation the percentage of variance explained ranges from 60- 88% for the rainfed crops and 62-93% for the irrigated crops. The emulator can be used to predict potential crop yield change under any future climate scenarios and management options

Climate change vulnerability and adaptation assessment for Fiji

All nations, including Fiji, that are signatories to the United Nations Framework Convention on Climate Change(UNFCCC) are obliged to provide National Communications to the Conference of Parties (COP) of the UNFCCC. The COP4 stressed the need for parties to the Convention to take into account the need for establishing implementation strategies for adaptation to climate and sea-level changes. As such, Fiji is required to submit a National Communication document that shall include information on climate change vulnerability and adaptation implementation policies and strategies. The methodology used in this assessment is based on the Intergovernmental Panel on Climate Change (IPCC) technical guidelines (Carter et al, 1994) for assessing climate change impacts and adaptation. Firstly, the present conditions are examined and key sectors identified. Then, future climatic and non-climatic scenarios are used to examine the possible effects of climate and sea-level changes on the various sectors identified. These then form the basis for identifying possible adaptation response measures for endorsement, adoption and implementation by the Fiji government. Because of the many gaps in present knowledge, and the fact that this study is focussed only on Viti Levu, the recommendations in this report should be seen as starting point for an on-going process of vulnerability and adaptation assessment in Fij