Measuring and assessing the effects of climate change on crop yields : A multilevel approach
The thesis examines the effects of climate change on crop yields at several geospatial levels of analysis. Yields, the amount of crop production per area, is an important measure for topics ranging from food security to sustainable energy. While recent increases in productivity, mainly through increased yields, has temporarily reduced stress in agricultural markets, demand for these products, triggered mainly by population growth and increases in the demand for meat and biofuels by developing countries, is expected to increase significantly. In contrast, the supply of agricultural products is under increasing pressure from both climate change and, ironically, efforts to mitigate those effects. Climate changes are expected to decrease the production of important food crops and lead to higher global food prices all else equal. One consequence of The Paris Agreement was the wide-scale adoption of a framework for global action to address climate change. Some have argued that stringent climate mitigation policies will have a greater negative impact on global food security than the impacts of climate change itself.Accurately measuring and forecasting crop yields has become an increasingly relevant topic for the topic of food security and agricultural prices. All of the research questions addressed in this thesis concern yields at various levels of aggregation ranging from groups of countries to countries to farms within a specific country. Why study yields, and specifically, why not study crop production? Crop production is an explicit measure of the amount of a crop available for use, however, it is subject to the vagaries of the moment. Yield, in contrast, is a more robust measure of the potential production of a crop through time because it measures production per area, and thereby includes a measure of technical development and, in combination with the land price, it is closely related to the competitiveness of countries and the determination of international trade flows. Five research questions are addressed. The first asks whether the effects of climate change will vary across countries and crops. Using standard econometric techniques, results show that when regressions are significant, global regions and crops will experience a wide range of effects, although generally the results will be negative. These results suggest that, at a minimum, the effects of climate change should be both country and crop specific. They also indicate the importance of using a statistical approach in order to assess the significance of forecasts.The next research question asks whether yields in Europe are converging and if so, what will be the effects on the supply of crops used in the production of biomass products. Scenarios were run using estimated yields as input into a computable general equilibrium (CGE) model. The CGE model provides a narrative framework through which the total economic impact of changes in yields can be analyzed. Together, the complementary approaches of econometrics and general equilibrium models allow a more complete economic analysis of the consequences of yield changes for important biofuels crops to emerge. The overall question of whether significant yield increases will necessarily lead to large increases in land available to produce bioenergy crops is rejected. Land freed by wheat yield increases will go to the production of a wide range of agricultural products that value it as an input. The same reasoning which links yields and land use applies to all agricultural products when there are well functioning markets.The third question asks how changing climate patterns will affect the global trade of major food crops and, in particular, asks what the effects will be on less developed countries. If we accept that the effects of changing weather patterns caused by climate changes will have diverse effects on yields globally, then global trade patterns are likely to change as well. Results for crops with statistically significant estimates show that increasing temperatures have negatively affected yields. These results hold for both poor and rich countries, however, the degree to which yields are reduced is crop specific and sensitive to a country’s level of wealth. Results show that changes in weather will have significant effects on the production, trade, and, in some cases, the consumption of major food crops.The fourth research question examines the implications of extreme weather events on yields. The effects of changing weather patterns will likely have local as well as regional effects, this is especially true for extreme weather events when compared to the average effects of climate change over time. The approach used to answer this question was to assemble a panel database consisting of features such as fertilizer, pesticides, capital, and other inputs from 334 wheat farms in the Netherlands for over a decade. Analyzes show that the number of days with extreme high temperatures in Dutch wheat growing regions has significantly increased since the early 1900s, while the number of extreme low temperature events has fallen over that same period. The effects of Extreme weather events on wheat yields were found to be time specific in that the week in which an event occurred partially determines their effects on yields. High temperature events and precipitation events were found to significantly decrease yields.The last research question examines various methods to forecast yields. It provides an accessible and transparent framework to allow policy makers to assess the trade-offs involved when forecasting yields and measure the value of those forecasts. Yields of ten important global food crops are forecasted and their accuracy reported. A comparison is made between the results of a standard technique used to forecast yields, and auto-regressive, integrated, moving average (ARIMA) forecasts. ARIMA forecasts generally out-perform those of the standard methodology and provide a convenient means to assess their added value. While the mean forecasts of top producers for most crops are expected to increase, the amount of associated uncertainty is large, and forecasts beyond only a few years should be made with caution.
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| Format: | Doctoral thesis biblioteca |
| Language: | English |
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Wageningen University
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| Subjects: | Life Science, |
| Online Access: | https://research.wur.nl/en/publications/measuring-and-assessing-the-effects-of-climate-change-on-crop-yie |
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