Enciclopédia da Energia Natural CPMA.COMUNIDADES.NET
DisciplinaEletricidade4.720 materiais • 23.112 seguidores
the effects of climate change are underestimated. Finally, as Ricardian analyses are based on statistical estimates, the same limitations as discussed for econometric methods apply. Crop yield studies are used as an input to estimate the economic impact of climate change to simulate the impact of climate change on economic outcomes. Models used to 26 Climate Change and Policy | Climate Change and Food Situation estimate the economic impact of climate change are either partial equilibrium models or general equilibrium models. Partial equilibrium models consider only one economic sector \u2013 in this context, the agricultural sector \u2013 but take into account a wide range of economic and institutional forces. The precision with which markets are detailed depends on the level of disaggregation. All models determine profit maximizing input and output bundles. Cross-sectoral interactions are ig- nored by partial equilibrium models and therefore climate change impacts in one sector do not alter resource allocations in other sectors. This limitation is not serious in industrialized and semi-industrialized countries given the relatively small share of agricultural output in their national economies, but may be significant in other countries. The consideration of only certain countries or regions constitutes another con- straint, as bilateral trade flows are not represented and changes in international commodity prices are not accounted for. Global assessment studies use computable general equilibrium (CGE) models to capture interactions between the agricultural sector and other economic sectors. The inter-sectorial nature of these models allows the simulation of economic activity through incomes and expenditures. Furthermore, CGE models include international trade flows, which allow these models to account for inter-regional effects. One of the weaknesses of general equilibrium models is the calibration of the economic model. Typically, CGE models are assigned to fit production data for a single year and some parameters are \u2018guesstimated.\u2019 Another shortcoming relates to the imprecise representation of the different economic sectors in countries considered. That is, as CGE models include all sectors, the sectoral detail of pro- duction functions is often less sophisticated than in partial equation models. Choices regarding crops considered as input in the CGE model also have large influences on results. The omission of important crops can significantly bias the results. Alternatively, considering only crops highly sensitive to weather conditions (e.g., wheat and maize) constitutes an- other form of selection bias. The global impact analyses that focus only on those crops are likely biased in favor of predict- ing revenue losses. The consideration of less sensitive crops, such as irrigated crops adapted to warmer climates, mitigates these results by representing potential gains induced by climate warming. Finally and most importantly, many economic models assume that crop areas are completely exogenous and treat agricultural land as a fixed factor. These models, therefore, simply reallocate crop land among existing uses. The estimation of such an ensemble of effects is compli- cated due to the numerous interaction effects. Integrated assessment modeling frameworks, which couple economic models with ecosystem and climate models, are better suited to represent the complex interactions and feedbacks of the global system and therefore provide better estimates of climate change impact on food. Literature Review of Impact Assessments The methods described above have been used extensively to estimate the effect of climate change on crop production and food supply. The most direct effect of climate change is on crop yields. Extreme temperature and precipitation have a negative effect on crop yields, but the net effect of climate change on crop yields is dependent on the crops and the regions consid- ered. Most studies find that while crop growth will be nega- tively affected by temperature increases in temperate regions, crop yields in cold regions are expected to benefit from tem- perature increases. CO2 concentration in the atmosphere will also improve crop yields through a CO2 fertilization effect. When combining this fertilization effect with climate change, studies predict higher crop yields than when only considering the impact of climate change, even under relatively high warm- ing scenarios. Climate change will also have indirect effects on crop yields. For instance, global warming will benefit crop productivity in cold regions by lengthening the growing season. On the other hand, temperature rises will favor pest and disease prolifera- tion in tropical regions and entail further crop damage. Live- stock is less sensitive to weather but is nonetheless vulnerable to extreme events such as heat waves and droughts. Livestock can also be indirectly affected through the effect of climate change on feedstock crops. Most early economic research focused on the aggregate economic effects of climate change on agriculture. Crop yield reductions result in an increase in crop prices and therefore reduce consumer surplus. Therefore, consumers from regions where yields are predicted to be negatively affected by climate change will be penalized. The opposite effect is predicted in regions where climate change will entail positive impacts on yields. On the other hand, price changes will modify producer surplus (revenue for farmers). A rise in food price will benefit agricultural exporting regions but harm importing regions. But these economic effects are different in developing countries. In regions such as SSA, where food production is almost entirely used for domestic consumption, a climate change induced crop yield decrease is expected to result in an increase in land use to compensate for the loss of production, although this response will only partially offset the decrease in production due to climate change. Assessments of climate change damages to agriculture must also consider adaptation measures at the global level. For instance, a spatial shift of crop growing areas toward more suitable regions will make the effect of decreased yields in one region only temporary. Additionally, impact assessments must consider the profitability of such measures in the context of global agricultural markets. The development of irrigation systems in regions predicted to become more drought-prone can be justified if crop prices rise substantially. However, a global crop price decrease may render this adaption system uneconomical, even if irrigation restores crop yields. Finally, as research interests evolve toward identifying viable adapta- tion strategies, it is important to consider broader global changes. The latest studies estimate comprehensive environmental impacts by considering a dynamic framework of agricultural systems in the context of fluctuating economic growth, population, and competing demands for land (including bio- fuels and recreational activities). For instance, one study ana- lyzed the impact of climate change, CO2 fertilization, and ozone damages on agriculture. This study found opposite ef- fects of ozone and climate change as ozone damages are pre- dicted to be the largest in the northern temperate regions, while these regions are expected to benefit from climate change. Climate Change and Policy | Climate Change and Food Situation 27 Mitigation Policies and Their Impacts on Agriculture and Food Mitigation policies aim to reduce GHG emissions and increase carbon sequestration in order to limit anthropogenic changes in climate.