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Public policy supports biofuels for their benefits to agricultural economies, energy security and the environment. The environmental rationale is premised on greenhouse gas (GHG, 'carbon') emissions reduction, which is a matter of contention. This issue is challenging to resolve because of critical but difficult-to-verify assumptions in lifecycle analysis (LCA), limits of available data and disputes about system boundaries. Although LCA has been the presumptive basis of climate policy for fuels, careful consideration indicates that it is inappropriate for defining regulations. This paper proposes a method using annual basis carbon (ABC) accounting to track the stocks and flows of carbon and other relevant GHGs throughout fuel supply chains. Such an approach makes fuel and feedstock production facilities the focus of accounting while treating the CO emissions from fuel end-use at face value regardless of the origin of the fuel carbon (bio- or fossil). Integrated into cap-and-trade policy and including provisions for mitigating indirect land-use change impacts, also evaluated on an annual basis, an ABC approach would provide a sound carbon management framework for the transportation fuels sector. [ABSTRACT FROM AUTHOR]

The great human-environmental diversity of Mexico provides a framework for an initial understanding of the wide disparities between rich and poor. Mexico is still dominated in many regions by agriculture, and during the last 25 years, weather-related disasters have accounted for about 80% of economic losses. This is dramatic, especially considering that this sector produces only ca. 4% of GDP while providing a livelihood to one-quarter of the country’s population. Based on a spatial model, this paper tests the contribution of natural disasters to catalyzing the emigration process in vulnerable regions throughout Mexico. Besides coping and adaptive capacity, we assess the effect of economic losses from disasters in combination with adverse production and trade conditions during the 1990s in triggering out-migration. [ABSTRACT FROM AUTHOR]

This paper evaluates the role of trade as a mechanism of economic adjustment to the impacts of climate change on agriculture. The study uses a model of the world economy able to reflect changes in comparative advantage; the model is used to test the hypotheses that trade can assure that, first, satisfying global agricultural demand will not be jeopardized, and, second, general access to food will not decrease. The hypotheses are tested for three alternative scenarios of climate change; under each scenario, regions adjust to the climatic assumptions by changing the land areas devoted to agriculture and the mix of agricultural goods produced, two of the major mechanisms of agricultural adaptation. We find that trade makes it possible to satisfy the world demand for agricultural goods under the changed physical conditions. However, access to food decreases in some regions of the world. Other patterns also emerge that indicate areas of concern in relying on trade as a mechanism for the adjustment of agriculture to likely future changes in climate. [ABSTRACT FROM AUTHOR]

Using recent advances in statistical crop yield modelling and a unique dataset consisting of yield time series for Russian regions over the period from 1955 to 2012, the study investigates the potential impact of climate change (CC) on the productivity of the three most important grains. Holding current grain growing areas fixed, the aggregate productivity of the three grains is predicted to decrease by 6.7% in 2046-2065 and increase by 2.6% in 2081-2100 compared to 1971-2000 under the most optimistic representative emission concentration pathway (RCP). Based on the projections for the three other RCPs, the aggregate productivity of the three studied crops is assessed to decrease by 18.0, 7.9 and 26.0% in the medium term and by 31.2, 25.9 and 55.4% by the end of the century. Our results indicate that CC might have a positive effect on winter wheat, spring wheat and spring barley productivity in a number of regions in the Northern and Siberian parts of Russia. However, due to the highly damaging CC impact on grain production in the most productive regions located in the South of the country, the overall impact tends to be negative. Therefore, a shift of agricultural production to the Northern regions of the country could reduce the negative impact of CC on grain production only to a limited extent. More vigorous adaptation measures are required to maintain current grain production volumes in Russia under CC. [ABSTRACT FROM AUTHOR]

100-year Global Warming Potentials (GWPs) are used almost universally to compare emissions of greenhouse gases in national inventories and reduction targets. GWPs have been criticised on several grounds, but little work has been done to determine global mitigation costs under alternative physics-based metrics . We used the integrated assessment model MESSAGE to compare emission pathways and abatement costs for fixed and time-dependent variants of the Global Temperature Change Potential (GTP) with those based on GWPs, for a policy goal of limiting the radiative forcing to a specified level in the year 2100. We find that fixed 100-year GTPs would increase global abatement costs (discounted and aggregated over the 21 century) under this policy goal by 5-20 % relative to 100-year GWPs, whereas time-varying GTPs would reduce costs by about 5 %. These cost differences are smaller than differences arising from alternative assumptions regarding agricultural mitigation potential and much smaller than those arising from alternative radiative forcing targets. Using the land-use model GLOBIOM, we show that alternative metrics affect food production differently in different world regions depending on regional characteristics of future land-use change to meet growing food demand. We conclude that under scenarios of complete participation, the choice of metric has a limited impact on global abatement costs but could be important for the political economy of regional and sectoral participation in collective mitigation efforts, in particular changing costs and gains over time for agriculture and energy-intensive sectors. [ABSTRACT FROM AUTHOR]

Perennial crops are among the most valuable of California's diverse agricultural products. They are also potentially the most influenced by information on future climate, since individual plants are commonly grown for more than 30 years. This study evaluated the impacts of future climate changes on the 20 most valuable perennial crops in California, using a combination of statistical crop models and downscaled climate model projections. County records on crop harvests and weather from 1980 to 2005 were used to evaluate the influence of weather on yields, with a series of cross-validation and sensitivity tests used to evaluate the robustness of perceived effects. In the end, only four models appear to have a clear weather response based on historical data, with another four presenting significant but less robust relationships. Projecting impacts of climate trends to 2050 using historical relationships reveals that cherries are the only crop unambiguously threatened by warming, with no crops clearly benefiting from warming. Another robust result is that almond yields will be harmed by winter warming, although this effect may be counteracted by beneficial warming in spring and summer. Overall, the study has advanced understanding of climate impacts on California agriculture and has highlighted the importance of measuring and tracking uncertainties due to the difficulty of uncovering crop-climate relationships. [ABSTRACT FROM AUTHOR]

California agriculture is driven by the interactions between technology, resources, and market demands. Future production is a balance between the rates of change in these variables and environmental factors including climate change. With tight statewide water supplies and agriculture being an important part of the California economy, quantifying the economic consequences of changes in these variables is important for addressing related policy questions. We estimate the economic effects of climate change on California crop farming by year 2050 using the Statewide Agricultural Production Model (SWAP). With climate warming, crop yields are expected to decline, production costs to increase, and water supplies to fall. These negative effects may be partially offset by higher crop prices and technological improvements. Results indicate that gross agricultural revenues across all regions are reduced under climate change, as is water usage. However, given the climate-induced reductions in water supply and crop yields, reductions in revenue are proportionally less due to shifting crop demands, technological change, and a shift to higher value less water intensive crops. Given the long time horizon required in this study, the results should not be considered a projection or forecast, but as a probable outcome of the interaction of several uncertain driving forces. [ABSTRACT FROM AUTHOR]

Using county-level data from the United States Department of Agriculture's Census of Agriculture, this study evaluates the effect of weather and climate on agricultural profits in the State of California. The approach is to estimate revenue less variable production cost per acre as a function of land characteristics, weather realizations, and climate. This model is then used to evaluate the effect of two scenarios of climate change for the state of California over the coming century. The preferred estimates indicate that climate change is associated with a negative effect on aggregate agricultural profits by the end of the century. There are significant caveats to this result, including the lack of statistical precision, and keeping water supply and farm prices constant. [ABSTRACT FROM AUTHOR]

n assessment of the potential impact of climate change and the concurrent increase of atmospheric CO concentration on eastern Washington State agriculture was conducted. Climate projections from four selected general circulation models (GCM) were chosen, and the assessment included the crops with larger economic value for the state (apples, potatoes, and wheat). To evaluate crop performance, a cropping system simulation model (CropSyst) was utilized using historical and future climate sequences. Crops were assumed to receive adequate water (irrigated crops), nutrients, and control of weeds, pests and diseases. Results project that the impact of climate change on eastern Washington agriculture will be generally mild in the short term (i.e., next two decades), but increasingly detrimental with time (potential yield losses reaching 25% for some crops by the end of the century). However, CO elevation is expected to provide significant mitigation, and in fact result in yield gains for some crops. The combination of increased CO and adaptive management may result in yield benefits for all crops. One limitation of the study is that water supply was assumed sufficient for irrigated crops, but other studies suggest that it may decrease in many locations due to climate change. [ABSTRACT FROM AUTHOR]

During the Holocene strong gradients in the distribution of technology including subsistence ways emerged on a global scale. These patterns were further amplified in historic times and are still visible through worldwide differences in national wealth. In order to evaluate major factors responsible for the shift from foraging to food production we here employ quantitative methods by developing a deterministic but simple model. After compiling existing maps of potential vegetation at 5000 BP the inhabited world is split into 197 regions with homogeneous environmental conditions. Suitable variables for the macro-economic and cultural development in the Neolithic period are found to be farming to hunting-gathering ratio, number of agricultural economies and a technological development index. The model explicitly describes economic adaptation, growth and migration of human populations together with the spread of their cultural characteristics; it accounts for over-exploitation of natural resources, crowding mortality and the climate variability on a millennium scale. In a thorough model validation region specific trajectories are compared to archaeological evidence revealing a high correspondence. Major parts of the known sequence of Neolithic centers including the timing differences are robustly reproduced. A series of known problems in prehistory is discussed comprising the lag between domestication and full scale farming, the off-leveling of the technological boost following the transition, the emergence of distinct migration waves and sensitivity to climate fluctuations. Not mere population pressure but continuous innovation and competition between subsistence strategies is identified as a prime mover of agricultural development. The results suggest that few aspects of biogeography may have determined the observed continental gradients in the number of domesticable species ultimately leading to an increasing differentiation in technology and demography. [ABSTRACT FROM AUTHOR]