Roy Darwin

U.S. agriculture and climate change: New results

We examined the impacts on U.S. agriculture of transient climate change assimulated by 2 global general circulation models focusing on the decades ofthe 2030s and 2090s. We examined historical shifts in the location of cropsand trends in the variability of U.S. average crop yields, finding thatnon-climatic forces have likely dominated the north and westward movement ofcrops and the trends in yield variability. For the simulated future climateswe considered impacts on crops, grazing and pasture, livestock, pesticide use,irrigation water supply and demand, and the sensitivity to international tradeassumptions, finding that the aggregate of these effects were positive for theU.S. consumer but negative, due to declining crop prices, for producers. Weexamined the effects of potential changes in El Niño/SouthernOscillation (ENSO) and impacts on yield variability of changes in mean climateconditions. Increased losses occurred with ENSO intensity and frequencyincreases that could not be completely offset even if the events could beperfectly forecasted. Effects on yield variability of changes in meantemperatures were mixed. We also considered case study interactions ofclimate, agriculture, and the environment focusing on climate effects onnutrient loading to the Chesapeake Bay and groundwater depletion of theEdwards Aquifer that provides water for municipalities and agriculture to theSan Antonio, Texas area. While only case studies, these results suggestenvironmental targets such as pumping limits and changes in farm practices tolimit nutrient run-off would need to be tightened if current environmentalgoals were to be achieved under the climate scenarios we examined

Estimates of the economic effects of sea level rise

Regional estimates of direct cost (DC) are commonly used to measure the economic damages of sea level rise. Such estimates suffer from three limitations:(i) values of threatened endowments are not well known, (ii) loss of endowments does not affect consumer prices, and (iii) international trade is disregarded. Results in this paper indicate that these limitations can significantly affect economic assessments of sea level rise. Current uncertainty regarding endowment values (as reflected in two alternative data sets), for example, leads to a 17 percent difference in coastal protection, a 36 percent difference in the amount of land protected, and a 36 percent difference in DC globally. Also, global losses in equivalent variation (EV), a welfare measure that accounts for price changes, are 13 percent higher than DC estimates. Regional EV losses may be up to 10 percent lower than regional DC, however, because international trade tends to redistribute losses from regions with relatively high damages to regions with relatively low damages.

Land use and cover in ecological economics

A basic premise of ecological economics is that the world economy is embedded in and dependent upon Earths ecosystem. Because land is a basic source of mass and energy throughput in all terrestrial ecosystems, land use and cover represents an integrating element in ecological economics. We have developed a global model that captures this concept. We illustrate this concepts usefulness by showing how global changes in climate, human populations, and international trade policies might affect tropical forests. Results from our scenarios indicate that such changes would likely have adverse effects on the health and integrity of tropical forest ecosystems. Results from our scenarios also indicate that forest depletion in Southeast Asia can be correlated with numerous economic indicators. Whether the correlation with a particular economic variable is positive or negative depends on the global change scenario. This merely reflects the fact that interactions between economic and ecological phenomena are complex. Modeling capabilities can be expanded by adding economic and ecological detail, including more material on throughput, and developing methods for simulating dynamic analyses.

Effects of Greenhouse Gas Emissions on World Agriculture, Food Consumption, and Economic Welfare

Because of many uncertainties, quantitative estimates of agriculturally related economic impacts of greenhouse gas emissions are often given low confidence. A major source of uncertainty is our inability to accurately project future changes in economic activity, emissions, and climate. This paper focuses on two issues. First, to what extent do variable projections of climate generate uncertainty in agriculturally related economic impacts? Second, to what extent do agriculturally related economic impacts of greenhouse gas emissions depend on economic conditions at the time of impacts? Results indicate that uncertainty due to variable projections of climate is fairly large for most of the economic effects evaluated in this analysis. Results also indicate that economic conditions at the time of impact influence the direction and size of as well as the confidence in the economic effects of identical projections of greenhouse gas impacts. The economic variable that behaves most consistently in this analysis is world crop production. Increases in mean global temperature, for example, cause world crop production to decrease on average under both 1990 and improved economic conditions and in both instances the confidence with respect to variable projections of climate is medium (e.g.,67%) or greater. In addition and as expected, CO2 fertilization causesworld crop production to increase on average under 1990 and improved economic conditions. These results suggest that crop production may be a fairly robust indicator of the potential impacts of greenhouse gas emissions.A somewhat unexpected finding is that improved economic conditions are not necessarily a panacea to potential greenhouse-gas-induced damages, particularly at the region level. In fact, in some regions, impacts of climate change or CO2 fertilization that are beneficial undercurrent economic conditions may be detrimental under improved economic conditions (relative to the new economic base). Australia plus New Zealand suffer from this effect in this analysis because under improved economic conditions they are assumed to obtain a relatively large share of income from agricultural exports. When the climate-change and CO2-fertilization scenariosin this analysis are also included, agricultural exports from Australia plus New Zealand decline on average. The resultant declines in agricultural income in Australia plus New Zealand are too large to be completely offset by rising incomes in other sectors. This indicates that regions that rely on agricultural exports for relatively large shares of their income may be vulnerable not only to direct climate-induced agricultural damages, but also to positive impacts induced by greenhouse gas emissions elsewhere.

Resource use and technological progress in agriculture: a dynamic general equilibrium analysis

We analyze the global effects of economic and population growth and the impact of a slowdown in agricultural total factor productivity (TFP) on agriculture and forest resources using a dynamic multi-region computable general equilibrium model with land use and cover detail. Given the current consensus about the growth of the world economy, our results suggest that food security will not be threatened and agricultural activities will not encroach on forest resources over the next decade. A slowdown in agricultural TFP growth might lead to higher crop prices in all regions, with South East Asia facing the steepest increases. A slowdown in agricultural TFP growth also might be accompanied by higher conversion rates of forestland to farmland as well as by greater environmental or ecological damages on the remaining forestland.

Estimating costs of protecting global ecosystem diversity

We estimate the costs to regional economies (as measured by the value of market goods and services forgone) from setting aside land to protect ecosystem diversity. Globally, our framework incorporates 43 unique sets of biological resources. The total annual costs (in 1990 dollars) of retiring 5, 10, and 15% of the worlds land area to protect these resources are

World Agriculture and Climate Change: Economic Adaptations

45.5,

The Impact of Global Warming on Agriculture: A Ricardian Analysis: Comment

93.3, and

FARM: A Global Framework for Integrated Land Use/Cover Modeling

143.8 billion, respectively. About 45% of global costs occur in Japan and the EC; the US cost share is 15%. Among regional economies, the most impacted sectors are crops, livestock, and forest products.