The increasing global demand for biofuels will require conversion of conventional agricultural or natural ecosystems. Expanding biofuel production into areas now used for agriculture reduces the need to clear natural ecosystems, leading to indirect climate benefits through reduced greenhouse-gas emissions and faster payback of carbon debts. Biofuel expansion may also cause direct, local climate changes by altering surface albedo and evapotranspiration, but these effects have been poorly documented.
This paper was prepared for Stanford University’s Global Food Policy and Food Security Symposium Series, hosted by the Center on Food Security and the Environment, and supported by the Bill and Melinda Gates Foundation. The talk was delivered April 7, 2011.
Improved understanding of the influence of climate on agricultural production is needed to cope with expected changes in temperature and precipitation, and an increasing number of undernourished people in food insecure regions. Many studies have shown the importance of seasonal climatic means in explaining crop yields. However, climate variability is expected to increase in some regions and have significant consequences on food production beyond the impacts of changes in climatic means.
New approaches are needed to accelerate understanding of climate impacts on crop yields, particularly in tropical regions. Past studies have relied mainly on crop-simulation models, or statistical analyses based on reported harvest data, each with considerable uncertainties and limited applicability to tropical systems. However, a wealth of historical crop-trial data exists in the tropics that has been previously untapped for climate research.
Biomass-derived energy offers the potential to increase energy security while mitigating anthropogenic climate change, but a successful path toward increased production requires a thorough accounting of costs and benefits. Until recently, the efficacy of biomass-derived energy has focused primarily on biogeochemical consequences.
Marine aquaculture is expanding rapidly without reliable quantification of effluents. The present study focuses on understanding the transport of dissolved wastes from aquaculture pens in near-coastal environments using the hydrodynamics code SUNTANS (Stanford Unstructured Nonhydrostatic Terrain-following Adaptive Navier-Stokes Simulator), which employs unstructured grids to compute flows in the coastal ocean at very high resolution.
Climate volatility could change in the future, with important implications for agricultural productivity. For Tanzania, where food production and prices are sensitive to climate, changes in climate volatility could have severe implications for poverty. This study uses climate model projections, statistical crop models, and general equilibrium economic simulations to determine how the vulnerability of Tanzania's population to impoverishment by climate variability could change between the late 20th Century and the early 21st Century.
This Statement summarizes the results of the third in a series of consultations between agricultural scientists (in particular those interested in the conservation and use of crop diversity in plant improvement) and climate scientists on how to adapt agriculture to climate change. The first meeting, also held at Bellagio (3-7 September 2007), looked at the Conservation and Use of Global Crop Genetic Resources in the Face of Climate Change.
This paper examines climate adaptation strategies of farmers in the Limpopo Basin of South Africa. Survey results show that while many farmers noticed long-term changes in temperature and precipitation, most could not take remedial action. Lack of access to credit and water were cited as the main factors inhibiting adaptation. Common adaptation responses reported included diversifying crops, changing varieties and planting dates, using irrigation, and supplementing livestock feed.
Prevailing opinion assigns the Tibetan Plateau a crucial role in shaping Asian climate, primarily by heating of the atmosphere over Tibet during spring and summer. Accordingly, the growth of the plateau in geologic time should have written a signature on Asian paleoclimate. Recent work on Asian climate, however, challenges some of these views. The high Tibetan Plateau may affect the South Asian monsoon less by heating the overlying atmosphere than by simply acting as an obstacle to southward flow of cool, dry air.
This paper aims to demonstrate the relationships between ENSO and rice production of Jiangxi province in order to identify the reason that ENSO might have little effect on Chinese rice production. Using a data set with measures of Jiangxi's climate and rice production, we find the reason that during 1985 and 2004 ENSO's well correlated with rainfall did not promote Chinese rice production. First, the largest effects of ENSO mostly occur in the months when there is no rice in the field. Second, there is almost no temperature effect.
Deforestation is a main driver of climate change and biodiversity loss. An incentive mechanism to reduce emissions from deforestation and forest degradation (REDD) is being negotiated under the United Nations Framework Convention on Climate Change. Here we use the best available global datasets on terrestrial biodiversity and carbon storage to map and investigate potential synergies between carbon and biodiversity-oriented conservation. A strong association (rS= 0.82) between carbon stocks and species richness suggests such synergies would be high, but unevenly distributed.
Roughly a billion people around the world continue to live in state of chronic hunger and food insecurity. Unfortunately, efforts to improve their livelihoods must now unfold in the context of a rapidly changing climate, in which warming temperatures and changing rainfall regimes could threaten the basic productivity of the agricultural systems on which most of the world's poor directly depend.
Brazil has developed a large-scale commercial agricultural system, recognized worldwide for its role in domestic economic growth and expanding exports. However, the success of this sector has been associated with widespread destruction of Brazilian ecosystems, especially the Cerrado and the Brazilian Amazon rainforest, as well as environmental degradation. Brazil's agricultural development has also led to land consolidation, aggravating a historical land distribution inequality.
The recent upheavals in staple food prices, financial markets, and the global economy raise questions about the state of food insecurity, the nature of price variability, and the appropriate strategies for international agricultural development. For decades preceding this turmoil, agriculture had received waning attention from the global development community as real food prices declined on trend. Analysts who worried about food insecurity focused on the fate of poor producers.
Expanding croplands to meet the needs of a growing population, changing diets, and biofuel production comes at the cost of reduced carbon stocks in natural vegetation and soils. Here, we present a spatially explicit global analysis of tradeoffs between carbon stocks and current crop yields. The difference among regions is striking. For example, for each unit of land cleared, the tropics lose nearly two times as much carbon (∼120 tons·ha-1 vs. ∼63 tons·ha-1) and produce less than one-half the annual crop yield compared with temperate regions (1.71 tons·ha-1·y-1 vs. 3.84 tons·ha-1·y-1).
Predicting the potential effects of climate change on crop yields requires a model of how crops respond to weather. As predictions from different models often disagree, understanding the sources of this divergence is central to building a more robust picture of climate change's likely impacts. A common approach is to use statistical models trained on historical yields and some simplified measurements of weather, such as growing season average temperature and precipitation.
Global demand for agricultural products such as food, feed, and fuel is now a major driver of cropland and pasture expansion across much of the developing world. Whether these new agricultural lands replace forests, degraded forests, or grasslands greatly influences the environmental consequences of expansion. Although the general pattern is known, there still is no definitive quantification of these land-cover changes.
This paper analyses the vulnerability of South African agriculture to climate change and variability by developing a vulnerability index and comparing vulnerability indicators across the nine provinces of the country. Nineteen environmental and socio-economic indicators are identified to reflect the three components of vulnerability: exposure, sensitivity, and adaptive capacity. The results of the study show that the regions most exposed to climate change and variability do not always overlap with those experiencing high sensitivity or low adaptive capacity.
Is it possible to combine modern tropical agriculture with environmental conservation? Brazilian agriculture offers encouraging examples that achieve high production together with adequate environmental protection. However, these effective practices may soon lose ground to the conventional custom of resource overexploitation and environmental degradation.
In a recent paper, we documented strong historical linkages between temperature and civil conflict in Africa (1). Sutton et al. (2) raise two concerns with our findings: that the relationship between temperature and war is based on common trends and is therefore spurious, and that our model appears overly sensitive to small specification changes. Both concerns reflect a basic misunderstanding of the analysis.
Although China and the United States are the two largest emitters of greenhouse gases, China’s emissions on a per capita basis are significantly lower than those of the U.S.: in 2005, per capita emissions in China were 5.5 metric tons—much less than the U.S. (23.5 metric tons per capita), and also lower than the world average of 7.03 metric tons. China’s total GHG emissions were 7,234.3 million tons of CO2 equivalent (tCO2e) in 2005, 15.4 percent of which came from the agricultural sector. By comparison, total U.S.
Improving crop yields in major agricultural regions is one of the foremost scientific challenges for the next few decades. In Northwest India, the stagnation of wheat yields over the past decade presents a distressing contrast to the tremendous yield gains achieved during the Green Revolution. One commonly proposed way to raise yields is to reduce the often considerable gap between yield potential and average yields realized in farmers' fields, yet the likely effectiveness of different strategies to close this gap has been poorly known.