Potential consequences of climate change on crop production can be studied using mechanistic crop simulation models. While a broad variety of maize simulation models exist, it is not known whether different models diverge on grain yield responses to changes in climatic factors, or whether they agree in their general trends related to phenology, growth, and yield. With the goal of analyzing the sensitivity of simulated yields to changes in temperature and atmospheric carbon dioxide concentrations [CO2 ], we present the largest maize crop model intercomparison to date, including 23 different models. These models were evaluated for four locations representing a wide range of maize production conditions in the world: Lusignan (France), Ames (USA), Rio Verde (Brazil) and Morogoro (Tanzania). While individual models differed considerably in absolute yield simulation at the four sites, an ensemble of a minimum number of models was able to simulate absolute yields accurately at the four sites even with low data for calibration, thus suggesting that using an ensemble of models has merit. Temperature increase had strong negative influence on modeled yield response of roughly -0.5 Mg ha(-1) per °C. Doubling [CO2 ] from 360 to 720 μmol mol(-1) increased grain yield by 7.5% on average across models and the sites. That would therefore make temperature the main factor altering maize yields at the end of this century. Furthermore, there was a large uncertainty in the yield response to [CO2 ] among models. Model responses to temperature and [CO2 ] did not differ whether models were simulated with low calibration information or, simulated with high level of calibration information.

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Potato and its derivatives increasingly become globally traded products. Commercial companies more and more want to quantify the environmental footprints such as the efficiency of the use of land and water, greenhouse gas emissions, and the risks of eutrophication and contamination of the environment with pesticides. From various sources, global maps with grid cells of circa 8,600 ha (near the equator) were drawn representing potatoharvested area, potato fresh tuber yield (land use efficiency), slopes (risks of erosion), precipi-tation deficit (risks of depletion of fresh water resources through irrigation), and average daily maximum temperature throughout the season (risks of occurrence of pest epidemics and emission of pesticides). Hotspots for erosion are the slopes of the mountains in the Andes, African Rift, Southern China and volcanic areas in southern China, and the island countries in Southeast Asia. Fresh water availability may become limited in the East of North America, northern India, and China. Risks of insects are increased in continental hot summer climates and short spring crops with high temperatures towards harvest. Late blight is a threat in all humid areas such as maritime Europe, equatorial tropical highlands, and the humid western Pacific Ring. The examples discussed in this paper can be elaborated for more soil and weather-related factors such as acidity and salinity and heat waves or torrential rains. Sustainable long-term and long-range sourcing is deliberated as well as repercussions of trends such as globalization and climate change; the latter being relative favorable for the root and tuber crop potato compared to grain crops.

In a bio-based economy, chemicals, materials, biofuels, and other forms of energy will be produced from biomass. Pressure on agricultural land will thus increase, calling for highly effi cient solutions in terms of land use, with minimal environmental impacts. In order to gain better insight into the available options and their trade-offs, this perspective studies the production of polylactic acid (PLA), bioethanol, and bio-based polyethylene (PE) from wheat, maize, sugarbeet, sugarcane, and Miscanthus. While in current agricultural practice some plants are harvested and used as whole crop (e.g. Miscanthus), for others only part of the plant is used, with the remainder being returned to the fi eld (e.g. wheat straw). In order to obtain an understanding of the unused potential we assume as default case that all agricultural residues and processing co-products are used for energy purposes, thereby replacing non-renewable energy. We conclude that this agricultural practice would allow to substantially reduce non-renewable energy use (NREU). We also fi nd a clear difference in ranking depending on whether we study (i) NREU per (metric) tonne of product or (ii) Avoided NREU per hectare of land. The latter seems a suitable choice in a world where land availability is limited. In this case, we identify PLA as the preferred choice, irrespective of the type of crop. The production of ethanol for the replacement of fuels scores as the worst option for all crops. For each of the products studied, sugarcane offers the highest savings per hectare followed by sugarbeet

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