Abstract: Here we present the results from an intercomparison of multiple global gridded crop models (GGCMs) within the framework of the Agricultural Model Intercomparison and Improvement Project and the Inter-Sectoral Impacts Model Intercomparison Project. Results indicate strong negative effects of climate change, especially at higher levels of warming and at low latitudes; models that include explicit nitrogen stress project more severe impacts. Across seven GGCMs, five global climate models, and four representative concentration pathways, model agreement on direction of yield changes is found in many major agricultural regions at both low and high latitudes; however, reducing uncertainty in sign of response in mid-latitude regions remains a challenge. Uncertainties related to the representation of carbon dioxide, nitrogen, and high temperature effects demonstrated here show that further research is urgently needed to better understand effects of climate change on agricultural production and to devise targeted adaptation strategies.

Abstract: Most people live in cities, but most food system studies and food security issues focus on the rural poor. Urban populations differ from rural populations in their food consumption by being generally wealthier, requiring food trade for their food security, defined as the extent to which people have adequate diets. Cities rarely have the self-provisioning capacity to satisfy their own food supply, understood as the extent to which the food consumed by the city’s population is produced from the city’s local agro-ecosystems. Almost inevitably, a city’s food security is augmented by production from remote landscapes, both internal and external in terms of a state’s jurisdiction. We reveal the internal and external food flows necessary for the food security of three wealthy capital cities (Canberra, Australia; Copenhagen, Denmark; Tokyo, Japan). These cities cover two orders of magnitude in population size and three orders of magnitude in population density. From traded volumes of food and their sources into the cities, we calculate the productivity of the city’s regional and non-regional ecosystems that provide food for these cities and estimate the overall utilised land area. The three cities exhibit differing degrees of food self provisioning capacity and exhibit large differences in the areas on which they depend to provide their food. We show that, since 1965, global land area effectively imported to produce food for these cities has increased with their expanding populations, with large reductions in the percentage of demand met by local agro-ecosystems. The physical trading of food commodities embodies ecosystem services, such as water, soil fertility and pollination that are required for land-based food production. This means that the trade in these embodied ecosystem services has become as important for food security as traditional economic mechanisms such as market access and trade. A future policy question, raised by our study, is the degree to which governments will remain committed to open food trade policies in the face of national political unrest caused by food shortages. Our study demonstrates the need to determine the food security and self-provisioning capacity of a wide range of rich and poor cities, taking into account the global location of the ecosystems that are provisioning them. (C) 2013 Elsevier B.V. All rights reserved.

Abstract: Government policy is a major human factor that causes changes in land use. Decisions on land management and land-use planning, as well as the analysis and quantification of policy consequences, may greatly benefit from the simulation of the dynamics of land-use systems. In the present study, we predicted land-use changes and their potential impacts on food security in the environmentally fragile Guyuan District, Ningxia Hui Autonomous Region (north-central China), under the influence of a program to convert sloping agricultural land to conservation uses. Baseline and conservation policy scenarios (2005 to 2020) were developed based on input from local stakeholders and expert knowledge. For the baseline and conservation policies, we formulated high-, moderate-, and low-growth scenarios, analyzed the driving mechanisms responsible for the land-use dynamics, and then applied a previously developed “dynamics of land systems” model to simulate changes in land uses based on the driving mechanisms. We found that spatially explicit policies can promote the conversion of land to more sustainable uses; however, decreasing the amount of agricultural and urban land and increasing grassland and forest cover will increase the risk of grain shortages, and the effect will be more severe under the conservation and high- growth scenarios than under the baseline and low-growth scenarios. The Guyuan case study suggests that, during the next decade, important trade-offs between environmental conservation and food security will inevitably occur. Future land-use decisions should carefully consider the balance between land resource conservation, agricultural production, and urban expansion.