The Climate Impacts: Global and Regional Adaptation Support Platform

This study describes the potential of peri-urban agriculture for 2,383 cities worldwide by determining their "carrying capacity". It combines several worldwide data sets to determine the food consumption demand of the inhabitants and the fraction which can be met with regional food production. This fraction is defined as the carrying capacity and is shown in figure 1. The carrying capacity is given for different food consumption scenarios and for different yield scenarios.

One big challenge of the 21st century is and will be massive urbanization. It is expected that more than 7 out of 10 people will live in a city by 2050. Crucial developments towards a sustainable future will therefore take place in cities. One important approach for sustainable city development is to re-localize food production and to close urban nutrient cycles through better waste management. The identification of areas that can increase food production, while ensuring the sustainability of natural resources and maintaining urban needs will be a major task for cities in the future.

Figure 1: Identified urban clusters and defined peri-urban areas for Austria

It is possible to feed cities by products grown in their peri-urban area, but there are large regional differences in production capabilities and high carrying capacities mainly result from high agricultural productivity in the peri-urban area. For a maximum crop yield scenario on today's already existing agricultural areas, 867 of the observed 2,838 cities are capable of supplying their entire population with their current respective national calories consumption. Even for a minimum crop yield scenario, 76 cities reach full supply.

Figure 2: Global carrying capacity for today's agricultural areas and a maximum yield scenario

Interpretation aid and possible limitations

The results are just possible yields and don't show the current state. Furthermore the results are not based on administrative areas, but on clustered land cover data, see figure 2. An example: Berlin has a carrying capacity of 32% for the maximum yield scenario and the current food consumption. In this example Berlin also includes Potsdam and several other close surrounding cities. The carrying capacity is calculated for all inhabitants, in this case 1.2 million people of the Berlin cluster could be supplied with enough kcal for their current food consumption, derived by the peri-urban agricultural areas. Considering a FAO recommended norm dietary this number would increase to 47% of the population.

Only peri-urban and no urban agriculture was considered. Havana, which is the most cited city for a complete self-sustaining food supply, does not have a high carrying capacity in this study. This is caused by the high fraction of urban agriculture in Havana. Due to the given resolution of the used datasets, these findings provide a large scale global overview and cannot replace local case studies.

Method

The following flow chart explains how the data was prepared and the analysis performed:

There are five food scenarios: actual diet on national level, minimum diet (2,100 kcal with 200 kcal of animal products), norm diet (2,800 kcal with 500 kcal of animal products), maximum diet (3,500 kcal with 1,000 kcal of animal products) and the crop diet which describes only the vegetarian part of today's diet. Additional two yield scenarios are available. The maximum yield scenario considers fertilizers and the most kcal yielding crop for each food group. The minimum yield scenario uses no fertilizer and considers only the crop with the lowest kcal content for each food group [6].

References

[1] Hernán D Rozenfeld, Diego Rybski, José S Andrade, Michael Batiy, H Eugene Stanley, and Hernán a Makse. Laws of population growth. Proceedings of the National Academy of Sciences of the United States of America, 105(48):18702-7, December 2008.

[2] ESA (European Space Agency) 2010 The Ionia GlobCover project. Globcover land cover v2.1. Website.
Available online at http://ionia1.esrin.esa.int. Last accessed 25 March 2013.

[3] Center for International Earth Science Information Network (CIESIN), Columbia University; International Food Policy Research Institute (IFPRI), The World Bank; and Centronternacional de Agricultura Tropical (CIAT). 2011. Global Rural-Urban Mapping Project, Version GRUMPv1: Settlement Points. Palisades, NY: Socioeconomic Data and Applications Center (SEDAC), Columbia University.
Available at: http://sedac.ciesin.columbia.edu/data/dataset/grump-v1-settlement-points. Last accessed 25 March 2013.

[4] FAO/IIASA, 2010. Global Agro-ecological Zones (GAEZ v3.0). FAO, Rome, Italy and IIASA, Laxenburg, Austria. Last accessed 25 March 2013.

[5] Food and Agriculture Organization of the United Nationst. Fao statistical database. Website.
Available online at http://faostat.fao.org/; last accessed 17 August 2012.

[6] Steffen Kriewald, Anselmo Garcia Cantu Ros, Till Sterzel, Prajal Pradhan, Jürgen P. Kropp. Feeding cities in the post-carbon age, can peri-urban agriculture reclaim a place? In preparation. 2013.

Data sources

Several datasets with global coverage were combined. Datasets included are: the GRUMPv1 Settlement Points (GSP) [3], the Global Land Cover Service (GlobCover) [2] and the Global Agroecological Zones (GAEZ) [4]. In addition, census based food consumption data at a national level was used. This data and the nutrient content of different crops are available at the Food and Agriculture Organization of the United Nations (FAO) website within the FAO Statistical Databases (FAOSTAT) [5].