New study reveals scale of cropping in and around cities

Gideon and Steven are brothers who farm maize, onions and other vegetables. They use a petrol pump to pump ground water for watering their plants. Photo: Nana Kofi Acquah / IWMI

Gideon and Steven are brothers who farm maize, onions and other vegetables.
Photo: Nana Kofi Acquah / IWMI

 

Food production, globally, is taking on an increasingly urban flavor, according to a new study that finds 456 million hectares—an area about the size of the European Union—under cultivation in and around the world’s cities, challenging the rural orientation of most agricultural research and development work.

“This is the first study to document the global scale of food production in and around urban settings, and it is surprising to see how much the table is definitely getting closer and closer to the farm,” said Pay Drechsel, a scientist at the International Water Management Institute (IWMI), and co-author of the study, which was published in the November 2014 issue of the journal Environmental Research Letters.

The analysis, a collaboration between IWMI (under the CGIAR Research Program on Water, Land and Ecosystems [WLE]), University of California, Berkeley, and Stanford University, is the first global assessment to quantify urban and peri-urban croplands and document the resources they consume, namely water, which has both environmental and food safety implications.

The authors of the paper stated that their goal was to highlight the proximity of farming to cities in the quest for urban food security and sustainable development, given the largely rural focus of most agricultural research and policy work. In addition, they wanted to spotlight the starkly different view of urban farming one finds in the developed and developing world.

“We see this dichotomy where urban farming in wealthy countries is praised for reducing various footprints and enhancing a green economy, while in developing countries it is usually regarded as an inconvenient vestige of rural life that stands in the way of modernization,” said Drechsel. “That’s an attitude that needs to change.”

Drechsel and his colleagues note that urban agriculture, in addition to contributing to food security, puts marginal lands into productive use, assists in flood control, increases income opportunities for the poor and strengthens urban biodiversity. IWMI’s research has shown that, as cities grow, farming in their core areas usually makes space for other sectors, while new agricultural land becomes urban in city fringes or is taken under cultivation where space allows. Thus, the urban farming phenomenon is not on a decline, but spatially very dynamic.

In Accra, up to 10% of household wastewater is indirectly recycled by urban vegetable farms. These farms are now ‘recycling’ more wastewater than local treatment plants

Overall, the researchers found that 456 million hectares of land—about 1.1 billion acres—is being farmed in urban proximity. Most of that land lies just outside the city proper—within 20 kilometers—but 67 million hectares (about 166 million acres) is being farmed in open spaces in urban agglomerations. These findings buttress previous studies documenting that up to 70% of urban households in developing countries are engaged in some type of farming and food production.

Related studies have also revealed that urban farms don’t typically grow ‘calorie rich’ cereals such as wheat or rice. Rather, they most often produce high-value and nutritionally important perishable crops such as fresh vegetables. In sub-Saharan Africa, for example, urban farmers supply up to 90% of the leafy salad greens consumed in the region’s rapidly growing cities.

In urban areas of Ghana, everyday there are about 2,000 urban vegetable farmers supplying greens to 800,000 people,” said Drechsel. “Moreover, most of these farmers irrigate their fields with highly polluted water. In Accra, for example, up to 10% of household wastewater is indirectly recycled by urban vegetable farms. These farms are now ‘recycling’ more wastewater than local treatment plants.”

 

Irrigation and water usage on urban farms

The study finds that, within cities alone, there are about 24 million hectares of land under irrigation, globally, and 44 million hectares that are under rainfed cultivation. Those numbers are larger than the respective total area under rice cultivation in South Asia, area under maize in sub-Saharan Africa, or the cultivated croplands of the cerrados and llanos in Latin America and the Caribbean. Going forward, the researchers note the prospect of “irrigated urban croplands playing a larger role in more densely populated and/or increasingly water-scarce regions such as South Asia.” “In fact, today, some countries such as large parts of India are already more peri-urban than rural. And here we see how urban water needs compete with agricultural demands,” said Drechsel.

The researchers observe that water usage by urban farms is not just a water recycling opportunity, it can also potentially become a significant food safety concern. For example, while irrigation allows consumers to get vegetables in the dry (lean) season, it also potentially exposes them to pathogens that can be present in the poorly treated water. However, the researchers stated that the food safety issues, while important, can be addressed to maintain the many valuable and sometimes underappreciated contributions of urban farms.

Global map of irrigated and rainfed urban croplands with examples from three world regions

Global map of irrigated and rainfed urban croplands with examples from three world regions

 

A new portrait of urban farming

The richly detailed portrait of urban farming presented in the study was derived, in part, from new data and maps generated by researchers at the Goethe University of Frankfurt and the National Aeronautics and Space Administration (NASA) that use satellite imagery and other sources to provider greater insights into the distribution of croplands, globally. The authors state that their study may have actually underestimated urban croplands, as they focused on farmed areas in and around cities with at least 50,000 residents, even though many countries define areas with smaller populations as ‘urban’.

“This is an important first step toward better understanding urban crop production at the global and regional scales,” said Anne Thebo, an environmental engineer at the University of California, Berkeley, who was the lead author of the study. “In particular, by including farmlands in areas just outside of cities, we can begin to see what these croplands really mean for urban water management and food production.”

Researchers stated that further study is warranted, exploring how crop production in and around cities affects ecosystem services in the rural-urban corridor and, in particular, what it means for managing water resources where sanitation remains a challenge to maintaining food safety.

Research support was provided through the CGIAR Research Program on Water, Land and Ecosystems, and through grants provided by the United States Agency for International Development (USAID), Stanford University and the United States Environmental Protection Agency.

 

Read the paper:

Thebo, A.L.; Drechsel, P.; Lambin, E.F. 2014. Global assessment of urban and peri-urban agriculture: Irrigated and rainfed croplands. Environmental Research Letters 9(11).

Pay Drechsel is Theme Leader, Resource Recovery, Water Quality and Health at the International Water Management Institute (IWMI), Colombo, Sri Lanka.