This policy brief, published by Science, outlines how scientists can evaluate the performance of food value chains in developing countries to establish practices that help smallholder farmers meet growing consumer demands for sustainable food.

The term 'food value chain' (FVC) describes the process of bringing farm products to consumers. It includes activities such as agricultural production, processing, storage, and distribution. In developing countries, these are changing rapidly because of urbanisation, income growth, and the expansion of modern food firms.

This means that consumers are now looking at more than just the price of food: at its nutrient content, safety, as well as its impact on natural resources, farm workers and greenhouse gas emissions ­— prompting regulators and firms to develop new labelling and production standards.

Scientists can help smallholder farmers meet these new demands by incorporating existing evidence into measuring the performance of FVCs and by following six principles that advance the research agenda.

Among these is the recommendation that they focus on identifying policies and innovations to improve domestic FVCs, not just those aimed at export, because these are likely to produce more economic benefits that can help reduce poverty.

Learning more about how to reduce the costs of FVCs will also help to enhance the efficiency of marketing channels.

And more research into post-harvest technologies can reduce unnecessary losses that put pressure on land and water resources — currently, farmers in developing countries lose up to 50 per cent of harvested food.

Researchers also need to explore how smallholders' participation in FVCs can improve the conservation of water, soil and energy, and what impact it might have on the value that consumers place on 'green' farming.

Finally, they must investigate whether certificates of compliance with product standards allow smallholders to enter higher-return markets, promote sustainable farming, or foster farming innovation.

Very little is known about how complex FVCs affect poverty and the environment, stress the authors, so scientists must be cautious when recommending policies.

But they must begin to develop rigorous measures to study these processes and establish practices that can benefit the poor and protect the environment. They must also use existing methods, such as models of consumer behaviour, to promote informed decision making by consumers and policymakers.

This policy brief was written by Miguel Gómez from Cornell University in Ithaca, United States, and colleagues.