Pretty Revised

Rio 20 years later

Is sustainable agriculture finally taking over?

The 1992 Earth Summit in Rio de Janeiro definitely increased the global focus on sustainability. As a result researchers and farmers have tried many ways to make agriculture more sustainable in the past two decades. These attempts had various levels of success.  However, one fervent advocate of sustainable agriculture, Jules Pretty, tirelessly informed the world about the increase and positive aspects of this type of agriculture. What can we say 20 years after Rio? Should we follow Pretty unconditionally or take a more differentiated opinion?

At the end of 1996 Jules Pretty and colleagues published a document to promote sustainable agriculture as a means to increase global food production.[1] Sustainable agriculture is here defined as the optimal use of internal resources and minimal use of external and non-renewable inputs. In this way by-products or wastes from one subsystem of the farm become inputs to another subsystem. Damage to the environment is sharply reduced. The document claims further that sustainable agriculture provides an opportunity to intensify and increase food production. From a sample of 63 projects in 20 countries it appeared that a transition to sustainable agriculture had the greatest yield impact in low-yielding rainfed agricultural systems. Average yields for maize, wheat, sorghum and millet under these circumstances showed a 100% increase over the yields in the unchanged, traditional systems.

In 2006 Pretty and others undertook a wider survey than the one of 1996 to convince possible non-believers.[2] This survey comprised 286 projects in 57 countries. A yield dataset from 198 projects revealed that sustainable agriculture caused an average crop yield increase of about 100% in smallholder rainfed agricultural systems. A recent publication of Pretty on the effects of sustainable agriculture focuses on Africa only.[3] This publication uses data from 40 sustainable agriculture projects in 20 African countries. Again it appears that agricultural intensification in a sustainable way increases average crop yields with a bit more than 100% without harm to the environment. For Pretty the challenge is now to spread sustainable agriculture to many more millions of generally small African farmers and pastoralists to attain food security.

For investigative readers the remarkable results from the surveys used by Pretty are difficult to verify. Robert Tripp commented on one survey that the conclusions are based almost entirely on reports of the sampled projects themselves and that these did not offer an independent means of verification.[4] The 1996 survey is also based mainly on project reports and secondary sources which are very often not accessible to the public. However, one accessible data source provides details on the remarkable yield successes in Senegal and Burkina Faso.[5] In the peanut basin of Senegal the combined use of manure with rock phosphate or the use of compost led to an increase of 200% in millet yield. The comparison was made to millet fields without applications of manure or compost. The farmer practice in this area is, however, to apply manure or compost every two years in an irregular way. Compared to this farmer practice the new method gives only a millet yield increase of 25-50%. In the Zabre region of Burkina Faso the use of compost increased millet and sorghum yields with 200% in dry years. These remarkable results have been obtained on a farm of 4.5 ha of an ecological farming association and on farms of members of a female association. It is, however, not specified how many women were able to obtain these results and what the size of their millet and sorghum fields were on which they applied the compost.

The crucial issue is actually not if you can double or triple yields with sustainable agriculture but if sustainable agriculture is applicable everywhere at any moment. Tripp (2006, p. 93) discovered that better access to labour, skills and contacts favours adoption of sustainable agriculture by better-resourced households. Pretty et al. (2011, p. 10) replied that successful projects of sustainable intensification by definition fit solutions to local needs and contexts, and thus take account of labour availability. But the same reasoning applies also to unsuccessful projects of introducing sustainable agriculture. A transition to sustainable agriculture takes only place when all conducive conditions are present.  Do most agricultural regions in the world have circumstances which enable the transition to sustainable agriculture?

Sustainable intensification of agriculture generally involves a higher use of labour per unit land due to labour intensive methods such as compost making and application of farmyard manure. Households invest these higher amounts of labour whenever they are forced or triggered to do so. They are forced when higher population densities decrease farm sizes and households have to increase food production per unit land in the absence of capital inputs. They are triggered when profitable markets are present which transform higher labour inputs into higher farm profits. Without force or trigger households are not eager to invest more labour per unit land. A good example of being forced to sustainable agriculture is Ukara, a small island in Lake Victoria, Tanzania. Prolonged population pressure and land shortage stimulated the intensive use of farmyard manure and green manure. However, farmers from Ukara who migrated to areas without land shortages immediately stopped the use of farmyard manure and green manure. Without force or trigger they started to grow crops on large farms in a labour-extensive way with a much higher return to invested labour in comparison to the situation on Ukara.[6]

A reversal from environmental friendly agriculture to increased use of external inputs took place in China on a wide scale in the past decades. The intensive use of farmyard manure, compost, green manure and azolla in irrigated rice has been replaced by heavy applications of mineral fertilizers. Reasons for this reversal in China are the increased availability of relatively inexpensive mineral fertilizers and labour shortages due to the disbanding of many agricultural communes.⁶ The China example shows that changed circumstances affect the usefulness of sustainable agriculture at a certain place and time. The focus of Pretty is on scaling up sustainable agriculture with no reference to possible reversals. Proper circumstances for sustainable agriculture are relatively high population densities with accompanying land-shortages, availability of sufficient livestock, good market access and absence of cheap, external, non-renewable inputs. These conditions are not everywhere present and if present can change any time. Instead of following Pretty as a devoted believer it is better to take a realistic position. Each agricultural region has to be analyzed properly if it fits a transition to sustainable agriculture. In the end it does not matter for the hungry if the increase in food production is based on compost or mineral fertilizers as long as it is sustainable.

Bert Meertens

Kweli Productions

June 2012

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[1] J.N. Pretty, J. Thompson and F. Hinchcliffe (1996) Sustainable Agriculture: Impacts on Food Production and Challenges for Food Security. Gatekeeper Series SA 60. International Institute for Environment and Development (IIED), London.

[2] J.N. Pretty et al. (2006) Resource-Conserving Agriculture Increases Yields in Developing Countries. Environmental Science & Technology, Vol. 40, No. 4, pp. 1114-1119.

[3] J. Pretty, C. Toulmin and S. Williams (2011) Sustainable intensification in African agriculture. International Journal of Agricultural Sustainability, Vol. 9 No. 1, pp. 5-24.

[4] R.Tripp (2006) Self-sufficient agriculture: labour and knowledge in small-scale farming. Earthscan, London.

[5] UNDP (1992) The Benefits of Diversity. An Incentive Towards Sustainable Agriculture.

[6] H.C.C. Meertens (2003) The prospects for integrated nutrient management for sustainable rainfed lowland rice production in Sukumaland, Tanzania. Nutrient Cycling in Agroecosystems, Vol. 65, pp. 163-171.