(by Jacqueline Loos, Dave Abson and Joern Fischer)
An increasing number of publications address the issue of food security in the context of a rapidly growing human population. In many such papers, sustainable intensification is implicitly presented as a panacea to meet increasing future demand for food. We are concerned that “sustainable intensification” is used a bit too loosely, for example in the article “Closing yield gaps through nutrient and water management” by Mueller et al. (Nature 490, 254-257; 2012).
Mueller et al. suggest that the environmental impacts of increases in irrigation and nitrogen application can be mitigated by reduced nitrogen application elsewhere; in a process they term ‘sustainable intensification’. We suggest that balancing global nutrient loads is an insufficient criterion to merit use of the term ‘sustainable’. The negative effects of fertilization on plant species richness are persistent, and decreasing fertilization in high nitrogen agroecosystems are unlikely to compensate for losses in in plant diversity (and biodiversity more broadly) in low nitrogen input regimes regions.
Mueller et al. note the high intensification potential of Eastern Europe and suggest crop yield gaps could be closed in this region by adding 50-100 kg Nha-1 yr-1, irrespective of soil conditions and habitat quality for biodiversity. Eastern Europe holds an extraordinary richness of agroecological biodiversity in highly heterogeneous landscapes, where low-nutrient grasslands and low intensity farming occur adjacently. The implied increases in nitrogen in Eastern Europe most likely would cause tremendous loss of biodiversity in arable fields and in fragile adjacent areas.
Furthermore, the authors promote agricultural intensification in response to the need to feed a growing global population, yet many of the regions targeted for intensification are not affected by food shortages. Increasing global food production will not reduce global hunger in the absence of measures to tackle issues of distribution. People go hungry not due to a lack of food, but a lack of access to food.
Readers should recognize that Mueller et al.´s findings, while an important contribution to the debate surrounding food security and agricultural sustainability, must be interpreted with caution and should not be considered a blueprint for action. Sustainable intensification requires a more holistic and multi-scale understanding of agroecological systems encompassing all the ecological and socio-economic impacts in changes in food production.