Dominic Moran, Professor of Agricultural and Resource Economics In a familiar comedy trope, the impetuously discarded item invariably ricochets back to the hapless protagonist’s head or posterior. The sketch reminds us to beware of unintended consequences of our actions and that systems can effectively push back in surprising and often uncomfortable ways. Disciplines including physics (Newton’s Third), economics (Keynes’ Paradox of Thrift), psychology (behavioural rebound effects) offer variants on the theme relevant to public policy. The point is that the systematic or secondary impacts need to be understood. However, as much as we try to capture these multiple rounds of effects, our models are at best typically a partial representation of the complexity of the world around us. This has relevance to our thinking on contemporary agri food challenges. Food systems are socio-ecological constructs. The most ingenious technologies are essentially adjuncts to complex biological systems that can be unstable and unpredictable. When we add the vagaries of human behaviour, it should not be surprising that policy and decision-making are less than deterministic in their outcome. Consider recent debates around livestock and meat consumption. Livestock production is a major contributor to land use change and global greenhouse gases, and this alone is a good reason to scrutinise the management of production systems. Adding the mounting evidence around the damaging human health effects of eating red meat and the case for policy intervention is even more compelling. As debate has become more strident, arguments have suggested the need to move beyond voluntary dietary advice to target reduction in subsidy, or taxation on either producers or consumers of livestock products. Putting aside questions of consumer versus producer liability and property rights, the prima facia economic case seems robust: tax the externality and make the polluter (whoever that is) pay. But this probably isn’t the end of the story. In the first instance, we should be wary about where modified consumption (i.e. demand) ends up. That is, substitution effects may have their own consequences, and these need to be part of the calculus. Millennial crazes for avocadoes and quinoa spring to mind. On the production side, we should be mindful that there is diversity in livestock systems, and that reducing production in intensive and extensive systems can plausibly lead to different outcomes. In other words, there is nothing axiomatic in the generic prescription that reduced production will deliver environmental benefits. In Brazil for example, extensive grassland production systems are a major contribution of the country’s agricultural sector. When pastures degrade, extensive producers are implicated in ecosystem damage when ranchers often compensate by moving into primary grasslands or forests. However, as observed in the Cerrado[i] intensively managed pastures can avoid such damages and sequester carbon as an offset to cattle emissions. These managed systems are in a delicate socio-ecological balance that can be destabilised by an abrupt shift in demand that reduces farmers’ incentives to invest in pasture management. In this case, a reduction in demand can plausibly result in increased emissions. Another tale of the unexpected, or perhaps the rational, emerges in the context of antimicrobial resistance, a latent crisis driven by uncontrolled drug use by humans and farmers. Antimicrobial compounds used in animal and crop production have been highly successful in managing bacterial infections, but liberal and unsupervised use of antibiotics in agriculture contributes to the diminishing effectiveness of medically important antibiotics. Use in livestock production can be therapeutic, prophylactic and, more controversially, for growth promotion; the latter being purely to accelerate finishing times for animals. As the sector has come under scrutiny for its role in antibiotic stewardship, use for growth promotion use has been subject to increased restriction or even bans in some countries including the European Union. However, evidence suggests that this is offset by increased administration under the guise of therapeutic or prophylactic treatments. In other words, producers are potentially not adjusting their overall use. This global health emergency is akin to diffuse pollution problem[ii] with both technological and often unobservable behavioural factors at play. Solely focussing new or as yet to be invented drugs, diagnostics and command and control regulations (i.e. bans), does not address some of the more subtle behavioural dimensions of the problem. Indeed a technological fixation on the supply side may simply put us on a treadmill against nature, which history suggests we will lose. The bottom line is to be more discriminating about our understanding of systemic effects of apparently good intentions, especially where human behaviours and incentives play a role. The road to hell is paved with good intentions, but as the sayings go, there is nothing as queer as folk and hell is other people… [i] De Oliveira Silva, R., Barioni, L. G. , Hall, J.A.J. , Folegatti Matsuura, M., Zanett Albertini, T., Fernandes, F. A., Moran, D. (2016) Decoupling livestock production from deforestation in Brazil: how increasing beef consumption can lower greenhouse gas emissions, 2016. Nature Climate Change. DOI: 10.1038/NCLIMATE2916 [ii] Moran, D (2018) Antimicrobial use and planetary health: developing a framework for priorities The Lancet Planetary Health Volume 2, Issue 7, July 2018, Pages e277–e278 , https://doi.org/10.1016/S2542-5196(18)30137-2