Small farms are significantly better than large farms at increasing food productivity and environmental sustainability

We conducted 3 types of analysis. First, for yields, biodiversity, resource-use efficiency and profitability, we examined “vote counts”, i.e., how many studies reported that smaller farms improved these outcomes versus not, and used hierarchical cumulative link models to synthesize these in probabilistic terms, i.e., what’s the probability that a study will find that farm size will have a particular outcome? Second, for a fewer set of studies for yields, resource-use efficiency, and profitability, where the studies reported regression coefficients for farm-size relationships, we conducted hierarchical meta-regressions to calculate pooled effect sizes summarizing the magnitude of change in outcome per 1 ha change in farm size. Pooled effects sizes were also calculated for GHG emissions using robust linear mixed-effects models.

So, what did we find? 79% of studies reviewed reported that smaller farms have higher yields, with yields increasing 5% per 1ha decrease in farm size. This is not an altogether surprising result – the inverse farm size-productivity relationship has fascinated agricultural economists for nearly a century, first reported by Chayanov in 1926. We also showed in a previous study that smaller farms have higher crop species richness; in that study we further found that smaller farms and larger farms grow a different portfolio of crops, and therefore, crop diversity at landscape scale may best benefit from having a mix of farm sizes. Our study also found that non-crop biodiversity increases with decreasing farm size, with 77% of studies finding that smaller farms have greater biodiversity at both farm and landscape scales. The primary studies we reviewed suggest that this is because of more ecological management practices on smaller farms (lower pesticide use, organic management, etc.), edge effects (smaller farms having larger margins that support biodiversity), or more diverse land cover in small-farming dominated landscapes. Our study found no statistical evidence for farm-size relationships with resource-use efficiency, greenhouse gas emissions, or profitability. We should note that we do not assess causality directly, i.e., that farm size is driving all the outcomes we reviewed (thanks to a reviewer for helping us clarify this in our paper). However, with both yields and biodiversity, we do believe there is strong theoretical support for a causal relationship as evidenced in the primary literature we reviewed.

Our summary of the evidence suggests that smaller farms have benefits for both productivity and biodiversity. This alone would suggest the need for increased policy support for smaller farms. But furthermore, there are nearly 500 million small farming households around the world, the majority of whom are found in low and middle-income countries, and who constitute some of the world’s poorest populations. Thus, smallholders are also the target of development support, with SDG 2.3 aiming to doubling the productivity and incomes of small-scale producers by 2030. Clearly, while smaller farms have benefits, smallholders are finding it challenging to make a living from agriculture. Supporting them would satisfy both humanitarian and environmental sustainability goals.