The causal effect of crop diversification obligations on crop diversity: An EU-level analysis

The Common Agricultural Policy (CAP) is a cornerstone policy of the European Union, increasingly focused on promoting environmentally sustainable practices. In 2014, the CAP introduced Greening payments and a crop diversification requirement to enhance soil resilience and mitigate ecosystem degradation. Despite its economic significance, the policy's effectiveness across the EU remains largely limited. This study evaluates the impact of the Greening crop diversification requirement on crop diversity itself and on a set of subsequent outcomes, including agricultural land allocation, the economic performance of farms and indirect environmental outcomes. Using farm-level data from the Farm Accountancy Data Network (2012–2017), causal relationships are identified, through a design that combines propensity score matching and difference-in-differences, by comparing farms needing to adapt to the new requirements to those who were already compliant. Additionally, a regression discontinuity design estimates local average treatment effects for 2017, thereby exploiting the diversification requirement's threshold-based design. Both strategies corroborate the conclusion that Greening measures have significantly increased crop diversity across the EU, impacting over the subset of farms that were not already compliant with regulation requirements, primary small- and medium-size crop farms; moreover, results for the remaining farm-level outcomes are consistent with adaptation responses to the new environmental requirements. Overall, the results highlight the policy's effectiveness in promoting sustainable agriculture throughout the EU.