Exposure to green areas: Modelling health benefits in a context of study heterogeneity

Although the beneficial health effects of green areas are gaining recognition, epidemiological studies show mixed results with significance varying considerably by study and context, indicating that there is no unique and clear evidence. This relationship is influenced by multiple factors and characterised by high complexity not previously been incorporated in one single analysis. This study proposes a new application of the Heckman selection model to find evidence of key patterns emerging throughout the literature and identify main determinants affecting the relationship. The model aggregates outcomes of different studies and allows an assessment of both significant and non-significant results from the literature in order to correct for unobserved selection bias. Close attention is paid to the relevance of the background, particularly socioeconomic context. The results show significant health benefits associated with increased exposure to green areas, where higher risk reductions are observed for old and adult age groups, as well as in poorer countries, taking into account the correction for the publication bias. This last issue points towards a redistributive impact of green areas in terms of health and the importance of co-benefits arising from Ecosystem-based Adaptation, especially in poorer neighbourhoods, translating in health care savings and reduced productivity loss.