The mortality impacts of implementing the 3-30-300 greenness rule in Taranto, Southern Italy

The '3-30-300' rule advocates for 30 % tree canopy cover in neighborhoods, with no one living more than 300 m from green space. This health impact assessment study evaluated how implementing this policy could reduce adult mortality in Taranto, an industrialized area in Southern Italy. Population-weighted exposures were calculated using 2020 population data, and 2022 satellite data at 10-meter resolution within 300 m from homes. The study derived a normalized difference vegetation index (NDVI) target corresponding to a 30 % tree-cover, and to interim targets from 10 % to 25 %. The uncertainty analysis was based on 100,000 Monte-Carlo simulations. The results for 2022 estimated that achieving the 30 % tree-cover target, currently achieved by only 1.4 % of the population and corresponding to an estimated NDVI of 0.33 (95 % confidence interval: 0.32–0.33), could prevent 123 (93–155) deaths and 1,246 (929–1,563) years of life lost, reducing mortality by 5.3 % (3.9–6.6 %). Three-cover, shrubland, grassland and cropland were associated with higher NDVI, while built-up areas and deprivation were linked to lower greenness.