Urban Forests: Environmental Health Values and Risks

We study a massive urban afforestation policy in Beijing that planted 1/3 of a million acres of greenery in less than a decade. The policy reduces PM₂.₅ concentration at population hubs by 4.2 percent, the health value of which amounts to 1.5% of the city’s annual GDP. Rapid vegetation growth unexpectedly led to a 7.4 percent increase in pollen exposure, triggering respiratory emergency room visits, although the medical costs are outweighed by the pollution benefits. Urban forests are only partially capitalized in housing values, with buyers mainly appreciating proximity to green spaces but not the air quality improvements they bring.