Fire air pollution reduces global terrestrial productivity

Fire emissions generate air pollutants ozone (O₃) and aerosols that influence the land carbon cycle. Surface O₃ damages vegetation photosynthesis through stomatal uptake, while aerosols influence photosynthesis by increasing diffuse radiation. Here we combine several state-of-the-art models and multiple measurement datasets to assess the net impacts of fire-induced O₃ damage and the aerosol diffuse fertilization effect on gross primary productivity (GPP) for the 2002-2011 period. With all emissions except fires, O₃ decreases global GPP by 4.0 ± 1.9 Pg C yr^-1 while aerosols increase GPP by 1.0 ± 0.2 Pg C yr^-1 with contrasting spatial impacts. Inclusion of fire pollution causes a further GPP reduction of 0.86 ± 0.74 Pg C yr^-1 during 2002-2011, resulting from a reduction of 0.91 ± 0.44 Pg C yr^-1 by O₃ and an increase of 0.05 ± 0.30 Pg C yr^-1 by aerosols. The net negative impact of fire pollution poses an increasing threat to ecosystem productivity in a warming future world.