Fire air pollution reduces global terrestrial productivity.

ABSTRACT

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.