Rapid (10-yr) recovery of terrestrial productivity in a simulation study of the terminal Cretaceous impact event

Investigations of short-term (up to 10³ yr) environmental change across the Cretaceous-Tertiary boundary provide evidence for reduced temperatures, consistent with the injection of debris and sulphate aerosols into the upper atmosphere by a large impact event. Concomitant with this was a postulated massive addition of CO₂ to the atmospheric carbon reservoir by impact vaporisation of the Chicxulub carbonate platform. Taken together, a high CO₂ but low irradiance environment would have created unusual conditions for the operation of the terrestrial biosphere. Here, we have evaluated this environmental influence on terrestrial ecosystems using a process-based dynamic global vegetation model forced with post-impact global climates, derived by modification of the GENESIS atmospheric climate model simulation for the latest Cretaceous. Our results suggest that terrestrial primary productivity initially collapsed and then recovered to pre-impact levels within a decade. Global terrestrial carbon storage in vegetation biomass exhibited a similar collapse but complete recovery took place on a 60-80 yr timescale. The recovery of both terrestrial net primary productivity and vegetation biomass was largely mediated by the high CO₂ concentration stimulating ecosystem photosynthetic productivity in the warm low latitudes. An apparently rapid recovery of terrestrial ecosystem function stands in marked contrast to the situation for the marine realm, where the organic carbon flux to the deep ocean was suppressed for up to 3 million years.