Climate-induced hysteresis of the tropical forest in a fire-enabled Earth system model
Potsdam-Institute for Climate Impact Research, Member of the Leibniz Association, P.O. Box 60 12 03, 14412, Potsdam, Germany
2 Humboldt Universität zu Berlin, Unter den Linden 6, 10099, Berlin, Germany
3 Institute of Physics and Astronomy, University of Potsdam, 14476, Potsdam, Germany
4 Instituto Nacional de Pesquisas Espaciais, Av. dos Astronautas, 1.758 - Jardim da Granja, 12227-010, São José dos Campos, SP, Brazil
5 Physics Institute, University of Sao Paulo (USP), Cidade Universitária, R. do Matão, 1371, SP, Brazil
Accepted: 21 April 2021
Published online: 14 June 2021
Tropical rainforests are recognized as one of the terrestrial tipping elements which could have profound impacts on the global climate, once their vegetation has transitioned into savanna or grassland states. While several studies investigated the savannization of, e.g., the Amazon rainforest, few studies considered the influence of fire. Fire is expected to potentially shift the savanna-forest boundary and hence impact the dynamical equilibrium between these two possible vegetation states under changing climate. To investigate the climate-induced hysteresis in pan-tropical forests and the impact of fire under future climate conditions, we employed the Earth system model CM2Mc, which is biophysically coupled to the fire-enabled state-of-the-art dynamic global vegetation model LPJmL. We conducted several simulation experiments where atmospheric CO concentrations increased (impact phase) and decreased from the new state (recovery phase), each with and without enabling wildfires. We find a hysteresis of the biomass and vegetation cover in tropical forest systems, with a strong regional heterogeneity. After biomass loss along increasing atmospheric CO concentrations and accompanied mean surface temperature increase of about 4 C (impact phase), the system does not recover completely into its original state on its return path, even though atmospheric CO concentrations return to their original state. While not detecting large-scale tipping points, our results show a climate-induced hysteresis in tropical forest and lagged responses in forest recovery after the climate has returned to its original state. Wildfires slightly widen the climate-induced hysteresis in tropical forests and lead to a lagged response in forest recovery by ca. 30 years.
© The Author(s) 2021
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