The influence of a changing disturbance regime on regional and global climate: Terry Chapin’s contributions to Earth System science

Background/Question/Methods

The structure and composition of ecosystems influences regional and global climate through multiple pathways. Changes in species composition expected with climate change over the next several centuries may accelerate or moderate temperature increases by influencing surface energy exchange, the buildup of greenhouse gases, atmospheric radiation, and by modifying ecosystem services that, in turn, influence how humans use energy resources. Here we conducted a synthesis of the different interactions expected between a changing disturbance regime and the climate system. In our analysis, we focused on fire as a disturbance agent, and considered its role in modifying surface biophysical processes, carbon fluxes, and aerosol impacts on nutrient redistribution and the hydrological cycle.

Results/Conclusions

In northern high latitude regions, fire impacts on ecosystem-climate feedbacks operate on multiple time scales and vary in important ways across and within arctic tundra and boreal forest biomes. Changes in the fire regime near boreal treeline, for example, may limit the northward movement of forests into tundra, and thus the magnitude of albedo-driven positive feedbacks associated with anthropogenic warming. Within arctic tundra ecosystems, carbon, aerosol, and surface biophysical changes after fire probably all contribute to warming. In boreal forests, in contrast, climate forcing from surface biophysical changes, including post-fire increases in albedo and surface conductance, probably offset some of the effects of greenhouse gas and aerosol emissions. Within boreal forests, differences in burn severity and post-fire succession vary in important ways across continents, influencing the dominant pathways by which fires influence climate. Human use of fires in southern boreal regions is pervasive, particularly across Eurasia. We argue that efforts to manage fires in boreal forest ecosystems are going to become increasingly important, both for the sustainability of the biome and for maintaining a robust cryosphere.  We conclude by comparing fire-climate interactions in high latitude ecosystems with interactions in savanna and tropical forest ecosystems.