Long-term experiments in natural locally-extreme high CO2 environments: Roadmap for future research

The potential for future biological research in locally extreme environments that serve as natural long-term experiments in ecology and evolution is presented. The study system is terrestrial mofettes, which are natural areas of geogenic release of CO2 that cause permanent soil hypoxia. Natural CO2 springs or mofettes, provide an innovative approach to the study of many ecological processes and natural phenomena that occur slowly and therefore require extensive and lengthy observations and experiments. They serve as a space-for-time or, in the case of steep environmental gradients, space-for-space substitutions. Mofettes have primarily served as natural models for future climate change scenarios, particularly for plant responses to increased CO2 concentrations over multiple generations. This could now be improved with the new technologies available, although the constraints associated with the characteristics of a particular natural site must be considered. More recently, the study of physiology, ecology, and evolution of various phylogenetically unique groups of organisms at different spatial scales in mofettes has matured. In this article, current developments of all these research avenues are presented. The scientific potential of locally extreme environments such as mofettes will undoubtedly contribute to further research on long-term ecological and evolutionary processes that are critical for understanding past evolutionary events, managing future ecosystems, and predicting ecological responses to global change.