Terrestrial carbon dioxide removal from the atmosphere: Ecological Principles

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Terrestrial ecosystems sequester about a third of anthropogenic CO2 emissions by natural processes and, thus, play a critical role in mitigating climate warming. As climate change become more aggravated, the need to remove CO2 from the atmosphere to the terrestrial and aquatic ecosystems becomes more urgent over time. A score of new techniques of carbon dioxide removal (CDR) have been recently proposed based on a notion of actively managing land carbon cycle processes to increase carbon sequestration and/or reduce greenhouse gas (GHG) emissions. These actively managed climate solutions by human (i.e., human-based) should be complementary to the nature-based climate solutions to combat climate change together with concurrent and dramatic economy-wide decarbonization. However, what are ecological principles behind the terrestrial CDR techniques? How can the ecological principles identified from these removal techniques be used to guide the design of more effective, future CDR techniques? These questions remain unanswered.   This presentation will show ecological principles we identified from our analysis of these existing CDR techniques and propose more effective techniques for carbon dioxide removal. We analyzed a dozen of existing CDR techniques, such as afforestation and reforestation, biochar from crop residues or slashed woods, and peatland restoration. All these existing CDR techniques manage carbon residence time more than carbon input. As carbon storage is jointly determined by carbon input and residence time, elongation of residence time or increase in carbon input or both all result in increased carbon sequestration (i.e., increased carbon dioxide removal from the atmosphere).  It appears that there are more rooms to manage carbon residence time than carbon input as carbon residence time can change from a few months or years to thousands of years. Thus, we can evaluate and design CDR techniques using methods that can substantially elongate carbon residence time.