Constraints and enablers for increasing carbon storage in the terrestrial biosphere

Abstract:

Harnessing natural climate solutions to help achieve climate and conservation goals simultaneously is an attractive “win-win.” However, near-term implementation challenges and long-term biogeochemical constraints may limit their ultimate contribution to an overall portfolio of climate action. Carbon storage in the terrestrial biosphere is controlled by a complex interplay of biogeography, biogeochemistry, land use change, and management choices. Here we aim to make implicit assumptions these controls explicit in order to transparently assess their implications. We introduce a spectrum from “silo,” where carbon storage is fundamentally limited to past losses, to “haystack,” where environmental and management changes increase carbon storage beyond historical levels. Estimates for additional terrestrial-biosphere storage potential range from less than 100 GtCO₂ to more than 800 GtCO₂. To determine safe, grounded potentials for carbon removal via the terrestrial biosphere, we assess a full range of environmental and social constraints and governance challenges. Needs include leveraging finance, measuring carbon stored, protecting ecosystem services, and minimizing economic and sociopolitical trade-offs. We conclude that implementation of natural climate solutions should focus on projects with clear co-benefits and must not come at the expense of rapid decarbonization and innovation on additional negative emissions technologies. A reasonable value for the expected impact of natural climate solutions is up to 200 GtCO₂ in negative emissions during the remainder of the 21^st century.