By counting on big, land-based carbon dioxide removal projects rather than curbing emissions now, governments, companies, and even the world’s leading climate science body risk missing climate goals and intensifying biodiversity loss, warns a new report in the journal Science.
Renewables expansion and real emissions cuts should be the focus of decarbonization plans, not overusing carbon-dioxide removal (CDR), which can “also pose major economic, technological, and social feasibility challenges; threaten food security and human rights; and risk overstepping multiple planetary boundaries, with potentially irreversible consequences,” write the authors of a policy forum submission in Science’s February issue.
Nevertheless, large-scale, land based CDR features prominently in official plans, which rely on practices like bioenergy with carbon capture and storage (BECCS) and afforestation and reforestation (A/R). Even the Intergovernmental Panel on Climate Change (IPCC), which advises governments on the latest climate research, charts land-based CDR options, laying out an upper “technical mitigation potential” of BECCS and A/R at 11.3 and 10 gigatonnes of carbon dioxide per year.
Those carbon offsets will come at a cost, say the researchers. The IPCC’s upper mitigation potential would require converting an area of land more than three times the size of the United States—up to 29 million square-kilometres—to bioenergy crops or trees. They add that the IPCC does not properly consider the full range of socioeconomic and environmental impacts of these measures, nor the scale at which CDR could be deployed without triggering negative outcomes, even though they’re a big part of the way the UH agency aims to address climate change.
“Although the IPCC is not ‘policy prescriptive,’ these pathways—and the policy options within them—strongly shape the ‘solution space’ as seen by policy-makers when considering how to meet the goals of the Paris Agreement,” the researchers write in Carbon Brief.
The Science paper aims to correct this oversight by comparing “IPCC mitigation potentials with recent studies that give greater attention to the ecological, biological, and societal impacts of land-based CDR, to provide quantified sustainability limits.” It finds that the ecological and societal risks of land-based CDR are initially triggered at far lower mitigation levels than the IPCC’s more ambitious scenario. For example, the projections for BECCS that result in lower risk scenarios remove between 0.7 and 1.2 GtCO2/year; for medium risk, BECCS would capture between 1.3 and 2.8 GtCO2/year.
Overemphasizing the potential of CDR to address the climate crisis can also deter other, faster options for reducing emissions that may seem comparatively more costly when the true consequences of CDR are underreported.
The authors boil it all down to a choice between deploying land-based CDR, with significant ecological and social consequences, to limit global warming while accommodating ongoing use of fossil fuels, or less extensive CDR accompanied by faster growth in renewable energy and real cuts to emissions. In support of the second option, they suggest using sociological thresholds to estimate sustainable CDR budgets, identifying viable emission reduction pathways that work within those thresholds, and reserving the limited CDR potential for only the most legitimate uses.
“Carbon dioxide removal into land and forests cannot legitimately be used to offset continuing fossil fuel emissions,” said co-author Dr. Kate Dooley of the University of Melbourne.
“Government climate plans should set separate, transparent targets for emission reductions and removals, which limit reliance on the latter, and meet climate and biodiversity commitments through restoring and maintaining natural ecosystems.”