Co-producing climate policy and negative emissions: Trade-offs for sustainable land-use

Abstract

Non-Technical summary Under the Paris Agreement, nations have committed to preventing dangerous global warming. Scenarios for achieving net-zero emissions in the second half of this century depend on land (forests and bioenergy) to remove carbon from the atmosphere. Modelled levels of land-based mitigation could reduce the availability of productive agricultural land, and encroach on natural land, with potentially significant social and environmental consequences. However, these issues are poorly recognized in the policy-uptake of modelled outputs. Understanding how science and policy interact to produce expectations about mitigation pathways allows us to consider the trade-offs inherent in relying on land for mitigation. Technical summary Science enables better understanding of climate change causes and impacts but may also define the 'climate problem' in technical terms, with technical solutions, as seen in the recent inclusion of negative emissions technologies (NETs) in Integrated Assessment Models (IAMs) to meet the Paris Agreement's temperature goals. This paper examines the sustainability of land-based carbon removal, using a co-production lens to explain the legitimization of NETs as key mitigation options. We evaluate the scale of NETs in the most recent generation of <2 °C scenarios, finding that projected levels of land-based mitigation imply strong trade-offs with other societal goals. Future demand for bioenergy from dedicated cropland drives large-scale land-use change across all models. Upper ranges of modelled outputs would require up to a doubling of global cropland, with potential losses of up to a quarter of both current pasture and natural lands by 2100. We find that the perception of model-based knowledge as 'objective science' lends authority to outcomes that might otherwise be more critically debated and contested. Closer engagement between modellers and policy experts for mitigation scenario development would allow for more negotiated forms of knowledge production that might better clarify and represent the multiple objectives and interests at stake in the utilization of limited land resources.