Scoping review of carbon pricing systems in forest sector models

Forest-based measures to mitigate climate change are increasingly being acknowledged as options for meeting the global targets of the Paris Agreement. In this context, carbon pricing systems may foster carbon sequestration in forests and harvested wood products. Forest sector models (FSMs) are established simulation instruments for assessing the possible impacts of carbon pricing systems on forest-based mitigation potentials, forestry, and forest product markets. However, the characteristics of the implemented carbon pricing systems differ among these assessment tools. To map and evaluate this variability, we conducted a scoping review of carbon pricing systems in FSMs, following the RepOrting standards for Systematic Evidence Syntheses (ROSES). Drawing on 49 modeling studies, including 351 scenarios, we provide an overview of the state-of-the-art methods for implementing carbon pricing systems in FSMs, discuss technical aspects and uncertainties, and identify possible future research trends. Our results reveal similarities in the types of carbon pricing systems and differences regarding the system boundaries and carbon price-related characteristics of the implemented systems. Geographically, since most studies target either the Northern Hemisphere or the world, we found a lack of in-depth assessments in tropical and boreal countries. Further, additionality, permanence, and leakage of forest-related mitigation measures are addressed using different approaches with varying practicability. Mostly, the observed heterogeneity in the implemented carbon pricing systems can be related to the attributes of pre-existing modeling frameworks. We systematically collect and highlight tools to analyze the role of forest-based mitigation measures in the context of climate commitments and outline carbon pricing policies that could support their implementation. For future studies, the assessment of policy mixes involving carbon pricing and the inclusion of climate change effects on forest growth appear to be crucial for delivering more robust projections of forest-based mitigation potentials and, hence, for increasing the reliability of the forest-based contribution to climate mitigation actions.