未来能源研究所-土地利用变化、无净损失政策和对二氧化碳清除的影响（英）-2023.10-30页_1mb

Land Use Change, No-Net-Loss Policies, and Effects on CO₂ Removals

This working paper examines carbon dioxide removal (CDR) from land uses, specifically forests, and how land-use change affects CDR projections. CDR is crucial for climate change mitigation but has been declining in the U.S. due to forest aging and land-use changes. Policies like afforestation and avoided deforestation are proposed to enhance CDR, but their effectiveness depends on accurate modeling.

A detailed model called CALM was developed to project land-based CDR by combining land-use change data (from USDA's National Resources Inventory) with forest carbon dynamics (from USFS Forest Inventory and Analysis). Two approaches were compared:

1. Net Change Approach: Tracks only net changes in forest area, leading to significant underestimation of CDR losses (up to 88% in the Southeast).
2. Component Change Approach: Accounts for differences in carbon stocks between forest gains and losses separately, providing more accurate results (54-59% more accurate nationally).

Key findings include:

• The net change model significantly underestimates CDR losses from land-use change.
• Deforestation losses outweigh afforestation gains over the modeled 45-year period, with afforestation benefits lagging.
• Planted forests provide faster CDR benefits compared to naturally regenerated forests in some regions.
• Avoided deforestation provides significantly more CDR benefit than increased afforestation. No-net-loss policies might only partially offset CDR losses in a 45-year timeframe; afforestation may take longer to fully compensate for deforestation, limiting the effectiveness of such policies for meeting near-term climate goals.