Mitigating climate change cost-effectively requires identifying least-cost-per-ton GHG abatement methods. Here, we estimate and map GHG abatement cost (US$ per tCO₂) for two common reforestation methods: natural regeneration and plantations. We do so by producing and integrating new maps of implementation costs and opportunity costs of reforestation, likely plantation genus and carbon accumulation by means of natural regeneration and plantations, accounting for storage in harvested wood products. We find natural regeneration (46%) and plantations (54%) would each have lower abatement cost across about half the area considered suitable for reforestation of 138 low- and middle-income countries. Using the more cost-effective method at each location, the 30 year, time-discounted abatement potential of reforestation below US$50 per tCO₂ is 31.4 GtCO₂ (24.2–34.3 GtCO₂ below US$20–100 per tCO₂)—44% more than natural regeneration alone or 39% more than plantations alone. We find that reforestation offers 10.3 (2.8) times more abatement below US$20 per tCO₂ (US$50 per tCO₂) than the most recent IPCC estimate.

经济有效地减缓气候变化需要确定每吨温室气体成本最低的减排方法。在这里，我们估算并绘制了两种常见重新造林方法的温室气体减排成本（每 tCO ₂美元）：自然更新和人工林。为此，我们制作并整合了重新造林的实施成本和机会成本的新地图，可能的人工林属以及通过自然更新和人工林进行的碳积累，并考虑了采伐木材产品的储存量。我们发现，在 138 个低收入和中等收入国家的大约一半被认为适合重新造林的地区中，自然更新 (46%) 和人工林 (54%) 的减排成本都较低。在每个地点使用更具成本效益的方法，30 年重新造林的时间贴现减排潜力低于每 tCO ₂ 50 美元为 31.4 GtCO ₂ （24.2–34.3 GtCO ₂低于每 tCO ₂ 20–100 美元）—44%比单独的自然再生多，或比单独的人工林多 39%。我们发现，重新造林带来的减排量比 IPCC 最新估计高出 10.3 (2.8) 倍，低于每 tCO ₂ 20 美元（每 tCO ₂ 50 美元）。