What will it cost to achieve the COP26 Glasgow forest agreement commitment and halt global forest loss?

We quantified the minimum payments to halt global net forest loss by 2030, as per the commitment made by countries to the Glasgow Leaders' Declaration on Forest and Land Use (GFA) at COP26 for the top 20 signatory countries (GFA20) in terms of net forest loss by area. We identified three possible pathways to achieve the GFA and quantified the differences in the avoided loss in carbon-sink capacity of forests in GFA20 countries due to forest loss. We calculated the difference in carbon-sink capacity between our best-case pathway (lowest net forest loss to achieve the GFA) and worst-case BAU pathway at 42 GtCO2e to 2030 and 152 GtCO2e to 2050. Further, we estimated the average per-hectare cost for each country and constructed a combined Marginal Abatement Cost Curve (MACC) for the GFA20. Based on the country-specific average cost and the MACC, we calculated that to deliver the GFA, at a minimum, would cost an additional 11-52 billion USD (2020 value) to 2030 and a further 343-694 billion USD between 2031 and 2050, over and above pre-COP26 funding commitments in forest conservation.