Land availability and policy commitments limit global climate mitigation from forestation

Area of Science:

• Environmental Science
• Climate Change Mitigation
• Forest Ecology

Background:

• Forestation, encompassing afforestation and reforestation, offers potential for climate change mitigation through carbon sequestration in biomass and soils.
• Uncertainty in global forestation mitigation estimates stems from variable soil carbon sequestration rates and land availability assessments.

Purpose of the Study:

• To develop global maps of soil carbon change associated with forestation.
• To provide more accurate estimates of carbon sequestration potential under different land availability scenarios.

Main Methods:

• Development of global maps detailing soil carbon gains and losses resulting from forestation.
• Analysis of carbon sequestration potential considering constraints on land availability to avoid negative impacts like albedo-induced warming, and to safeguard water resources and biodiversity.

Main Results:

• Forestation, with 389 million hectares available globally (considering constraints), could sequester 39.9 petagrams of carbon by 2050, a figure lower than prior projections.
• Carbon sequestration potential reduces to 12.5 petagrams of carbon when land availability is limited to current policy commitments (120 million hectares).
• Soil carbon changes were primarily observed in the topsoil layer.

Conclusions:

• Achieving higher carbon sequestration through forestation necessitates expanding dedicated forestation areas.
• Strengthening national commitments is crucial for nations possessing significant untapped forestation potential to enhance climate change mitigation efforts.