Matthew D. Potts, PhD

Chief Science Officer

Scientific understanding of how to best mitigate climate change constantly improves. This recurring blog post will showcase new academic papers focused on carbon management and removal and highlight why they matter. In this blog, we focus on forestation - currently the most available and scalable way to remove carbon dioxide from the atmosphere.

Rule of Thumb: Plant Trees Where It Rains (thanks for the title - Jacob)
Albedo, the degree to which the land surface reflects solar radiation, affects the efficacy of tree planting to mitigate climate change. Decreases in albedo by planting trees in drylands decreases climate change mitigation effectiveness by ⅔.

Why it matters: Location, location, location! To maximize value, tree planting efforts should focus in appropriate non-dryland areas, which could double the climate impacts of tree planting in half the area.

Bigger Bang for the Buck: Climate change may reduce land-based mitigation costs
Climate change will very likely increase the rate of forest dieback and cause cropland expansion. A dynamic bioeconomic model that accounts for climate change suggests increases in forest growth rates from CO2 fertilization may outweigh these negative impacts.

While not without substantial uncertainty, this may lead to a 64%-86% reduction in the costs of forest-focused climate change mitigation.

Why it matters: Indirect costs and impacts need to count too. It’s important to incorporate the effects of climate change on forests when calculating carbon sequestration costs.

Low-Cost Carbon Removal: Consider Restoring Tree Cover in Populated Agricultural Lands
Planting trees in populated tropical croplands, pasturelands, and degraded forests represents a previously undocumented low-cost solution to restore tree cover and mitigate climate change. While it may be possible to restore tree cover in a total area greater than 2.5 times the size of Mexico by 2050 (540 million hectares), economic, policy, and technical support are still lacking.

Why it matters: The right approach in the right place is key. Even though the Americas account for approximately half of 21st century tropical deforestation, smallholder-based reforestation might be more appropriate for Asia and Africa than in the Americas.

A depiction of how forestlands that underwent land use change to become croplands, pasturelands, or degraded forestlands can incorporate smallholder tree cover restoration to become agrosilviculture, silvopasture, woodlots or plantations, or restored forests.

Reforesting Abandoned Land: Ask First!
Restoring tree cover on abandoned agricultural lands will be critical to meeting climate goals. However, current estimates of abandoned lands available for reforestation are exaggerated. Improved definitions of land abandonment and proactive engagement of landowners are needed to accurately scale and reach global tree cover restoration goals.

Why it matters: Land ownership is a complex but necessary issue to tackle. Assuming land is abandoned is not sufficient; effort must be made (using a variety of tools) to determine and respect ownership.