Solar panels vs planting forests: which reduces climate change faster?

Planting forests and installing photovoltaic (PV) fields both have significant potential for mitigating climate change, either through carbon uptake by photosynthesis or replacing fossil-fuel emissions in energy production. However, both also increase global heat load because they make the land surface darker, which absorbs heat.

Rafael Stern, Jonathan Muller and colleagues investigated which land use — trees or solar panels — more quickly offsets the increased heat they produce due to surface darkening.

The authors quantified the climate change mitigation potential of both approaches, considering reduced atmospheric carbon, surface energy balance, and land area required to lower global carbon emissions across different climatic zones.

They measured surface albedo at a solar field in a hyper-arid region in the Arava valley in Israel, while the afforestation data was measured at a research station at the Yatir forest at the northern edge of the Negev desert. The authors then used this data to calculate the break-even time required to balance the positive radiative forcing due to reduced albedo, and negative radiative forcing due to carbon emission suppression of PV power generation or carbon sequestration by forests.

In semi-arid land, photovoltaic fields break even and begin offering climate change mitigation benefits after about 2.5 years, which is more than 50 times faster than afforestation.

In humid lands, the gap is not so wide, but solar panels continue to have the advantage.

The authors note that forests provide many benefits beyond climate change mitigation, including ecosystem, climate regulation and social services.

The findings have been published in the journal PNAS Nexus.

Image caption: One of the authors working on the measurement system. Image credit: Jonathan D. Muller