Planting trees, the solution to curb global warming?

Growing forests sequester carbon. Harnessing this capacity through afforestation (planting trees), which includes both afforestation to create new forests where there was no previous tree cover and reforestation to restore depleted forests, has been widely proposed as a promising strategy to counter rising carbon emissions in order to mitigate ongoing global climate change.

However, the actual climate benefits of afforestation are uncertain, because increased tree cover reduces the albedo (ability to reflect solar energy) of the landscape, which, depending on scale, could lead to local or global warming effects. This is especially true for dryland regions that cover nearly 40% of the global land area and where the albedo-warming effect of afforestation could far outweigh any cooling effect of carbon sequestration as lands reflective desert areas become a darker energy-absorbing forest cover.

To better understand the potential climate benefits of afforestation of drylands, the team of Shani Rohatyn of the Israel Institute of Technology (the Technion) conducted a high-resolution spatial analysis of global drylands and simulated the climatic effects of afforestation. in these regions.

Through their research, Rohatyn and colleagues identified 448 million hectares suitable for afforestation and the potential to sequester more than 32 billion tons of carbon over the next 80 years.

However, the study authors also found that this would do little to slow down the progressive warming of our climate.

Taking into account the significant decrease in albedo in these regions, the study authors show that afforestation of this vast area would only offset about 1 percent of the greenhouse gas emissions predicted under medium emissions climate scenarios at the current rate.

A forest. (Photo: NPS/K. Miller)

Despite these results, Rohatyn and colleagues note that carefully planned and implemented dryland afforestation could provide other, more local benefits and potential climate mitigation longer term than their 80-year assessment period.

The study is titled “Limited climate-change mitigation potential through forestation of the vast dryland regions.” And it has been published in the academic journal Science. (Source: AAAS)