In order to keep global warming under the 1.5C threshold, the IPCC warns that not only must we cut carbon emissions nearly in half by 2030, we must also draw massive amounts of CO2 out of the atmosphere.
The Intergovernmental Panel on Climate Change (IPCC) suggests that around 730 billion tons of CO2 (730 petagrams of CO2, or 199 petagrams of carbon, Pg C) must be taken out of the atmosphere by the end of this century. That is equivalent to all the CO2 emitted by the United States, the United Kingdom, Germany and China since the Industrial Revolution [Lewis 2019: 25].
The IPCC further advises that forests and wooded savannas could store enough carbon to get us a quarter of the way there. “In the near term, this means adding up to 24 million hectares (Mha) of forest every year from now until 2030” [Lewis 2019: 26].
Through the Bonn Challenge, 43 countries have pledged to reforest nearly 300Mha out of a goal of 350Mha by 2030. “However, plantations are the most popular restoration plan: 45% of all commitments involve planting vast monocultures of trees as profitable enterprises” [Lewis 2019: 26], which stores much less carbon than do natural forests. Agroforestry accounts for 21% of pledged land, while natural forest regeneration accounts for 34% of commitments.
While timber plantations technically fit the definition of a forest (greater than 0.5 hectares in area, trees at least five meters high and more than 10% canopy cover, according to UN FAO),
the key components of climate-change mitigation and biodiversity protection are missing. Plantations are important economically, but they should not be classified as forest restoration. That definition urgently needs an overhaul to exclude monoculture plantations [Lewis 2019: 27].
Illustrating vast differences in mitigation potential, Lewis et al. state that “if the entire 350 Mha [of the Bonn Challenge goal] is given over to natural forests, they would store an additional 42 Pg C by 2100. Giving the same area exclusively to plantations would sequester just 1 Pg C or, if used only for agroforestry, 7 Pg C” [Lewis 2019: 27].
The authors make four specific recommendations to ensure more effective climate change mitigation through conservation and restoration efforts:
(1) Countries should significantly increase the proportion of natural forest restoration in their commitments. (Natural forest restoration over an area the size of South Carolina could store 1 Pg of carbon by 2100.)
(2) Natural forest restoration should be prioritized in the tropics, where trees grow fastest and don’t risk countering the albedo effect since there’s never any reflective snow there anyway.
(3) “Target degraded forests and partly wooded areas for natural regeneration; focus plantations and agroforestry systems on treeless regions and, where possible, select agroforestry over plantations.”
(4) Natural forest once restored must be protected.
Lewis, Simon L., et al., 2019, Restoring natural forests is the best way to remove atmospheric carbon, Nature 568, https://www.nature.com/articles/d41586-019-01026-8.