Mapping carbon accumulation potential from global natural forest regrowth

Abstract

Regrowing natural forests is a prominent natural climate solution, but accurate assessments of its potential are limited by uncertainty and variability around carbon accumulation rates. To assess why and where rates differ, we compiled 13,112 georeferenced measurements of carbon accumulation. Climate explained variation in rates better than land use history, so we combined field data with 66 environmental covariate layers to create a global, 1-km resolution map of potential aboveground carbon accumulation rates for the first 30 years of forest regrowth. Our results indicate that on average default forest regrowth rates from the Intergovernmental Panel on Climate Change are underestimated by 32% and miss 8-fold variation within ecozones.Conversely, we conclude that previously reported maximum climate mitigation potential from natural forest regrowth is overestimated by 11% due to the use of overly high rates. Our results therefore provide a much needed and globally consistent method for assessing natural forest regrowth as a climate mitigation strategy. BackgroundTo constrain global warming, we must reduce emissions and capture excess carbon dioxide (CO2) in the atmosphere 1,2 . Restoring forest cover, defined here as the transition from < 25% tree cover to > 25% tree cover where forests historically occurred, is a promising option for additional carbon capture 3 and has been prioritized in many national and international goals 4,5 . It is deployable, scalable, and provides important biodiversity and ecosystem services 6 . Yet the magnitude and distribution of climate mitigation opportunity from restoring forest cover is poorly described, with large confidence intervals around estimates 2,3 . To evaluate the appropriateness of forest cover restoration for climate mitigation, compared to the multitude of other potential climate mitigation actions, countries, corporations, and multilateral entities need more accurate assessments of its potential 7 .Mitigation potential from restoring forest cover (reported here in terms of MgCO2 yr -1 ) is determined by the potential extent and location of new forest ("area of opportunity") and the rate at which those forests remove atmospheric CO2 (reported here in terms of MgC ha -1 yr -1 ). While there are now multiple estimates of area of opportunity based on diverse and often heavily debated criteria (e.g., references 3,8-11 ), we lack spatially explicit and globally comprehensive estimates of accumulation rates. This is especially true for natural forest regrowth, defined here as the recovery of forest cover on deforested lands through spontaneous regrowth after cessation of prior disturbance or land use. Many countries do not have nationally specific forest carbon accumulation rates and instead rely on default rates from the Intergovernmental Panel on Climate Change (IPCC) 12,13 . Although these rates were recently updated 8,12 , they nonetheless represent coarse estimates based on continent and ecological zone, and do not account for finer scale variation in rates due to mor...

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Modeling post-logging height growth of black spruce forests by combining airborne LiDAR and historical forestry maps in eastern Canadian boreal forest

“…This trend is likely to continue or even increase in the future (Boucher et al 2017, McDowell et al 2020). Thus, these young forests are playing an increasing and critical role in a variety of issues, for example, reaching a balance in global carbon dynamics (Cook-Patton et al 2020) and maintaining forest ecosystem services (Kroll et al 2020). These regenerating forests represent a critical stage in subsequent successional dynamics (Lindenmayer et al 2019) and generally exhibit the highest growth rates.…”

“…Yet, forest height growth is also mediated by a combination of environmental gradients operating at several scales. Regional climate plays an important role through three potential limiting factors: light, temperature and water (Boisvenue and Running 2006, Cook-Patton et al 2020). In boreal forests, temperature is the main climatic limiting factor for growth with a short growing season (Huang et al 2010), followed by regional drought events (D’Orangeville et al 2018).…”

Response of the Carbon Budget of Global Forest Ecosystems to Future Climate Change

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“…Photosynthesis and respiration lead to the exchange of substantial amounts of carbon with the atmosphere, and approximately 50% of the global terrestrial carbon is stored in forest ecosystems [21,27]. Therefore, with global climate change becoming increasingly signi cant, the NEP of forest ecosystems has also attracted attentions from the scienti c and social communities [5,6,15,16,33].…”