Active restoration accelerates the carbon recovery of human-modified tropical forests

Abstract

More than half of all tropical forests are degraded by human impacts, leaving them threatened with conversion to agricultural plantations and risking substantial biodiversity and carbon losses. Restoration could accelerate recovery of aboveground carbon density (ACD), but adoption of restoration is constrained by cost and uncertainties over effectiveness. We report a long-term comparison of ACD recovery rates between naturally regenerating and actively restored logged tropical forests. Restoration enhanced decadal ACD recovery by more than 50%, from 2.9 to 4.4 megagrams per hectare per year. This magnitude of response, coupled with modal values of restoration costs globally, would require higher carbon prices to justify investment in restoration. However, carbon prices required to fulfill the 2016 Paris climate agreement [$40 to $80 (USD) per tonne carbon dioxide equivalent] would provide an economic justification for tropical forest restoration.

Getting the message right on nature‐based solutions to climate change

“…Freshwater, coastal and marine habitats face similar issues due to water pollution, temperature increases, sea‐level rise, over‐fishing, the spread of invasive species and, in some cases, inappropriate management (Elliott & Lawrence, 1998). A balanced NbS approach would give greater priority to protecting these remaining intact ecosystems, as well as restoring partially degraded forests (Philipson et al, 2020), and other approaches such as ‘proforestation’—leaving forests to grow to their full potential, with minimal intervention (Moomaw et al, 2019), and natural regeneration of native ecosystems, where appropriate (Cook‐Patton et al, 2020; Guariguata et al, 2019; Holl, 2017; Holl & Aide, 2011; Meli et al, 2017; Molin et al, 2018).…”

Restoration concessions: a second lease on life for beleaguered tropical forests?

“…2017a,b; Philipson et al . 2020). It has been argued that forests could be sustainably harvested at around 60% of pre‐logging timber stocks (Putz and Romero 2015), but even at this level it may be more than 60 years before forests are harvestable without intervention.…”

“…2017a; Philipson et al . 2020), but the costs of such projects are typically very high (mean $1596 ha −1 , 95% CI: $1338 to $1854 ha −1 ; Philipson et al . 2020; for planting and subsequent control of competing vegetation for tropical rainforests, not including Australia).…”

“…2020), but the costs of such projects are typically very high (mean $1596 ha −1 , 95% CI: $1338 to $1854 ha −1 ; Philipson et al . 2020; for planting and subsequent control of competing vegetation for tropical rainforests, not including Australia). Assisted natural regeneration is less expensive ($100 ha −1 ) but up to 40 years will still be required for forests to recover to harvestable levels.…”

“…In addition, if C credit prices were to rise to $40 per metric ton, as proposed by the World Bank (CPLC 2017), then C storage would become a highly profitable option for ERCs (see also Philipson et al . 2020).…”