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

Christopher D Philipson,Philip G Brodrick,Mark E J Cutler,James A Margrove,Yap Sau Wai,Doreen S Boyd,Gregory P Asner,Geertje M F Van Der Heijden,Michelle A Pinard,Martijn Snoep,Glen Reynolds,Alicia Ledo,Hamzah Tangki,Pedro Moura Costa,Joel Fiddes,Giles M Foody,David F R P Burslem,Sol Milne,Philippa R Lincoln,Robert E Martin ,Charlotte Wheeler

doi:10.1126/science.aay4490

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.

Highlights

Tropical forests contain 55% of global stores of aboveground forest carbon [1], but the size of these stocks is declining rapidly because of forest loss and degradation [2]
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
Mean and maximum Aboveground Carbon Density (ACD) values are higher in Southeast Asian forests than in other tropical forests, and the highest values occur in Malaysia [12]

Summary

Main Text

Tropical forests contain 55% of global stores of aboveground forest carbon [1], but the size of these stocks is declining rapidly because of forest loss and degradation [2]. We report estimates of the response of ACD accumulation rates to active restoration using a combination of climber cutting and enrichment planting in a logged tropical forest over decadal time scales. An additional constraint is that the infrastructure and labor force required to implement this large-scale restoration across the global tropics are lacking in many sites, in Southeast Asia, where mast fruiting necessitates greater investment in seedling nurseries [33] Under these circumstances, an alternative approach is to implement generic lowcost measures such as climber cutting, combined with selective tree planting in accessible parts of the degraded forest landscapes where the density of mature trees is insufficient to ensure adequate natural regeneration.

Materials and Methods

Findings

America Mexico