Philipson et al. 2020
Over half of tropical forests have been degraded by human activities, such as timber harvesting, reducing carbon storage and biodiversity value, and making them more vulnerable to conversion to agriculture. This paper investigates the effect of natural regeneration and active restoration of degraded forests on recovery of carbon stocks in Sabah, Malaysia; restoration involved tree planting and cutting climbing plants which slow tree growth. The authors compared carbon recovery rates, in the 30-35 years following logging, between forest plots that regenerated naturally and those subjected to active restoration. This comparison showed that active restoration could increase carbon recovery rate from 2.9 to 4.4 tonnes of above-ground carbon per hectare per year.
The authors estimated the economic feasibility of active forest restoration by calculating the carbon price required to fund it. They found that implementing restoration uniformly across logged forest would need carbon prices 2- to 10-fold higher than those in current carbon markets. However, prices increasing this much is not unrealistic, in fact such increases are thought to be necessary to limit global warming to 2°C above pre-industrial levels. Hence, large-scale active restoration of degraded forest is a viable component of climate mitigation strategies. Restoration can initially be targeted at areas where it is most economically viable, and when carbon prices increase, restoration can be expanded to cover a larger area. Moreover, funding need not come solely from carbon markets; alternative funding could include valuation of other benefits of forest restoration, such as enhancing biodiversity, water security and flood protection.
Read the paper here.