Achieving cost‐effective landscape‐scale forest restoration through targeted natural regeneration

Abstract

High costs of tree planting are a barrier to meeting global forest restoration targets. Natural forest regeneration is more cost‐effective than tree planting, but its potential to foster restoration at scale is poorly understood. We predict, map, and quantify natural regeneration potential within 75.5 M ha of deforested lands in the Brazilian Atlantic Forest. Of 34.1 M ha (26.4%) of current forest cover, 2.7 M ha (8.0%) regenerated naturally from 1996 to 2015. We estimate that another 2.8 M ha could naturally regenerate by 2035, and a further 18.8 M ha could be restored using assisted regeneration methods, thereby reducing implementation costs by US$ 90.6 billion (77%) compared to tree planting. These restored forests could sequester 2.3 GtCO2 of carbon, reduce the mean number of expected species at risk of extinction by 63.4, and reduce fragmentation by 44% compared to current levels. Natural regeneration planning is key for achieving cost‐effective large‐scale restoration.

Fostering natural forest regeneration on former agricultural land through economic and policy interventions

“…At a landscape scale, naturally regenerating forests can cost-effectively contribute to the conservation and restoration of biodiversity through the creation of buffer zones, establishment of biological corridors and stepping stones in an agricultural matrix, and recovery of disturbed areas within protected areas (Guevara et al 2005, Evans et al 2017, Newmark et al 2017. Forest fragmentation could be reduced by 44% in the Brazilian Atlantic Forest if the 210 000 km 2 of land with a high capacity for spontaneous and assisted natural regeneration were left to recover (Crouzeilles et al 2020). In temperate agricultural southern Australia, shelterbelts composed of natural regeneration can act as critical habitats for a range of native biota while protecting crops from wind and storm damage and reducing erosion .…”

“…In Minas Gerais State, Brazil, Nunes et al (2017) projected that spontaneous and assisted natural regeneration could effectively restore 15 000 km 2 of forest over 20 years. Across the entire Atlantic Forest region of Brazil, 210 000 km 2 of degraded lands can potentially be restored through assisted natural regeneration, reducing implementation costs by US$ 90.6 billion (77%) compared to active restoration methods (Crouzeilles et al 2020).…”

“…Similar trends apply across the entire Atlantic Forest Region of Brazil. In this region with 755 000 km 2 of deforested land, 27 000 km 2 of forest regenerated naturally from 1996 to 2015, and a predictive model estimated that another 28 000 km 2 could regrow between 2015 and 2035 without human assistance (Crouzeilles et al 2020). Using assisted natural regeneration methods, an additional 188 000 km 2 of Atlantic Forest in Brazil has the potential to be restored (Crouzeilles et al 2020).…”

“…Planning the location of naturally regenerated areas relative to other parts of farms such as grazing paddocks, watercourses, and rocky outcrops is critical to effectively integrate agricultural production with areas of natural regeneration . In agricultural landscapes, patches of forest regeneration are more likely to be found adjacent to existing old-growth forest remnants , and natural regeneration is more likely to occur and have better biodiversity outcomes in landscapes with more forest cover (Crouzeilles et al 2016(Crouzeilles et al , 2020. Deforested areas on steep slopes with less intensive prior land use and close to forest remnants are the most likely to regenerate spontaneously (Rezende et al 2015, Molin et al 2018).…”

“…Economic and policy incentives will be needed as economies and markets transition from those driving further degradation of native forests to restoration and enhancement of native forests (Boillat et al 2017). We now have the capacity to identify specific target areas where natural regeneration is beneficial and feasible , Crouzeilles et al 2020, which can facilitate policy changes. Further development of these targeted approaches will need to be accompanied by innovative policies at multiple levels to reach the scale needed to restore native forests around the world by harnessing the power of nature (table 1).…”