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We present examples of large-scale farmer-managed natural regeneration of woody species in Africa to create new agroforestry systems. We also analyze two cases in Ethiopia of large-scale natural regeneration. The available evidence shows that the average costs per hectare of promoting on-farm natural regeneration are low as soon as farmers are familiar with this practice and begin to spontaneously adopt it. Based on these cases, current ambitious forest restoration targets can be achieved, but this goal requires a shift from tree planting to assisted natural regeneration. We propose a scaling-up strategy for natural regeneration based on experience gained mainly in the West African Sahel.

Forest restoration requires strategies such as passive restoration to balance financial investments and ecological outcomes. However, the ecological outcomes of passive restoration are traditionally regarded as uncertain. We evaluated technical and legal strategies for balancing economic costs and ecological outcomes of passive versus active restoration in agricultural landscapes. We focused in the case of Brazil, where we assessed the factors driving the proportion of land allocated to passive and active restoration in 42 programs covering 698,398 hectares of farms in the Atlantic Forest, Atlantic Forest/cerrado ecotone and Amazon; the ecological outcomes of passive and active restoration in 2955 monitoring plots placed in six restoration programs; and the legal framework developed by some Brazilian states to balance the different restoration approaches and comply with legal commitments. Active restoration had the highest proportion of land allocated to it (78.4%), followed by passive (14.2%) and mixed restoration (7.4%). Passive restoration was higher in the Amazon, in silviculture, and when remaining forest cover was over 50 percent. Overall, both restoration approaches showed high levels of variation in the ecological outcomes; nevertheless, passively restored areas had a smaller percentage canopy cover, lower species density, and less shrubs and trees (dbh > 5 cm). The studied legal frameworks considered land abandonment for up to 4 years before deciding on a restoration approach, to favor the use of passive restoration. A better understanding of the biophysical and socioeconomic features of areas targeted for restoration is needed to take a better advantage of their natural regeneration potential.

Large-scale and long-term restoration efforts are urgently needed to reverse historical global trends of deforestation and forest degradation in the tropics. Restoration of forests within landscapes offers multiple social, economic, and environmental benefits that enhance lives of local people, mitigate effects of climate change, increase food security, and safeguard soil and water resources. Despite rapidly growing knowledge regarding the extent and feasibility of natural regeneration and the environmental and economic benefits of naturally regenerating forests in the tropics, tree planting remains the major focus of restoration programs. Natural regeneration is often ignored as a viable land-use option. Here, we assemble a set of 16 original papers that provide an overview of the ecological, economic, and social dimensions of forest and landscape restoration (FLR), a relatively new approach to forest restoration that aims to regain ecological integrity and enhance human well-being in deforested or degraded forest landscapes. The papers describe how spontaneous (passive) and assisted natural regeneration can contribute to achieving multiple social and ecological benefits. Forest and landscape restoration is centered on the people who live and work in the landscape and whose livelihoods will benefit and diversify through restoration activities inside and outside of farms. Given the scale of degraded forestland and the need to mitigate climate change and meet human development needs in the tropics, harnessing the potential of natural regeneration will play an essential role in achieving the ambitious goals that motivate global restoration initiatives.

Assisted (or accelerated) natural regeneration (ANR) will play an important role in meeting the UN target to restore forest to 350 million hectares of degraded land, by 2030. However, since most accessible land is already used for agriculture, most of the sites, available for ANR, are far from roads and/or on difficult terrain, where implementing ANR with human labour is not practical. Therefore, this paper explores the potential of emerging technologies, such as low-cost UAVs (drones) and new imaging devices, to automate ANR tasks, including site monitoring (to assess site potential for natural regeneration, plan interventions and assess progress), maintenance of natural regeneration (particularly weeding) and species enrichment through aerial seeding. The usefulness of existing technologies is reviewed and future innovations needed, to provide practicable support for ANR, are discussed. Intensive collaboration, among technologists and forest ecologists, will be essential to ensure that technological innovations are based firmly on sound restoration science.

Effective management of understory vegetation is crucial for forest biodiversity conservation and ecosystem functions. However, the impact of various understory management practices on key ecosystem processes, such as soil nutrient cycling in tree crop plantations, remains poorly understood. This study quantified the 7-year cumulative effects on soil organic carbon (SOC) and total nitrogen (STN) stocks in rubber plantations under four understory management practices: (i) conventional management (RC) as the control, (ii) herbicide application (RH), (iii) natural regeneration (RN), and (iv) replacement with leguminous shrub (RA). Compared to RC, RN and RA increased the average number of native and invasive species and produced high above- and belowground biomass. Conversely, RH decreased the species number and belowground biomass. More SOC and STN were stored in 0.0–0.2 m topsoil in both RN (+ 9.6 Mg C ha –1 ; + 0.7 Mg N ha –1 ) and RA (+ 10.7 Mg C ha –1 ; + 0.6 Mg N ha –1 ) than RC, while they remained stable in RN but declined in RA from deeper layers of 0.2–1.0 m. Across the entire 1 m soil profile, the annual increment of SOC stocks in RN and RA reached 1.7 and 1.0 Mg C ha –1  yr –1 , respectively, and of STN stocks reached 0.02 and − 0.14 Mg N ha –1  yr –1 . However, RH decreased SOC and STN stocks and corresponding annual increments for the entire profile. The variations in SOC and STN stocks in the topsoil were attributed primarily to aboveground biomass and determined by belowground biomass in the deeper soil. Moreover, litter depth also effectively reflected SOC and STN dynamics. These results suggest that the implementation of natural regeneration and agroforestry system in the understory of rubber plantations offers significant potential for increasing soil C and N stocks. Our findings imply that sustainable understory management practices, especially natural regeneration and agroforestry system, will benefit for understory plants conservation and soil nutrient supply in tree crop plantations.

Promoting Farmer Managed Natural Regeneration (FMNR) aims to increase the productive capacities of farmer households. Under FMNR, farmers select and manage natural regeneration on farmlands and keep them under production. While FMNR contributes to the wealth of farming communities, its contribution to household food security has rarely been researched. We, therefore, used a mixed-methods approach to address the research gap by measuring FMNR’s contribution to food security among farmer households in the Talensi district of Ghana. We adopted the Household Dietary Diversity Score (HDDS) and Food Consumption Score (FCS) to estimate food security status among 243 FMNR farmer households and 243 non-FMNR farmer households. Also, we performed a Chi-square test of independence to compare the frequency of each food group (present vs not present) between FMNR adopters and non-FMNR adopters to establish the relationship between adopting FMNR and consuming the FCS and HDDS food groups. Our results reveal that FMNR farmer households are more food secure than non-FMNR farmer households. The HHDS of the FMNR farmer households was 9.6, which is higher than the target value of 9.1. Conversely, the HHDS of the non-FMNR farmer households was 4.3, which is lower than the target value of 9.1. Up to 86% and 37% of the FMNR farmer households and non-FMNR farmer households fell within acceptable FCS; 15% and 17% of FMNR farmer households and non-FMNR farmer households fell within borderline FCS. While none of the FMNR farmer households fell within poor FCS, 46% of non-FMNR farmer households fell within poor FCS. Adopting FMNR is significantly related to consuming all food groups promoted and benefiting from FMNR practices. The paper recommends enabling farmers in semi-arid environments to practice and invest in FMNR for long-term returns to food security.

Reforestation involves potential trade-offs: hard choices between environmental and social benefits, individual and community benefits, and among stakeholders who bear different costs and benefits. In this manuscript, we aim to show that successful long-term reforestation requires stakeholder engagement beyond planning stages and a recognition of the dynamism of stakeholder outlooks as stakeholders’ opportunities, relationships, interests, and roles change over time. We first summarize lessons from recent literature on stakeholder involvement within reforestation efforts. We then present findings from a multiple-stakeholder workshop organized in west-central Mexico, in which we illustrate their choices on how to navigate trade-offs among different reforestation intervention strategies (agroforestry/silvopastoral, natural regeneration, native species reforestation, commercial plantations). We confirm that individual stakeholders’circumstances, interests, and roles, as well as the contextual factors shaping them, are dynamic, continually changing the nature of the choices stakeholders face. Finally, we propose a four-phase pathway for addressing dynamic trade-offs and synergies in stakeholder participation in order to select, implement, and sustain successful reforestation activities. The pathway comprises four phases: (1) collaborate to devise a reforestation strategy through dialogue about dynamic trade-offs; (2) pledge robust stakeholder commitments to mutual arrangements for implementing reforestation; (3) implement reforestation interventions; and (4) adjust strategy through continuous evaluation of outcomes. We then elucidate how components of these four phases can be operationalized so that, on one side, scientists and practitioners might better understand the dynamic trade-offs reforestation poses for stakeholders, and on the other, stakeholders might balance their hard choices in ways that promote forest recovery.

Declining agricultural productivity, land clearance and climate change are compounding the vulnerability of already marginal rural populations in West Africa. ‘Farmer-Managed Natural Regeneration’ (FMNR) is an approach to arable land restoration and reforestation that seeks to reconcile sustained food production, conservation of soils, and protection of biodiversity. It involves selecting and protecting the most vigorous stems regrowing from live stumps of felled trees, pruning off all other stems, and pollarding the chosen stems to grow into straight trunks. Despite widespread enthusiasm and application of FMNR by environmental management and development projects, to date, no research has provided a measure of the aggregate livelihood impact of community adoption of FMNR. This paper places FMNR in the context of other agroforestry initiatives, then seeks to quantify the value of livelihood outcomes of FMNR. We review published and unpublished evidence about the impacts of FMNR, and present a new case study that addresses gaps in the evidence-base. The case study focuses on a FMNR project in the district of Talensi in the semi-arid Upper East Region in Ghana. The case study employs a social return on investment analysis, which identifies proxy financial values for non-economic as well as economic benefits. The results demonstrate income and agricultural benefits, but also show that asset creation, increased consumption of wild resources, health improvements, and psycho-social benefits created more value in FMNR-adopting households during the period of the study than increases in income and agricultural yields.

The Brazilian Cerrado is a hotspot of biodiversity conservation and an important global agricultural region. Cultivated pastures under different degradation levels are dominant in the landscape and are being targeted for sustainable agricultural intensification and restoration of native vegetation. In this study, we classified the cultivated pastures of the Brazilian Cerrado according to their potential for natural regeneration, based on field surveys and environmental predictors. We surveyed the native vegetation cover in 186 plots distributed along 93 cultivated pastures. The environmental predictors considered in this study were the proportion of sand in the soil, cation exchange capacity, climate water deficit, pasture age, slope, and pasture vigor index. We then applied the Random Forest regression algorithm to predict and map the cultivated pastures according to their potential for natural regeneration in the 19 Cerrado ecoregions. The potential for natural regeneration was classified into low (< 30% of native plant cover), medium (30–50%), and high (> 50%). Our prediction explained 75% of the data variability. Most of the cultivated pastures presented medium potential for natural regeneration (57%), while 31% and 12% presented high and low potentials, respectively. Cultivated pastures in ecoregions with high mechanization, due to their high water availability and extensive flat terrains, presented low potential for natural regeneration. This first attempt to map the potential for natural regeneration in the cultivated pastures of the Brazilian Cerrado can be used as a proxy for planning low-cost and predictable restoration or environmentally sustainable intensification in this major type of land use found in this biome.

The mechanistic basis underpinning forest succession is the gap-phase paradigm in which overstory disturbance interacts with seedling and sapling shade tolerance to determine successional trajectories. The theory, and ensuing simulation models, typically assume that understory plants have little impact on the advance regeneration layer's composition. We challenge that assumption by reviewing over 125 papers on 38 species worldwide that form dense and persistent understory canopies. Once established, this layer strongly diminishes tree regeneration, thus altering the rate and direction of forest succession. We term these dense strata recalcitrant understory layers. Over half of the cases reviewed were linked to increases in canopy disturbance and either altered herbivory or fire regimes. Nearly 75% of the studies declared that competition and allelopathy were the likely interference mechanisms decreasing tree regeneration, yet only 25% of the studies used manipulative field experiments to test these putative mechanisms. We present a conceptual model that links the factors predisposing the formation of recalcitrant understory layers with their interference mechanisms and subsequent impacts on succession. We propose that their presence constricts floristic diversity and argue for their explicit inclusion in forest dynamics theory and models. Finally, we offer management suggestions to limit their establishment and mitigate their impacts.