Hidden Costs of Passive Restoration

An introduction to key ecological concepts, financial opportunities, and risks underpinning aspirations for nature positive

Global biodiversity is in decline, and businesses and society are being required to urgently create new operating models to ameliorate the crisis. Among the strategies proposed to do this, implementing the concept of nature positive has captured worldwide attention. Critical to its success will be effective collaboration between ecologists and businesspeople, driven by a shared understanding of key nature positive terminology, concepts, and risks. To this end, we introduce three core aspects: the ecological concepts in the definition of nature positive (health, abundance, diversity, and resilience), a typology of financial instruments that may be applied to achieving nature positive, and an overview of risks to biodiversity and society. The pivotal findings include that ecological complexity and uncertainty belie the simplicity of the definition of nature positive and that managing risk requires embedding aspirations into existing and emerging biodiversity conservation and restoration science and policy. Although it is challenging, nature positive deserves pursuit.

Meta-analysis of carbon stocks and biodiversity outcomes across Brazilian restored biomes

Ecosystem restoration strategies vary widely in the techniques applied and ecological contexts. We conducted a meta-analysis to evaluate how restoration success varies across socio-ecological contexts, taxonomic groups and biomes. Restoration success is quantified as the percentage of each ecological metric value attained in the restoration site compared to the reference systems. We show that restoration success is different for plants, animals, and soils and across ecological indicators. Abundance of individuals is easier to restore than carbon stocks, which are easier than species diversity. However, abundance may be a poor indicator of ecosystem recovery because there is no unidirectional trend over time, and abundance often fails to distinguish restored from degraded areas. We also found that carbon stocks in the soil and in the vegetation are restored at analogous paces, but the recovery of soil carbon stocks is less variable than plant stocks across sites. Our results demonstrate that different restoration techniques are effective in recovering diversity and carbon stocks, but assisted natural regeneration showed a slightly higher success compared to other strategies. However, there is a considerable difficulty in restoring converted and degraded areas to achieve conditions similar to the original ecosystems. It is critical and timely to investigate benefits and effectiveness of ecosystem restoration techniques to biodiversity and carbon recovery different ecosystem types to improve the restoration effectiveness.

Unexpected consequences of afforestation in degraded drylands: Divergent impacts on soil and vegetation

Forestry has long been considered an effective means of restoring degraded drylands worldwide. Often, afforestation in such lands relies on the establishment of runoff harvesting systems that are formed as contour bench terraces on hillslopes, increasing water availability for the planted trees and shrubs. The construction of terraces requires intensive earthworks by heavy machinery. This study assessed the long-term (>10 yrs) effects of forestry-related land-use change on soil properties and herbaceous vegetation in 16-year-old and 12-year-old afforestation sites (established in 2005 and 2009), and in nearby control ("natural") areas in the semi-arid northern Negev, Israel. Mean herbaceous vegetation height in the 2005 afforestation sites (12.1 cm) was significantly (P = 0.0009) and 23% greater than in the control areas (9.8 cm), whereas in the 2009 afforestation sites (6.2 cm) it was 37% lesser than in the control areas. Mean herbaceous vegetation aboveground biomass was similar in the 2005 afforestation (0.39 Mg ha-1) and control areas (0.38 Mg ha-1), and almost significantly (P = 0.0510) and twofold greater than in the 2009 afforestation sites (0.19 Mg ha-1). The effect of hillslope aspect on these variables was substantial; their mean values were higher in the northern (mesic) hillslopes than in the southern (xeric) hillslopes. Soil samples were obtained from depths of 0-5 and 5-10 cm and physio-chemo-biological properties were assessed in the laboratory. The overall soil quality - as calculated by two soil quality indices (SQIs), including the generalized SQI (SQIgen) and the minimum dataset SQI (SQIMDS) - was significantly (P < 0.0001 for both indices) and 13-22% greater in the control areas (0.52 and 0.61, respectively) than that in the afforestation treatments (0.44-0.46 and 0.50-0.51, respectively). These results are generally attributed to the removal of soil's A-horizon during earthworks, and the exposure of the underlying B-horizon. The similar SQI values of both hillslope aspects, as well as of both soil depths, indicate the generally degraded state of the entire region. In conclusion, while contour bench terracing may facilitate the recovery of herbacaeous vegetation to some extent, the effectiveness of this practice for soil restoration is questionable. Overall, insights of this study demonstrate a caveat that converting natural drylands to forestry systems may not yield sufficient ecological benefits, and therefore should be implemented with caution.

Integrating public engagement to intensify pollination services through ecological restoration

Globally, human activities impose threats to nature and the provision of ecosystem services, such as pollination. In this context, ecological restoration provides opportunities to create managed landscapes that maximize biodiversity conservation and sustainable agriculture, e.g., via provision of pollination services. Managing pollination services and restoration opportunities requires the engagement of distinct stakeholders embedded in diverse social institutions. Nevertheless, frameworks toward sustainable agriculture often overlook how stakeholders interact and access power in social arenas. We present a perspective integrating pollination services, ecological restoration, and public engagement for biodiversity conservation and agricultural production. We highlight the importance of a comprehensive assessment of pollination services, restoration opportunities identification, and a public engagement strategy anchored in institutional analysis of the social arenas involved in restoration efforts. Our perspective can therefore guide the implementation of practices from local to country scales to enhance biodiversity conservation and sustainable agriculture.

Spontaneous Primary Succession and Vascular Plant Recovery in the Iberian Gypsum Quarries: Insights for Ecological Restoration in an EU Priority Habitat

Gypsum covers a vast area of the Iberian Peninsula, making Spain a leader in its production. Gypsum is a fundamental raw material for modern societies. However, gypsum quarries have an obvious impact on the landscape and biodiversity. Gypsum outcrops host a high percentage of endemic plants and unique vegetation, considered a priority by the EU. Restoring gypsum areas after mining is a key strategy to prevent biodiversity loss. For the implementation of restoration approaches, understanding vegetation's successional processes can be of invaluable help. To fully document the spontaneous succession in gypsum quarries and to evaluate its interest for restoration, 10 permanent plots of 20 × 50 m were proposed, with nested subplots, in which vegetation change was recorded for 13 years in Almeria (Spain). Through Species-Area Relationships (SARs), these plots' floristic changes were monitored and compared to others in which an active restoration was carried out, as well as others with natural vegetation. Furthermore, the successional pattern found was compared to those recorded in 28 quarries distributed throughout the Spanish territory. The results show that an ecological pattern of spontaneous primary auto-succession is widely recurring in Iberian gypsum quarries, which is capable of regenerating the pre-existing natural vegetation.

The framework species method: harnessing natural regeneration to restore tropical forest ecosystems

As interest in restoring tropical forests surges, so does the need for effective methods to ensure success. The framework species method (FSM) restores forest ecosystems by densely planting open sites, close to natural forest, with woody species, indigenous to the reference ecosystem and selected for their ability to accelerate ecological succession. Criteria for selecting framework species include: (i) representative of the reference forest ecosystem, (ii) tolerant of open conditions, (iii) ability to suppress weeds, (iv) attractiveness to seed-dispersing animals and (v) easily propagated. The method is effective where forest remnants and viable populations of seed dispersers remain. The origins and elements of the FSM are discussed. We review its adoption in 12 countries. Adherence to original principles was mostly high, but some misuse of the term was evident. The need for clearer definitions was identified. We place the FSM on a scale of restoration methods, matched with degradation levels and compare its establishment costs with those of other methods. Obstacles to its wider adoption, both technical and socio-economic, are discussed, along with how these might be overcome. Finally, the FSM is more clearly defined to facilitate its use in contributing towards the goals of the UN Decade on Restoration. This article is part of the theme issue 'Understanding forest landscape restoration: reinforcing scientific foundations for the UN Decade on Ecosystem Restoration'.

The road to recovery: a synthesis of outcomes from ecosystem restoration in tropical and sub-tropical Asian forests

Current policy is driving renewed impetus to restore forests to return ecological function, protect species, sequester carbon and secure livelihoods. Here we assess the contribution of tree planting to ecosystem restoration in tropical and sub-tropical Asia; we synthesize evidence on mortality and growth of planted trees at 176 sites and assess structural and biodiversity recovery of co-located actively restored and naturally regenerating forest plots. Mean mortality of planted trees was 18% 1 year after planting, increasing to 44% after 5 years. Mortality varied strongly by site and was typically ca 20% higher in open areas than degraded forest, with height at planting positively affecting survival. Size-standardized growth rates were negatively related to species-level wood density in degraded forest and plantations enrichment settings. Based on community-level data from 11 landscapes, active restoration resulted in faster accumulation of tree basal area and structural properties were closer to old-growth reference sites, relative to natural regeneration, but tree species richness did not differ. High variability in outcomes across sites indicates that planting for restoration is potentially rewarding but risky and context-dependent. Restoration projects must prepare for and manage commonly occurring challenges and align with efforts to protect and reconnect remaining forest areas. The abstract of this article is available in Bahasa Indonesia in the electronic supplementary material. This article is part of the theme issue 'Understanding forest landscape restoration: reinforcing scientific foundations for the UN Decade on Ecosystem Restoration'.

Facilitating Reforestation Through the Plant Microbiome: Perspectives from the Phyllosphere

Tree planting and natural regeneration contribute to the ongoing effort to restore Earth's forests. Our review addresses how the plant microbiome can enhance the survival of planted and naturally regenerating seedlings and serve in long-term forest carbon capture and the conservation of biodiversity. We focus on fungal leaf endophytes, ubiquitous defensive symbionts that protect against pathogens. We first show that fungal and oomycetous pathogen richness varies greatly for tree species native to the United States (n = 0-876 known pathogens per US tree species), with nearly half of tree species either without pathogens in these major groups or with unknown pathogens. Endophytes are insurance against the poorly known and changing threat of tree pathogens. Next, we review studies of plant phyllosphere feedback, but knowledge gaps prevent us from evaluating whether adding conspecific leaf litter to planted seedlings promotes defensive symbiosis, analogous to adding soil to promote positive feedback. Finally, we discuss research priorities for integrating the plant microbiome into efforts to expand Earth's forests.

Terrestrial ecosystem restoration increases biodiversity and reduces its variability, but not to reference levels: A global meta-analysis

Ecological restoration projects often have variable and unpredictable outcomes, and these can limit the overall impact on biodiversity. Previous syntheses have investigated restoration effectiveness by comparing average restored conditions to average conditions in unrestored or reference systems. Here, we provide the first quantification of the extent to which restoration affects both the mean and variability of biodiversity outcomes, through a global meta-analysis of 83 terrestrial restoration studies. We found that, relative to unrestored (degraded) sites, restoration actions increased biodiversity by an average of 20%, while decreasing the variability of biodiversity (quantified by the coefficient of variation) by an average of 14%. As restorations aged, mean biodiversity increased and variability decreased relative to unrestored sites. However, restoration sites remained, on average, 13% below the biodiversity of reference (target) ecosystems, and were characterised by higher (20%) variability. The lower mean and higher variability in biodiversity at restored sites relative to reference sites remained consistent over time, suggesting that sources of variation (e.g. prior land use, restoration practices) have an enduring influence on restoration outcomes. Our results point to the need for new research confronting the causes of variability in restoration outcomes, and close variability and biodiversity gaps between restored and reference conditions.

The biodiversity and ecosystem service contributions and trade-offs of forest restoration approaches

Forest restoration is being scaled-up globally to deliver critical ecosystem services and biodiversity benefits, yet we lack rigorous comparison of co-benefit delivery across different restoration approaches. In a global synthesis, we use 25,950 matched data pairs from 264 studies in 53 countries to assess how delivery of climate, soil, water, and wood production services as well as biodiversity compares across a range of tree plantations and native forests. Carbon storage, water provisioning, and especially soil erosion control and biodiversity benefits are all delivered better by native forests, with compositionally simpler, younger plantations in drier regions performing particularly poorly. However, plantations exhibit an advantage in wood production. These results underscore important trade-offs among environmental and production goals that policymakers must navigate in meeting forest restoration commitments.

Is it best to add native shrubs to a coastal sage scrub restoration project as seeds or as seedlings?

Ecological restoration frequently involves the addition of native plants, but the effectiveness (in terms of plant growth, plant survival, and cost) of using seeds versus container plants has not been studied in many plant communities. It is also not known if plant success would vary by species or based on functional traits. To answer these questions, we added several shrub species to a coastal sage scrub restoration site as seeds or as seedlings in a randomized block design. We measured percent cover, density, species richness, size, survival, and costs. Over the two years of the study, shrubs added to the site as seeds grew more and continued to have greater density than plants added from containers. Seeded plots also had greater native species richness than planted plots. However, shrubs from containers had higher survival rates, and percent cover was comparable between the planted and seeded treatments. Responses varied by species depending on functional traits, with deep-rooted evergreen species establishing better from container plants. Our cost analysis showed that it is more expensive to use container plants than seed, with most of the costs attributed to labor and supplies needed to grow plants. Our measurements of shrub density, survival, species richness, and growth in two years in our experimental plots lead us to conclude that coastal sage scrub restoration with seeds is optimal for increasing density and species richness with limited funds, yet the addition of some species from container plants may be necessary if key species are desired as part of the project objectives.

Dietary change in high-income nations alone can lead to substantial double climate dividend

A dietary shift from animal-based foods to plant-based foods in high-income nations could reduce greenhouse gas emissions from direct agricultural production and increase carbon sequestration if resulting spared land was restored to its antecedent natural vegetation. We estimate this double effect by simulating the adoption of the EAT-Lancet planetary health diet by 54 high-income nations representing 68% of global gross domestic product and 17% of population. Our results show that such dietary change could reduce annual agricultural production emissions of high-income nations' diets by 61% while sequestering as much as 98.3 (55.6-143.7) GtCO₂ equivalent, equal to approximately 14 years of current global agricultural emissions until natural vegetation matures. This amount could potentially fulfil high-income nations' future sum of carbon dioxide removal (CDR) obligations under the principle of equal per capita CDR responsibilities. Linking land, food, climate and public health policy will be vital to harnessing the opportunities of a double climate dividend.

Salt Marsh Restoration for the Provision of Multiple Ecosystem Services

Restoration of salt marsh is urgent, as these ecosystems provide natural coastal protection from sea-level rise impacts, contribute towards climate change mitigation, and provide multiple ecosystem services including supporting livelihoods. This study identified potential restoration sites for intervention where agricultural and degraded land could be returned to salt marsh at a national scale in South African estuaries. Overall, successful restoration of salt marsh in some estuaries will require addressing additional pressures such as freshwater inflow reduction and deterioration of water quality. Here, we present, a socio-ecological systems framework for salt marsh restoration that links salt marsh state and the well-being of people to guide meaningful and implementable management and restoration interventions. The framework is applied to a case study at the Swartkops Estuary where the primary restoration intervention intends to route stormwater run-off to abandoned salt works to re-create aquatic habitat for waterbirds, enhance carbon storage, and provide nutrient filtration. As the framework is generalized, while still allowing for site-specific pressures to be captured, there is potential for it to be applied at the national scale, with the largest degraded salt marsh areas set as priorities for such an initiative. It is estimated that ~1970 ha of salt marsh can be restored in this way, and this represents a 14% increase in the habitat cover for the country. Innovative approaches to restoring and improving condition are necessary for conserving salt marshes and the benefits they provide to society.

Post-fire forest restoration in the humid tropics: A synthesis of available strategies and knowledge gaps for effective restoration

Humid tropical forests are increasingly exposed to devastating wildfires. Major efforts are needed to prevent fire-related tipping points and to enable the effective recovery of fire-affected areas. Here, we provide a synthesis of the most common forest restoration strategies, thereby focusing on post-fire forest dynamics in the humid tropics. A variety of restoration strategies can be adopted in restoring humid tropical forests, including natural regeneration, assisted natural regeneration (i.e. fire breaks, weed control, erosion control, topsoil replacement, peatland rewetting), enrichment planting (i.e. planting nursery-raised seedlings, direct seeding) and commercial restoration (i.e. plantation forests, agroforestry). Our analysis shows that while natural regeneration can be effective under favourable ecological conditions, humid tropical forests are often ill-adapted to fire, and therefore less likely to recover unassisted after a wildfire event. Active restoration practices may be more effective, but can be costly and challenging to implement. We also identify gaps in knowledge needed for effective restoration of humid tropical forests after fire, hereby taking into account the ecosystems and socio-economic conditions in which these fires occur. We suggest to incorporate fire severity in future studies, to better understand and predict post-fire ecosystem responses. In addition, as fire poses a recurring and intensifying threat throughout the recovery process, more emphasis should be placed on post-restoration management and the prevention of fire throughout the different phases of the restoration process. Furthermore, as tropical wildfires are increasing in scale, establishing collaborative capacity and setting priorities for efficient resource allocation should become a major priority for restoration practitioners in the humid tropics. Finally, as global fire regimes are changing and expected to intensify in the context of climate change, land use and land cover change, we suggest to put continuous effort into fire monitoring and modelling to inform the development of effective restoration strategies in the long-run.

Challenges during the execution, results, and monitoring phases of ecological restoration: Learning from a country-wide assessment

Outcomes from restoration projects are often difficult for policymakers and stakeholders to assess, but this information is fundamental for scaling up ecological restoration actions. We evaluated technical aspects of the interventions, results (ecological and socio-economic) and monitoring practices in 75 restoration projects in Mexico using a digital survey composed of 137 questions. We found that restoration projects in terrestrial ecosystems generally relied on actions included in minimal (97%) and maximal (86%) intervention, while in wetlands, the preferred restoration strategies were intermediate (75%) and minimal intervention (63%). Only a third of the projects (38%) relied on collective learning as a source of knowledge to generate techniques (traditional management). In most of the projects (73%), multiple criteria (>2) were considered when selecting plant species for plantings; the most frequently used criterion was that plant species were found within the restoration area, native or naturalized (i.e., a circa situm criterion; 88%). In 48% of the projects, the biological material required for restoration (e.g., seeds and seedlings) were gathered or propagated by project implementers rather than purchased commercially. Only a few projects (between 33 and 34%) reached a high level of biodiversity recovery (>75%). Most of the projects (between 69 to71%) recovered less than 50% of the ecological services. Most of the projects (82%) led to improved individual relationships. The analysis revealed a need to implement strategies that are cost-effective, the application of traditional ecological knowledge and the inclusion of indigenous people and local communities in restoration programs at all stages—from planning to implementation, through monitoring. We also identified the need to expand research to develop effective tools to assess ecosystems’ regeneration potential and develop theoretical frameworks to move beyond short-term markers to set and achieve medium- and long-term goals. Cautious and comprehensive planning of national strategies must consider the abovementioned identified gaps.

Forest landscape restoration: state of play

Tree planting has been widely touted as an inexpensive way to meet multiple international environmental goals for mitigating climate change, reversing landscape degradation and restoring biodiversity restoration. The Bonn Challenge and New York Declaration on Forests, motivated by widespread deforestation and forest degradation, call for restoring 350 million ha by 2030 by relying on forest landscape restoration (FLR) processes. Because the 173 million ha commitments made by 63 nations, regions and companies are not legally binding, expectations of what FLR means lacks consensus. The frequent disconnect between top-level aspirations and on-the-ground implementation results in limited data on FLR activities. Additionally, some countries have made landscape-scale restoration outside of the Bonn Challenge. We compared and contrasted the theory and practice of FLR and compiled information from databases of projects and initiatives and case studies. We present the main FLR initiatives happening across regional groups; in many regions, the potential need/opportunity for forest restoration exceeds the FLR activities underway. Multiple objectives can be met by manipulating vegetation (increasing structural complexity, changing species composition and restoring natural disturbances). Livelihood interventions are context-specific but include collecting or raising non-timber forest products, employment and community forests; other interventions address tenure and governance.

Comparing the success of active and passive restoration in a tropical cloud forest landscape: A multi-taxa fauna approach

Tropical forest restoration initiatives are becoming more frequent worldwide in an effort to mitigate biodiversity loss and ecosystems degradation. However, there is little consensus on whether an active or a passive restoration strategy is more successful for recovering biodiversity because few studies make adequate comparisons. Furthermore, studies on animal responses to restoration are scarce compared to those on plants, and those that assess faunal recovery often focus on a single taxon, limiting the generalization of results. We assessed the success of active (native mixed-species plantations) and passive (natural regeneration) tropical cloud forest restoration strategies based on the responses of three animal taxa: amphibians, ants, and dung beetles. We compared community attributes of these three taxa in a 23-year-old active restoration forest, a 23-year-old passive restoration forest, a cattle pasture, and a mature forest, with emphasis on forest-specialist species. We also evaluated the relationship between faunal recovery and environmental variables. For all taxa, we found that recovery of species richness and composition were similar in active and passive restoration sites. However, recovery of forest specialists was enhanced through active restoration. For both forests under restoration, similarity in species composition of all faunal groups was 60–70% with respect to the reference ecosystem due to a replacement of generalist species by forest-specialist species. The recovery of faunal communities was mainly associated with canopy and leaf litter covers. We recommend implementing active restoration using mixed plantations of native tree species and, whenever possible, selecting sites close to mature forest to accelerate the recovery of tropical cloud forest biodiversity. As active restoration is more expensive than passive restoration, both strategies might be used in a complementary manner at the landscape level to compensate for high implementation costs.

Optimal multi-instrument management of interrelated resources and a groundwater dependent ecosystem

We develop and operationalize an integrated groundwater and watershed management model using data from the Kīholo aquifer on the west coast of Hawai'i Island. Results from a numerical simulation suggest that investment in fencing (passive management) is preferred to invasive species removal (active management) if we are limited to selecting a single conservation tool. However, using both instruments jointly increases net present value relative to using either instrument independently in most cases tested, and the additional benefit of invasive species removal increases as water becomes scarcer. The general results are largely insensitive to variations in the invasive species uptake rate and recharge benefits of fencing, and in all cases, use of both instruments reduces the loss resulting from the imposition of a safe minimum standard for groundwater-dependent ecosystems more effectively than either instrument alone.

Forest Landscape Restoration—What Generates Failure and Success?

Research Highlights: The global Forest Landscape Restoration ambitions could be impaired by projects that ignore key principles such as the engagement of local communities in decision making and implementation, equitable benefit sharing, and monitoring for adaptive management. This entails the danger of continued degradation, disappointed local stakeholders, and ultimately, project failure. Other projects face technical problems related to tree establishment and nursery production. Background and Objectives: There are high hopes for Forest and Landscape Restoration to regain ecosystem integrity and enhance human well-being in deforested and degraded areas. We highlight various problems and success factors experienced during project implementation on a global scale. Materials and Methods: We use data from a global online survey to identify common obstacles and success factors for the implementation of forest restoration. Results: While the majority of respondents reported successful projects, others indicate drastic problems and failed projects. Major obstacles to forest restoration experienced by survey respondents were a lack of local stakeholder involvement and a mismatch between goals of local communities and restoration managers, as well as environmental, anthropogenic, and technical barriers to tree regeneration. Conclusions: When local communities, their goals, and needs are disregarded in project planning and implementation, as reported from various cases in our survey and the limited available literature, there is a risk of project failure. Failed projects and disappointed stakeholders, as well as discouraged funders and policy-makers, could lessen the momentum of global forest restoration ambitions. Adhering to key principles of Forest and Landscape Restoration can promote much-needed community support, with the potential to overcome barriers to forest regeneration and enable communities for the protection, management, and monitoring of the restored forests beyond the limited project and funding periods. Research is needed to gain a better understanding of the perception of local communities towards restoration activities. Further studies on the implementation of forest restoration at the intersection of environmental factors, socioeconomic conditions, forest regeneration/silviculture, and nursery production are needed.

Key Principles for Managing Recovery of Kelp Forests through Restoration

There is increasing interest in mitigating the loss of kelp forests through restoration, but this has received scant attention relative to other coastal habitats. We evaluate current knowledge centered on key restoration principles to provide guidelines for best practice in kelp restoration. The cause and scale of degradation is fundamental in determining if kelp can be restored and the methods required to promote reestablishment. Removal of stressors may be adequate to achieve restoration goals where degradation is not too widespread or acute. Extensive losses of kelp forests will often require active reseeding of areas because of the low dispersal ability of many kelp species. Restoration efforts have generally taken a trial-and-error approach at experimental scales to develop techniques for establishing individuals. Furthermore, studies that inform cost–benefit analysis and the appropriate spatial scales for restoration of sustainable kelp forests are urgently needed for prioritizing and scaling up restoration efforts globally.

Planning forest restoration within private land holdings with conservation co-benefits at the landscape scale

Forest loss is mainly due to the conversion of forest to agriculture, mostly in private lands. Forest restoration is a global priority, yet restoration targets are ambitious and budget-limited. Therefore, assessing the outcome of alternative decisions on land-use within private lands is paramount to perform cost-effective restoration. We present a novel framework that incorporates spatial planning for forest restoration within private lands with conservation co-benefits at the landscape scale. As a case study, we used three real landscapes of 10.000 ha with differing amounts of forest cover in the Atlantic Forest region of Brazil, and three hypothetical animal species with different dispersal abilities. We estimated the total amount of forest that landholders must restore to comply with the Native Vegetation Protection Law, which requires landholders to reforest 20% of their land within a 20-year time frame. We compared the cost-effectiveness of five restoration strategies based on the improvement in habitat availability and restoration costs. The most cost-effective strategy depends on a landscape's initial amount of forest cover and the species of concern. We revealed that spatial planning for restoration in private lands increased habitat availability up to 12 times more than random restoration, which was always the least cost-effective strategy. Cost-effective large-scale restoration in Brazil depends on public policies that assist landholders to comply with the law and on prioritizing areas for restoration within private lands. We show that by adding habitat availability as target in spatial prioritization, benefits for biodiversity can be hastened at low additional cost, even in real world scenarios with severe spatial constraints. Despite constraints, spatially planned restoration for law compliance in Brazil increased landscape permeability by creating corridors and stepping stones. Our framework should be used to plan restoration in Brazilian private lands and can be customized for other regions worldwide.

Water runoff harvesting systems for restoration of degraded rangelands: A review of challenges and opportunities

Mismanagement of rangelands worldwide has accelerated processes of overland flow and soil erosion, resulting in extensive land degradation. Wherever self-restoration processes of degraded rangelands are hindered or negated, active recovery efforts, coupled with livestock pressure management, might be needed. The objective of this review paper is to provide land managers and environmental planners with applied and practical knowledge on advantages and disadvantages of the main methodologies and practices for runoff harvesting in rangelands. Preferably, restoration efforts should focus on forming low-footprint runoff harvesting systems on hillslopes which encompass the runoff's source area. These systems should imitate natural patchiness, strengthening source-sink relations, accelerating re-establishment of herbaceous and woody vegetation, maximizing the retaining of water on hillslopes, regulating hydrological connectivity, lessening soil erosion, and minimizing transmission of water to stream channels. The resulting lower-energy floods are expected to negate the need for massive check dams in channels. If flood dissipation in streams is still necessary, then high-to medium-porosity check dams, made of local materials, might be effective for lessening scour processes and sediment transport. Furthermore, in terms of environmental sustainability, a large number of pointed (e.g., branch bundles; brush or woody piles; micro-catchments) or low-to medium-footprint lineal means for regulating surface processes in hillslopes (e.g., stone terraces; contour furrows/trenches/ditches) and channels (e.g., log check dams; loose rock check dams; porous or semi-permeable rock check dams; gabions) are expected to be more cost-effective than a small number of massive means (e.g., contour bench terraces; earth bunds/dykes; concrete check dams). If runoff harvesting systems are properly designed, restoration processes over time are expected to generate geo-ecological feedbacks and recover eco-hydrological functioning, increasing pasture productivity and sustaining rangeland carrying capacity.

Recovery of Soil Hydraulic Properties for Assisted Passive and Active Restoration: Assessing Historical Land Use and Forest Structure

Tree planting and natural regeneration are the main approaches to achieve global forest restoration targets, affecting multiple hydrological processes, such as infiltration of rainfall. Our understanding of the effect of land use history and vegetation on the recovery of water infiltration and soil attributes in both restoration strategies is limited. Therefore, we investigated the recovery of top-soil saturated soil hydraulic conductivity (Ks), soil physical and hydraulic properties in five land use types: (i) a secondary old-growth forest; (ii) a forest established through assisted passive restoration 11 years ago; (iii) an actively restored forest, with a more intensive land use history and 11 years of age; (iv) a pasture with low-intensity use; and (v) a pasture with high-intensity use, in the Brazilian Atlantic Forest. For these land use types, we determined the historical land use patterns and conducted soil sampling, using the Beerkan method to determine Ks values in the field. We also measured tree basal area, canopy cover, vegetation height, tree density and species richness in forest covers. The Ks decreased when land use was more intense prior to forest restoration actions. Our results indicate that land use legacy is a crucial factor to explain the current difference in soil and vegetation attributes among study sites.

Diversity of terrestrial mammal seed dispersers along a lowland Amazon forest regrowth gradient

There is increasing interest in the restoration/regeneration of degraded tropical habitats yet the potential role of natural regenerators remains unclear. We test the hypothesis that the richness and functional diversity of terrestrial mammals differs between forest regrowth stages. We quantified the richness and functional diversity of eight terrestrial mammal seed-disperser species across a forest regrowth gradient in the eastern Brazilian Amazon. We installed camera-traps in 15 sites within small-holder properties with forest regrowth stage classified into three groups, with five sites each of: late second-regrowth forest, early second-regrowth forest and abandoned pasture. Species richness and functional dispersion from the regrowth sites were compared with 15 paired forest control sites. Multi model selection showed that regrowth class was more important for explaining patterns in richness and functional diversity than other variables from three non-mutually exclusive hypotheses: hunting (distance to house, distance to river, distance to town, small holder residence), land cover (% forest cover within 50 meters, 1 kilometer and 5 kilometers) and land use (regrowth class, time since last use). Differences in functional diversity were most strongly explained by a loss of body mass. We found that diversity in regrowth sites could be similar to control sites even in some early-second regrowth areas. This finding suggests that when surrounded by large intact forest areas the richness and functional diversity close to human small-holdings can return to pre-degradation values. Yet we also found a significant reduction in richness and functional diversity in more intensely degraded pasture sites. This reduction in richness and functional diversity may limit the potential for regeneration and increase costs for ecological regeneration and restoration actions around more intense regrowth areas.

Early ecological outcomes of natural regeneration and tree plantations for restoring agricultural landscapes

Mixed tree plantings and natural regeneration are the main restoration approaches for recovering tropical forests worldwide. Despite substantial differences in implementation costs between these methods, little is known regarding how they differ in terms of ecological outcomes, which is key information for guiding decision making and cost-effective restoration planning. Here, we compared the early ecological outcomes of natural regeneration and tree plantations for restoring the Brazilian Atlantic Forest in agricultural landscapes. We assessed and compared vegetation structure and composition in young (7-20 yr old) mixed tree plantings (PL), second-growth tropical forests established on former pastures (SGp), on former Eucalyptus spp. plantations (SGe), and in old-growth reference forests (Ref). We sampled trees with diameter at breast height (DBH) 1-5 cm (saplings) and trees at DBH > 5 cm (trees) in a total of 32 20 × 45 m plots established in these landscapes. Overall, the ecological outcomes of natural regeneration and restoration plantations were markedly different. SGe forests showed higher abundance of large (DBH > 20 cm) nonnative species, of which 98% were resprouting Eucalyptus trees, than SGp and PL, and higher total aboveground biomass; however, aboveground biomass of native species was higher in PL than in SGe. PL forests had lower abundance of native saplings and lianas than both naturally established second-growth forests, and lower proportion of animal dispersed saplings than SGe, probably due to higher isolation from native forest remnants. Rarefied species richness of trees was lower in SGp, intermediate in SGe and Ref and higher in PL, whereas rarefied species richness of saplings was higher in SG than in Ref. Species composition differed considerably among regeneration types. Although these forests are inevitably bound to specific landscape contexts and may present varying outcomes as they develop through longer time frames, the ecological particularities of forests established through different restoration approaches indicate that naturally established forests may not show similar outcomes to mixed tree plantings. The results of this study underscore the importance that restoration decisions need to be based on more robust expectations of outcomes that allow for a better analysis of the cost-effectiveness of different restoration approaches before scaling-up forest restoration in the tropics.