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This study adapts and applies the evidence‐based approach for causal inference, a medical standard, to the restoration and sustainable management of large‐scale aquatic ecosystems. Despite long‐term investments in restoring aquatic ecosystems, it has proven difficult to adequately synthesize and evaluate program outcomes, and no standard method has been adopted. Complex linkages between restorative actions and ecosystem responses at a landscape scale make evaluations problematic and most programs focus on monitoring and analysis. Herein, we demonstrate a new transdisciplinary approach integrating techniques from evidence‐based medicine, critical thinking, and cumulative effects assessment. Tiered hypotheses about the effects of landscape‐scale restorative actions are identified using an ecosystem conceptual model. The systematic literature review, a health sciences standard since the 1960s, becomes just one of seven lines of evidence assessed collectively, using critical thinking strategies, causal criteria, and cumulative effects categories. As a demonstration, we analyzed data from 166 locations on the Columbia River and estuary representing 12 indicators of habitat and fish response to floodplain restoration actions intended to benefit culturally and economically important, threatened and endangered salmon. Synthesis of the lines of evidence demonstrated that hydrologic reconnection promoted macrodetritis export, prey availability, and juvenile fish access and feeding. Upon evaluation, the evidence was sufficient to infer cross‐boundary, indirect, compounding, and delayed cumulative effects, and suggestive of nonlinear, landscape‐scale, and spatial density effects. Therefore, on the basis of causal inferences regarding food‐web functions, we concluded that the restoration program is having a cumulative beneficial effect on juvenile salmon. The lines of evidence developed are transferable to other ecosystems: modeling of cumulative net ecosystem improvement, physical modeling of ecosystem controlling factors, meta‐analysis of restoration action effectiveness, analysis of data on target species, research on critical ecological uncertainties, evidence‐based review of the literature, and change analysis on the landscape setting. As with medicine, the science of ecological restoration needs scientific approaches to management decisions, particularly because the consequences affect species extinctions and the availability of ecosystem services. This evidence‐based approach will enable restoration in complex coastal, riverine, and tidal‐fluvial ecosystems like the lower Columbia River to be evaluated when data have accumulated without sufficient synthesis.

In coastal and estuarine systems, foundation species like seagrasses, mangroves, saltmarshes or corals provide important ecosystem services. Seagrasses are globally declining and their reintroduction has been shown to restore ecosystem functions. However, seagrass restoration is often challenging, given the dynamic and stressful environment that seagrasses often grow in. From our world‐wide meta‐analysis of seagrass restoration trials (1786 trials), we describe general features and best practice for seagrass restoration. We confirm that removal of threats is important prior to replanting. Reduced water quality (mainly eutrophication), and construction activities led to poorer restoration success than, for instance, dredging, local direct impact and natural causes. Proximity to and recovery of donor beds were positively correlated with trial performance. Planting techniques can influence restoration success. The meta‐analysis shows that both trial survival and seagrass population growth rate in trials that survived are positively affected by the number of plants or seeds initially transplanted. This relationship between restoration scale and restoration success was not related to trial characteristics of the initial restoration. The majority of the seagrass restoration trials have been very small, which may explain the low overall trial survival rate (i.e. estimated 37%). Successful regrowth of the foundation seagrass species appears to require crossing a minimum threshold of reintroduced individuals. Our study provides the first global field evidence for the requirement of a critical mass for recovery, which may also hold for other foundation species showing strong positive feedback to a dynamic environment. Synthesis and applications. For effective restoration of seagrass foundation species in its typically dynamic, stressful environment, introduction of large numbers is seen to be beneficial and probably serves two purposes. First, a large‐scale planting increases trial survival – large numbers ensure the spread of risks, which is needed to overcome high natural variability. Secondly, a large‐scale trial increases population growth rate by enhancing self‐sustaining feedback, which is generally found in foundation species in stressful environments such as seagrass beds. Thus, by careful site selection and applying appropriate techniques, spreading of risks and enhancing self‐sustaining feedback in concert increase success of seagrass restoration.

Deforestation and forest degradation continue to take place at alarming rates in Africa despite global net forest loss reductions. This is prompting large-scale forest restoration involving community volunteers to prevent, halt and reverse the loss of biodiversity for the sustainable development of forest landscapes in Africa. The study explored the motivations, challenges, barriers and negotiation strategies of community volunteers in ecosystem restoration and conservation initiatives in Cameroon’s Western Highlands (Mount Bamboutos landscape), given that many such interventions are not achieving desired targets and goals. A total of 134 respondents involving farmers and local implementing NGO workers were interviewed, using semi-structured open-ended questionnaires. One focus group discussion was held with paramount traditional rulers to assess the strength, weaknesses, opportunities and threats (SWOT) of the community-led ecosystem restoration and conservation initiative. The principal components analysis with oblique (Direct oblimin) rotation was used to reduce the number of constitutive items in each dimension of motivation, challenge and barrier to community participation. Linear regression analysis was used to examine how the different dimensions of motivations, challenges and barriers influence community participation. Community participation was initially driven more by environmental motivations given the highly deforested and degraded Mount Bamboutos landscape, but later on driven more by economic and community motivations. Social factors were least expressed and non-significant predictors of participation. Community participation was primarily limited by management, financial, psychological, personal, and information challenges and barriers. Providing financial incentives to cover daily subsistence costs of food and transport was a key negotiation strategy that increased community participation. Conservation organisations should capitalise on environment, community and social motivational appeals during community education and awareness campaigns to increase voluntary community participation. The local knowledge on ecosystem restoration and conservation motivations, challenges, barriers, negotiation strategies, recommendations and SWOT analysis provide relevant baseline information for environment management decision-makers in Cameroon and other Sub-Saharan African countries. Highlights Community participation was initially driven mainly by environmental factors. Community participation was later on driven more by economic and community motives. Social factors were least frequently expressed and non-significant predictors of participation. Financial, management and psychological challenges and barriers mainly limited participation. Providing financial incentives to cover daily subsistence costs of food and transport increased participation.

Restoration of marginal and degraded lands is essential for regaining biodiversity and ecosystems services, and thereby attaining UN-Sustainable Development Goals. During the last few decades, many fast growing and hardy trees have been introduced worldwide to restore the marginal and degraded lands for ecosystem stability. Unfortunately, most of these introduced species have become invasive and invaded the nearby productive systems, leading to significant biodiversity loss and land degradation. Therefore, it is imperative to conduct a sustainability analysis of the introduced species for necessary course correction and also for preventing the future utilisation of such species for land restoration. With this backdrop, the present study was conducted to analyse the socio-ecological impacts of a widely used species, i.e., Prosopis juliflora (Sw.) DC based restoration of degraded land of Lucknow, North India. For this, ecological (soil quality and plant biodiversity) and social (livelihood) indicators have been studied over a period of two years (2015–16) through direct field sampling and questionnaire-based surveys. While there was a positive difference (p < 0.01) in the key physico-chemical properties of the P. juliflora-invaded soil than the non-invaded site, the belowground microbial load was significantly lower (19.46 × 106 g−1 of soil) in invaded land as compared to the non-invaded one (31.01 × 106 g−1). Additionally, the invasion of P. juliflora had significantly reduced the biodiversity by displacing the local flora such as Achyranthes aspera L., Amaranthus spinosus L., Cynodon dactylon (L.) Pers, Euphorbia hirta L., etc. The invaded area had only eight plant species having an effective number of species (ENS) of 7.2, whereas the non-invaded area had the presence of 26 plant species with an ENS of 23.8. Although the local people utilised P. juliflora as fuelwood mostly during summer and winter seasons, the invasion resulted in a fodder deficit of 419.97 kg household−1 y−1 leading to resource scarcity in the invaded area in comparison to the non-invaded area. Ecodistribution mapping clearly showed that P. juliflora is already found in most of the tropical and subtropical countries (~103) including in India and has become invasive in many countries. Therefore, we recommend that P. juliflora must be wisely used for the land restoration programs targeted during the United Nations Decade of Ecosystem Restoration (2021–2030) as this species has invasive traits and thereby reduces the ecosystem sustainability of the invaded areas.

Measures aimed at conservation or restoration of ecosystems are often seen as net‐cost projects by governments and businesses because they are based on incomplete and often faulty cost‐benefit analyses. After screening over 200 studies, we examined the costs (94 studies) and benefits (225 studies) of ecosystem restoration projects that had sufficient reliable data in 9 different biomes ranging from coral reefs to tropical forests. Costs included capital investment and maintenance of the restoration project, and benefits were based on the monetary value of the total bundle of ecosystem services provided by the restored ecosystem. Assuming restoration is always imperfect and benefits attain only 75% of the maximum value of the reference systems over 20 years, we calculated the net present value at the social discount rates of 2% and 8%. We also conducted 2 threshold cum sensitivity analyses. Benefit‐cost ratios ranged from about 0.05:1 (coral reefs and coastal systems, worst‐case scenario) to as much as 35:1 (grasslands, best‐case scenario). Our results provide only partial estimates of benefits at one point in time and reflect the lower limit of the welfare benefits of ecosystem restoration because both scarcity of and demand for ecosystem services is increasing and new benefits of natural ecosystems and biological diversity are being discovered. Nonetheless, when accounting for even the incomplete range of known benefits through the use of static estimates that fail to capture rising values, the majority of the restoration projects we analyzed provided net benefits and should be considered not only as profitable but also as high‐yielding investments. Beneficios de Invertir en la Restauración de Ecosistemas

As an inevitable consequence of increased environmental degradation and anticipated future environmental change, societal demand for ecosystem restoration is rapidly increasing. Here, I evaluate successes and failures in restoration, how science is informing these efforts, and ways to better address decision-making and policy needs. Despite the multitude of restoration projects and wide agreement that evaluation is a key to future progress, comprehensive evaluations are rare. Based on the limited available information, restoration outcomes vary widely. Cases of complete recovery are frequently characterized by the persistence of species and abiotic processes that permit natural regeneration. Incomplete recovery is often attributed to a mixture of local and landscape constraints, including shifts in species distributions and legacies of past land use. Lastly, strong species feedbacks and regional shifts in species pools and climate can result in little to no recovery. More forward-looking paradigms, such as enhancing ecosystem services and increasing resilience to future change, are exciting new directions that need more assessment. Increased evidence-based evaluation and cross-disciplinary knowledge transfer will better inform a wide range of critical restoration issues such as how to prioritize sites and interventions, include uncertainty in decision making, incorporate temporal and spatial dependencies, and standardize outcome assessments. As environmental policy increasingly embraces restoration, the opportunities have never been greater.

Given that few ecosystems on the Earth have been unaffected by humans, restoring them holds great promise for stemming the biodiversity crisis and ensuring ecosystem services are provided to humanity. Nonetheless, few studies have documented the recovery of ecosystems globally or the rates at which ecosystems recover. Even fewer have addressed the added benefit of actively restoring ecosystems versus allowing them to recover without human intervention following the cessation of a disturbance. Our meta-analysis of 400 studies worldwide that document recovery from large-scale disturbances, such as oil spills, agriculture and logging, suggests that though ecosystems are progressing towards recovery following disturbances, they rarely recover completely. This result reinforces conservation of intact ecosystems as a key strategy for protecting biodiversity. Recovery rates slowed down with time since the disturbance ended, suggesting that the final stages of recovery are the most challenging to achieve. Active restoration did not result in faster or more complete recovery than simply ending the disturbances ecosystems face. Our results on the added benefit of restoration must be interpreted cautiously, because few studies directly compared different restoration actions in the same location after the same disturbance. The lack of consistent value added of active restoration following disturbance suggests that passive recovery should be considered as a first option; if recovery is slow, then active restoration actions should be better tailored to overcome specific obstacles to recovery and achieve restoration goals. We call for a more strategic investment of limited restoration resources into innovative collaborative efforts between scientists, local communities and practitioners to develop restoration techniques that are ecologically, economically and socially viable.

Farmland afforestation has been promoted in recent decades and is one of the main strategies included in the UN Decade on Ecosystem Restoration to recover degraded areas. However, the impacts of afforestation on plant diversity and soil quality indicators are still not well-understood in semiarid environments. In this study, we assessed the relationships between plant diversity indicators (abundance, total richness, richness by functional groups, and Shannon diversity) and a large number of variables in 48 afforestation sites in southeast Spain. We considered associated environmental factors, such as geographical, climatic or edaphic variables, age, and land-use history. We compared plant diversity and soil properties following land-use change from cereal cropping to afforestation, which is one of the most common land-use changes in Mediterranean areas. Plant diversity in afforested sites was found to be dependent on previous land use, the proximity of natural vegetation, several soil properties (texture, pH, and total nitrogen), and plantation age. Afforested soils showed higher plant diversity and an improvement in edaphic parameters related to multifunctionality in semiarid ecosystems (i.e., soil organic carbon, nitrogen, and potassium) than arable cropped soils.

Ecosystem recovery from anthropogenic disturbances, either without human intervention or assisted by ecological restoration, is increasingly occurring worldwide. As ecosystems progress through recovery, it is important to estimate any resulting deficit in biodiversity and functions. Here we use data from 3,035 sampling plots worldwide, to quantify the interim reduction of biodiversity and functions occurring during the recovery process (that is, the 'recovery debt'). Compared with reference levels, recovering ecosystems run annual deficits of 46-51% for organism abundance, 27-33% for species diversity, 32-42% for carbon cycling and 31-41% for nitrogen cycling. Our results are consistent across biomes but not across degrading factors. Our results suggest that recovering and restored ecosystems have less abundance, diversity and cycling of carbon and nitrogen than 'undisturbed' ecosystems, and that even if complete recovery is reached, an interim recovery debt will accumulate. Under such circumstances, increasing the quantity of less-functional ecosystems through ecological restoration and offsetting are inadequate alternatives to ecosystem protection.

1. During the past three decades, conservation and restoration biologists have increasingly recognized that ecological communities are likely to exhibit threshold changes in structure. However, because long-term monitoring data are generally lacking, little is known about the consequences of such ecological thresholds for the processes of ecosystem degradation and recovery. 2. To identify whether a degradation threshold exists that defines the boundary between the possibility of natural recovery and the need for artificial restoration of an ecosystem and to use this knowledge to support the development of a suitable strategy for environmental restoration, we performed long-term monitoring of vegetation recovery in China's Changting County since 1984. 3. A major problem was identified, which we refer to as the 'irreversible loss of soil services'; when vegetation cover decreases below a degradation threshold, this leads to sustained degeneration of the vegetation community, erosion of the surface soil and declining soil fertility. These changes represent a severe and long-lasting disturbance that will prevent ecosystem recovery in the absence of comprehensive artificial restoration measures. 4. Synthesis and applications. We identified a degradation threshold at about 20% vegetation cover suggesting that for some sites, vegetation cover can serve as a simple proxy for more sophisticated approaches to identifying thresholds; restoration must start with the restoration of soil fertility and continue by facilitating vegetation development. Our results support the concept of ecological thresholds (specifically, for soil services in a warm and wet region) and provide a model to inform restoration strategies for other degraded ecosystems.