Restoration Success: How Is It Being Measured?

The added value of the long-term ecological research network to upscale restoration in Europe

Achieving global restoration targets poses challenges including the need for long-term research and effective monitoring of success, fostering collaborations across diverse fields and actors, ensuring the availability of suitable reference ecosystems, and securing sustained funding. Yet, these conditions are often lacking, limiting the effectiveness of restoration. We provide an overview of ecological restoration practices in the pan-European region of the Long-term Ecological Research Network (eLTER) and demonstrate the importance of eLTER and its potential contributions to support the implementation of the EU Nature Restoration Law. We developed an online questionnaire to collect information on eLTER restoration experts and restoration projects details including the use of eLTER contributions (e.g. infrastructure, data and knowledge), between November 2021 and March 2022. We identified 62 restoration experts and 42 restoration projects from 18 countries. Our results show that eLTER restoration expertise covers most of the European habitats, diverse degradation states and restoration techniques. Most restoration projects (78%) involved long-term monitoring exceeding the average project lifespan, which has proven necessary to achieve restoration success. No common protocol was used for monitoring and evaluation or cost-benefit estimates, but respondents reported effective projects, mostly financed from national funds, and benefits in five ecosystem services on average covered per project. Key eLTER contributions included providing reference ecosystems, biotic and abiotic background data, and interdisciplinary discussion or stakeholder management. Ecological restoration is time intensive and requires long-term research and monitoring standardization to fully understand the restoration process and to ensure comparability across ecosystems. The eLTER network can help address these challenges providing added-value contributions through its infrastructure, long-term datasets, diversity of expertise and strategies that can help identify best restoration practices and support the EU Nature Restoration Law. Finally, additional and long-term funding from the EU and the private sector is needed to achieve global larger-scale restoration targets.

Fast grassland recovery from viable propagules after reintroducing traditional mowing management on a steep slope

Semi-natural grasslands on steep slopes often show high plant species diversity. These grasslands were traditionally maintained through mowing and/or grazing. The traditional management practices help to maintain species diversity, whereas land abandonment reduces diversity by increasing competition from dominant species and reducing seedling recruitment. The reintroduction of management can reverse species diversity declines, but suitable grassland restoration programs are scarce in Japan. To study the effect of short-term abandonment on seedling ecology, we monitored the vegetation of a Susogari grassland that had been abandoned for 3 years; the grassland occupies a steep slope (ca. 50°) on a hillside above paddy fields, and was traditionally mown. We monitored the vegetation before abandonment, in the 3rd year of abandonment, and in the 1st and 2nd years after restoration of mowing management. Emergence and survival of seedlings was monitored for 18 months after reintroduction of management. We monitored 1,183 seedlings of grassland species and non-target annuals in ten 1-m2 plots. After mowing was reintroduced, most grassland species reappeared or increased in the first and second years. Few seedlings of perennial plants and no seedlings of annuals flowered. An exotic species, Solidago altissima, had a lower survival rate (10%) than grassland species (>30%), and all but two grassland species survived over the 18-month period. Although vegetation composition was not fully recovered, our findings suggest that a steep slope acts as a strong filter that inhibits the establishment of non-target species while enhancing persistence of target grassland species.

Leveraging co-production within ecosystem restoration to maximize benefits to coastal birds

Coastal Louisiana's ecosystems are threatened by anthropogenic factors exacerbated by climate change induced sea-level rise. The 2010 Deepwater Horizon oil spill resulted in injuries and deaths to coastal birds in Louisiana, and the ongoing loss of habitat has limited the potential for successful nesting of resident birds throughout the coast. Habitat loss is being addressed through increased large-scale ecosystem restoration as a result of settlement funds from the Deepwater Horizon oil spill. To further inform bird restoration in Louisiana, an avian restoration guidance document (Guidance for Coastal Ecosystem Restoration and Monitoring to Create or Improve Bird-NestingHabitat, 2023) was developed to maximize restoration benefits for coastal breeding birds while also achieving broader habitat restoration objectives. The developed restoration guidance was co-produced by subject-matter experts and professionals, including avian experts, engineers, and coastal restoration project managers. The result of this cross-disciplinary effort was specific and targeted guidance that presents designable habitat features that are in the control of project engineers and are also important high-value bird nesting habitats (e.g., shoreline access, elevation heterogeneity and edge habitat). For the first time in Louisiana, defined nest-site characteristics and monitoring approaches are readily available to inform ecosystem restoration project implementation. The restoration document specifically emphasizes bird species that breed and nest in coastal habitats in Louisiana, and restoration managers can use these guidelines to explicitly incorporate bird nesting habitat features into coastal restoration planning, design, and implementation. In developing this guidance, many knowledge gaps and data needs were identified specific to engineering and project design, enabling the research community to frame research questions around specific coastal restoration questions. The co-production of science model applied here for avian resources is applicable to a wide range of other living marine resources that may benefit from large-scale ecosystem restoration and is an example of the benefits of working relationships, communications, and common goal setting.

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.

What Makes A Bank A Bank? Differences and Commonalities in Credit Calculation, Application, and Risks in Mitigation Banks Targeting Freshwater Fish Species and Associated Ecosystems

Mitigation banking is part of the ever-expanding global environmental market framework that aims to balance negative approved anthropogenic impacts versus third-party provided ecosystem benefits, sold in the form of credits. Given the need to conserve freshwater biodiversity and habitat, banking has received great traction for freshwater species and systems. While extensive reviews and studies have been conducted on evaluating if equivalency between impacts and offset can be achieved, there is almost no research being done on the way credits are being generated and banks are managed to inform future best practice and policy. Synthesizing banking data through cluster analyzes from 26 banks in the United States generating credits for freshwater species and associated systems, we show two generalizable approaches: removing barriers and targeting whole communities. Both address crucial freshwater conservation needs but come with their risks and caveats. Using common characteristics and management practices founded in federal and district level guidance within these two groups, we showcase and conclude that credit generation via barrier removal can be at risk of granting credit generation for too large of an area, leading to over-crediting. Banks targeting whole freshwater communities and accounting for landscape-level interactions and influences can potentially be detrimental for species on an individual level and large-scale credit availability as well as transfer can incentivize non-compliance with the mitigation hierarchy.

Testing the hierarchy of predictability in grassland restoration across a gradient of environmental severity

Ecological restoration is critical for recovering degraded ecosystems but is challenged by variable success and low predictability. Understanding which outcomes are more predictable and less variable following restoration can improve restoration effectiveness. Recent theory asserts that the predictability of outcomes would follow an order from most to least predictable from coarse to fine community properties (physical structure > taxonomic diversity > functional composition > taxonomic composition) and that predictability would increase with more severe environmental conditions constraining species establishment. We tested this "hierarchy of predictability" hypothesis by synthesizing outcomes along an aridity gradient with 11 grassland restoration projects across the United States. We used 1829 vegetation monitoring plots from 227 restoration treatments, spread across 52 sites. We fit generalized linear mixed-effects models to predict six indicators of restoration outcomes as a function of restoration characteristics (i.e., seed mixes, disturbance, management actions, time since restoration) and used variance explained by models and model residuals as proxies for restoration predictability. We did not find consistent support for our hypotheses. Physical structure was among the most predictable outcomes when the response variable was relative abundance of grasses, but unpredictable for total canopy cover. Similarly, one dimension of taxonomic composition related to species identities was unpredictable, but another dimension of taxonomic composition indicating whether exotic or native species dominated the community was highly predictable. Taxonomic diversity (i.e., species richness) and functional composition (i.e., mean trait values) were intermittently predictable. Predictability also did not increase consistently with aridity. The dimension of taxonomic composition related to the identity of species in restored communities was more predictable (i.e., smaller residuals) in more arid sites, but functional composition was less predictable (i.e., larger residuals), and other outcomes showed no significant trend. Restoration outcomes were most predictable when they related to variation in dominant species, while those responding to rare species were harder to predict, indicating a potential role of scale in restoration predictability. Overall, our results highlight additional factors that might influence restoration predictability and add support to the importance of continuous monitoring and active management beyond one-time seed addition for successful grassland restoration in the United States.

Seed sourcing for climate-resilient grasslands: The role of seed source diversity during early restoration establishment

Restoration advocates for the use of local seed in restoration, but theory suggests that diverse seed sources may enhance genetic diversity and longer term evolutionary potential within restored communities. However, few empirical studies have evaluated whether species and genetic diversity within species impacts plant community composition following restoration. The goal of this research is to compare the effects of single and multi-sourced seed mix treatments on plant community diversity following restoration. Species establishment, abundance, and diversity were compared following two restoration seed mix treatments created to include 14 species commonly used in grassland restoration. We compared the application of seed mixes designed using a single population per species with those containing five populations per species across sites in Minnesota and South Dakota, United States. Early plant establishment and richness mostly reflected non-seeded species across both sites, although seeded species established at a slightly higher rate in year two following restoration. At the South Dakota site, community composition largely reflected changes associated with establishment across the growing season as opposed to seed mix treatment. This contrasted with the Minnesota site, where community composition appeared to be strongly influenced by seed mix treatment. While there is some evidence seed mix treatment may be influencing the emergent community across sites, spatial heterogeneity across the Minnesota restoration site likely influenced diversity in early emergence over that of seed mix treatment. Indeed, varying land-use history across both sites likely contributed to differences in species composition observed at this early stage of the restoration. This suggests that seed mix treatment may have limited impact on early post-restoration emergence diversity relative to the importance of land-use history. However, future monitoring will be needed to evaluate whether the impact of seed mix treatment on community composition changes over time.

Five Year Analyses of Vegetation Response to Restoration using Rock Detention Structures in Southeastern Arizona, United States

Rock detention structures (RDS) are used in restoration of riparian areas around the world. The purpose of this study was to analyze the effect of RDS installation on vegetation in terms of species abundance and composition. We present the results from 5 years of annual vegetation sampling which focused on short term non-woody vegetation response within the riparian channel at 3 restoration sites across southeastern Arizona. We examined the potential ways that RDS can preserve native species, encourage wetland species, and/or introduce nonnative species using a Control-Impact-Paired-Series study design. Species composition and frequency were measured within quadrats and zones on an annual basis. Multivariate bootstrap analyses were performed, including Bray-Curtis dissimilarity index and non-metric multidimensional scaling ordination. We found that response to RDS was variable and could be related to the level of degradation or proximity to groundwater. The non-degraded site did not show a response to RDS and the severely degraded site showed a slight increase in vegetation frequency, but the moderately degraded site experienced a significant increase. At the moderately degraded site, located between two historic ciénegas (desert wetlands), species composition shifted and nonnative species invaded, dominating the vegetation increase at this location. At the severely degraded site, pre-existing wetland species frequency increased in response to the installation of RDS. These findings extend the understanding of RDS effects on vegetation, provide scenarios to help land and water resource managers understand potential outcomes, and can assist in optimizing success for restoration projects.

Genetic assessment of the value of restoration planting within an endangered eucalypt woodland

Assessment of woodland restoration often focusses on stand demographics, but genetic factors likely influence long-term stand viability. We examined the genetic composition of Yellow Box (Eucalyptus melliodora) trees in endangered Box-Gum Grassy Woodland in SE Australia, some 30 years after planting with seeds of reportedly local provenance. Using DArT sequencing for 1406 SNPs, we compared genetic diversity and population structure of planted E. melliodora trees with remnant bushland trees, paddock trees and natural recruits. Genetic patterns imply that natural stands and paddock trees had historically high gene flow (among group pairwise F_ST = 0.04-0.10). Genetic diversity was highest among relictual paddock trees (H_e = 0.17), while diversity of revegetated trees was identical to natural bushland trees (H_e = 0.14). Bayesian clustering placed the revegetated trees into six genetic groups with four corresponding to genotypes from paddock trees, indicating that revegetated stands are mainly of genetically diverse, local provenance. Natural recruits were largely derived from paddock trees with some contribution from planted trees. A few trees have likely hybridised with other local eucalypt species which are unlikely to compromise stand integrity. We show that paddock trees have high genetic diversity and capture historic genetic variety and provide important foci for natural recruitment of genetically diverse and outcrossed seedlings.

Fifteen essential science advances needed for effective restoration of the world's forest landscapes

There has never been a more pressing and opportune time for science and practice to collaborate towards restoration of the world's forests. Multiple uncertainties remain for achieving successful, long-term forest landscape restoration (FLR). In this article, we use expert knowledge and literature review to identify knowledge gaps that need closing to advance restoration practice, as an introduction to a landmark theme issue on FLR and the UN Decade on Ecosystem Restoration. Aligned with an Adaptive Management Cycle for FLR, we identify 15 essential science advances required to facilitate FLR success for nature and people. They highlight that the greatest science challenges lie in the conceptualization, planning and assessment stages of restoration, which require an evidence base for why, where and how to restore, at realistic scales. FLR and underlying sciences are complex, requiring spatially explicit approaches across disciplines and sectors, considering multiple objectives, drivers and trade-offs critical for decision-making and financing. The developing tropics are a priority region, where scientists must work with stakeholders across the Adaptive Management Cycle. Clearly communicated scientific evidence for action at the outset of restoration planning will enable donors, decision makers and implementers to develop informed objectives, realistic targets and processes for accountability. This article paves the way for 19 further articles in this theme issue, with author contributions from across the world. This article is part of the theme issue 'Understanding forest landscape restoration: reinforcing scientific foundations for the UN Decade on Ecosystem Restoration'.

The role of incentive mechanisms in promoting forest restoration

Forest restoration has been proposed as a scalable nature-based solution to achieve global environmental and socio-economic outcomes and is central to many policy initiatives, such as the Bonn Challenge. Restored forests contain appreciable biodiversity, improve habitat connectivity and sequester carbon. Incentive mechanisms (e.g. payments for ecosystem services and allocation of management rights) have been a focus of forest restoration efforts for decades. Yet, there is still little understanding of their role in promoting restoration success. We conducted a systematic literature review to investigate how incentive mechanisms are used to promote forest restoration, outcomes, and the biophysical and socio-economic factors that influence implementation and program success. We found that socio-economic factors, such as governance, monitoring systems and the experience and beliefs of participants, dominate whether or not an incentive mechanism is successful. We found that approximately half of the studies report both positive ecological and socio-economic outcomes. However, reported adverse outcomes were more commonly socio-economic than ecological. Our results reveal that achieving forest restoration at a sufficient scale to meet international commitments will require stronger assessment and management of socio-economic factors that enable or constrain the success of incentive mechanisms. This article is part of the theme issue 'Understanding forest landscape restoration: reinforcing scientific foundations for the UN Decade on Ecosystem Restoration'.

Local seed sourcing for sustainable forestry

Seed sourcing strategies are the basis for identifying genetic material meeting the requirements of future climatic conditions and social demands. Specifically, local seed sourcing has been extensively promoted, based on the expected adaptation of the populations to local conditions, but there are some limitations for the application. We analyzed Strict-sense local and Wide-sense local (based on climatic similarity) seed sourcing strategies. We determined species and genetic pools based on these strategies for 40 species and deployment zones in Spain. We also obtained the total number of seed sources and stands for these species in the EU countries. We analyzed the richness of the pools, the relationship with variables related to the use of the species in afforestation, and the availability of seed production areas approved for the production of reproductive material destined to be marketed. This study confirms the existence of extensive species and genetic local pools. Also, that the importance of these pools differs for different species, limitations being derived from the use of forest reproductive material and the existence of approved basic materials. Strategies derived from local seed sourcing approaches are the basis for the use of forest reproductive material because a large number of the species in the area considered in the study are under regulation. However, despite the extensive work done to approve basic materials, limitations based on the availability of seed production areas to provide local material for sustainable forestry are found in those species. Considering a Wide-sense local seed sourcing strategy we provide alternative pools in order to meet social demands under the actual regulations on marketing of reproductive materials.

Key factors to consider in the use of environmental DNA metabarcoding to monitor terrestrial ecological restoration

Ecological restoration of terrestrial environments is a globally important process to combat the loss of biodiversity and ecosystem services. Holistic monitoring of restored biota and active management of restoration is necessary to improve restoration processes and outcomes, and provide evidence to stakeholders that targets are being achieved. Increasingly, environmental DNA (eDNA) metabarcoding is used as a restoration monitoring tool because it is able to generate biodiversity data rapidly, accurately, non-destructively, and reliably, on a wide breadth of organisms from soil microbes to mammals. The overall objective of this review is to discuss the key factors to consider in the use of environmental DNA for monitoring of restored terrestrial ecosystems, hopefully improving monitoring, and ultimately, restoration outcomes. We identified that the majority of eDNA based studies of ecosystem restoration are currently conducted in Europe, North America, and Australia, and that almost half of total studies were published in 2021-22. Soil was the most popular sample substrate, soil microbial communities the most targeted taxa, and forests the most studied ecosystem. We suggest there is no 'one size fits all' approach to restoration monitoring using eDNA, and discuss survey design. Factors to consider include substrate selection, sample collection and storage, assay selection, and data interpretation, all of which require careful planning to obtain reliable, and accurate information that can be used for restoration monitoring and decision making. We explore future directions for research and argue that eDNA metabarcoding can be a useful tool in the restoration monitoring 'toolkit', but requires informed application and greater accessibility to data by a wide spectrum of stakeholders.

Restoration intensity shapes floristic recovery after forest road decommissioning

Forest roads fragment and degrade ecosystems and many have fallen into disrepair and are underutilized, to address these issues the United States Forest Service is restoring, or "decommissioning," thousands of kilometers of forest roads each year. Despite the prevalence of decommissioning and the importance of vegetation to restoration success, relatively little is known about floristic responses to different forest road decommissioning treatments or subsequent recovery to reference conditions. Over a ten year period, this study assessed floristic cover, diversity, and composition responses to and recovery on forest roads decommissioned using three treatments varying in intensity (abandonment, ripping, recontouring), in Montana, USA. Initially, floristic cover groups were lowest on the recontoured roads, however, they demonstrated the fastest temporal response (e.g. increased litter and vegetative cover). The floristic communities of both active treatments (ripped and recontoured) had more species and were more diverse than the communities of the abandoned (control) treatment. Among the three on-road plant communities, the recontoured treatment was most associated with desirable species, including the native shrubs Rosa woodsii and Spirea betulifolia, while the abandoned treatment was most associated with two non-native species, Taraxacum officinale and Trifolium repens. Assessed using a restoration index, recovery to reference conditions was limited in all treatments, however, the recontoured treatment had a positive restoration trajectory in seven of eight metrics and was the best recovered treatment. Community composition on the recontoured treatment had more native species than the other treatments, and was moving toward, though still substantially different from, reference communities. These findings demonstrate that restoration of forest roads benefit from active restoration methods and, while forest road recontouring facilitates floristic recovery in the first decade after decommissioning, full recovery will likely take years to decades longer.

Application of modern coexistence theory to rare plant restoration provides early indication of restoration trajectories

Restoration ecology commonly seeks to re-establish species of interest in degraded habitats. Despite a rich understanding of how succession influences re-establishment, there are several outstanding questions that remain unaddressed: are short-term abundances sufficient to determine long-term re-establishment success, and what factors contribute to unpredictable restorations outcomes? In other words, when restoration fails, is it because the restored habitat is substandard, because of strong competition with invasive species, or alternatively due to changing environmental conditions that would equally impact established populations? Here, we re-purpose tools developed from modern coexistence theory to address these questions, and apply them to an effort to restore the endangered Contra Costa goldfields (Lasthenia conjugens) in constructed ("restored") California vernal pools. Using 16 years of data, we construct a population model of L. conjugens, a species of conservation concern due primarily to habitat loss and invasion of exotic grasses. We show that initial, short-term appearances of restoration success from population abundances is misleading, as year-to-year fluctuations cause long-term population growth rates to fall below zero. The failure of constructed pools is driven by lower maximum growth rates compared with reference ("natural") pools, coupled with a stronger negative sensitivity to annual fluctuations in abiotic conditions that yield decreased maximum growth rates. Nonetheless, our modeling shows that fluctuations in competition (mainly with exotic grasses) benefit L. conjugens through periods of competitive release, especially in constructed pools of intermediate pool depth. We therefore show how reductions in invasives and seed addition in pools of particular depths could change the outcome of restoration for L. conjugens. By applying a largely theoretical framework to the urgent goal of ecological restoration, our study provides a blueprint for predicting restoration success, and identifies future actions to reverse species loss.

Hidden effects of habitat restoration on the persistence of pollination networks

Past and recent studies have focused on the effects of global change drivers such as species invasions on species extinction. However, as we enter the United Nations Decade of Ecosystem Restoration the aim must switch to understanding how invasive-species management affects the persistence of the remaining species in a community. Focusing on plant-pollinator interactions, we test how species persistence is affected by restoration via the removal of invasive plant species. Restoration had a clear positive effect on plant persistence, whereas there was no difference between across treatments for pollinator persistence in the early season, but a clear effect in late season, with higher persistence in unrestored sites. Network structure affected only pollinator persistence, while centrality had a strong positive effect on both plants and pollinators. Our results suggest a hidden effect of invasive plants-although they may compete with native plant species, invasive plants may provide important resources for pollinators, at least in the short term.

Heavy metal wombats? Metal exposure pathways to bare-nosed wombats (Vombatus ursinus) living on remediated tin mine tailings

Rehabilitation of disused mine sites through stabilisation and botanical restoration is ecologically important, but metal transfer pathways to colonising wildlife are often less understood and have never been studied in marsupials. The rehabilitated Royal George tin mine tailings (Tasmania, Australia) and colonisation by bare-nosed wombats (Vombatus ursinus) represented an opportunity to examine potential metal transfer from mine tailings to an herbivorous marsupial. The aim of this study was to examine metal transfer pathways from the mine tailings to wombats, and to determine if wombats are at risk from metal exposure. Concentrations of metals were measured in the tailings substrate, surface water and vegetation, as well as fur samples from a resident wombat, and non-resident (control) wombats. The mineralogy of the tailings is dominated by quartz, muscovite, feldspars, topaz, kaolinite and calcite. Concentrations of several metals were high (exceeding varying health standards) in the tailings (As, Cu, Hg, Pb, Ni, Zn), water (As, Cd, Cu, Zn) and vegetation (As, Cd, Cu, Pb, Mn, Zn). Relative to non-resident wombats, elevated levels of As, Cd, Cu, Pb and Sn were measured in the fur of a resident wombat. Based on modelling of the exposure pathways, consumption of plant material is the most likely metal transfer pathway for As, Cu and Pb, although the risks from ingestion of tailings to this fossorial marsupial should not be discounted. This study is the first to investigate metal exposure pathways to marsupials using rehabilitated mine tailings. Further research is needed to accurately quantify ecological risks and toxicity for wombats and other marsupials native to mining landscapes.

Nine actions to successfully restore tropical agroecosystems

Well-designed approaches to ecological restoration can benefit nature and society. This is particularly the case in tropical agroecosystems, where restoration can provide substantial socioecological benefits at relatively low costs. To successfully restore tropical agroecosystems and maximise benefits, initiatives must begin by considering 'who' should be involved in and benefit from restoration, and 'what', 'where', and 'how' restoration should occur. Based on collective experience of restoring tropical agroecosystems worldwide, we present nine actions to guide future restoration of these systems, supported by case studies that demonstrate our actions being used successfully in practice and highlighting cases where poorly designed restoration has been damaging. We call for increased restoration activity in tropical agroecosystems during the current UN Decade on Ecosystem Restoration.

The long-term effect of initial restoration intervention, landscape composition, and time on the progress of Pannonic sand grassland restoration

To help upscale ecological restoration of degraded lands, landscape factors and longer time scales should be considered when assessing restoration efforts. We evaluated the impact of initial restoration intervention, landscape composition, and elapsed time since the restoration began on the long-term progress of Pannonic sand grassland restoration. Treatments (seeding, mowing, and carbon amendment) were implemented for 6–7 years and monitoring lasted up to 23 years after the first treatment applications in eight experimental blocks belonging to three field experiments. The abundance of target/neophyte species, and distance from primary grasslands and plantations (as major source of target/neophyte species) were estimated in 500 m landscape buffers around each block to characterize landscape composition. Restoration progress was calculated as the difference between the relative cover of target/neophyte species in treatment and control plots. Restoration intervention and neophyte abundance in the landscape had a significant effect on the restoration progress, but time did not. Seeding had the highest positive effect on target species and also prevented invasion by neophyte species. Higher abundance of neophytes in the landscape and the proximity to plantations increased the cover of neophytes in treatment plots. We conclude that restoration interventions may have a greater impact on restoration progress in the longer term than landscape factors or elapsed time. Seeding proved to be the best method in restoring sand grasslands by both favoring target species and controlling invasion. From the landscape factors, the abundance of neophyte species and distance to plantations should be considered when prioritizing areas and efforts for restoration.

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.

Enlightening the Pathway of Phytoremediation: Ecophysiology and X-ray Fluorescence Visualization of Two Chilean Hardwoods Exposed to Excess Copper

In the present climate emergency due to global warming, we are urged to move away from fossil fuels and pursue a speedy conversion to renewable energy systems. Consequently, copper (Cu) will remain in high demand because it is a highly efficient conductor used in clean energy systems to generate power from solar, hydro, thermal and wind energy across the world. Chile is the global leader in copper production, but this position has resulted in Chile having several hundred tailing deposits. We grew two Chilean native hardwood species, quillay (Quillaja saponaria Molina) and espino (Vachellia caven (Molina) Seigler & Ebinger, under three increasing Cu levels (0, 50, and 100 µM) for 6 months in a greenhouse setting. We measured growth, photosynthetic performance and elemental contents of leaves and roots to further evaluate their potential for phytoremediation. Growth of quillay was unaffected by Cu treatment but growth of espino was enhanced, as was its photosynthetic performance, indicating that espino may have an unusually high requirement for copper. Excess Cu was mostly restricted to the roots of both species, where X-ray fluorescence (XRF) mapping indicated some tendency for Cu to accumulate in tissues outside the periderm. Calcium oxalate crystals were prominently visible in XRF images of both species. Nickel (but not Cu) showed a concurrent distribution pattern with these crystals.

Variation in Bacterial Community Structures and Functions as Indicators of Response to the Restoration of Suaeda salsa: A Case Study of the Restoration in the Beidaihe Coastal Wetland

Microbes play an essential role in the restoration of degraded coastal wetlands. However, few studies have focused on the role of key bacteria in the restoration process. Here, Suaeda salsa was planted to recover the biodiversity in the degraded Beidaihe coastal wetland. We monitored omics and soil environmental factors to understand the complex relationship between the bacterial community and wetland health during the restoration period. After planting S. salsa in the degraded area, the soil quality was improved in the later stage of restoration (LPR). Bacterial α-diversity increased with restoration and was positively correlated with TOC. Proteobacteria is the dominant bacterial phylum during the restoration period, and Bacteroidetes, Planctomycetes, Gemmatimonadetes, and Acidobacteria were sensitive to the planting restoration. Random forest analysis picked 30 key OTUs, showing the key bacterial variation of successful restoration. The result indicated that the sum of the relative abundances of key bacterial OTUs was more than 2% in the health wetland. The β-diversity showed that the growth of S. salsa reshaped the soil bacterial community structure and function in the LPR, which recovered to the level in the control area. Putative biogeochemical functions showed that symbionts and aromatic compound degradation were dominant bacterial functions in the growth period of S. salsa. Our study proposed a new indicator to assess wetland health and the planting restoration of S. salsa increased bacteria groups with the ability of symbionts and aromatic compound degradation in the Beidaihe coastal wetland. This study expanded our knowledge of coastal wetland restoration and its ecological contributions.

Insect Abundance and Diversity Respond Favorably to Vegetation Communities on Interim Reclamation Sites in a Semi-Arid Natural Gas Field

Natural resource extraction has been linked to habitat loss and declines in biodiversity. Insects, the most diverse and abundant animals on Earth, provide a wide array of critical ecosystem services, but are typically understudied in terrestrial restoration projects. Here, we examine how insects and other arthropods respond to reclamation efforts in the Pinedale Anticline natural gas field in semi-arid Wyoming, USA. Vegetation on two-year-old well pads seeded with native grass or one-year-old well pads seeded with a native annual forb, Rocky Mountain bee plant (Cleomeserrulata), was measured and compared to reference areas adjacent to the well pads with a free software program called SamplePoint. Reference areas in the Pinedale Anticline natural gas field consist primarily of decadent sagebrush stands with low floral diversity. Insect and arthropod communities were also collected and assessed for family richness and abundance on these well pads and reference areas over two years. Based on the mass flowering hypothesis, we expected higher insect abundance and diversity on well pads seeded with the Rocky Mountain bee plant compared to adjacent reference areas. Based on the plant vigor hypothesis, we expected higher insect abundance and diversity on well pads seeded with native grass than reference communities. In year one, 893 insects from 30 insect families with an additional 12 arthropods from 4 families were captured. In year two, 685 insects from 17 families were collected. Reclaimed well pads had significantly higher abundance in both years and vegetation types. In year one, we did not detect a significant difference in richness on native-grass-treated well pads vs. the reference site. We found a significant difference in richness on bee-plant-treated well pads vs. the reference in both years, as well as native-grass-treated well pads vs. the reference in year two. Implications of these findings are discussed in the manuscript.

What Can Restoration Do for Bee Communities? An Example in the Atlantic Rainforest in Paraná State, Southern Brazil

Biodiversity conservation is a challenge for today. Studies regarding different ecosystems have become extremely important for understanding communities and promoting strategies for conservation, especially those involving forest restoration as strategy to reverse biodiversity loss. We compared bee diversity indices between three remnants of Atlantic rainforest in southern Brazil and four adjacent areas that were reforested after shale mining, and which are now under different restoration levels. Seven sites were monitored for over 5 years (2011-2016), by sampling bees directly on flowers or in flight using an entomological net, with 400 collected individuals/site/year. Bee species composition differed between post-mining ages and between sites. In all, we sampled 14.185 specimens and 236 bee species. The introduced Africanized Apis mellifera Linnaeus was the most frequent and abundant species, followed by Trigona spinipes and Psaenythia bergii Holmberg. Among habitats, the reforested area in initial phase showed lower richness and diversity in relation all others sample sites. Conversely, all indices were higher in forest remnants, middle phase II, and advanced phase reforested areas, reinforcing the importance of reforestation for conservation, notably endangered species, such as Oxytrigona sp., Schwarziana quadripunctata (Lepeletier), and the solitary species of the genus Hylaeus, all found in the restored areas. These results represent an important contribution for understanding the recovery of the bee fauna in restored mining habitats. The dataset reveals an interesting response in areas that were mined for shale extraction and are now undergoing different levels of restoration, suggesting that older reforested habitats have a higher probability of having a fully recovered bee community.

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.

Salt marsh restoration: an overview of techniques and success indicators

Coastal wetlands including salt marshes are among the most productive ecosystems on Earth. They are known for improving the quality of coastal water and provisioning coastal fisheries. However, this ecosystem is under potential threat due to urban coastal land reclamation, limited sediment supply, increased nutrient/eutrophication, and sea level rise. Therefore, restoration efforts to protect the degraded salt marsh habitat are considerably increasing worldwide. In this paper, we present an overview of salt marsh restoration techniques and success indicators. Published scientific literature in English language was collected by searching the most relevant keywords from popular search engines, namely, Google Scholar, Scopus, and Mendeley to get the information about salt marsh restoration techniques and success indicators. This study comprehensively reviewed data from 78 peer-reviewed papers. Results indicated that much of the salt marsh was restored through assisted abiotic strategies (e.g., recovery of tidal exchange, managed realignment, and sediment level amendment). A total of 214 indicators were found, spanning over six major ecological attributes such as structural diversity, ecosystem functions, physical conditions, species composition, external exchange, and absence of threat. Author keywords analysis revealed several hotspots for recent research (e.g., 16 s rRNA, fungi, microbial communities, carbon accumulation, and blue carbon). This paper proposes a model for restoring degraded salt marsh, as well as tracking their success. The information presented here will assist the marine ecosystem restoration practitioners in getting a comprehensive understanding of salt marsh restoration success evaluation.

Tropical Forest Landscape Restoration in Indonesia: A Review

Indonesia has the second-largest biodiversity of any country in the world. Deforestation and forest degradation have caused a range of environmental issues, including habitat degradation and loss of biodiversity, deterioration of water quality and quantity, air pollution, and increased greenhouse gas emissions that contribute to climate change. Forest restoration at the landscape level has been conducted to balance ecological integrity and human well-being. Forest restoration efforts are also aimed at reducing CO2 emissions and are closely related to Indonesia’s Nationally Determined Contribution (NDC) from the forestry sector. The purpose of this paper is to examine the regulatory, institutional, and policy aspects of forest restoration in Indonesia, as well as the implementation of forest restoration activities in the country. The article was written using a synoptic review approach to Forest Landscape Restoration (FLR)-related articles and national experiences. Failures, success stories, and criteria and indicators for forest restoration success are all discussed. We also discuss the latest silvicultural techniques for the success of the forest restoration program. Restoration governance in Indonesia has focused on the wetland ecosystem such as peatlands and mangroves, but due to the severely degraded condition of many forests, the government has by necessity opted for active restoration involving the planting and establishment of livelihood options. The government has adapted its restoration approach from the early focus on ecological restoration to more forest landscape restoration, which recognizes that involving the local community in restoration activities is critical for the success of forest restoration.

Thinning and plantation of resprouting species redirect overstocked pine stands towards more functional communities in the Mediterranean basin

Post-fire regeneration in Pinus halepensis' forests, one of the most abundant vegetation types in the Mediterranean basin, often generates overstocked and vulnerable stands. They accumulate a high fuel load, increasing the risk of further fires, and present high levels of vulnerability due to their reduced seed production. In addition, these dense stands substantially reduce the availability of light and nutrients, which may hinder the recruitment of other species, often generating mono-specific and homogeneous stands, which potentially supply fewer ecosystem services than mixed forests with more heterogeneous structures. In these dense pine stands, management is of high priority to reduce fire hazards and promote their functionality. In overstocked pine stands (>75,000 trees·ha^-1), we assessed the long-term effects (10 years) of two thinning levels (600 and 1200 trees·ha^-1), in combination with the plantation of Quercus faginea (a resprouter species typical of advanced successional stages in our study area) on 28 above and belowground ecosystem attributes, including fire hazard. After ten years, thinning and plantation interacted to enhance ecosystem attributes associated with disturbance regulation and biodiversity conservation (up to 200%) and food production (up to 90%), while no effects were observed on those attributes related to carbon sequestration and supporting services. These effects were mainly driven by aboveground attributes, as they responded more strongly to our treatments than those belowground. Our results are relevant for the restoration of Mediterranean degraded ecosystems, and show that tree thinning in overstocked pine stands, combined with the plantation of resprouter species, may not only reduce fire risks and accelerate post-fire succession but also enhance the supply of multiple ecosystem services in the long run.

Remediation of heavy metal-contaminated iron ore tailings by applying compost and growing perennial ryegrass (Lolium perenne L.)

Improper disposal of heavy metal-contaminated iron ore tailings poses a significant risk to the surrounding environments. Adding compost and growing ryegrass could be a cost-effective long-term solution for remediation of iron ore tailings. We conducted a glasshouse study to investigate the impact of compost amendment (0, 50, 75 and 100% w/w) on growth and accumulation of heavy metals (Cu, Fe, Mn, Pb, Ni and Zn) and As in shoots of perennial ryegrass (Lolium perenne L.) grown in two iron ore tailings (Site A and Site B mines, Pilbara, Western Australia). Ryegrass was harvested 45 and 60 days after sowing. Site A iron ore tailings had total concentrations (mg kg^-1) of Fe (449,000), Mn (6900), Zn (109), Co (16) and As (7.3). Site B mine tailings had total concentrations (mg kg^-1) of Fe (457,000), Ni (21), Zn (109) and As (45). Both tailings had low cation exchange capacity, organic matter, air porosity and near-neutral pH, but varied in particle size distribution (Site A-clay loam and Site B-sandy loam). Ryegrass germination was higher in the extract of Site B than Site A tailings. Increasing compost-to-tailings ratio increased dry shoot biomass at 45 days. The heavy metal/metalloid concentrations in shoots significantly decreased with increasing compost-to-tailings ratio, except for Cu and Zn. The bioconcentration factor (BCF) of heavy metals (metal concentration in shoot/total metal concentration in substrate) significantly decreased with an increasing proportion of compost in growth substrate. The BCF was >1 for Zn and Cu, and <1 for other heavy metals. A high concentration of organic matter in compost treatments likely contributed to the enhanced mobilisation of Cu and Zn for plant uptake. In contrast, compost stabilised other metals/metalloids in the tailings to decrease their uptake by ryegrass and maintain plant growth despite relatively high Mn, Fe, As and Pb concentrations in iron ore tailings.

Evaluating restoration trajectories using DNA metabarcoding of ground-dwelling and airborne invertebrates and associated plant communities

Invertebrates are important for restoration processes as they are key drivers of many landscape‐scale ecosystem functions; including pollination, nutrient cycling and soil formation. However, invertebrates are often overlooked in restoration monitoring because they are highly diverse, poorly described, and time‐consuming to survey, and require increasingly scarce taxonomic expertise to enable identification. DNA metabarcoding is a relatively new tool for rapid survey that is able to address some of these concerns, and provide information about the taxa with which invertebrates are interacting via food webs and habitat. Here, we evaluate how invertebrate communities may be used to determine ecosystem trajectories during restoration. We collected ground‐dwelling and airborne invertebrates across chronosequences of mine‐site restoration in three ecologically disparate locations in Western Australia and identified invertebrate and plant communities using DNA metabarcoding. Ground‐dwelling invertebrates showed the clearest restoration signals, with communities becoming more similar to reference communities over time. These patterns were weaker in airborne invertebrates, which have higher dispersal abilities and therefore less local fidelity to environmental conditions. Although we detected directional changes in community composition indicative of invertebrate recovery, patterns observed were inconsistent between study locations. The inclusion of plant assays allowed identification of plant species, as well as potential food sources and habitat. We demonstrate that DNA metabarcoding of invertebrate communities can be used to evaluate restoration trajectories. Testing and incorporating new monitoring techniques such as DNA metabarcoding is critical to improving restoration outcomes.

Restoration Trajectories and Ecological Thresholds during Planted Urban Forest Successional Development

Successfully reconstructing functioning forest ecosystems from early-successional tree plantings is a long-term process that often lacks monitoring. Many projects lack observations of critical successional information, such as the restoration trajectory of key ecosystem attributes and ecological thresholds, which signal that management actions are needed. Here, we present results from a 65 ha urban temperate rainforest restoration project in Aotearoa New Zealand, where trees have been planted annually on public retired pasture land, forming a 14 years chronosequence. In 25 plots (100 m2 each), we measured key ecosystem attributes that typically change during forest succession: native tree basal area, canopy openness, non-native herbaceous ground cover, leaf litter cover, ground fern cover, dead trees, and native tree seedling abundance and richness. We also monitored for the appearance of physiologically-sensitive plant guilds (moss, ferns, and epiphytes) that may be considered ecological indicators of succession. Linear regression models identified relationships between all but one of the key ecosystem attributes and forest age (years since planting). Further, using breakpoint analysis, we found that ecological thresholds occurred in many ecosystem attributes during their restoration trajectories: reduced canopy openness (99.8% to 3.4%; 9.6 years threshold), non-native herbaceous ground cover (100% to 0; 10.9 years threshold), leaf litter cover (0 to 95%; 10.8 years threshold), and increased tree deaths (0 to 4; 11 years threshold). Further, juvenile native plant recruitment increased (tree seedling abundance 0 to ~150 per 4 m2), tree seedling species richness (0 to 13 per 100 m2) and epiphytes colonized (0 to 3 individuals per 100 m2). These and other physiologically-sensitive plant guilds appeared around the 11 years mark, confirming their utility as ecological indicators during monitoring. Our results indicate that measurable, ecological thresholds occur during the restoration trajectories of ecosystem attributes, and they are predictable. If detected, these thresholds can inform project timelines and, along with use of ecological indicators, inform management interventions.

The recovery of functional diversity with restoration

Ecological restoration aims at recovering biodiversity in degraded ecosystems, and it is commonly assessed via species richness. However, it is unclear whether increasing species richness in a site also recovers its functional diversity, which has been shown to be a better representation of ecosystem functioning. We conducted a quantitative synthesis of 30 restoration projects and tested whether restoration improves functional diversity. We compared actively and passively restored sites with degraded and reference sites with respect to four key measures of functional diversity (richness, evenness, dispersion and functional turnover) and two measures of species diversity (richness and evenness). We separately analyzed longitudinal studies (which monitor degraded, reference and restored sites through time) and space-for-time substitutions (which compare at one point in time degraded and reference sites with restored sites of different ages). Space-for-time studies suggested that species and functional diversity improved over time. However, replicated longitudinal data showed no sustained benefits of active or passive restoration for functional diversity measures, relative to degraded sites. This could suggest that the positive results in space-for-time designs may have been unreliable, but the relative short duration of longitudinal studies suggests a need for longer-term longitudinal research to robustly demonstrate the absence of any effect. These differences across study designs may explain the variable results found in recent studies directly measuring the response of functional diversity to restoration. We recommend that future assessments of ecological community dynamics include control sites in monitoring, to ensure the consequences of treatments, including but not limited to restoration, are correctly partitioned from unassisted temporal changes. This article is protected by copyright. All rights reserved.

Restoration of marine ecosystems: Understanding possible futures for optimal outcomes

Accelerating declines in the extent, quality and functioning of the world's marine ecosystems have generated an upsurge in focus on practical solutions, with ecosystem restoration becoming an increasingly attractive mitigation strategy for systems as diverse as coral reefs, mangroves and tidal flats. While restoration is popular because it promises positive outcomes and a return to something approaching unimpacted condition and functioning, it involves substantial public and private investment, both for the initial restoration activity and for on-going maintenance of the restored asset. This investment often affords one big chance to get things right before irretrievable damage is done. As a result, precise, well considered and accountable decision-making is needed to determine the specific focus for restoration, the scale of restoration, the location for deploying restoration activities, and indeed whether or not restoration is necessary or even possible. We explore the environmental/ecological considerations and constraints governing optimal decisions about the nature, location and prioritisation of restoration activities in marine ecosystems, and in particular the constraints on achieving understanding of possible futures and the likelihood of achieving them. We conclude that action must be informed by a context-specific understanding of the historical situation, the current situation, the constraints on change, the range of potential outcome scenarios, and the potential futures envisioned.