Passive Restoration Research Articles

Recovery and Restoration of Disturbed Sand Bars of the Apalachicola River, Florida

abstract: Large, low-lying rivers have a variety of societal uses and show a wide range of disturbances. One such example, the Apalachicola River in the Florida Panhandle, experienced anthropogenic activities that altered its hydrologic, geomorphic, and ecologic condition. The river's sand bars enlarged more than threefold in area because of dredge disposal and localized incision from anthropogenic activities during a navigation project. Once dredging ended, the river experienced passive recovery through the slow regrowth of riparian vegetation, with sand bars reducing in area ~18% from 2005 to 2015. The outcomes of tree-line change analyses from 1999 to 2019 indicate a higher recovery rate in the first decade (1999-2010), migrating fastest in locations where vegetation islands stabilize sediments. To help accelerate vegetation regrowth, during the growing seasons of 2018 and 2019, we planted willow stakes at various positions and microhabitats covering ~3.6 ha of three enlarged sand bars near Blountstown, FL. Our mapping shows some synergies between passive recovery and active restoration as tree-line expansion had the fastest rates between 2019 and 2021. Our study gives insights and guidance into passive recovery and restoration projects involving plantings on large, low-lying rivers.

Systematic review on the implementation of mangrove community-based restoration in Indonesia and beyond

World’s mangroves are decreasing, and the remaining are continuously at risk, so restoration seen as one of key strategies in the mangrove management. Mangrove ecosystems are ecologically important for coastal life, as well as play a key role for the livelihood and food security that put coastal community as important actor in the mangrove restoration efforts, including in Indonesia. This study aims to understand the current practices and lesson learned from the implementation of community-based mangrove restoration (CBMR). We used a combination of systematic review and co-learning workshops to identify relevant case studies, interventions, and outcomes from the implementation CBMR. We selected 71 relevant case studies from nine countries and ran a Principal Component Analysis (PCA). We identified four group of intervention implemented in the case studies, those are active restoration (include replanting), passive restoration (focus on protection and depend on natural regeneration), model business development and strengthening the community institution. Case studies analysis suggested that combination of four type of interventions helps to achieve both aims of CBMR which are restored mangrove and improved livelihood.

Revisiting the effectiveness of biodiversity offsets in coastal wetlands of China through landscape connectivity

We modified the landscape connectivity calculation method and applied it to assess changes in temporal connectivity under different offsetting scenarios in the Yellow River Delta High-efficiency Ecological Economic Zone of China. We evaluated landscape connectivity based on resistance surfaces, least-cost distances, habitat areas, and the probability of dispersal between wetland patches in the landscape. The landscape connectivity declined between 1980 and 2015, with the degree of decline varying with the type of wetland. The cumulative percentages of freshwater marsh, salt marsh, and tidal marsh habitat areas that could be offset were 100 %, 100 %, and 34 %, respectively. However, the maximum landscape connectivity that was compensated for was only 1.2–10.4 %. When the offset patches were restored to freshwater marsh, the highest connectivity of coastal wetlands was achieved. There were substantial gaps between the area of habitat restoration offset required to achieve no net loss and the landscape connectivity that would ensure ecological effectiveness. The compensation area required to achieve no net loss of landscape connectivity was greater than that required to achieve no net loss of habitat area. We provide guidance for policy makers on how to implement offsetting to develop and manage green corridors, thus allowing movement that will ensure species’ survival. It was suggested that the passive restoration of isolated coastal wetland may be difficult to achieve. Policies that seek to increase landscape connectivity offsets can effectively promote population diffusion and migration, avoid habitat fragmentation, and are key to improving no net loss effectiveness.

Ecological restoration of coastal wetlands in China: Current status and suggestions

Globally, coastal wetlands have experienced extensive loss and degradation over the past half-century. Ecological restoration is widely recognized as essential for maintaining ecosystem services. China has increased restoration efforts over the past twenty years, but there has been limited understanding of restoration's effectiveness. Through a review of 86 coastal wetland restoration projects in China, we analyzed restoration objectives, restoration measures, funding sources, and restoration effectiveness. We found that quantitative restoration objectives were unavailable from 90.7 % of those projects; active restoration was the primary measure (94.2 %), with vegetation management (40.6 %), topography modification (28.6 %), and hydrological regulation (24.8 %) being the main techniques. Restoration funding came mainly from governments (94.7 %), and the restoration costs per unit area decreased as the restoration area increased. Unrestored wetlands were mainly (75.6 %) used as references for restoration effectiveness evaluation, generally using species diversity (54.7 %) and physicochemical traits (48.8 %) as indicators. Most restorations were deemed as effective (89.5 %). We propose the following for future coastal wetland restorations: setting quantitative restoration targets focusing on protecting threatened species and enhancing ecological services; combining active with passive restoration measures that employ ecosystems' self-healing capabilities; expanding funding sources through diversified stakeholder collaborations; and establishing a comprehensive evaluation system for restoration effectiveness that includes ecosystem functions. This study provides a reference for the design, implementation, and adaptive management of future coastal wetland restoration in China and other coastal countries.

Soil quality: an indicator of recovery in a nature reserve in the Colombian Andes

Soils provide essential ecosystem services for the existence of ecosystems and biodiversity. It is crucial to understand their quality through the evaluation of ecological processes. However, only some studies estimate the effectiveness of ecosystem restoration based on evaluating soil quality (SQ) indicators. This research evaluated the five most common land-use scenarios in Andean ecosystems within the Natural Reserve of the Civil Society (RNSC) “La Montaña Mágica” under natural forest, coffee plantation, badlands, and active and passive restoration. The main objective was to analyze the physical, chemical, and biological characteristics concerning land use, establish the baseline for SQ indicators in different land use activities, and determine the status of restoration systems for other land uses in the study site. ANOVA and Dunnett's test evaluated SQ parameters. In passive and active restoration, soil bulk density, porosity, and the number of individuals and families of macroinvertebrates were improved. The latter presented low pH and aluminum values but increased potassium compared to other soil uses. The restoration strategies favored changes in SQ indicators due to the contribution of organic carbon, a developed root system, and the recirculation of nutrients in the edaphic system. This study provided information on changes in SQ with soil usage as a practical tool to evaluate ecological restoration methods in natural areas of the eastern Colombian Andes.

Litter stock and nutrients under different restoration methods in the eastern Amazon

Litter production contributes to soil fertility through the decomposition process, especially in Amazonian soils, which have low fertility. Amazonian ecosystems are dependent on the forest to ensure their maintenance through nutrient cycling, via litter. The objective of this work was to evaluate litter stock and nutrient content under different restoration methods in abandoned pasture areas in the eastern Amazon. The macronutrient content via litter followed the order: Ca > N > P >Mg > K >Na. Calcium was the macronutrient that most returns to the soil via litter. The restoration method through silvipastoral system presented the highest values of nitrogen. The area under passive restoration proved to be the most efficient method to recover areas degraded by pasture in the eastern Amazon, due to the highest litter stock and nutrient content.

Variation in understorey floristic composition regeneration and fire hazard under Acacia invaded forest canopy in New Zealand

Acacia species are considered invasive exotic species in many regions globally, and influence the floristic composition and fire hazard of ecosystems they invade. Managing such species requires an understanding of their invasion capability, and persistence through succession in the community. New Zealand is one of the countries that have experienced Acacia invasion in the forest canopy, however, the potential long-term successional trajectories and future fire hazards of these communities have rarely been studied impeding management. We investigated the variation in woody plant species composition that was regenerating at different height tiers, and the comparative flammability of constituent species, under the canopy of Acacia-invaded forest sites in New Zealand, and evaluated the likely long-term changes in vegetation succession and fire hazards. From the floristic survey of 24 10 × 10 m plots in Acacia-invaded sites, we found a significantly higher number of native species (7.33 ± 0.67) than exotic species (4.83 ± 0.38) regenerating under Acacia-invaded canopies. While exotic stems dominated the lowest height tiers (<0.3 m), native stems outnumbered exotics at other understorey height tiers (0.3–2 m, 2–5 m and 5–12 m) and were recruiting successfully. We also found that invaded Acacia species and other exotic species at the sites were comparatively higher in flammability than most of the native species in the area, and can potentially increase the flammability of the invaded forest area if not managed appropriately. The successful regeneration and recruitment of natives in all height tiers under the Acacia canopy indicates a potential native succession in the longer term. Thus, the Acacia invasion can be managed through passive restoration where the dominant Acacia-invaded canopy in the forest area is replaced by native species, while also likely decreasing the fire hazard of the vegetation. This study provides evidence for the regeneration potential of native species in the understorey of Acacia-invaded forest sites and the knowledge helps forest managers make appropriate decisions to manage this woody exotic invasion and fire hazard of the invaded forest sites in New Zealand as well as other Acacia-invaded sites globally.

Twenty years of population dynamics in European beech-oak forest at their rear range margin anticipate changes in its structure and composition

There is an increasing interest in restoring degraded forests, which occupy half of the forest areas. Among the forms of restoration, passive restoration, which involves the elimination of degrading factors and the free evolution of natural dynamics by applying minimal or no management, is gaining attention. Natural dynamics is difficult to predict due to the influence of multiple interacting factors such as climatic and edaphic conditions, composition and abundance of species, and the successional character of these species. Here, we study the natural dynamics of a mixed forest located in central Spain, which maintained an open forest structure, due to intensive use, until grazing and cutting were banned in the 1960s. The most frequent woody species in this forest are Fagus sylvatica, Quercus petraea, Quercus pyrenaica, Ilex aquifolium, Sorbus aucuparia, Sorbus aria and Prunus avium, with contrasting shade and drought tolerance. These species are common in temperate European deciduous forest and are found here near their southern distribution limit, except for Q. pyrenaica. In order to analyze forest dynamics and composition, three inventories were carried out in 1994, 2005 and 2015. Our results show that, despite the Mediterranean influence, the natural dynamics of this forest has been mainly determined by different levels of shade tolerance. After the abandonment of grazing and cutting, Q. pyrenaica expanded rapidly due to its lower shade tolerance, whereas after canopy closure and forest densification, shade-tolerant species gained ground, particularly F. sylvatica, despite its lower drought and late-frost tolerance. If the current dynamics continue, F. sylvatica will overtake the rest of the species, which will be relegated to sites with shallow soils and steep slopes. Simultaneously, all the multi-centennial beech trees, which are undergoing a rapid mortality and decline process, will disappear.

Factors influencing early natural regeneration in areas under passive restoration in Araucaria Forest, southern Brazil

Factors influencing early natural regeneration in areas under passive restoration in Araucaria Forest, southern Brazil

Fungal community composition changes and reduced bacterial diversity drive improvements in the soil quality index during arable land restoration

Arable land is facing the growing challenge of land degradation due to intensive use and this is beginning to affect global food security. However, active and passive restoration can improve soil characteristics and reshape microbial communities. Despite the increasing focus on changes in microbial communities during restoration, the mechanisms underlying how microbes drive the soil quality index (SQI) in arable land restoration remain unclear. In this study, we selected conventional farmland (CF, heavily intensified) and two restoration strategies (AR, artificial restoration; NR, natural restoration), with the same context (including soil texture, climate, etc.), and measured the microbial indicators over 2 years to investigate the mechanisms driving SQI improvement on restored arable land. The AR and NR treatments resulted in a 50% and 58% increase in SQI, respectively, compared to CF as soil nutrient levels increased, resulting in higher microbial biomasses and enzyme activities. Microbial abundance on the AR land was approximately two times greater than on the NR land due to the introduction of legumes. Bacterial diversity declined, while fungi developed in a more diverse direction under the restoration strategies. The AR and NR areas were mainly enriched with rhizobium (Microvirga, Bradyrhizobium), which contribute to healthy plant growth. The pathogenic fungi (Gibberella, Fusarium, Volutella) were more abundant in the CF area and the plant pathogen guild was about five times higher in the restored areas. Following arable land restoration, microbial life history strategies shifted from r-to K-strategists due to the higher proportion of recalcitrant SOC (DOC/SOC decreased by 18%–30%). The altered microbial community in the restored areas created new levels of functionality, with a 2.6%–4.3% decrease in bacterial energy metabolism (oxidative phosphorylation, C fixation, and N metabolism decreased by 7%, 4%, and 6%, respectively). Structural equation modelling suggested that restoration strategy affected SQI either directly by increasing total soil nutrient levels or indirectly by altering the microbial community and that fungal community composition and bacterial diversity made the largest contributions to SQI. These results provided new insights into soil quality improvement from a microbial perspective and can help guide future arable land restoration.

Ants in restoration ecology: Why, what's and the way forward

AbstractGlobal changes call for more nature‐based solutions, especially in nature conservation involving ecological restoration. Current methods essentially based on civil engineering are both expensive and costly in non‐renewable energy consumption and pollution terms. The non‐sustainability of these techniques is leading to the direct use of certain species to restore degraded ecosystems. Ants, because of their central role in ecosystem functioning and their occurrence on almost all terrestrial ecosystems, are promising candidates for environmental monitoring and such ecological restoration projects. We provide here a narrative review of the ecological functions performed by ants, and we take stock of how ants are currently considered in passive and active restoration. We then propose a trait‐based approach to facilitate their use by practitioners in future restoration projects. We list and discuss both life‐history traits relevant for environmental monitoring and functional traits known to affect abiotic (physical and chemical soil properties) and biotic (plant and fauna communities) components.

Frugivore-mediated seed dispersal in fragmented landscapes: Compositional and functional turnover from forest to matrix.

Seed dispersal by frugivores is a fundamental function for plant community dynamics in fragmented landscapes, where forest remnants are typically embedded in a matrix of anthropogenic habitats. Frugivores can mediate both connectivity among forest remnants and plant colonization of the matrix. However, it remains poorly understood how frugivore communities change from forest to matrix due to the loss or replacement of species with traits that are less advantageous in open habitats and whether such changes ultimately influence the composition and traits of dispersed plants via species interactions. Here, we close this gap by using a unique dataset of seed-dispersal networks that were sampled in forest patches and adjacent matrix habitats of seven fragmented landscapes across Europe. We found a similar diversity of frugivores, plants, and interactions contributing to seed dispersal in forest and matrix, but a high turnover (replacement) in all these components. The turnover of dispersed seeds was smaller than that of frugivore communities because different frugivore species provided complementary seed dispersal in forest and matrix. Importantly, the turnover involved functional changes toward larger and more mobile frugivores in the matrix, which dispersed taller, larger-seeded plants with later fruiting periods. Our study provides a trait-based understanding of frugivore-mediated seed dispersal through fragmented landscapes, uncovering nonrandom shifts that can have cascading consequences for the composition of regenerating plant communities. Our findings also highlight the importance of forest remnants and frugivore faunas for ecosystem resilience, demonstrating a high potential for passive forest restoration of unmanaged lands in the matrix.

Passive restoration of fynbos after afforestation with exotic pines, South Africa

Plantations, and associated invasions, of exotic Pinus trees occur extensively in the southern hemisphere, threatening the persistence of biodiverse Mediterranean‐climate vegetation. Large‐scale decommissioning of such plantations in the eastern Cape Floristic Region (South Africa) enabled a wide‐ranging study showing successful passive restoration of fynbos vegetation after afforestation. Using a paired study design, we compared the diversity, and floristic and growth‐form composition of post‐fire recovering fynbos in former plantations with that in recently burnt neighboring fynbos in a natural state within the Garden Route National Park. The fynbos of the study area showed good autogenic recovery after several decades of pine afforestation and a fire subsequent to the clearcutting of these trees. On average, native plant abundance and species richness (particularly of shrubs) were significantly lower, and non‐native plant species richness significantly higher, in former plantation areas than in natural fynbos, but these differences were small. Species diversity (Shannon–Wiener index) did not differ significantly between the two vegetation states. The former plantations harbored 91% of the number of native species that the natural fynbos had, while the similarity of the two floras was 65%. Non‐metric multidimensional scaling ordination and multivariate generalized linear models accordingly showed no clear distinction in community composition between the two vegetation states. We concluded that the restoration potential of the montane grassy fynbos in the study area is superior to that previously documented in montane proteoid fynbos, and that fire and invasive alien plant control after clearcutting of the plantations is essential to promote fynbos restoration.

Climate change accelerates ecosystem restoration in the mountain forests of Central Europe

Abstract Restoring degraded forest ecosystems is an important element in the ongoing challenge to sustain the integrity and functioning of the biosphere. However, the evaluation of restoration success is hampered by long lead times of management measures in forests. Moreover, forest change is accelerating also in the absence of management because of ongoing climate change. Yet, because a counterfactual is frequently missing, it remains unclear whether restoration measures are aided or impeded by climate change. Here, we analysed the pace and success of forest restoration under climate change, combining field data and simulation modelling. We focused on the management zone of Berchtesgaden National Park (BGNP), Germany, where restoration aims to restore homogeneous Norway spruce (Picea abies) forests to structurally diverse mixed mountain forests. We evaluated three alternative restoration strategies: Two active strategies focused on planting the currently underrepresented silver fir (Abies alba) and European beech (Fagus sylvatica) but differing in the creation of gap‐cuts, and a third passive restoration strategy without interventions. Strategies were simulated with the forest landscape model iLand from 2020 to 2100 under different climate scenarios (historic, RCP 2.6, 4.5, and 8.5). The forests of BGNP developed into structurally diverse and mixed forests under all evaluated management strategies, and differences between active and passive restoration were generally small. While restoration goals for forest structure were largely met by 2100, forest composition remained far from target in all strategies. Climate change aided restoration by significantly increasing the prevalence of silver fir and European beech (+104.2% to +258.6%). Field data on short‐term restoration effects were in line with simulated long‐term trajectories. Synthesis and applications: We here show that forest restoration efforts in Central European mountain forests will likely be accelerated by climate change. Nonetheless, the slow pace of restoration underscores the need for taking action. Our study highlights that active restoration measures such as tree planting can bring the system closer to restoration targets. However, it also demonstrates that passive restoration (no intervention) is a viable option for management, highlighting the need to evaluate restoration measures against the counterfactual of a no intervention strategy.

Meta‐analysis reveals that enhanced practices accelerate vegetation recovery during peatland restoration

The provision of critical ecosystem services like carbon sequestration by peatlands has been degraded around the globe. Peatland restoration represents an opportunity to tackle the twin global emergencies of climate breakdown and biodiversity decline. Nonetheless, restoration success relies on a sound understanding of recovery trajectories associated with different restoration techniques. Focusing on temperate/boreal Sphagnum‐dominated peatlands, we used a quantitative meta‐analysis of 28 studies representing 275 sites in 11 countries to test for effects of peatland status (intact, restored, and degraded), varying restoration interventions and time since restoration on vegetation as a key indicator of peatland condition and functioning. Enhanced restoration (such as active revegetation) resulted in recovery to predisturbance levels within 30–35 years for Sphagnum mosses, and 20–25 years for many other peatland specialist species, and was the only restoration approach where positive outcomes were seen across all vegetation response variables. The use of standard restoration techniques, such as rewetting, was projected to result in cover of Sphagnum mosses and peatland specialist plants reaching that of intact sites within 45–55 years post‐restoration. Passive restoration (cessation of the degrading activity with no active restoration) generally elicited limited recovery of keystone peatland vegetation (Sphagnum spp.) even after multiple decades. A lack of standardization in monitoring severely constrains the analysis of peatland restoration outcomes. Increased funding for monitoring and reporting outcomes, and improved monitoring consistency, could greatly enhance our understanding of peatland restoration ecology and improve practice.

Active versus passive restoration of tallgrass prairie in the U.S. Midwest: plant species diversity and assemblage, net primary production and soil carbon sequestration

We investigated the plant species diversity, community assemblage, net primary production and soil carbon sequestration in an old field (OF), which went through passive restoration with spontaneous secondary succession, and a restored prairie (RP), which went through active restoration with reintroduction of native plants. The passive restoration in OF did not attain as high diversity and richness of plant species as did in RP. Our NMS (nonmetric multidimensional scaling) ordination revealed a clear divergence of RP and OF vegetation with dissimilar species compositions to separate paths of succession trajectory. The spontaneous succession in OF has made very little progress due to a potentially strong inhibitory priority effect of invasive plants. The belowground biomass in the high‐diversity RP was 1.3× higher than the low‐diversity OF. We found no measurable difference in soil C sequestration between RP and OF at this time, possibly due to edaphic factors, lack of legumes, or both. Human intervention is needed for restoring abandoned croplands—highly disturbed, fragmented and isolated habitats—to tallgrass prairies in the U.S. Midwest. Our recommended intervention includes but is not limited to removal of exotic plants, further augmentation of native plants (particularly legumes), and periodic burns.

Combining passive and active restoration to rehabilitate a historically polluted marine site

IntroductionPassive and active restoration approaches have been often considered as different alternatives to achieve the ecological restoration of a degraded site. This false dichotomy has been overcome in terrestrial ecosystems, for which a range of restoration approaches have often been applied within the same restoration project, creating a continuum of interventions. In the marine environment, the combined approach based on passive and active restoration is less studied.MethodsHere, we tested the possibility of actively restoring a macroalgal population in a historically polluted industrial site, subjected to decadal passive restoration (i.e., unassisted, or spontaneous recovery following cessation of industrial activity), in the Mediterranean Sea. Recently, it has been demonstrated that in the site under scrutiny, there is no longer any sign of the historical contamination or impact on benthic fauna therefore the environmental conditions are indistinguishable from surrounding non-impacted areas. We used artificial breakwater barriers already present in the site to restore a population of the brown algae Gongolaria barbata. The intervention was conducted by applying an in situ recruitment approach and a complementary action using cages to exclude the herbivores. The G. barbata recruits were transplanted on the artificial reefs and after they reached the maximum growth inside the cages, one cage was opened and another one was completely removed to also test the grazing pressure. The associated benthic assemblages were also analysed in terms of meio- and macrofaunal abundance, the richness of taxa, and taxonomic composition.Results and discussionOur results indicate that, at least over a relatively short period (i.e., 6 months), the use of the cages represents a useful tool to let the macroalgae grow enough to counterbalance the herbivory pressure. The associated fauna below the macroalgae was characterized by a different taxonomic composition when compared to controls (i.e., artificial reefs without the macroalgae), particularly when considered the rare taxa. In conclusion, the combination of passive and active restoration can be considered a useful approach to restore marine sites degraded by historical industrial activities.

Characterisation and Dynamics of an Emerging Seagrass Meadow

Seagrasses are habitat-forming species that support biodiversity and a wide range of associated ecosystem services, from blue carbon capture to providing nursery areas for a variety of organisms. Their decline has been documented worldwide and is attributed to human impacts ranging from habitat loss and eutrophication to the effects of climate change. However, recent recovery trends have also been documented due to reductions in stressors, passive and active restoration, and even changes in environmental conditions owing to local management. In this study, we document for the first time the occurrence of Zostera noltei in the downstream area of the River Minho Estuary. This occurrence was unexpected given the hydrological conditions of the estuary, characterised by dredging and siltation. We reconstructed the occurrence and historical distribution of seagrass beds, and showed that they have existed in the region for more than a decade. The current distribution area was mapped using high-resolution multispectral remote sensing techniques, and in situ photoquadrats to complement the remote sensing information with an evaluation of the seagrass cover. A current seagrass area of 0.81 ha was found with an average cover of 70%. However, the Minho Estuary continues to be strongly affected by sediment deposition, which may affect the seagrass population in the long term. Continued surveys are recommended to confirm the long-term trend of colonisation of this important habitat, which ultimately provides so many benefits to coastal ecosystems and humankind.

Success of passive and active restoration of lowland hay meadows with regard to current and historical references

The restoration of hay meadows is one of the major challenges in temperate Europe, to overcome the drastic loss and degradation of these semi-natural habitats. Evaluation of restoration success requires the definition of a relevant reference ecosystem. Historical phytosociological relevés dating from the 1960s–1970s, before large scale agriculture intensification, may be used as the reference framework for such purposes. However, this reference framework may no longer be pertinent in our present-day ecological and socio-economic context. In this study, we assessed the success of three restoration techniques for lowland hay meadows, based on plant species richness and composition and functional traits, by comparing the restoration trajectories to historical and current references. The three restoration techniques, passive restoration mowing, active fresh hay transfer and active sowing of threshing material, were implemented depending on the initial level of degradation and the proximity to well-preserved meadows. The species composition of restored meadows clearly differed from historical references but converged toward current references, for both passive and active restoration techniques. Historical references are characterized by short, stress-tolerant dicotyledonous plant species with small specific leaf area, indicators of nutrient-poor environments. The gap observed between plant communities of historical and current meadows suggests that the historical data are an over-ambitious target for restoration purposes and can hardly be considered relevant to our present-day context. Therefore, creation of a new reference framework of lowland hay meadows is needed for the adequate implementation of restoration projects. Successful outcomes of active and passive techniques must encourage practitioners to adapt the choice of the restoration method depending on the local ecological context, i.e., level of degradation and proximity to well-preserved habitats.

Positive effects of two decades of passive ecological restoration in a historically polluted marine site

The Mediterranean Sea is one of the most exploited regions of the world’s oceans. Here industrial activities have determined either acute or long-term impacts on coastal marine ecosystems. In this study, we investigated macrofauna distribution and diversity, and food-web functioning in a coastal area of the Mediterranean Sea facing an industrial chemical plant abandoned in the ‘90s to assess benthic ecosystem health. This area has been identified as a Site of National Interest (SNI) since 2002 and has been closed to any human activity awaiting to be remediated according to national laws. Our results indicate that, two decades after the SNI declaration (a decade after the plant decommissioning), there is no longer any sign of the impact of historical contaminations on macrofauna and benthic food web functioning. Overall, all the thirty-six sites showed high/good ecological quality according to the score assigned by AMBI and M-AMBI indexes, reflecting the absence of chronic impacts. Our findings reveal, for the first time, the positive effects of passive restoration (i.e., unassisted, or spontaneous recovery following cessation of anthropogenic impacts) on historically impacted coastal ecosystems since their health conditions, in terms of both abiotic (environmental variables and contaminant concentration) and biotic (macrofauna diversity and community composition, and benthic food-web structure) factors, were indistinguishable from surrounding non-impacted areas. These findings also suggest that other effective area-based conservation measures (OECMs) could be useful not only for biodiversity conservation of vulnerable and priority habitats in larger ocean sectors but also to promote the passive recovery of historically contaminated ecosystems.