Invasion of alien species is one of the main drivers of land degradation threatening both natural and managed ecosystems. Ecological restoration is crucial in controlling invasion to improve biotic resistance and avoid further land degradation. We investigated the possibility of controlling the establishment of invasive alien species (IAS) by native seed addition. We tested if trait similarity or increased propagule pressure of native species results in the suppression of IAS at the early stage of development. We set up a sowing experiment with three widespread IAS in Hungary of different life forms and functional groups (Asclepias syriaca, Conyza canadensis, Tragus racemosus) and four Pannonic sand grassland species (Festuca vaginata, Galium verum, Gypsophila paniculata, Saponaria officinalis). We found no significant differences in germination ability and seedling emergence between native species and IAS, despite the differences in thousand‐seed weight. Using univariate general linear models, we found that the seedling establishment of IAS can be reduced by adding native species at high densities but also depending on the species identity. Instead of species of similar traits, the seeding of a competitor perennial grass of sand grasslands (F. vaginata) reduced the seedling emergence of all studied IAS the most. Our results confirm that IAS can be effectively controlled by native seed addition in the early establishment stage, especially applying higher densities and competitive species. We conclude that invasion‐resistant restoration can be achieved by the combination of several factors, including high‐density sowing of native species that match IAS in the early stage of development.

Invasive species are among the main threats to grassland biodiversity, and nature conservation management seeks the best methods to eliminate them and to restore natural habitats. We studied the long‐term effect of mowing on the restoration of Pannonian sand grassland after elimination of invasive black locust (Robinia pseudo‐acacia) plantation in Hungary, Europe. Stands of R. pseudo‐acacia at three sites were felled and stumps herbicide‐treated in the winter of 1994–1995. Mowing with hay removal treatment was applied twice a year in 1995–2001 to assist grassland recovery. A block of 12 adjacent plots of 10 m by 10 m was assigned for the experiment at each site, with six control (unmowed) and six treatment (mowed) plots randomly selected. Vegetation was sampled in June and August yearly in 1995–1999 in all sites, plus in seminatural reference grasslands then re‐sampled six times until 2017 in two sites. Herbicide application with repeated mowing successfully eliminated R. pseudo‐acacia. In the unmowed plots, dense woody cover developed at all sites. Vegetation of mowed plots approached the reference grasslands in sites with better propagule availability of target species according to trajectory analyses. In these sites, higher cover of target species was found in mowed compared to unmowed plots, though still significantly lower than in the reference. Mowed plots were more prone to secondary invasion than the unmowed. The long‐term monitoring revealed that initial mowing assisted the restoration of Pannonian sand grassland, but further management is needed to control secondary invasion and increase target species cover.

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.

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.

Evaluating and monitoring forest areas during a restoration process is indispensable to estimate the success or failure of management intervention and to correct the restoration trajectory through adaptive management. However, the field measurement of several indicators in large areas can be expensive and laborious, and establishing reference values for indicators is difficult. The use of supervised classification techniques of high resolution images, combined with an expert system to generate management recommendations, can be considered promising tools for monitoring and evaluating restoration areas. The objective of the present study was to elaborate an expert system of management recommendation generation for areas under restoration, which were monitored by two different remote sensors: UAV (Unmanned Aerial Vehicle) and LiDAR (Light Detection and Ranging). The study was carried out in areas under restoration with about 54 ha and five years of implementation, owned by Fibria Celulose S.A. (recently acquired by Suzano S.A.), in the southern region of Bahia State, Brazil. We used images from Canon S110 NIR (green, red, near infrared) on UAV and LiDAR data compositions (intensity image, digital surface model, digital terrain model, normalized digital surface model). The monitored restoration indicator entailed land cover separated into three classes: Canopy cover, bare soil and grass cover. The images were classified using the Random Forest (RF) and Maximum Likelihood (ML) algorithms and the area occupied by each land cover classes was calculated. An expert system was developed in ArcGIS to define management recommendations according to the land cover classes, and then we compared the recommendations generated by both algorithms and images. There was a slight difference between the recommendations generated by the different combinations of images and classifiers. The most frequent management recommendation was “weed control + plant seedlings” (34%) for all evaluated methods. The image monitoring methods suggested by this study proved to be efficient, mainly by reducing the time and cost necessary for field monitoring and increasing the accuracy of the generated management recommendations.

Biodiversity loss caused by invasive alien species is a major problem in planetary perspective. Ecological restoration can play a critical role in mitigating the impact of invasive species, but the presence of invasive plants in the landscape may simultaneously pose challenges to restoration success, and these processes are influenced by the life history of invasive species. We investigated long-term changes in annual and perennial invasive plant abundance as a function of restoration intervention, invasive species propagule pressure from the surrounding landscape and time since intervention in three sand grassland restoration experiments. Restoration interventions (native low diversity seeding, mowing and carbon amendment) were conducted at a total of eight sites in the Kiskunság region of Hungary. The interventions took place between 1995 and 2003 and were monitored for 17–25 years. To assess invasive propagule pressure around the experimental sites, total shoot numbers in adjacent 1 m by 1 m plots along 100-m-long transects were counted in 2020–2021 from the center of the eight experimental sites. Invasive propagule pressure within a 100-m buffer did not explain changes in the abundance of annual and perennial invasive species. The cover of annual invasive species has mostly decreased over time, and treatment (mainly seeding) accelerated this process. The cover of perennial invasive species increased over time irrespective of applied treatments and landscape invasive propagule pressure. Our research showed that seeding with native species is an effective tool for restoring sandy grasslands and preventing the spread of annual invasive species, but our toolbox for preventing perennial invasion in grassland restoration is limited.