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Ecologists have worked to ascribe function to the variation found in plant populations, communities and ecosystems across environments for at least the past century. The vast body of research in functional ecology has drastically improved understanding of how individuals respond to their environment, communities are assembled and ecosystems function. However, with limited exceptions, few studies have quantified differences in plant function during the earliest stages of the plant life cycle, and fewer have tested how this early variability shapes populations, communities and ecosystems. Drawing from the literature and our collective experience, we describe the current state of knowledge in seedling functional ecology and provide examples of how this subdiscipline can enrich our fundamental understanding of plant function across levels of organisation. To inspire progressive work in this area, we also outline key considerations involved in seedling functional research (who, what, when, where and how to measure seedling traits) and identify remaining challenges and gaps in understanding around methodological approaches. Within this conceptual synthesis, we highlight three critical areas in seedling ecology for future research to target. First, given wide variation in the definition of a ‘seedling’, we provide a standard definition based on seed reserve dependence while emphasising the need to measure ontogenetic variation more clearly both within and following the seedling stage. Second, studies demonstrate that seedlings can be studied in multiple media (e.g. soil, agar, filter paper) and conditions (e.g. field, greenhouse, laboratory). We recommend that researchers select methods based on explicit goals, yet follow standard guidelines to reduce methodological noise across studies. Third, research is critically needed to assess the implications of different methodologies on trait measurement and compatibility across studies. By highlighting the importance of seedling functional ecology and suggesting pathways to address key challenges, we aim to inspire future research that generates useful and comparable data on seedling functional ecology. This work is critical to explain variation within and among populations, communities and ecosystems and integrate this most vulnerable stage of plant life into ecological frameworks.

Active grassland restoration has gained importance in mitigating the dramatic decline of farmnland biodiversity. While there is evidence that such operations are generally effective in promoting plant diversity, little is known about the effectiveness of the different methods applied. Restoration methods can differ in intensity of seed bed preparation, seed source and method of seed application. In this systematic literature search and meta‐analysis, we screened the literature for studies of the restoration of mesic grasslands in temperate Europe. We focused on active restoration experiments that included a treatment and lasted for more than 3 years. We evaluated the influence of restoration factors on plant species richness relative to non‐restored controls. We found 187 articles that investigated the outcome of operations aimed at actively restoring mesic temperate grasslands. Most articles focused on plants, with only 9.6% dealing with other organisms (e.g. beetles, pollinating insects). Many papers had to be excluded due to incomplete data, too short study duration and/or lack of an adequate control. This resulted in 13 articles fulfilling our criteria for inclusion, yielding a total of 56 data points for the meta‐analysis. Restoration actions increased plant species richness by, on average, 17.4%, compared to controls. The seed source explained a significant amount of variation in plant species richness: seeds originating from a speciose donor grassland had a positive effect. This effect was even enhanced when combined with a commercial seed mix, whereas commercial seed mixes alone had no significant effect. We did not observe any effect of other factors, such as the type of seed bed preparation or the seed application method. A seed‐source obtained from species‐rich grasslands seems to be key to efficient grassland restoration in mesic grasslands of temperate Europe. Even though seeds from a speciose donor grassland should be preferred over commercial seeds, associating natural and commercial seed mixes increases plant species richness. This systematic literature search further revealed two major research gaps in grassland restoration ecology: a deficit in long‐term investigations as well as a deficit in studies focusing on non‐plant organisms. We conducted a systematic literature search and meta‐analysis to evaluate the influence of restoration factors on plant species richness relative to non‐restored controls on mesic grasslands in temperate Europe. Restoration actions increased plant species richness by, on average, 17.4%, compared to controls, with seed source explaining a significant amount of variation. This systematic literature search further revealed two major research gaps in grassland restoration ecology: a deficit in long‐term investigations as well as a deficit in studies focusing on non‐plant organisms.

The Decade on Ecosystem Restoration aims to provide the means and incentives for upscaling restoration efforts worldwide. Although ecosystem restoration is a broad, interdisciplinary concept, effective ecological restoration requires sound ecological knowledge to successfully restore biodiversity and ecosystem services in degraded landscapes. We emphasize the critical role of knowledge and data sharing to inform synthesis for the most robust restoration science possible. Such synthesis is critical for helping restoration ecologists better understand how context affects restoration outcomes, and to increase predictive capacity of restoration actions. This predictive capacity can help to provide better information for evidence‐based decision‐making, and scale‐up approaches to meet ambitious targets for restoration. We advocate for a concerted effort to collate species‐level, fine‐scale, ecological community data from restoration studies across a wide range of environmental and ecological gradients. Well‐articulated associated metadata relevant to experience and social or landscape contexts can further be used to explain outcomes. These data could be carefully curated and made openly available to the restoration community to help to maximize evidence‐based knowledge sharing, enable flexible re‐use of existing data and support predictive capacity in ecological community responses to restoration actions. We detail how integrated data, analysis and knowledge sharing via synthesis can support shared success in restoration ecology by identifying successful and unsuccessful outcomes across diverse systems and scales. We also discuss potential interdisciplinary solutions and approaches to overcome challenges associated with bringing together subfields of restoration practice. Sharing this knowledge and data openly can directly inform actions and help to improve outcomes for the Decade on Ecosystem Restoration. We detail how integrated data, analysis and knowledge sharing via synthesis can support shared success in restoration ecology by identifying successful and unsuccessful outcomes across diverse systems and scales. We also discuss potential interdisciplinary solutions and approaches to overcome challenges associated with bringing together subfields of restoration practice.

Climate change is one of the most pressing threats to humanity, inducing a global increase in temperatures and more frequent extreme climatic events. Considering this, global reforestation initiatives are proposed to capture carbon and mitigate climate change. Global restoration and reforestation programs and their targets have inspired both unparalleled enthusiasm worldwide and intense scientific criticism and debate regarding their feasibility and implementation. We agree that global reforestation forecasting and efforts require a nuanced discussion and approach. In that vein, we would like to emphasize the potential of increasing existing forest diversity to enhance climate change mitigation by increasing aboveground and belowground carbon storage. Moreover, we argue that focusing on planting diverse forests in reforestation efforts can help to reduce climate change effects on ecosystems: first, by increasing resistance and resilience to extreme climatic events, and second, by buffering microclimatic conditions in natural and urban areas. Diversifying forests plantations and reforestation projects may not always be feasible and cannot solve the climate crisis by itself. However, we highlight that a focus on diverse forests could maximize the benefits of reforestation programs by promoting sustainable land management. Climate change is one of the most pressing threats to humanity, inducing a global increase in temperatures and more frequent extreme climatic events. We would like to emphasize the potential of increasing forest diversity to enhance climate change mitigation by increasing aboveground and belowground carbon storage. Moreover, we argue that focusing on planting diverse forests in reforestation efforts can help to reduce climate change effects on ecosystems: first, by increasing resistance and resilience to extreme climatic events, and second, by buffering microclimatic conditions in natural and urban areas.

Understanding the factors governing grassland biodiversity across different spatial scales is crucial for effective conservation and management. However, most studies focus on single grain sizes, leaving the scale‐dependent mechanisms of biodiversity drivers unclear. We investigated how climate, soil properties, abiotic disturbance, and land use influence plant diversity across two fine spatial scales in various grassland types in Ukraine. Using spatially explicit data on plant species presence and their cover, collected at smaller (10 m2) and larger (100 m2) grain sizes, we assessed spatial β‐diversity—the variability of biodiversity between scales. We analyzed whether the effects of ecological drivers on β‐diversity are mediated by changes in species evenness, density (total cover), and intraspecific aggregation in plant community. In our study, the most influential factors of local plant diversity at both grain sizes were climate variables, followed by soil humus content, litter cover, and soil pH. Soil and litter effects were primarily driven by the response of locally rare species, while climate and grazing effects were driven by locally common species. The strength of most of these effects varied between spatial scales, affecting β‐diversity. Soil properties influenced β‐diversity through changes in total plant community cover, while the effects of climate and litter operated via changes in species evenness and aggregation. Our findings highlight that biodiversity responses to climate, soil factors, and litter depend on the size of the sampled area and reveal the role of total plant cover, evenness, and aggregation in driving fine‐scale β‐diversity in grasslands across different habitat types. Our findings support the idea that the responses of biodiversity to climate, soil factors, and litter depend on the size of the sampled area. We have identified main mechanisms behind the scale‐dependency of biodiversity drivers and highlighted the significance of locally rare and common species. Our results underscore the importance of incorporating the scale‐dependency of biodiversity drivers in conservation efforts, management strategies, and analyses of global change impacts, which would enhance our ability to predict potential biodiversity change.

1. Globally the prevalence and impact of invasive non-native plant species is increasing rapidly. Experimentally based research aimed at supporting management is limited in its ability to keep up with this pace, partly because of the importance of understanding historical abiotic and biotic conditions. Contrastingly, landholders are in unique positions to witness species turnover in grasslands, adapt management practices in response and learn from successes and failures. 2. This local knowledge could be crucial for identifying feasible solutions to land degradation, and ecological restoration, but local knowledge is rarely explicitly embedded in ecological research. 3. We use a sequential exploratory strategy where we first interview (semi-directive approach) 15 landholders within the Bega region of New South Wales, Australia concerning the changing ecological characteristics of both extensively and intensively managed grassy woodlands and perceived impacts following arrival of the invasive exotic introduced species, African lovegrass (ALG), Eragrostis curvula. 4. Based on the results of these interviews, we then conducted a field study where we tested 7 landholder-generated hypotheses at 57 sites. 5. The field study validated many of the landholder management perceptions including: ALG was negatively correlated with species richness, canopy cover and dominant grasses like Themeda triandra. Mechanical slashing increased exotic ALG abundance. The prevalence of ALG in the soil seed bank was positively correlated with its abundance above-ground. Study observations that contradicted landholder perceptions included: ALG was not more palatable nor did its abundance decline in response to increasing soil fertility. Spot spraying with herbicides was effective at controlling abundance, despite its reputation as ineffective. Landholder observations also highlighted key hypotheses concerning modes of spread that require long-term studies including the roles of drought and overgrazing. 6. Synthesis and applications. Overall, we found local knowledge coupled with scientific methods can act in tandem as a highly effective approach for developing management recommendations. This approach identifies local perceptions that are not substantiated by scientific data to halt potentially harmful practices, and observations that are insightful predictions about the dynamics and impacts of non-native species that need long-term experiments to corroborate scientifically.

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.

Globally, annual expenditure on ecological restoration of degraded areas for habitat improvement and biodiversity conservation is approximately $18bn. Seed farming of native plant species is crucial to meet restoration goals, but may be stymied by the disconnection of academic research in seed science and the lack of effective policies that regulate native seed production/supply. To illustrate this problem, we identified 1,122 plant species important for European grasslands of conservation concern and found that only 32% have both fundamental seed germination data available and can be purchased as seed. The “restoration species pool,” or set of species available in practice, acts as a significant biodiversity selection filter for species use in restoration projects. For improvement, we propose: (1) substantial expansion of research and development on native seed quality, viability, and production; (2) open‐source knowledge transfer between sectors; and (3) creation of supportive policy intended to stimulate demand for biodiverse seed.

Nutrient enrichment typically causes local plant diversity declines. A common but untested expectation is that nutrient enrichment also reduces variation in nutrient conditions among localities and selects for a smaller pool of species, causing greater diversity declines at larger than local scales and thus biotic homogenization. Here we apply a framework that links changes in species richness across scales to changes in the numbers of spatially restricted and widespread species for a standardized nutrient addition experiment across 72 grasslands on six continents. Overall, we find proportionally similar species loss at local and larger scales, suggesting similar declines of spatially restricted and widespread species, and no biotic homogenization after 4 years and up to 14 years of treatment. These patterns of diversity changes are generally consistent across species groups. Thus, nutrient enrichment poses threats to plant diversity, including for widespread species that are often critical for ecosystem functions.

This Open Letter highlights plant regeneration as a critical and overlooked dimension of ecosystem resilience under global environmental change. Biodiversity monitoring, conservation and agricultural assessments typically focus on adult plant performance and vegetative growth, yet the processes that enable plants to reproduce and establish new individuals—pollination, seed production, germination and seedling establishment—often remain poorly monitored. Failures during these stages can silently undermine ecosystem recovery, restoration success, species conservation and crop productivity. We call for integrating regeneration processes into ecological monitoring, climate risk assessments and policy frameworks to better safeguard biodiversity, ecosystem services, food security and long‐term ecosystem resilience.