Claudio Gratton

Introduction: Human land use intensification and the resulting habitat loss are primary drivers of insect pollinator declines. Habitat restoration offers a promising approach to counteract these declines, yet landscape‐level evaluations of bee responses to restoration and management remain limited. We conducted a 2‐year, landscape‐scale study in Wisconsin, United States, to assess how different intensities of tallgrass prairie restoration and management affect bumble bees ( Bombus spp.). Objectives: This study aimed to determine whether (1) bumble bee abundance and diversity increase with active restoration, and (2) outcomes differ between low‐ (seeded only) and moderate‐intensity (seeded and managed with prescribed fire) interventions. Methods: Using catch‐and‐release surveys, we measured bumble bee abundance and diversity at 32 sites representing a gradient in restoration intervention: no‐intervention (passive recovery), low‐intervention, and moderate‐intervention. Results: Bumble bee abundance and diversity were higher at active restoration sites (low‐ and moderate‐intervention) than at no‐intervention sites. Although both abundance and diversity tended to be greater at moderate than low‐intervention intensities, these differences were not statistically significant. Bumble bee community composition also differed across intervention intensity, driven by shifts in dominant species (e.g. Bombus impatiens and B. griseocollis ). Rarer taxa, including endangered and vulnerable species, occurred only at active restoration sites, with the largest populations at moderate‐intervention sites. Across all sites, bumble bee responses were strongly and positively associated with floral abundance, but not with semi‐natural habitat in the surrounding landscape. Conclusion: Our findings demonstrate that active grassland restoration can effectively increase bumble bee abundance and diversity, supporting its value as a conservation practice for pollinators.

Integrated pest management (IPM) has been criticized for its inability to move agriculture beyond “curative” approaches for crop management. Today, IPM is primarily a set of tactics aimed at controlling pests, still relying on pesticides and pesticide management as a main tool. Yet, from its inception, the intent of IPM was to redesign agricultural systems, through planning and reliance on ecological processes, such that pest problems were largely avoided in the first place. The pathways and processes for achieving widespread cropping system redesign, however, were never fully articulated in the IPM concept. Frameworks from the field of sustainability transitions, such as the multi‐level perspective (MLP), can shed light on the dynamics and drivers of change in socio‐technological systems. In this framing, the ecological intensification and diversification of farms and landscapes that can create pest‐suppressive environments can be conceptualized as novel “technological” innovation niches that challenge the dominant socio‐technological regime. The conventional agri‐food system, however, is dominated by “lock‐ins” that have coevolved over time among farmers, supply chain participants, businesses, research institutions, policy, and public institutions to be resilient to change. Enabling IPM to transform agroecosystems requires overcoming a range of interconnected hurdles. When seen through the lens of the MLP, successful IPM will require not only new technologies and management practices but also social and political innovations that support collective action, social learning and transdisciplinary partnerships. Novel decision support tools for managing and predicting the dynamics of agroecosystems at farm and landscape scales can be instrumental for planning and implementing diversified production systems. Ultimately, institutional supports are needed to foster innovations currently obstructed by political pressure and to reconfigure power dynamics that maintain the status quo. Finally, conceptualizing agriculture and pest management as one component of a broader landscape that affects human well‐being reveals points of leverage and synergy to facilitate a much needed transition away from the pesticide‐intensive approaches that still dominate today.

Understanding the capacity of mobile organisms such as insects to utilize resources across different patches in a landscape can reveal strategies for their conservation. Past research suggests that higher levels of non‐crop habitat or landcover diversity in agricultural regions typically benefit generalist predators who can fortify their diets with prey from multiple adjacent habitats. For some taxa such as lady beetles (Coccinellidae), dietary diversity is associated with improved fitness, but foraging patterns in real landscapes are hard to measure. We used a DNA metabarcoding approach to explore how the presence and taxonomic richness of arthropod prey in lady beetle diets varied by local habitat (crop vs. non‐crop) and landscape complexity (non‐crop habitat and landcover diversity in a 250 m radius). We collected over 500 individual lady beetles from a range of landscapes in 2019 and 2021 in southern Wisconsin (USA), performed whole‐body DNA extractions, amplified arthropod DNA using primers optimized for insectivore diets, and used Illumina sequencing to characterize the taxonomic composition and diversity of prey. We found 50 unique prey taxa in lady beetle guts from eight arthropod orders (mostly flies, true bugs, and thrips). Lady beetles in landscapes with a greater proportion of crops were slightly more likely to have prey in their gut, and community‐level prey richness was strongly positively correlated with surrounding landcover diversity. This effect was dampened slightly in high‐crop landscapes, likely due to a smaller prey species pool available to predators. Our results enhance knowledge of lady beetle trophic ecology and demonstrate that supplementation of diets through increased habitat diversity may be an important mechanism for the success of mobile generalists in complex landscapes.

Human land-use intensification and the resulting habitat loss are primary drivers of insect pollinator declines. Habitat restoration offers a promising approach to counteract these declines, yet landscape-level evaluations of bee responses to restoration and management remain limited. We conducted a two-year, landscape-scale study in Wisconsin, USA, to assess how different intensities of tallgrass prairie restoration and management affect bumble bees (Bombus spp.). Our objectives were to determine whether (1) bumble bee abundance and diversity increase with assisted restoration, and (2) outcomes differ between low- (seeded only) and moderate-intensity (seeded and managed with prescribed fire) interventions. Using catch-and-release surveys, we measured bumble bee abundance and diversity at 32 sites representing a gradient in restoration intervention: no intervention (unassisted recovery), low intervention, and moderate intervention. We found that abundance and diversity were higher at assisted restoration sites (low and moderate intervention) than at unassisted sites. Although both tended to be greater at moderate than low intervention intensities, these differences were not statistically significant. Bumble bee community composition also differed across intervention intensity, driven by shifts in dominant species (e.g., B. impatiens and B. griseocollis). Rarer taxa, including endangered and vulnerable species, occurred only at assisted restoration sites, with the largest populations at moderate intervention sites. Across all sites, bumble bee responses were strongly and positively associated with floral abundance, but not with semi-natural habitat in the surrounding landscape. Our findings demonstrate that assisted grassland restoration can effectively increase bumble bee abundance and diversity, supporting its value as a conservation practice for pollinators. Implications for Practice: - Grassland restorations targeting plant communities can successfully support nontarget pollinators across a range of management intensities and landscape contexts. Adding seeds of pollinator-preferred plants could improve restorations with low floral abundance and diversity. - Management of existing restorations is important to maintain abundant floral resources and diverse pollinator communities. Because sites varied widely in prescribed fire use, our findings likely represent a conservative estimate of its benefits, and higher intervention intensity (e.g., repeated seeding, regular fire, mechanical or chemical shrub and invasive plants control) may further enhance outcomes for bumble bees.

Pesticide use and habitat loss are major anthropogenic drivers of bee decline, raising global concerns about impaired crop pollination. However, the relative importance of these stressors and their combined impact on bee assemblages comprising species with different traits, such as body size or nesting strategy, remains unknown. Here we addressed these key knowledge gaps in a global quantitative synthesis analysing bee assemblage data from 681 crop fields across three continents. We found that both local pesticide hazards and decreasing proportions of semi-natural habitats in surrounding landscapes negatively affected wild bee abundance and species richness in crop fields, while pesticides additionally reduced functional and phylogenetic diversity. Semi-natural habitat availability did not buffer against these negative pesticide effects, nor did we identify any specific traits rending bees more vulnerable to one of the two drivers. Our findings highlight the pressing need to reduce non-target effects of pesticide use and emphasize that conservation and restoration of semi-natural habitats successfully promote wild bees, but are insufficient strategies to mitigate pesticide-driven losses of wild bee pollinators from crop fields.

Apple is one of the most important pollinator‐dependent fruit crops worldwide. To secure high‐quality yields, it is crucial to know which, and to what extent, pollinating insects contribute to its pollination success as measured by fruit set, fruit weight and seed set. We perform a meta‐analysis of field studies conducted across multiple orchards on insect‐mediated pollination in apple cultivation, using raw data from 29 studies, totalling 532 orchard replicates. We assessed the extent of pollen limitation on different pollination outcomes and assessed the contribution of honeybees, wild bees and bee species richness to apple pollination. Across all studies, we detected strong evidence of pollen limitation for fruit set and seed set, but not for fruit weight. Honeybees were the most abundant flower visitors (average relative visitation of 71.9%) compared to wild bees; but when correcting for their pollination efficiency, the relative pollination contribution of honeybees was lower compared to their relative visitation (vice versa for solitary bees). We conclude that honeybee visitation rate did not influence fruit or seed set; yet increasing honeybee visitation had a small, negative effect on fruit weight. Fruit set was not influenced by wild bee visitation rate, whereas wild bee visitation had a small, but clear positive effect on fruit weight and seed set. Bee species richness had a small, positive effect on seed set; whereas it did not affect fruit set and fruit weight. Syntheses and applications. Our study highlights that pollen limitation is common in this global crop. While managed honeybees are dominant pollinators, a diverse community of wild bees contributes significantly to apple pollination and high‐quality yield. The positive effect of wild bees and species richness on fruit weight and seed set demonstrates that wild bee pollination results in better‐quality fruit production (increased weight & seed set). Therefore, our synthesis highlights the importance of conserving pollinator diversity to maintain pollination services. The absence of a clear effect of honeybee visitation rate on fruit and seed set, coupled with its negative impact on fruit weight, suggests a need for further optimisation of honeybee management to improve the cost‐efficiency of pollination management.