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Variability in population densities is key to the ecology of natural systems but also has great implications for agriculture. Farmers’ decisions are heavily influenced by their risk aversion to pest outbreaks that result in major yield losses. However, the need for long-term pest population data across many farms has prevented researchers from exploring the drivers and implications of pest population variability (PV). Here, we demonstrate the critical importance of PV for sustainable farming by analyzing 13 years of pest densities across >1300 Spanish olive groves and vineyards. Variable populations were more likely to cause major yield losses, but also occasionally created temporal windows when densities fell below insecticide spray thresholds. Importantly, environmental factors regulating pest variability were very distinct from factors regulating mean density, suggesting variability needs to be uniquely managed. Finally, we found diversifying landscapes may be a win–win situation for conservation and farmers, as diversified landscapes promote less abundant and less variable pest populations. Therefore, we encourage agricultural stakeholders to increase the complexity of the landscapes surrounding their farms through conserving/restoring natural habitat and/or diversifying crops.

Faced with the biodiversity extinction crisis and climate change, alternative approaches to food production are urgently needed. Decades of chemical-based weed control have resulted in a dramatic decline in weed diversity, with negative repercussions for agroecosystem biodiversity. The simplification of cropping systems and the evolution of herbicide resistance have led to the dominance of a small number of competitive weed species, calling for a more sustainable approach that considers not only weed abundance but also community diversity and composition. Agroecological weed management involves harnessing ecological processes to minimize the negative impacts of weeds on productivity and maximize biodiversity. However, the current research effort on agroecological weed management is largely rooted in agronomy and field-scale farming practices. In contrast, the contributions of landscape-scale interventions on agroecological weed management are largely unexplored (e.g., interventions to promote pollinators and natural enemies or carbon sequestration). Here, we review current knowledge of landscape effects on weed community properties (abundance, diversity, and composition) and seed predation (a key factor in agroecological weed management). Furthermore, we discuss the ecological processes underlying landscape effects, their interaction with in-field approaches, and the implications of landscape-scale change for agroecological weed management. Notably, we found that (1) landscape context rarely affects total weed abundance; (2) configurational more than compositional heterogeneity of landscapes is associated with higher alpha, beta, and gamma weed diversity; (3) evidence for landscape effects on weed seed predation is currently limited; and (4) plant spillover from neighboring habitats is the most common interpretation of landscape effects on weed community properties, whereas many other ecological processes are overlooked. Strikingly, the drivers of weed community properties and biological regulation at the landscape scale remain poorly understood. We recommend addressing these issues to better integrate agroecological weed management into landscape-scale management, which could inform the movement towards managing farms at wider spatiotemporal scales than single fields in a single season.

Bactrocera oleae is the main pest in olive groves, and its management requires a sustainable perspective to reduce the use of chemical products. Landscape context is being considered as an important driver of pest reduction, but results on B. oleae show inconsistency to date. Most of landscape-pest control studies focus on the dynamics of the pests within the focal crop, ignoring these dynamics in other land uses. Here we present a study in which we analyze the seasonal population dynamics of the olive pest B. oleae in the most important land uses of a typical olive landscape in Portugal. We found that B. oleae is present in all the land uses and the dynamics are very similar to those in the olive groves. However, the presence of these land uses in the landscape did not display any increase in B. oleae abundance within the olive groves. In contrast, a landscape mainly composed by olive groves increased the abundance of this pest. Importantly, more diverse landscapes surrounding olive groves reduce the abundance of the olive fly. Based on these findings, we can conclude that B. oleae is present in all the land uses of the studied landscape but that this presence does not imply an increase of B. oleae in olive groves. Indeed, other land uses can promote landscape diversification which is a driver of the reduction of B. oleae populations in olive groves. We thus encourage olive stakeholders to increase landscape diversification around their farms by promoting/restoring other crops/habitats.

Purpose of Review To describe how general prescriptions to protect temperate and boreal forests against pests have been affecting the conservation of insect diversity, (2) to identify potential conflicts between biodiversity conservation actions and pest control, and (3) to provide future directions to reconcile forest pest management with insect conservation. Recent Findings Despite dealing with the same habitats and organisms, forest pest management and insect conservation have been separate disciplines, often pursuing conflicting goals. However, there is a large intersection between the two, as interventions to control pests can have repercussions on biodiversity and vice versa. In several regions, forest pest management is shifting from reactive measures to contain on-going outbreaks to proactive strategies to create forest landscapes that are more resistant and resilient against pests in the long-term. These developments suggest a possible convergence between pest management and insect conservation objectives. Summary Several reactive measures adopted to control pests can cause negative impacts on non-target insects, although effects are sometimes localized and often context-dependent. Following ecological, economic, and social considerations, pest management has been evolving towards diversifying forests across multiple spatial scales to reduce the severity of outbreaks and the risk of damage. Such strategies concur with multiple conservation goals to increase insect diversity across intensive forest landscapes. Insect conservation has traditionally targeted saproxylic organisms, neglecting the conservation of other insect guilds and seldom assessing side effects on pests. Despite some important knowledge gaps, we propose complementary approaches to combine multiple diversification strategies at the landscape scale to reconcile pest management with insect conservation.

For insects, surviving winter depends on their capacity to store enough energy and find proper hibernation sites. A common strategy is to minimize movement and hibernate near autumn food sources. We investigated the efficiency of autumnal hosts to act as trap crops where insects could be exposed to targeted repressive treatments. This approach could reduce the local populations of insect pests in the next production season, reducing the need for insecticides. First, we tested the mullein plant’s attractiveness as an autumn trap crop for Lygus lineolaris (Hemiptera: Miridae) in strawberry fields by comparing peak population density among mullein (Verbascum thapsus), strawberry plants (Fragaria × ananassa), buckwheat (Fagopyrum esculentum), and mustard (Sinapis alba). Second, we tested four treatments applied to the autumn trap crops to reduce L. lineolaris winter survivorship: (1) hot water, (2) a pathogen (Beauveria bassiana), (3) insecticide (cypermethrin), and (4) a control. The density of the L. lineolaris population on mullein in autumn and on buckwheat in summer was higher than on strawberry and mustard. Of the overwintering L. lineolaris, 0% survived the winter when treated with the insecticide cypermethrin, while 38.3% survived in the control treatment (without repressive treatment). The B. bassiana and hot water treatments did not differ from the control. The mullein autumn trap crops combined with insecticide treatments could contribute to reducing the overwintering population, hence potentially reducing population during the following growing season.

• Arbuscular mycorrhizal fungi (AMF) are keystone symbionts of agricultural soils but agricultural intensification has negatively impacted AMF communities. Increasing crop diversity could ameliorate some of these impacts by positively affecting AMF. However, the underlying relationship between plant diversity and AMF community composition has not been fully resolved. • We examined how greater crop diversity affected AMF across farms in an intensive agricultural landscape, defined by high nutrient input, low crop diversity and high tillage frequency. We assessed AMF communities across 31 field sites that were either monocultures or polycultures (growing > 20 different crop types) in three ways: richness, diversity and composition. We also determined root colonization across these sites. • We found that polycultures drive the available AMF community into richer and more diverse communities while soil properties structure AMF community composition. AMF root colonization did not vary by farm management (monocultures vs polycultures), but did vary by crop host. • We demonstrate that crop diversity enriches AMF communities, counteracting the negative effects of agricultural intensification on AMF, providing the potential to increase agroecosystem functioning and sustainability.

1. Field-margin diversification through conservation and restoration of hedgerows is becoming a prominent intervention for promoting biodiversity and associated ecosystem services in intensive agricultural landscapes. However, how increasing cover of hedgerows in the landscape can affect ecosystem services has rarely been considered. 2. Here, we assessed the effect of increased field-margin complexity at the local scale and increasing cover of hedgerows in the landscape on the provision of pest control, weed control and potential pollination. Locally, three types of field margin were compared as follows: (i) standard grass margin, (ii) simple hedgerow and (iii) complex hedgerow, along two independent gradients of hedgerow cover and arable land cover in the landscape. We performed an exclusion experiment to measure biological control of cereal aphids and assessed natural enemy and pest abundance in the field. We sampled plant weed communities and performed a phytometer experiment to test the effects of pollinators on plant reproductive success. 3. At the local scale, planting a new hedgerow or improving its structural complexity and vegetation diversity did not enhance the delivery of ecosystem services in the neighbouring field. 4. However, high cover of hedgerows in the landscape enhanced aphid parasitism (from 12 to 18%) and potential pollination (visitation rate and seed set increased up to 70%) irrespective of local margin quality. The cover of arable land in the landscape reduced the abundance of plant-dwelling predators and weed diversity, but did not affect the delivery of the investigated ecosystem services. 5. Synthesis and applications. Our results highlight the key importance of the surrounding landscape context, rather than local factors, to the delivery of ecosystem services. This suggests a need for new policies that pay particular attention to the conservation of hedgerows at large scales for promoting multiple ecosystem services in agroecosystems. Specifically, hedgerows can serve to develop a network of ecological corridors that can facilitate the movement of beneficial organisms, such as pollinators and natural enemies in the agricultural matrix. Such interventions may be a 'low cost-high benefit solution', since farmers can create or conserve high-quality habitats taking little or no land from crop production and without the need to change their crop management.

Context Implementing heterogeneous rural landscapes with high agricultural diversity and a substantial proportion of natural habitats has been proposed to ensure food production while reducing negative impacts on ecosystem services. However, evidence of an increased supply of ecosystem services (ES) in more heterogeneous landscapes remains limited, with no consensus. Objectives To evaluate the effect of the spatial cropland system’s diversity and landscape configuration on indicators of the supply of ES in agricultural landscapes of the Rio de la Plata Grasslands region. Methods We analyzed the relationship between indicators of ES supply and the heterogeneity of 1121 microwatersheds. We assessed the Ecosystem Services Supply Index (ESSI), the Hydrological Yield (HY), and the Absorbed Photosynthetically Active Radiation (APAR) in agricultural areas. We calculated the average grassland patch area, the structural and functional cropland diversity, the cropland percentage, and the grasslands’ juxtaposition to assess landscape heterogeneity. Results Microwatersheds with higher cropland functional diversity showed higher values for indicators of ES supply. They were positively related to the ESSI and APAR, and negatively with HY, indicating positive effects on Carbon gains and water regulation processes. In contrast, grasslands’ juxtaposition had opposite effects to those of cropland functional diversity, so the spatial segregation of grasslands favored the ES supply. Conclusions Functional cropland diversification and the segregation of natural grasslands improved proxies of ES and counteracted the negative effects of cropland amount. These findings contribute to the design of multifunctional landscapes and suggest that cropland functional diversity and grassland configuration should be considered in food production systems aimed at preserving ES supply.

Context Intensive agriculture drives insect decline impacting insect-mediated ecosystem services that support production. Crop diversification shows promise in increasing crop productivity and enhancing ecosystem services, however, the impact on biodiversity conservation, particularly of pollinators, is unclear. Objectives Here, we synthesize the mechanisms and current evidence base of how increasing the spatial and temporal diversity of crops within and across agricultural fields can benefit pollinator biodiversity. Methods We focus on research in the highly intensified agricultural regions, in Western Europe and North America, from which we know a lot about pollinator decline, but use inspiration from tropical regions. Results We find that higher crop diversity, with sequentially flowering cultivars, intercropping practices, and a larger coverage of flowering crops, for example through integrating the cultivation of forgotten, novel, and woody crops increases flower resource availability throughout the active flight period of pollinators. All practices can increase landscape heterogeneity, which is further enhanced by decreasing field sizes. As a result, the functional connectivity increases, which improves the flower accessibility within the foraging ranges of pollinators. Conclusions Our review highlights the potential benefit of various crop diversification measures for supporting pollinating insects without taking land out of production, as well as the limitations, including that only a subset of pollinator species may benefit. Empirical evidence suggest that diversification practices could benefit pollinators, but landscape-wide studies are needed to properly evaluate the true potential of crop diversification for pollinator conservation as part of the solution for bending the curve of pollinator decline.