Pollinator-dependent Crops Research Articles

Impact of local practices and landscape on the diversity and abundance of pollinators in an insect-dependent crop

Insects are a functionally diverse group, with economically relevant roles on key ecosystem services, such as pollination. The current trend of biodiversity loss and consequent degradation of ecosystem services delivered by insects is leading to additional pressure on modern agriculture, particularly in crops that depend on insects for pollination. Understanding how insect pollinator diversity varies at local and landscape scales is very important to recognize trends in pollinator populations. The present work quantified the effect of in-field management practices and different landscape types on insect pollinator communities in kiwifruit, a pollinator-dependent crop. Twenty-two orchards were selected and characterized for in-field practices, landscape structure, plant-pollinator interactions, and productivity. We observed that orchards with practices that are less harmful to insect pollinators are related to a higher pollinator diversity and higher abundances of certain wild pollinator groups, although this was not related with increased productivity. Additionally, in the studied production region, agricultural dominated landscapes harbor lower pollinator diversity, lower wild pollinators abundance and higher managed honeybee abundance than forest and herbaceous dominated landscapes, but no differences were detected in productivity among landscape types. In turn, abundance of Bombus spp. and the use of pollination support practices were significantly and positively correlated with orchard productivity. Despite the differences in pollinator communities, comparable yields were observed across different landscape types. Additionally, simple changes towards less harmful agricultural practices and the presence of forest and herbaceous habitats can promote wild pollinators and respective pollination services.

On-farm experiences shape farmer knowledge, perceptions of pollinators, and management practices

Mitigating pollinator declines in agriculturally dominated landscapes to safeguard pollination services requires the involvement of farmers and their willingness to adopt pollinator-friendly management. However, farmer knowledge, perceptions, and actions to support on-farm pollinators and their alignment with science-based knowledge and recommendations are rarely evaluated. To close this knowledge gap, we interviewed 560 farmers from 11 countries around the world, cultivating at least one of four widely grown pollinator-dependent crops (apple, avocado, kiwifruit, oilseed rape). We particularly focused on non-bee crop pollinators which, despite being important pollinators of many crops, received less research attention than bees. We found that farmers perceived bees to be more important pollinators than other flower-visiting insects. However, around 75% of the farmers acknowledged that non-bees contributed to the pollination of their crops, seeing them as additional pollinators rather than substitutes for bees. Despite farmers rating their own observations as being most important in how they perceived the contribution of different crop pollinator taxa, their perception aligned closely with results from available scientific studies across crops and countries. Farmer perceptions were also linked with their pollinator management practices, e.g. farmers who used managed bees for crop pollination services (more than half the farmers) rated these managed bees as particularly important. Interestingly, their willingness to establish wildflower strips or manage hedgerows to enhance pollinator visitation was linked to their ecological knowledge of non-bees or to government subsidies. Farmers adapted practices to enhance pollination services depending on the crop, which indicates an understanding of differences in the pollination ecology of crops. Almost half of the farmers had changed on-farm pollination management in the past 10 years and farm practices differed greatly between countries. This suggests integrated crop pollination measures are being adapted by farmers to reach best pollinator management practices. Our findings highlight the importance of studying local knowledge as a key to co-design locally-adapted measures to facilitate pollinator-integrated food production as ecological intensification tools.

Does agri-environment scheme participation in England increase pollinator populations and crop pollination services?

Agri-environment schemes are programmes where landholders enter into voluntary agreements (typically with governments) to manage agricultural land for environmental protection and nature conservation objectives. Previous work at local scale has shown that these features can provide additional floral and nesting resources to support wild pollinators, which may indirectly increase floral visitation to nearby crops. However, the effect of entire schemes on this important ecosystem service has never previously been studied at national scale. Focusing on four wild pollinator guilds (ground-nesting bumblebees, tree-nesting bumblebees, ground-nesting solitary bees, and cavity-nesting solitary bees), we used a state-of-the-art, process-based spatial model to examine the relationship between participation in agri-environment schemes across England during 2016 and the predicted abundances of these guilds and their visitation rates to four pollinator dependent crops (oilseed rape, field beans, orchard fruit and strawberries). Our modelling predicts that significant increases in national populations of ground-nesting bumblebees and ground-nesting solitary bees have occurred in response to the schemes. Lack of significant population increases for other guilds likely reflects specialist nesting resource requirements not well-catered for in schemes. We do not predict statistically significant increases in visitation to pollinator-dependent crops at national level as a result of scheme interventions but do predict some localised areas of significant increase in bumblebee visitation to crops flowering in late spring. Lack of any significant change in visitation to crops which flower outside this season is likely due to a combination of low provision of nesting resource relative to floral resource by scheme interventions and low overall participation in more intensively farmed landscapes. We recommend future schemes place greater importance on nesting resource provision alongside floral resource provision, better cater for the needs of specialised species and promote more contiguous patches of semi-natural habitat to better support solitary bee visitation.

Increasing wild bee richness and abundance on sequentially flowering cultivars of a pollinator-dependent crop

Many insects have a crucial role as pollinators in both natural ecosystems and agricultural systems. Reports of declining pollinator populations highlight the question how we can support them. Next to semi-natural habitat, different land use types can provide resources for pollinators. However, whether and how different cultivars of pollinator-dependent crops support pollinator populations has not been studied to date. This preliminary study investigated how the abundance of Osmia cornuta and the richness, abundance and community composition of wild pollinators (i.e. wild bees and hover flies) fluctuates throughout the bloom period of three sequentially flowering sweet cherry (Prunus avium) cultivars. Total pollinator richness and abundance increased throughout the bloom period of the different cherry cultivars. This increase was driven by an increase of wild bee richness and abundance, coupled with a decrease of nest-searching bees. The abundance of O. cornuta was found to increase throughout the bloom period. Furthermore, the composition of the pollinator community was significantly different across the different cultivars. Results of this preliminary study reflect the dynamics of wild bee emergence, mating and nest construction, which results in an increase in pollinator diversity and abundance in spring. This study also provides the first evidence that sequentially flowering cultivars of a pollinator-dependent crop can provide complementary floral resources that support complementary pollinator communities. Given the importance of wild pollinators for crop pollination, these results have implications for crop production and pollinator persistence in agricultural landscapes.

Pollinator-dependent crops in Brazil yield nearly half of nutrients for humans and livestock feed

Animal pollination services provide multiple benefits to humanity as they contribute to 35% of global food production and directly account for up to 40% of the dietary nutrient supply to humanity worldwide. Population declines of vertebrate and invertebrate pollination vectors may threaten human nutrition and well-being, particularly where agriculture relies heavily on animal pollinators. We examined the relative differences in nutrient concentrations of 45 leading crops produced throughout Brazil, the world's largest tropical agricultural producer and exporter. We also estimated the overall reductions in nutrient yields under different scenarios of pollinator declines, based on annual agricultural production. Of the 45 top-ranking crops, 29 and 16 were classified as pollinator-dependent and non-dependent, respectively. Pollinator-dependent crops provided 47% of all dietary nutrients supplied in 2017, which had significantly higher concentrations of lipids, vitamin B9, and potassium, while pollinator non-dependent crops provided higher carbohydrate content. Under either a best- or worst-case pollinator declines scenario, we estimate overall nutritional losses of 7.9% and 29.5%, respectively. These losses ranged from 4% to 18% for all macronutrients, 6.8%–26.2% for all minerals, and 2.4%–31.5% for all vitamins. We emphasize the need for land-use strategies that sustain, if not increase pollinator abundance and species diversity to ensure agricultural viability and future food security.

Precision management of pollination services to blueberry crops

While the cultivated area of pollinator-dependent crops is increasing, pollinator availability is decreasing, leading to problems in many agroecosystems. For this reason, pollinator-dependent crop growers often rent beehives to support their pollination requirements to sustain fruit productivity. However, the efficiency of those pollination systems has not been extensively studied. Here, we compared the effect of “precision” pollination (i.e., application of pesticides coordinated with growers, audit of hives, dietary supplementation and individual distribution of hives) with conventional practices (i.e., pesticides applications without coordination with growers and no audit of hives, low maintenance of hives and hives distributed in large groups) on the mean level of pollination and fruit production and quality in blueberry crops. In nine blueberry fields, we measured bee visitation rate to flowers, fruit set, fruit firmness and fruit weight. On average, precision-pollinated plots had 70% more bee visits to flowers and produced 13% more fruits that were 12% heavier and 12% firmer than those obtained through conventional practices. These results showed that pollination efficiency could be improved if key management related to bee strength, distribution and health care are taken into account. Due to these results, we encourage growers and beekeepers to include precision pollination practices to both increase the productivity of blueberry fields and the wellbeing of honey bees within agroecosystems.

Contribution of animal pollination to food nutrient production in Benin-West Africa

BackgroundPollinators play a key role in human food production by improving the yield and quality of crops. Several studies assessed the economic value of pollination services delivered by animals through yield improvement. However, little is known about the contribution of animal pollinators to nutrient production. This study assessed the contribution of animal pollination to nutrient production in Benin. Food and Agriculture Organization data on crop production and United States Department of Agriculture crop composition data of 37 leading crops were used. These crops were categorized into five classes, depending on their degree of dependence on animal pollinators for fruit production.ResultsThe study showed that more than half of the studied crops (56.75%) relies at different levels on animal pollination for fruit production. Minerals, namely fluoride (83.92%) and selenium (52.62%), were the most delivered by animal-pollinated crops. Roughly 50% of lipids outputs and 24% of proteins outputs were obtained from pollinator-dependent crops. Significant outputs of fat-soluble vitamins up to 65% were also attributed to animal pollination. A low contribution of animal pollination (up to 8%) was reported for water-soluble vitamins.ConclusionAnimal-pollinated crops significantly contribute to the supply of nutrients and consequently to nutritional and food security in Benin. Conservation of pollinators should be considered as an important component of food security programs in the country.

Native flower strips increase visitation by non-bee insects to avocado flowers and promote yield

Pollination is an essential ecosystem service for pollinator-dependent crops and plant communities. Apis mellifera L. is by far the most commonly used species to obtain this service in agriculture. However, there is growing evidence of the importance for crop yields of the service provided by wild bees and non-bee insect pollinators. Establishing flower resources in agricultural landscapes is a management practice that can increase insect pollinator populations and improve crop yields. We established perennial native flower strips (NFS) in four avocado orchards in central Chile during autumn 2017. We monitored flower visitors and counted newly formed fruits in avocados near and far from NFS in spring 2019, to assess flower visitor groups, flower visitation rates and fruit numbers. Only A. mellifera visited avocado flowers within bees, whereas both the managed A. mellifera and wild bees were the main visitors to the NFS. NFS increased visitation rates to adjacent avocado of flies, and with a trend for the sum of all non-managed flower visitors (i.e. excluding A. mellifera). However, there were no differences in the rates of A. mellifera visitation to avocados near and far from NFS. Avocado fruit numbers were higher among avocados near NFS than among those farther away. This difference could be due to better pollination by the increased visits to avocado flowers by flies or other wild insects. Therefore, NFS could contribute to crop fruit number, as well as conservation of native flora, wild bees and non-bee pollinators on fruit farms in the “Central Chile” biodiversity hotspot.

Evaluation of Cowpea (Vigna unguiculata) in an Intercropping System as Pollinator Enhancer for Increased Crop Yield

Production of pollinator-dependent crops (PDCs) is increasing. However, pollinators are declining partly due to loss of floral resources. There is urgency to mitigate this decline and the potential risks to the production of PDCs and food security. One way is by promoting farming systems that enhance flower-rich habitats. In a two-year study, Pinkeye Purple Hull and Whippoorwill cowpea varieties attractive to pollinators were intercropped with three PDCs (squash, okra, and watermelon). We evaluated whether cowpea intercrop increases the abundance and diversity of pollinators, other beneficial insects, and crop yield, and decreases the abundance of the brown marmorated stink bug (BMSB). Diverse pollinators were recorded in both years for a total of 80,379, representing seven pollinator families (Andrenidae, Apidae, Crabronidae, Formicidae, Halictidae, Tachinidae, and Vespidae) captured in pan traps, six families (Apidae, Crabronidae, Halictidae, Pyralidae, Tachinidae, and Vespidae) from sticky traps, and five pollinator types (bumble bees, carpenter bees, honeybees, butterflies and moths, and wasps) through direct visual count. Pollinator abundance and diversity was highest on the cowpea-intercropped treatments than controls. PDCs intercropped with cowpea recorded more beneficial insects than BMSB. Okra, squash, and watermelon intercrops produced 7%, 27%, and 54% more fruits than the control, respectively. Our findings indicate that intercropping cowpeas with PDCs attracted more and diverse pollinators and resulted in increased crop yield. However, to optimize pollination, factors such as planting dates to synchronize the flowering of both cowpeas and PDCs should be taken into consideration.

Areas Requiring Restoration Efforts are a Complementary Opportunity to Support the Demand for Pollination Services in Brazil.

Crop pollination is one of Nature's Contributions to People (NCP) that reconciles biodiversity conservation and agricultural production. NCP benefits vary across space, including among distinct political-administrative levels within nations. Moreover, initiatives to restore ecosystems may enhance NCP provision, such as crop pollination delivered by native pollinators. We mapped crop pollination demand (PD), diversity of pollinator-dependent crops, and vegetation deficit (VD) (vis-a-vis Brazilian legal requirements) across all 5570 municipalities in Brazil. Pollinator-dependent crops represented ∼55% of the annual monetary value of agricultural production and ∼15% of the annual crop production. Municipalities with greater crop PD (i.e., higher degree of pollinator dependence of crop production) also had greater VD, associated with large properties and monocultures. In contrast, municipalities with a greater diversity of pollinator-dependent crops and predominantly small properties presented a smaller VD. Our results support that ecological restoration prompted by legal requirements offers great potential to promote crop productivity in larger properties. Moreover, conservation of vegetation remnants could support food security in small properties. We provided the first steps to identify spatial patterns linking biodiversity conservation and pollination service. Using Brazilian legal requirements as an example, we show that land-use management policies may be successfully used to ensure agricultural sustainability and crop production.

A global-scale expert assessment of drivers and risks associated with pollinator decline.

Pollinator decline has attracted global attention and substantial efforts are underway to respond through national pollinator strategies and action plans. These policy responses require clarity on what is driving pollinator decline and what risks it generates for society in different parts of the world. Using a formal expert elicitation process, we evaluated the relative regional and global importance of eight drivers of pollinator decline and ten consequent risks to human well-being. Our results indicate that global policy responses should focus on reducing pressure from changes in land cover and configuration, land management and pesticides, as these were considered very important drivers in most regions. We quantify how the importance of drivers and risks from pollinator decline, differ among regions. For example, losing access to managed pollinators was considered a serious risk only for people in North America, whereas yield instability in pollinator-dependent crops was classed as a serious or high risk in four regions but only a moderate risk in Europe and North America. Overall, perceived risks were substantially higher in the Global South. Despite extensive research on pollinator decline, our analysis reveals considerable scientific uncertainty about what this means for human society.

Socioecological Factors and Farmer Perceptions Impacting Pesticide Use and Pollinator Conservation on Cucurbit Farms

While research suggests that pollinator decline is linked with agricultural practices, it is unclear whether farmers share this view and adapt management to promote pollinators based on their understanding of these threats. To address these issues, we surveyed farmers of pollinator-dependent cucurbit crops across four states in the Midwest, USA. We grouped farmers by their perceptions of pollinator declines and routes of pesticide exposure and used statistical models to evaluate if farmers manage pests and pollinators based on these perceptions. Out of 93 completed surveys, 39% of farmers believed pollinators were in decline. When grouped, 17% of farmers were classified as proponents, ranking (on a 1–5 Likert scale) the factors mediating pesticide exposure and pollinator declines as important or highly important. For comparison, 44 and 39% of farmers were classified as neutral or skeptical, respectively, of these same factors. Compared to the neutral and skeptic groups, proponents were on average younger, had fewer years farming but more years in family farming, and were more dependent on income from outside the farming system. Proponents also on average reported smaller farms, higher pest richness, more land in cucurbit production, and greater richness of crops that are not pollinator dependent, when compared to the neutrals and skeptics. We did not find pest and pollinator management to be related to farmer perceptions of pollinator decline or routes of pesticide exposure, but farmers classified as pollinator “proponents” were more likely to indicate participation in future pollinator habitat restoration programs. Rather, management strategies were better explained by on-farm environmental conditions (e.g., pest richness, farm size, number of pollinator dependent crops) and economic factors (e.g., sources of income). Generally, our research shows that farmers who perceive pollinator threats may not be using pollinator supportive practices. Thus, while some farmers believe in pollinator declines, there remains a need to connect this knowledge with on-farm practices.

Insect pollination enhances yield stability in two pollinator-dependent crops

One of the most important challenges facing global agriculture is to ensure an adequate, stable food supply while conserving soil, water and biodiversity. The yield stability of pollinator-dependent crops, such as pear and apple, can be negatively affected by variability of the pollination service, which in turn can reduce mean yield. We explored how mean crop yield and yield variability were affected by pollinators and variability in their provision of the pollination service. Over four seasons we conducted a manipulative experiment in six pear and eight apple farms; fruit set (i.e., no. fruits/ no. flowers) was compared between flowers exposed to pollinators and those excluded from pollinators. We also recorded pollinator visitation rate to exposed flowers. We estimated the mean levels and spatial and temporal variability of both pollinator visitation and yield response by calculating the mean values per farm and the spatial (i.e., across trees within farm) and temporal (i.e., across seasons within farm) coefficients of variation (CV) for visitation rate and fruit set. Despite homogeneous irrigation and fertilization, we found strong variability in fruit set in both crops (pear spatial and temporal CV: 0.57 and 0.4, respectively; apple: 0.62 and 0.52). Pollinator exclusion reduced mean fruit set considerably in both crops (pears: a reduction of 50%, apples: 71–92%), and increased spatial and temporal variability (pears: 296% and 197% for spatial and temporal variability, respectively; apples: 385% and 329%). Visitation rates in pears were positively associated with mean fruit set and negatively related to its spatial CV. Also, in this crop we found a positive relation between the spatial CV of visitation rate and fruit set. However, there was no evidence that visitation rate in open-pollinated apple flowers affected either mean fruit set or its spatial or temporal variability. Apple trees received one order of magnitude more visits per flower than pear trees, suggesting that in this system the pollination service meets the pollination demand of the apple crop. Overall, our results highlight the importance of management practices that prioritize pollination service, thus ensuring a high, stable yield.

Nocturnal Pollinators Significantly Contribute to Apple Production.

Agricultural dependency on insect-mediated pollination is increasing at the same time that pollinator populations are experiencing declines in diversity and abundance. Current pollinator research in agriculture focuses largely on diurnal pollinators, yet the evidence for pollination by moths and other nocturnal pollinators is growing. Apples are one of the most valuable and important fruits produced globally, and apple production is dependent on insect-mediated cross-pollination to generate a profitable crop. We examined contributions to apple production provided by nocturnal insects via an exclusion experiment. We compared the relative contributions to apple production provided by nocturnal and diurnal pollinators using fruit set, the likelihood of cluster pollination, and seed set. We found nocturnal pollinators capable of facilitating the production of as many apples at similar levels of pollination as diurnal pollinators. We further found evidence that nocturnal and diurnal pollinators pollinate synergistically, with pollination contributions being additive in one year of our study. Our research identifies significant contributions to apple production provided by nocturnal pollinators, which may interact with diurnal pollinators in ways that are currently unrecognized. Expansions of this research into additional pollinator-dependent crops and focused investigations on specific nocturnal insects will provide more accurate assessments of nocturnal-pollinator roles in agriculture and improve our overall understanding of pollination in agriculture.

Evaluating honey bee foraging behaviour and their impact on pollination success in a mixed almond orchard

Although Apis mellifera is the dominant managed pollinator used to enhance crop production, the variation of its foraging behaviour among crop-cultivars is not considered as a factor influencing pollination success and, thus, yield. Almond production is highly dependent on cross-pollination. Herein, we examined honey bees foraging behaviour and pollen limitation in ‘Nonpareil’ and ‘Independence’ cultivars. Nectar and pollen-foragers differed in the flower handling behaviour, regardless of the cultivar. However, most bees on ‘Independence’ flowers collected pollen in the morning and bees exhibited less floral constancy in this cultivar, potentially promoting cross-pollination. Also, supplementation of ‘Nonpareil’ flowers with ‘Independence’ pollen had a positive effect in nut-set, suggesting that higher visitation rates are needed to increase yield. Our study underlines the importance of integrating behavioural knowledge of pollinators to optimize practices in pollinator-dependent crops.

Supplemental forage ameliorates the negative impact of insecticides on bumblebees in a pollinator-dependent crop.

Insecticide use and insufficient forage are two of the leading stressors to pollinators in agroecosystems. While these factors have been well studied individually, the experimental designs do not reflect real-world conditions where insecticide exposure and lack of forage occur simultaneously and could interactively suppress pollinator health. Using outdoor enclosures, we tested the effects of insecticides (imidacloprid + lambda-cyhalothrin) and non-crop forage (clover) in a factorial design, measuring the survival, behaviour and performance of bumblebees (Bombus impatiens), as well as pollination of the focal crop, watermelon. Colony survival was synergistically reduced to 17% in watermelon alone + insecticides (survival was 100% in all other treatments). However, behavioural shifts in foraging were mainly owing to insecticides (e.g. 95% reduced visitation rate to watermelon flowers), while impacts on hive performance were primarily driven by clover presence (e.g. 374% increase in the number of live eggs). Insecticide-mediated reductions in foraging decreased crop pollination (fruit set) by 32%. Altogether, these data indicate that both insecticides and non-crop forage play integral roles in shaping pollinator health in agricultural landscapes, but the relative importance and interaction of these two factors depend on which aspect of ‘health’ is being considered.

Seasonal dynamics of plant pollinator networks in agricultural landscapes: how important is connector species identity in the network?

Farm habitat enrichment is crucial for sustainable production of pollinator-dependent crops. Correct choice of crop and non-crop plant species in habitat management support resilient pollinator fauna and effective pollination service delivery. We identify key network metrices to recognize suitable crop and non-crop plant species for farm habitat enrichment. We also highlight the importance of seasonal variation of the key plant and pollinator species that will crucially inform farm management. Crop species played a key role in maintaining plant-pollinator network integrity. In contrast to the conventional practice of focussing on non-crop plants for pollination service restoration, we find crop plants across seasons hold a key role in maintaining healthy plant-pollinator networks. Our study highlights the importance of non-bee pollinators especially, flies and butterflies in sustaining healthy plant-pollinator network. Bees were important as connector species and controlled other species in the network. Only 16.67% bees and 33.33% of plant species acted as connector species. Our study also shows that the identity of connector species in a plant-pollinator network can change drastically across seasons.

Temporal Trends in Pollination Deficits and Its Potential Impacts on Chinese Agriculture.

Worldwide, there is increasing evidence that shows a decline in pollinators, limiting crop pollination and production. However, it is unclear to what extent Chinese agriculture could be impacted by pollinator deficits. Data for 84 major crops in China between 1961 and 2018 were analyzed for the temporal trends in crop area and production, agricultural economic contribution of pollination, crop yield deficits, and honey bee pollination demand. We found a rapid increase in agricultural dependence on insect pollinators: both the cultivated area and total production of pollinator-dependent crops increased faster than those of pollinator-independent crops during 1961-2018. The total economic value of pollination amounted to US$ 106.08 billion in 2010, representing 19.12% of the total production value of Chinese agriculture, approximately twice the 9.5% value estimated for global agriculture. Crops with higher pollinator dependence showed greater mean growth in cultivated area than those with lower dependence, but lower mean growth of crop production and yield. Crop yield growth was also more unstable with increasing pollinator dependence. The minimum pollination demand for honey bee colonies was about three times the stock of honey bee colonies available in 2018. Furthermore, we found a decline in crop yield deficit with the increase in honey bee colony pollination service capacity. We considered that the shortage of pollinators resulted in the yield deficits for pollinator-dependent crops. Future increase in the area of pollinator-dependent crops will increase the need for more pollinators, suggesting the importance of implementing measures to protect pollinators to ensure a better-secured future for agricultural production in China.

The melliferous flora of Veracruz, Mexico

Objective: To contribute to the knowledge of the situation of the melliferous flora in Veracruz for pollinators and to communicate it for the benefit of beekeepers and stingless beekeepers, as well as to develop comprehensive strategies with these activities. Design/Methodology/Approach: The information was obtained through a bibliographic review in reference databases such as Scopus, Web of Science Group, Academic Google, Elsevier and Springer Link, using the following keywords: flora, bees, pollinators, honey, pollen. Results: 63 families were recorded, with 176 genera and 216 species of melliferous flora, finding that the largest number of species are found in the Fabaceae family (20%) and Asteraceae (16.55%). There were also 44 crops with 22 families. Study Limitations/Implications: There were no limitations in conducting this study. Findings/Conclusions: The greatest diversity of melliferous flora species is seen in wild plants, and strategies need to be implemented for their protection and multiplication. For these actions, various actors must be involved at different levels of government, educational and private institutions, civil society, farmers, beekeepers, and stingless beekeeping. Conservation actions include the use of melliferous plants in gardens and their protection in crops, sites surrounding crops and on edges. It is necessary to preserve natural landscapes and restore damaged ones, as well as to lead favorable practices in pollinator-dependent crops.

Resampling of wild bees across fifteen years reveals variable species declines and recoveries after extreme weather

Despite concerns about the status of wild bees, there have been few studies with repeated sampling of these insects at the same locations using the same method. There is an urgent need for longitudinal studies to understand species- and population-level dynamics and the drivers of change, especially in pollinator-dependent crop systems. We sampled wild bees in highbush blueberry fields in three multi-year sampling periods between 2004 and 2018 to determine changes in the wild bee community active during bloom. We captured 35% (162 species) of the known Michigan bee fauna across the three sampling periods. Andrena, Lasioglossum and Ceratina were the dominant genera, though species composition varied significantly between sampling periods. Wild bee abundance (measured as captures in the pan traps) declined 61% and richness declined 33% between the first (2004–2006) and second (2013–2014) sampling periods. This was followed by limited recovery in species abundance and richness in the third sampling period (2017–2018). Some species showed dramatic abundance declines, particularly the blueberry specialist Andrena carolina. By contrast, other species showed stable or increasing prevalence, and population trajectories were not correlated with life history traits. Potential causes of the observed decline include increased use of insecticides and extreme spring weather in 2012. While farms varied in pest management intensity and overall insecticide program risk increased over time, there was no correlation between bee declines and insecticide use. Insecticide program risk increased between the second and third sampling periods, while most species increased in abundance. We therefore conclude the observed declines were most likely caused by extreme spring weather in 2012 resulting in widespread damage to flowering plants that provide resources for bees. Long-term monitoring to identifying species more vulnerable to environmental perturbations can help guide conservation recommendations as extreme weather events become more common.