Progress 07/01/20 to 12/30/22
Outputs
Target Audience:This work reached growers and industries reliant on bumble bees for pollination services, as well as the scientific communities interested in the impacts of climate change on plant-insect and plant-pollinator interactions. Specifically, we interfaced with the California Almond Board and a variety of small CSA farms throughout the Central Valley in the region surrounding Davis, CA. For the scientific community, the work described here was presented at two international conferences in North America and Europe/UK. Changes/Problems:The COVID-19 pandemic required us to deviate slightly from the proposed research due to international travel restrictions as well as local restrictions in research activity. We detailed many of these in our 2020 annual report. What opportunities for training and professional development has the project provided?Several parties have received training opportunities through this project. (1) The postdoctoral scholar this project was awarded to has gained experience in project management, grantsmanship, and developed a variety of new skillsets associated with studying long-term climatological patterns at large, continental scales. Moreover, the postdoc has gained valuable experience in mentoring a graduate student that was an equal collaborator on the work published in Functional Ecology, as well as two undergraduate researchers who assisted conducting the 2022 field work using remote cameras to link ambient environmental conditions to pollinator activity. How have the results been disseminated to communities of interest?Our results have been disseminated via publications (1 out, 3 additional pending), professional conference presentations, and meetings with interested stakeholder groups such as the California Almond Board. What do you plan to do during the next reporting period to accomplish the goals?
Nothing Reported
Impacts
What was accomplished under these goals?
Over the past several years, a number of record-breaking heatwaves have brought the impending climate-crisis to the forefront of the minds of scientists, growers, policymakers, and citizens alike. These events have led to massive losses in crop yields due to the direct stress of heat on developing fruits, seeds, and vegetation. Many of these crops, dependent on insects for pollination, have also experienced losses, however the extent to which losses are due to reductions in pollination or direct stress on plants is largely unknown. Pollinating insects contribute to the yields of almost 2/3 of economically important crops, as such understanding how extreme heat impacts their behavior, populations, and pollination services is critical. Bumble bees are a group of pollinating insects that may be especially vulnerable to increases in extreme heat. These large-bodied bees that are essential pollinators of squash, melons, blueberries, cranberries, beans, and cucumbers, are adapted for relatively cool conditions below 85F. Recent heatwaves have led to temperatures far exceeding this threshold. We have developed a multi-faceted project to explore how bumble bees are impacted by extreme heat and what the consequences are for their behavior, populations and communities, and ultimate the pollination services they provide to economically important crops. 1. Impact of extreme heat on pollinator behavior and plant pollination We developed an experiment to test the impact of simulated heat waves on bumble bee foraging behavior and plant pollination for an economically important crop, canola. We found that heatwaves impacted bumble bee foraging activity directly through thermal stress on the bees, reducing the duration of their foraging bouts by ~50%. Simulated heat waves also reduced nectar production by the canola plants, further reducing how long bumble bees foraged. Bees were far more likely to give up and return to their colony, with many visiting no plants (therefore providing no pollination services) in the face of extreme heat. This ultimately resulted in significant negative effects for plant pollination, with canola plants often receiving effectively no pollination and producing few if any seed pods. This was exacerbated by direct heat effects on the plants themsvles, further reducing yields and, in many cases, leading to the total failure of the crop in many of our experimental plants. These results stress the importance of considering heat as a major factor in pollinator-dependent crop production and suggests that strategies that mitigate heat exposure to insects and crop plants are critical in agricultural landscapes as heat waves become more frequent, longer, and intense. In addition, we explored this same concept in field conditions by examining how pollinator visitation and acitivity levels responded to season-long trends in temperature and naturally occurring heat waves in California's Central Valley. We deployed a series of custom-built, autonomous camera traps to record insect visitation to sunflowers from May-August of 2022. These cameras continuously monitored plots of sequentially planted sunflowers and recorded all pollinator visitations to sunflower heads along with ambient temperature conditions. Over 3 months, we recorded almost 240,000 pollinator visitations and are currently processing and analyzing these data to understand the thermal preferences of the species we observed along with the impacts of heat waves on pollinator activity and services to sunflowers, an economically important crop. 2. Impact of warming summer temperatures on pollinator communities in North America Average temperatures in summer have been steadily increasing over the last century, with some of the most dramatic increases occurring in the last 15 years. The 2010's was the hottest decade on record, and such dramatic, quick increases in temperature may have significant implications for cold-blooded insect communities that are entirely dependent on ambient temperatures for their phenology, activity, and reproduction. We explored whether one group of heat-sensitive pollianators, bumble bees, have responded to the steady increase in summer temperature through changes in their range and relative abundance. That is, as locations warm, we may expect certain, more heat-tolerant species to thrive while those preferring cooler conditions to struggle, leading to a shift in the balance of bumble bee communities. We have found that, across North America, there has been a substantial shift in the balance of bumble bee communities, with most becoming increasingly dominated by heat-tolerance species. These changes are strongly related to long-term summertime maximum temperature trends. We found that the changes are most pronouced within ecologically at-risk regions such as the high-arctic and high-elevation, mountainous regions. On average, the bumble bee community temperature index, a measure of the balance of heat and cool-tolerant species, has increased by 1°C. While this may seem small, this is akin to an almost 1000km range shift in bumble bee communities. Particularly alarming is that the changes in bumble bee communities appear to be accelerating and have been increasing in magnitude since 2010. This analysis provides some of the most convincing evidence yet that ongoing climate change is rapidly affecting biological and ecological communities, with some species losing out those that are more adaptable and tolerant of a wide range of environmental conditions.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2022
Citation:
Hemberger, J. A., Rosenberger, N. M. & Williams, N. M. Experimental heatwaves disrupt bumblebee foraging through direct heat effects and reduced nectar production. Funct Ecol (2022) doi:10.1111/1365-2435.14241.
- Type:
Journal Articles
Status:
Under Review
Year Published:
2022
Citation:
Hemberger, J., Bernauer, O., Gaines-Day, H., Gratton, C. Landscape-scale floral resource discontinuity decreases bumble bee occurrence and alters community composition. In review, Journal of Applied Ecology
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2022
Citation:
Experimental heat waves disrupt bumble bee foraging through direct heat effects and reduced nectar
production. Climate Science for Ecological Forecasting. London, UK
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2022
Citation:
Experimental heat waves disrupt bumble bee foraging through direct heat effects and reduced nectar
production. Climate Science for Ecological Forecasting. Joint Annual Meeting of Entomological Society of America, Entomological Society of Canada
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Progress 07/01/21 to 06/30/22
Outputs
Target Audience:This work is intended for growers and industries reliant on bumble bees for pollination services, as well as the scientific community writ large for which this work can serve as a framework to evaluate heat wave impacts on other taxa. Additionally, my intent is to share this work with the public via outreach and educational experiences not limited to classroom instruction, community science events, websites, and popular press articles. Changes/Problems:Due to the ongoing effects of the COVID-19 pandemic, our approach for objective 2 was forced to shift from an individual based modeling (IBM) approach to understand the consequences of extreme heat on foraging behavior to a community-based assessment of ongoing global climate change. The reason for this is that the IBM was meant to be a collaboration with colleagues in the EU who had developed a prototype model. The necessary travel and meetings to develop this model further were not easily attainable given COVID travel restrictions and concerns over COVID variants that raised case numbers considerably. What opportunities for training and professional development has the project provided?PD Hemberger was able to attend a workshop and conference in the UK in May, 2022 to share the results of the experiment for Objective 1, as well as the Entomological Society of America's North Central Branch meetings in March, 2022. Additionally, PD Hemberger presented a seminar for the University of Minnesota Department of Entomology describing all NIFA sponsored work thus far. How have the results been disseminated to communities of interest?Thus far, we have one manuscript current in review, but are still in the process of developing materials that share our results to grower, government, and agency groups that this work is germane to. What do you plan to do during the next reporting period to accomplish the goals?Over the next reporting period, we will continue to develop our community-based assessment of climate change impacts on bumble bees across North America. In addition, we aim to develop materials specific to agricultural regions that may be impacted by reductions in bumble bee foraging or occurrence as a result of extreme heat or long-term changes in summer temperatures.
Impacts
What was accomplished under these goals?
There has been a substantial increase in the frequency, duration, and intensity of extreme heat events. These events pose a clear, direct risk for agricultural operations through direct impacts on crop plants, as well as critical organisms that facilitate plant production, such as pollinators. Bumble bees, an important group of insect pollinators for a variety of crops, are particularly susceptible to these periods of extreme heat due to their life-history and adaptation to cooler, temperate conditions. In this project, we aim to quantify the response of bumble bees to extreme heat through targeted experiments, and large-scale eco-informatics ("big data") approaches. In 2021, we completed a large experiment designed to understand the interaction of direct and indirect effects of simulated heatwaves on bumble bee foraging behavior on canola, an economically important crop in the US, Canada, and the EU. We found that temperatures simulating a moderate heatwave negatively impacted bumble bee foraging by reducing the number of successful foraging trips that bees take, reducing how long bees spend out foraging, and reducing the number of plants that bees visit. These effects were due to both direct (heat stressing foraging bees) and indirect (reductions in nectar production by heat stressed plants) mechanisms. Our results show the first mechanistic link between climate change, plants, and pollinators and suggest that conditions from heatwaves may have profound, negative consequences for bumble bees and the pollination services they provide (Objective 1). Given the results of our work under objective 1, we expected that the increasing trend in extreme heat events and average temperatures, generally may have an impact on bumble bees beyond their foraging behavior. For example, long-term trends of increasing summer temperatures may impact bumble bee species persistence and ranges, shifting communities in accordance with their tolerance to new temperature extremes. To address this, we have taken an eco-informatics approach, analyzing several "big data" sets to link long-term changes in summer temperatures to shifts in bumble bee communities. In this work, we have found that there has been a substantial shift in bumble bee community composition, and this shift is partially explained by a recent increase in summer temperatures (specifically from 2010 to present). Bumble bee community composition has shifted most drastically in the inter-mountain west, but also throughout major crop growing regions in the US Midwest, Central Valley, and Pacific Northwest. We are now exploring methods to determine which species are largely responsible for these shifts, and what this may mean for agricultural regions that contain pollinator-dependent crops that are serviced by bumble bee communities (Objective 2)
Publications
- Type:
Journal Articles
Status:
Submitted
Year Published:
2022
Citation:
Hemberger, J.A., Rosenberger, N.M., Williams, N.M. Experimental heat waves disrupt bumble bee foraging through direct effects and reduced nectar production. Under review, Functional Ecology
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2022
Citation:
Hemberger, J.A., Rosenberger, N.M., Williams, N.M. Experimental heat waves disrupt bumble bee foraging through direct effects and reduced nectar production. Climate Science for Ecological Forecasting. London, UK. May 2022
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Progress 07/01/20 to 06/30/21
Outputs
Target Audience:This work is intended for growers and industries reliant on bumble bees for pollination services, as well as the scientific community writ large for which this work can serve as a framework to evaluate heat wave impacts on other taxa. Additionally, my intent is to share this work with the public via outreach and educational experiences not limited to classroom instruction, community science events, websites, and popular press articles. Thus far, we have sent outreach documents to those in the Davis community and several growers on the Yolo county region. Changes/Problems:The COVID-19 pandemic prevented almost all of our planned field experiments and delayed many laboratory experiments by 6-8 months. We are still planning to pursue all objectives to the fullest extent possible, but field validation of laboratory experiments may be limited due to time constraints associated with the end of the project period. We will plan to use results from laboratory experiments in our second modeling objective if field validation is not possible. What opportunities for training and professional development has the project provided?Given the COVID-19 pandemic, training and PD opportunities were limited. PD Hemberger presented his research at the annual meetings of the Entomological Society of America in November of 2020. How have the results been disseminated to communities of interest?We participated in community outreach during UC Davis' annual picnic day which was held virtually this year. In this, we disseminated info graphics to explain the importance of our research activities. Given the large increase in extreme heat in California, audiences were heartened to see ongoing efforts to understand how these novel conditions will impact California pollinators. What do you plan to do during the next reporting period to accomplish the goals?We have begun experimental protocols in earnest following successful pilot studies of bumble bee foraging in climate-controlled laboratory flight chambers. The conclusion of these experiments will provide a suite of data describing temperature thresholds and predicted demographic impacts of extreme heat and heat waves. We will then use these data in conjunction with our climate models (see accomplishments) to create predicted maps of bumble bee and crop pollination risk.
Impacts
What was accomplished under these goals?
Thus far, we have developed and piloted several experimental protocols to measure the foraging and colony growth response of bumble bees to extreme heat in the lab utilizing heated foraging chambers and managed colonies of bumble bees. Additionally, we have collated, geocorrected, and modeled extreme heat from 2000-2100 for the study region in California to be used to identify regions of relative risk with the results of lab and field experiments.
Publications
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