Pollinator Conservation

Recent scientific literature reviews have shown that changing habitats are the greatest driver of insect and pollinator decline [6].

Habitat loss reduces the availability of the floral resources (such as nectar, pollen, floral oils, and resins), nest materials, and nest sites that pollinators need. Changes in habitat can also shift the normal parasites and predators a pollinator may be exposed to in an area [7]. When habitat loss isolates pollinators in one area or prevents them from moving between remaining habitats, this can reduce population sizes and genetic diversity. As a result, there is a greater chance that pollinators will become locally extinct and become less able to adapt to changing environments. Pollinators who can’t move far distances between these extant patches, or those who specialize in a specific habitat are particularly threatened by habitat loss [6].

Most of today’s habitat losses are driven by expanding agriculture and urbanization. The main drivers of pollinator habitat loss include agriculture and urbanization. Agriculture accounts for a huge portion – 37% – of global land use according to recent FAO estimates [8]. Oftentimes, agricultural land is a poorer habitat for pollinators. For example, one study that compared farm fields to regional bee diversity found that 95% of bees are not present in agricultural fields [9]. This is because agriculture replaces diverse communities of native host plants with few crop species and frequent disturbance and pollution from mechanical tilling, crop rotation, and pesticides [7]. Likewise, expanding urban landscapes are heavily transformed compared to the natural landscapes they replace. Many square miles of pavement, commercial and residential developments, and introduced garden plant species do not provide the floral resources or nest sites that pollinators need [7].

Pesticides are an integral part of conventional agriculture. Insecticides, herbicides and fungicides help maximize crop quantity and quality by reducing the pests and diseases that cause damage. Unfortunately, non-target organisms such as pollinators can come in contact with these pesticides while foraging. In addition, beekeepers also apply pesticides to their colonies to control Varroa mites.

Pollinator exposure to pesticides is pervasive. For example, scientists have found traces of pesticides in honey bee hives including in the pollen, honey, wax, and adult bees [10–13]. Cornell’s own New York State Beekeeper Tech Team found thiamethoxam, a neonicotinoid insecticide posing high risk to bees, present in 39% honey bee colonies across New York in 2021 [3, 14]. While pesticide testing almost always occurs in honey bees (a pollinator that is not native to North America), one study found 19 out of the 136 pesticides they screened for in the bodies of foraging wild bees. These pesticides included neonicotinoid insecticides, fungicides, and herbicides [15].

Unfortunately, research is becoming clear that some pesticides are harmful for pollinators. Even if a pollinator doesn’t die soon after contact with a pesticide, there can be many less-than-lethal (or sublethal) effects on pollinators. These include reductions in brain function, foraging and nest locating ability, growth, and reproduction, and even reductions in egg laying [6, 7, 16]. In social pollinators, pesticides can impact colony growth, overwintering, and honey production. Pesticides can even impact bee immune systems [17, 18], and indirectly make bees more susceptible to pathogens and disease, particularly those spread by non-native or managed bee species [19].

For more information about the impacts of pesticides, particularly neonicotinoid insecticides on New York’s pollinators, please review our 2020 Neonicotinoid report.

Oftentimes, humans move plants and animals from their native region to places they are not normally found for their agricultural or aesthetic value, including pollinators and plants.

A recent survey in Rochester, NY, found that, on average, 72% of the plants in suburban gardens are not native to the Eastern US [20]. While garden plants have aesthetic value for humans, they have been bred for their showy blooms, and provide little, if any, nectar or pollen for pollinators. Without natural predators or diseases, introduced plants can become invasive and displace populations of native plants. This is a problem, because New York’s native pollinators have evolved with native plants and cannot forage on exotic species.

Many important agricultural pollinators are not native to New York, either. Several species of leafcutting bees (genus Megachile), mason bees (genus Osmia), and bumble bees (genus Bombus) have been introduced to the US for crop pollination. Even the western honey bee (Apis mellifera) was once introduced to North America.

Sometimes, introduced pollinators and native pollinators depend on the same host plants. This is called interspecific competition and is the most studied interaction between native and non-native bees. A recent review of scientific literature found that most studies – 53% – report managed bee species have a negative effect on wild bees through interspecific competition [21]. With non-native bees using the host plants native bees prefer, wild bees can be forced to shift to less desirable and nutritious plants, or forage longer and farther from their nest to find unoccupied resources [21]. This is especially true when floral resources are scarce.

Introduced bees can also transmit diseases to native bees in a process called spillover. Studies show that introduced honey bees are the source of viruses and parasites in wild bumble bee colonies [22, 23]. In Upstate New York, honey bees share parasites with 46 other bee species [24]. A growing body of research including studies like these point to a clear conclusion: that diseases in managed bees pose risks to wild bees [21].

That said, factors such as habitat quality, landscape heterogeneity, and prevalence of diseases within managed bee populations likely determine whether and how much introduced plants and pollinators impact native pollinators.

Scientists are already beginning to see the impact of changing climates on pollinator populations. As average temperatures rise, the geographic distribution of pollinators and other insects adapted to warm environments has increased, while the species that are adapted to colder environments are decreasing [19]. For example, one long-term study found that climate change reduced the number of butterfly species and the amount of habitat available within California’s Sierra Nevada mountains [25]. As the climate changes, we can expect this trend to continue: climate change may alter the geographic distribution of bee species, and cause range reductions or habitat fragmentation.

Shifts in temperatures and precipitation can even change the plants that pollinators depend on. This can change quantity or quality of floral resources. For example, the number and size of flowers, and the amount of pollen and nectar, and even the quality of protein in pollen are impacted by warming temperatures and rising levels of carbon dioxide [7].

Changing climates can also alter the times at which flowers bloom and when bees forage. One review of eastern North American bee specimens revealed that bees and flowering plants are active, on average, 10 days earlier in the spring, and that this relationship correlates with the rise in global temperatures [26]. If climate change continues to cause these times to differ, then both bee and plant reproduction will be impacted.

1. Gallai, N., Salles, J.-M., Settele, J., & Vaissière, B. E. (2009). Economic valuation of the vulnerability of world agriculture confronted with pollinator decline. Ecological Economics, 68(3), 810–821. https://doi.org/10/dg3sph
2. Calderone, N. W. (2012). Insect Pollinated Crops, Insect Pollinators and US Agriculture: Trend Analysis of Aggregate Data for the Period 1992–2009. PLOS ONE, 7(5), e37235. https://doi.org/10/f3zv78
3. Grout, T. A., Koenig, P. A., Kapuvari, J. K., & McArt, S. H. (2020). Neonicotinoid Insecticides in New York State: economic benefits and risk to pollinators. Cornell University. https://cornell.app.box.com/v/2020-neonicotinoid-report
4. White, E. L., Schlesinger, M. D., & Howard, T. G. (2022, June 30). The Empire State Native Pollinator Survey (2017-2021). New York Natural Heritage Program. https://www.nynhp.org/projects/pollinators/
5. Bee Informed Partnership. (2022). National Management Survey Map. Retrieved July 26, 2022, from https://research.beeinformed.org/loss-map/
6. Vanbergen, A. J., Mathilde Baude, Jacobus C Biesmeijer, Nicholas F Britton, Mark JF Brown, Mike Brown, … Geraldine A Wright. (2013). Threats to an ecosystem service: pressures on pollinators. Frontiers in Ecology and the Environment, 11(5), 251–259. https://doi.org/10/f42bz2
7. Danforth, B. N., Minckley, R. L., Neff, J. L., & Fawcett, F. (2019). The solitary bees: biology, evolution, conservation. Princeton: Princeton University Press.
8. Food and Agriculture Organization of the United Nations. (2022, July 15). Land Use. FAOSTAT. Retrieved September 9, 2022, from https://www.fao.org/faostat/en/#data/RL
9. Kleijn, D., Winfree, R., Bartomeus, I., Carvalheiro, L. G., Henry, M., Isaacs, R., … Potts, S. G. (2015). Delivery of crop pollination services is an insufficient argument for wild pollinator conservation. Nature Communications, 6(1), 7414. https://doi.org/10/f3m2zc
10. Kubik, M., Nowacki, J., Pidek, A., Warakomska, Z., Michalczuk, L., Goszczyñski, W., & Dwuzpnik, B. (2000). Residues of captan (contact) and difenoconazole (systemic) fungicides in bee products from an apple orchard. Apidologie, 31(4), 531–541. https://doi.org/10/cb4nsd
11. Simon-Delso, N., San Martin, G., Bruneau, E., Minsart, L.-A., Mouret, C., & Hautier, L. (2014). Honeybee Colony Disorder in Crop Areas: The Role of Pesticides and Viruses. PLoS ONE, 9(7), e103073. https://doi.org/10/ghbxb3
12. Pettis, J. S., Lichtenberg, E. M., Andree, M., Stitzinger, J., Rose, R., & vanEngelsdorp, D. (2013). Crop Pollination Exposes Honey Bees to Pesticides Which Alters Their Susceptibility to the Gut Pathogen Nosema ceranae. PLoS ONE, 8(7), e70182. https://doi.org/10/gfvpsv
13. Sánchez-Bayo, F., & Goka, K. (2014). Pesticide Residues and Bees – A Risk Assessment. PLoS ONE, 9(4), e94482. https://doi.org/10/ghf6mp
14. Hinsley, C. A., Parry, S., Mahoney, J., Wyns, D., Fauvel, A. M., & Walters, E. K. (2022). 2021 New York State Beekeeper Tech Team Report. Cornell University. https://cornell.app.box.com/v/2021-tech-team-annual-report
15. Hladik, M. L., Vandever, M., & Smalling, K. L. (2016). Exposure of native bees foraging in an agricultural landscape to current-use pesticides. Science of The Total Environment, 542, 469–477. https://doi.org/10/gqx4qw
16. Mader, E., Shepherd, M., Vaughan, M., Hoffman Black, S., & LeBuhn, G. (2011). Attracting native pollinators: protecting North America’s bees and butterflies: the Xerces Society guide. North Adams, MA: Storey Pub.
17. Sánchez-Bayo, F., Goulson, D., Pennacchio, F., Nazzi, F., Goka, K., & Desneux, N. (2016). Are bee diseases linked to pesticides? — A brief review. Environment International, 89–90, 7–11. https://doi.org/10/gphj8x
18. Tesovnik, T., Cizelj, I., Zorc, M., Čitar, M., Božič, J., Glavan, G., & Narat, M. (2017). Immune related gene expression in worker honey bee (Apis mellifera carnica) pupae exposed to neonicotinoid thiamethoxam and Varroa mites (Varroa destructor). PLOS ONE, 12(10), e0187079. https://doi.org/10/gqx4qx
19. Sánchez-Bayo, F., & Wyckhuys, K. A. G. (2019). Worldwide decline of the entomofauna: A review of its drivers. Biological Conservation, 232, 8–27. https://doi.org/10/gfvb6r
20. Ward, S. G., & Amatangelo, K. L. (2018). Suburban gardening in Rochester, New York: Exotic plant preference and risk of invasion. Landscape and Urban Planning, 180, 161–165. https://doi.org/10/gfp324
21. Mallinger, R. E., Gaines-Day, H. R., & Gratton, C. (2017). Do managed bees have negative effects on wild bees?: A systematic review of the literature. PLOS ONE, 12(12), e0189268. https://doi.org/10/gqx4qv
22. McMahon, D. P., Fürst, M. A., Caspar, J., Theodorou, P., Brown, M. J. F., & Paxton, R. J. (2015). A sting in the spit: widespread cross-infection of multiple RNA viruses across wild and managed bees. The Journal of Animal Ecology, 84(3), 615–624. https://doi.org/10/f68936
23. Fürst, M. A., McMahon, D. P., Osborne, J. L., Paxton, R. J., & Brown, M. J. F. (2014). Disease associations between honeybees and bumblebees as a threat to wild pollinators. Nature, 506(7488), 364–366. https://doi.org/10/gqzrmw
24. Graystock, P., Ng, W. H., Parks, K., Tripodi, A. D., Muñiz, P. A., Fersch, A. A., … McArt, S. H. (2020). Dominant bee species and floral abundance drive parasite temporal dynamics in plant-pollinator communities. Nature Ecology & Evolution, 4(10), 1358–1367. https://doi.org/10/gh2zdm
25. Forister, M. L., McCall, A. C., Sanders, N. J., Fordyce, J. A., Thorne, J. H., O’Brien, J., … Shapiro, A. M. (2010). Compounded effects of climate change and habitat alteration shift patterns of butterfly diversity. Proceedings of the National Academy of Sciences of the United States of America, 107(5), 2088–2092. https://doi.org/10/fhrd4v
26. Bartomeus, I., Ascher, J. S., Wagner, D., Danforth, B. N., Colla, S., Kornbluth, S., & Winfree, R. (2011). Climate-associated phenological advances in bee pollinators and bee-pollinated plants. Proceedings of the National Academy of Sciences, 108(51), 20645–20649. https://doi.org/10/fb6jch