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Climate change impacts on pollinators and pollination

Do you agree that the weather has been getting a bit crazy? Summers are getting extreme, some being dry, others overly wet and too hot, the winters too warm, hurricanes and tornadoes becoming more common and stronger. Climate change is here, but what does it mean? Does it even matter? In this post I want to spend some time talking about why these strong changes in our climate do not just affect us, but mostly organisms that help us survive, like our beloved pollinators and the plants with which they interact.

What is climate change?

Climate change is any change in the mean and/or the variability of the climate, which persists for an extended period (decades or longer). This means that when we hear about climate change, people can be referring to any long-term change that has been detected in the records of temperature and precipitation, as well as the variations in their extremes and averages over time. Although we tend to think about the current climate change as increases in temperature, temperature is just one aspect of it. Often, it is also the precipitation patterns that are affected, leading to extreme rainfalls or droughts. Climate change is not just a climatic curiosity; because all the places and environments we live in and obtain our foods and livelihoods from are affected by climate, changes in climate affect our lives and those of other organisms with which we coexist.

How does climate change affect pollinators and pollination?

Like all organisms, plants and pollinators are only able to survive under specific climatic conditions. If the conditions change, their options are adapting to the new conditions, migrating to regions where their optimal conditions are still present, or going extinct.

Evolving and adapting to the new and fast-evolving climatic conditions has not been often observed in the case of pollination interactions. Most species are either observed to display what is called plasticity and use their already-evolved ability to adjust to different conditions. This allows them to tolerate more extreme conditions with possibly a small loss in their ability to obtain food, grow, or mate. In the USA, it was shown that some species of bees can advance their emergence time when the winters are warmer, and match to some extent the advancing in the flowering season associated with warmer winters or early springs.

The Orange-legged Furrow Bee (Halictus rubicundus) is a species that has been shown to be advancing its time of emergence with increasing temperatures. Photo: M.L. Legrand.

Most species, however, respond to these changes in the climatic conditions by dispersing to new regions, where their preferred conditions are still present. For example, species from Maryland, may disperse further north under a warming climate. Likewise, species that live on the slopes of mountains may disperse upwards, to higher altitudes. However, this is often impossible, when, for example, northern latitudes do not offer the right habitat (e.g., the preferred plants are not available or there is no more natural habitat left due to human pressure), when it is impossible to disperse further to the poles (e.g., for cold-adapted species), or when it is impossible to move higher on a mountain (e.g., for alpine species). These species see their ranges become smaller and smaller, until their population becomes too small to avoid extinction.

Some species, like the Giant Swallowtail and the White-M and Red-banded Hairstreaks, have been expanding their ranges northward (top row, left to right). Others, like the cold-adapted Atlantis Fritillary or the Arctic Skipper are likely to become at least locally extinct (bottom row, left to right). Photos: T. Eagle, S. McCann, G. Lasley, S. Elliott, S. King.

Finally, other species are unable to disperse at all, because they may not be mobile or because they move too slowly for the pace of climate change. Although only through modelling approaches, studies suggest that this may be the fate of many mid-Atlantic bumblebee species like the Perplexing or the Golden Northern bumblebees, which may become slowly doomed to extinction.

Perplexing and Golden Northern Bumblebees have been predicted to become unable to track their preferred climatic conditions under many climate change scenarios. Photos: P. Pieluszyński, Molanic.

Climate change and extreme weather events however, also can affect the survival of pollination interactions, and not only of individual species. For example, species that are specialized on their floral preferences or their pollinators may be unable to survive climate change. If the winter is warmer than usual, certain plants and insects may start emerging and developing earlier than usual. If these advances in their developments do not match between the plant and the pollinator, the partners will not co-exist, which can have drastic consequences such as loss of food, nesting sites, or lack of seed production for lack of cross-pollination. This is one of the reasons why the Baltimore Checkerspot, Maryland’s state insect, is at such high risk from warming winters and is currently endangered in the state.

If there are warm spells during the winter, the Baltimore Checkerspot’s larvae leave their “winter sleep” too early, when their plant food is still unavailable to them, and are at high risk of dying from starvation. Photos: WikiCommons, S. Snyder.

Another way these changes in climate can affect pollination is through changes in the functioning of the interacting species. For instance, it has been recently shown that extreme rainfalls and heat are able to affect the quality and composition of nectar and pollen, the odor compounds present in flowers, and the ability of insects to move and reach the flowers for reward collection. This means that even if species were to still co-occur, these extreme climate events can affect their ability to encounter each other, which again, leads to their survival being harmed!

This is complicated! Can I do anything to help?

It’s true! Understanding all biological interactions and protecting species IS complex, but that doesn’t mean that there’s nothing one can do to help! Some ways to support pollination include providing a lot of resources for both the plants and the pollinators to survive. For example, planting many different native species and providing nesting resources in our green spaces supports pollinators that may be migrating to new areas, or ones that may be just under a lot of climatic stress.

Also, it has been thoroughly demonstrated that increased concentrations of carbon in our atmosphere are leading to the climate change patterns we are observing. The good news (if we react quickly) is that we may still be able to do something to revert it, and this does not have to be anything that affects our ability to survive. Even relatively simple behavioral changes like turning off unused lights at home, bringing the thermostat even 4 degrees higher in the summer, or reducing meat consumption make a huge difference in our carbon footprints.

If you would like to start helping pollinators by reducing your carbon footprint, I strongly recommend visiting this website to receive “personalized” free recommendations to successfully reduce your carbon footprints through simple (and also more complex) and very feasible actions. And if you would like to learn more, I also strongly recommend the webinar series by University of Maryland Professor Dr. Sara Via.

By Anahí Espíndola, Assistant Professor, Department of Entomology, University of Maryland, College Park. See more posts by Anahí.

Anahí also writes an Extension Blog in Spanish! Check it out here,, and please share and spread the word to your Spanish-speaking friends and colleagues in Maryland. ¡Bienvenidos a Extensión en Español!

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