The Problem: Climate Change
How will climate change impact bees?
Climate change refers to a shift in the typical distribution of climate variables such as temperature or rainfall. Current projections indicate Australia’s climate will become warmer and extreme heat events will become more frequent. This is expected to harm native and European bee populations in two ways. Firstly, a change in seasonal temperature timings may interfere with the close relationship developed between bees and flowers. Secondly, bees are vulnerable to high temperatures, resulting in decreased pollination activity.
Phenology is the timing of when something occurs, in this context the timing that floral resources becomes available may be altered due to changes in climate patterns. Flower blooms are triggered by multiple factors, including temperature, weather and sunlight availability. We expect under warming scenarios that flowers may be triggered to bloom earlier than usual. This change in phenology may threaten flower-bee relationships, as the floral resources need to be available during the flight and foraging season of native and honeybees in order to provide the bees food and allow the plants to reproduce through pollination.
Bees are highly sensitive to extreme temperatures, both heat and cold. On hot days a proportion of worker bees will cease pollination activities and direct their attention towards cooling the hive. This means with an increasing frequency of extremely hot days, rates of pollination, resource collection and honey production will drop, leaving bees more vulnerable to pests or cold winters.
The good news is, native bee species are adapting well to increasing temperatures, likely because of their solitary nature and decreased competition with honeybees for food resources during extreme heat. In fact, research suggests that pollination by native bees will increase under these scenarios compared to their current pollination rates. This means native bees should be embraced and encouraged in agriculture, acting as a buffer against climate change to secure future crop pollination. However, the increasing expansion of industrial scale monoculture farming means that supporting native bee populations through mixing small-scale farms and native habitat are unlikely.
The other sad news is their adaptive capacity to phenology changes is limited. Some native bees are incredibly fussy eaters, meaning an interruption to their usual foraging sources may be detrimental. However, this potential change is not definitive, and the good news is native plants tend to be more resilient to changes in climate. This means whilst their foraging patterns may change, their food sources are more secure compared to other introduced species.
Another concerning issue is the enhancement of the urban heat island effect. The urban heat island effect is a phenomenon where urbanised areas are warmer than their surrounding rural counter parts under the exact same climate conditions. This is because their surfaces are dark and impervious meaning they capture and store more thermal energy and have less water available to lose that energy through evaporation. This effect is a growing concern given that urban beekeeping is becoming ever more popular. Extreme heat events will be even more extreme in urban areas, placing greater stress on colonies to keep their hives cool.
Native bees are expected to struggle not from the increasing temperatures but primarily because of the clearance of available habitat. Impervious surfaces and buildings are replacing soil and vegetation burrows, their homes. You can help your local natives by placing a bee hotel in your garden and planting native species.
All bees will benefit extensively from having an available water source to drink form. You can place a shallow dish filled with water out in your garden or on your balcony with stones and sticks in it for the bees to land on. This simple gesture can be done by anyone and is a great step to helping bees keep their homes and themselves cool.
Burdine, J., Seidel, M. & McCluney, K., 2018, ‘Too Hot or too Dry? Differential Sensitivity of Bees to Changes in Temperature and Water Balance with Urbanization’, The Ohio Journal of Science, Vol. 118, Iss. 1, pp. A31-A32. Available here
Rader, R., Reilly, J., Bartomeus, I. & Winfree, R., 2013, ‘Native Bees Buffer the Negative Impact of Cliamte Warming on Honey Bee Pollination of Watermelon Crops’, Global Change Biology, Vol. 19, Iss. 10, pp. 3103-3110. Available here
Robbirt, K., Roberts, D., Hutchings, M. & Davy, A., 2014, ‘Climate Change: Bees and Orchids Lose Touch’, Current Biology, Vol. 24, Iss. 23, pp. 2845-2849. Available here
Commonwealth Scientific and Industrial Research Organisation & Bureau of Meteorology, 2018, ‘State of the Climate, 2018’. Available here