In California, the 2022 almond bloom has started early and is progressing rapidly. This has raised the issue of how climate change will impact the seasonal dynamics of the biggest pollination event on earth– when 2.5 million beehives are moved to pollinate over 1 million acres of almonds. One of the key impacts is the shifting of seasons, which become less predictable, and weather patterns such as mild winters, summer droughts, cold springs, and coastal storms become more frequent. The almond tree is classified as deciduous, so changes in seasonal weather patterns can alter the physiology of every growth stage. These changes will also impact the health and development of honeybee colonies, which already suffer from multiple stressors and high mortality rates.

Almond bloom phenology and intensity are crucial to pollination management and are one of the key determinants for successful nut production. The key factors that determine the initiation of flowering are the accumulation of winter chill and subsequent heat during the dormant phase. Winter chill hours are forecast to decrease, and combined with increases in pre-blossom temperatures, will mean bloom could start earlier and progress more rapidly.

In the case of honeybees, milder winters in temperate climates may alter colony phenology and negatively impact hive strength and fitness. Worker bees are more active and can rapidly consume winter food stores and there is more opportunity for the transfer of parasites and pathogens. The scenario of an earlier and more rapid almond bloom combined with increased stress on overwintering bees will create additional challenges for pollination management. The California almond is already the earliest pollination crop in the U.S. Hive availability and colony strength are highly variable at this time of year, depending on winter mortality rates.

As well as influencing the timing of the start of bloom, weather conditions during bloom will impact bloom length and pollination efficacy. Unpredictable or extreme weather conditions that reduce honeybee flight can result in poor cross-pollination. Furthermore, research has shown that if a bloom is rapid and dense, low worker populations will not match the rate of opening flowers. Strong colonies are especially needed at the beginning of bloom because the earliest flowers of each variety have the highest potential to set nuts.

However, breakthrough developments in sensor technology mean it is now possible to remotely monitor all the essential variables in almond pollination: bee health and activity, orchard microclimate, and bloom phenology. For example, in-Hive sensors are now available and can provide insights into the strength (number of bees) and health of colonies through winter and into early spring, a critical time of year. This information is vital to beekeepers during winter when physical inspections are not possible, enabling remote monitoring of an overwintering colony’s vital signs in real-time. Such technology can also enable beekeepers to evaluate different overwintering strategies in terms of feeding regimes and colony treatments to reduce losses and optimize colony strength ready for almond pollination. For almond growers, it is now possible to monitor pollination progress in real-time. They can do so with sentinel stations equipped with sensors to monitor bee pollination activity, weather and bloom progress are strategically located throughout the almond growing area.

Over time, data gathered from the aforementioned technologies can provide a deeper understanding of how almond bloom phenology, bee health, and foraging activity will fare under shifting climates. It will inform optimal strategies for hive placement in the crop such as the timing of introduction, positioning, spacing between hives, and the stocking density. Data-driven best practices can be developed for different varieties, locations, climates, and field sizes, rather than the current ‘rule of thumb’ applied across highly variable situations. The application of advanced sensors and data analytics offers solutions to monitor, mitigate and adapt to the impacts of climate change. It will translate the impacts of a global issue to implications at a local farm and field-scale for more informed decision-making on pollination management.

Written by George Clouston, Head of Scientific Strategy at BeeHero

For more research on how the rapidness and density of blooms affect the workers' population's ability to match the rate of opening flowers, check out the following publications:

Thorp, R. W. (1996). Bee management for pollination. In W. C. Micke (Ed.), Almond Production Manual (pp. 132-154): UC ANR.
Bosch, J., Kemp, W. P., & Peterson, S. S. (2000). Management of Osmia lignaria (Hymenoptera: Megachilidae) populations for almond pollination: methods to advance bee emergence. Environmental Entomology, 29(5), 874-883.