Loss of horticultural pollination services from wild insects following bushfires (PH20002)
What’s it all about?
This investment is conducting a detailed case study of the impact of a major bushfire on wild pollinator communities and the pollination services they provide to an apple crop. The case study approach to this work can be extrapolated to understand the value of wild pollinators to the horticulture sector, enabling growers to better understand their reliance on wild pollinators and the potential impact of Varroa mite to their pollination security.
Extreme weather events, such as bushfires and floods, are important features of the Australian environment and are predicted to increase in frequency with climate change. However, little is known about how this may impact crop pollination.
A unique opportunity to investigate how bushfires disrupt pollination presented itself after a three-year study of apple pollination in Bilpin NSW through Hort Frontiers project Healthy bee populations for sustainable pollination in horticulture (PH15001) was followed by a major bushfire event in 2019/20. Under PH15001 the contribution of wild honeybees to orchard pollination was estimated, therefore these learnings will be combined with post-fire pollination surveys to provide a case study.
Key activities of this investment include…
- Measurement of the immediate impact of an extreme bushfire event on pollinator communities, floral resources and crop pollination services for apples, and communication of these effects to researchers, industry and growers.
- Understanding of how pollinator communities, floral resources and crop pollination services change, and hopefully recover, over three years post-fire, along with recommendations for on-ground measures to mitigate impacts for apple and other horticultural crop pollination following an extreme bushfire event.
- Estimation of the relative contribution of managed honey bees in on-farm hives versus wild honey bees to apple pollination in Bilpin as a methodological case study, using a mark-recapture survey approach on the bees from on-farm hives.
- Integration of multiple lines of evidence from this project and PH15001 to estimate the likely impact of a Varroa mite incursion (and establishment) on pollination services.
- Presentation of findings and recommendations to commercial beekeepers, growers (especially in bushfire affected areas such as Batlow, Bilpin, Adelaide Hills and Stanthorpe) and bee pollination researchers through workshops, factsheets, and online materials (e.g. short video and downloadable factsheets).
Regular (6-8 weeks) monitoring of floral resources on and off-farm in the bushfire affected region of Bilpin continued, with results added to the time series of data covering pre-fire (2016-2019) and post-fire (2020 onwards) periods.
Analysis was undertaken on the vegetation patterns for 2018-2021 over a wider landscape scale using satellite photos. Major changes were found between one month before and one month after the fire event. There has since been substantial vegetation recovery, but effects are still evident two years post-fire, and vary greatly between orchards at the local scale. So far, an increase in the number of plant species in flower post-fire was recorded.
Preliminary analysis of crop pollinator data from the first post-fire crop flowering season suggests that numbers of both honey and stingless bees (the two main pollinator species) were slightly reduced following the bushfires. In contrast, hoverflies increased in abundance by an order of magnitude, suggesting that they might partially compensate for any decreases in bees. However, further data analysis is needed because (a) ambient temperature affects crop visitation rates and (b) there were considerable differences between farms that might correlate with the between-farm differences in surrounding vegetation recovery.
Apple landscape field work is underway to determine the changes in pollinators and pollination following bushfires.
Previous research in Bilpin under project, Healthy bee populations for sustainable pollination in horticulture (PH15001) provided 3-years of pre-fire data followed by a major bushfire. Project work has continued to use the same field sites and same methods to obtain 3 years post-fire data for comparison
The use of satellite imagery is also being used as another form of monitoring, with visual inspection of satellite images used before and after the bushfire event to observe the extent impact and the trajectory of vegetation recovery. Preliminary results show that native vegetation surrounding the apple orchards impacted by fire did not flower until about 7-8 months after the fire event.