How are fires impacting our pollinators?

The ability of a plant species to thrive in the long term is underpinned by its ability to reproduce, and in more than 85% of plant species, this ability to reproduce is dependent on, or benefits from, pollen delivery by pollinators.

Noisy friarbird (Philemon corniculatus) feeding on the flowers of Xanthorrhoea johnsonii

We know plants and pollinators are impacted by fires and that they have adapted to these conditions over millennia in Australia. Periodic disturbances in communities by fire are also likely to be essential for the maintenance of diversity in pollination systems through space and time.

However, we don’t know how changes to fire frequency and intensity are impacting – or could impact – pollinator populations, or what the flow-on effects to successful plant reproduction and dispersal might be.

A Saving our Species Science and Research project – led out of the University of New England – is studying pollinator communities and pollination processes under different fire-history regimes; e.g., fire free intervals 20+ years, intermediate (e.g. 1 fire in 15 years) and frequent (3 to 4 fires in 20 years).

The key research questions are:

  1. How do complex pollination systems respond to variation in fire frequency?
  2. How long does it take for pollinator communities to recover after severe fire?

This project is led by Professor Caroline Gross and Dr David Mackay.

Professor Caroline Gross

Professor Caroline GrossProfessor Caroline Gross is an ecologist who has studied the mechanisms behind the high levels of endangered and rare species in Australia (about 25% of the flora) and that of endangered ecological communities, as seen through the lens of plant reproduction, for 35 years.

Her work has shown that small genera are more likely to contain extinct species than larger genera and that phylogeny plays a role in being endangered, coupled with uni-sexual breeding systems and fruit types. Her research has also found that reproductive failure can be linked to intrinsic factors (e.g., female and male sterility), probably exacerbated by too frequent fires and extrinsic environmental factors and possible across-species breeding events, as well as a combination of factors (reproductive failure and habitat loss).

Caroline’s work has shown that endangered ecological communities can be hard to rehabilitate once a threshold of disturbance has been reached, but passive restoration is possible before that threshold.

Population persistence can be linked to a lack of disturbance in the landscape and natural rarity is common, imposing constraints on management.

 “The last three years of drought then fire then good rains has seen poor recruitment and a lack of pollination services in many habitats in northern NSW,” Caroline says. “The key for recovery lies in the seed bank and we are also learning that drought then rain can stimulate flowering in the absence of fire. Xanthorrhoeas are a great example of this and provide a welcome supply of nectar for many vertebrate and invertebrate floral visitors”.

See Professor Gross’ publications through Google Scholar.

Dr David Mackay 

Dr David Mackay, ecologist at University of New EnglandDr David Mackay is an ecologist at the University of New England with several decades of experience working in collaboration with team members from DPIE (formerly OEH) on stabilising and/or recovering populations of threatened plant species.

His research focus is primarily on identifying problems in reproduction and dispersal by these plants and devising sustainable methods for improving and maintaining plant reproductive success and species recovery. 

“There is no silver bullet for species recovery. In my experience it always involves multiple strategies,” says David. “For example, for one of the species in this project – a mint bush (Prostanthera staurophylla) – we are conducting a translocation experiment with the aim of increasing the number of wild populations from the single, small population currently extant on top of a single mountain.”

“Our research suggests, though, that without catering for the needs of the pollinators of this plant the project will fail in the long term. The main pollinator of this mint bush is a native bee, Exoneura bicolor, and we found this bee also uses co-flowering New England tea tree, Leptospermum novae-angliae, as a nectar source. So, unless we ensure this tea tree is also in the translocation sites then the bee populations may not be supported and then reproduction and the long-term survival of the translocated mint-bush populations may fail.” 

David says that sorting out problems and solutions like this are critical in the face of climate change and changing fire regimes that impact on plants and their pollinators.

“The long-term survival of this mint bush and its pollinator look assured. This has been made possible through the dedication of our team of scientists, other conservation-agency staff and private landowners – a model for future success.”