I submitted my PhD in February 2022. Despite 2 years in some sort of covid related lockdown I had a wonderful PhD experience with fantastic supervision from Professor Trent Penman and Associate Professor Lauren Bennett. I was able to use field data and fire simulation modelling (including helping develop aspects of FROST) to examine changes to the fire regime under a changing climate in south-eastern Australia. Having come from an ecology background I was also interested in implications for biodiversity under the predicted changes, including those most vulnerable to the joint threats of altered fire regimes and changing climate. I also completed my Masters of Science (Ecosystem Science) in FLARE in 2017 where I used an ecological flammability model to examine how past fire shapes future fire risks.
Thesis – Predicting future fire regimes and the implications for biodiversity in temperate forest ecosystems
Fire regimes are changing around the world. Fire seasons are lengthening, high severity fires are occurring more often and in unexpected places. Relationships among fire, climate, and vegetation are varied, dynamic, and under-examined in many ecosystems. While some studies have explored links between fire, climate, and vegetation such as species distributions or future fire weather under changing climate, relatively few have considered the dynamic interactions among all three simultaneously. In this thesis, I develop and apply modelling approaches to predict future fire regimes in south-eastern Australia and explore the implications for fire-responsive functional plant types.
In the first quantitative chapter of my thesis (Chapter 2), I develop a new fuel model for south-eastern Australia. I use edaphic, climatic, and fire variables to build a predictive fuel model that is independent of vegetation classes and their future distributions. In Chapter 3, I use my fuel model in a landscape fire regime simulator, alongside multiple predictions of future climate, to examine the immaturity risk to an obligate seeder tree species (Eucalyptus delegatensis). My simulations indicate that this species will be under increased immaturity risk under future fire regimes, particularly for those stands located on the periphery of the current distribution, closer to roads or surrounded by a drier landscape at lower elevations.
In Chapter 4, I expand the application of the above simulation approach to examine the relative importance of future fuel and future climate to changing fire regimes in six case study areas across temperate south-eastern Australia. My results indicate that the direct influence of climate on fire weather will be the principal driver of changes in future fire regimes (most commonly involving increased extent, decreased intervals, and an earlier start to the fire season). The indirect influence of climate on vegetation and therefore fuel was also important, acting synergistically or antagonistically with weather depending on the area and the fire regime attribute.
Finally, in my fifth chapter, I consider future climate and fire impacts on plant persistence by combining the landscape fire regime simulator with spatially explicit population viability analyses. Obligate seeder species were at risk of population extinction or reduction in more simulation scenarios than facultative resprouters. However, my approach highlighted that the resilience of facultative resprouters might also be tested by climate related changes in demographic processes and fire regimes.
Overall, my research has provided new methods and scientific insights into the changing nature of fire regimes in temperate south-eastern Australia. Some negative impacts on biodiversity from a changing fire regime, particularly on more vulnerable plant functional types like obligate seeders, appear inevitable. Further understanding of the complex interactions among fire, climate, and vegetation will enable improved integration of risks to people, property, and biodiversity into land and fire management planning.
Questions we asked Sarah about her PhD
Q: What “day to day” type activities did you do?
My PhD was mostly computer based. I did a lot of data wrangling, simulation modelling and statistical analysis. But everyday was still totally different even though it was computer based. Near the end of my PhD, my day was often a combination of writing and analysis and a surprisingly large amount of googling R problems. I particularly loved data visualisation and often spent a few hours perfecting plot… it’s fun I promise… well I found it fun.
Q: What pathway did you take to get into the research?
I took a fairly traditional pathway, I just couldn’t seem to stay away from uni! I did both my Bachelor of Science and Masters of Science at unimelb. I found the FLARE group (then the bushfire behaviour and management group) at the end of my undergrad after doing a forest ecosystem subject and thought that fire and ecosystems was a pretty great area to learn more about. So I did a Masters of Science which contains a large research project spread over two years and a few coursework subjects. I did a heap of fieldwork for my project, looking at the flammability of different ecosystems in the Otway Ranges and how flammability changes over time. I applied for a few industry jobs at the end of my masters and actually ended up being successful in one, but in the end decided that research was a pathway I wanted to pursue. I started my and have never regretted the pathway I took.
Q: Was there any unexpected achievements along the way?
After completing a science communication subject in my masters I wanted to keep practising those skills. So I tried out the three minute thesis. It’s a competition where you have to explain your research project in three minutes to a non-specialist audience. Normally you speak in person, but again, pandemic, so I did it all online. Surprisingly, I won the Science faculty competition and was a finalist at the university wide competition! It was a great way to really think about your audience and what you want the key takeaways of your research to be.
Q: What’s the most interesting thing that you did during your PhD?
I was very lucky to sneak in an international conference a couple of months before the covid pandemic began. I attended and presented at the International Fire Ecology and Management congress in Tucson, Arizona. Although I really enjoyed presenting (even though the audience was mostly fellow Australians), it was hearing about all the other different yet related research international colleagues are doing that was the most interesting. I particularly enjoyed meeting other young researchers who will continue to be my peers and colleagues moving forward. I must thank twitter for allowing many of those connections to continue. It was also a great opportunity to get to know other Australian researchers in a more approachable setting as we had a lovely inclusive group all head over for the conference. Plus, Tucson is a pretty amazing city to travel around, I have never seen so many cactus before!
Q: Who did you collaborating with outside of your supervisors?
I had a number of opportunities pop up over my PhD which have given me a much wider research network than just my supervisors. I was on a joint project with Greening Australia and Parks Victoria looking at future fire risk to Alpine Ash. One of my confirmation examiners invited a few members of the group over to his research group in Perth to present at a workshop and see their field sites. There I met some researchers from the US who I still keep in contact with and would love to visit. Collaboration within FLARE was also great and you are definitely not restricted to just working with your supervisors.