A year ago I posted about the formidable Hawkweed Eradication Program, which is primarily focused on the Alpine National Park of south-eastern Australia. All summer parks staff, private contractors and volunteers scour likely locations to weed out Hieracium species. Detector dogs Sally and Connor are now very much part of the action, too!
Last week we gathered in Falls Creek to evaluate Sally and Connor’s search skills in the Victorian environment. We sent them – plus a team of the High Plains’ proud volunteer searchers – to some specially selected plots where live hawkweeds were known to be hiding. The three search teams found almost all of those known plants, and additionally spotted several undocumented infestations!
Both projects address how we can best search for rare targets in ecological surveys. They’ll involve experimental design, data collection in the remote and ruggedly beautiful Alpine National Park, statistical modelling and conservation decision-making.
Jos’ and my project also rolls in concepts of novel search methods and how we can best integrate them into existing programs. It’s an opportunity to learn from the state government agencies managing a hawkweed eradication program as they investigate the combination of human search teams, trained dogs and unmanned aerial vehicles that will best detect every last hawkweed.
I’ve spent the past week in Kosciuszko National Park, contributing to the mammoth team effort eradicating hawkweeds (Hieracium species) from mainland Australia. Dozens of parks staff, state weeds staff, contractors and volunteers train their eyes on rosettes that could otherwise be mistaken for common daisies. Their goal is to find and kill every last one of these interlopers.
The searchers’ newest team-mate Sally prefers to follow her nose. She’s a working dog trained specifically to distinguish hawkweeds’ scent from the other plants occurring in the Alpine National Park. I’ve been helping set up fully- and partially- controlled experiments to evaluate detection dogs’ strengths and weaknesses, and compare them to the skills that human teams have been honing for years.
‘Delimitation’ is a crucial process during a weed eradication program, whereby the full extent of the invasion is mapped out. There’s really no other way of ensuring that your removal method is successfully targeting every last pesky plant. In 2011 the Hawkweed Eradication Project Control Group were wondering whether they’d nailed it. They’d been sending out search teams for years and had drawn a minimum convex polygon (MCP, dashed line mapped above) around the infestations they’d found. But could there be more hawkweed beyond those boundaries? The worst case scenario was that hawkweeds had actually spread much further south, where the terrain gets so tough that they’d probably have to give up on eradication entirely.
‘Further south’ encompasses a huge area, and the Control Group consulted Kate Giljohann and I to prioritise locations for search. While working on a biosecurity surveillance review for ACERA the previous year, I’d learned that very little research literature directly addresses how we should design delimitation surveys! So Kate and I started afresh, adapting my previous hawkweed survey design to increase the value of hawkweeds detected outside the known population boundary. This process also accounts for hawkweed occurrence (via dispersal and habitat suitability) and detection rates, ensuring that search teams visit places where they’re most likely to find far-reaching hawkweed infestations.
The hawkweed project managers used the shaded map we supplied (a above) to direct their GPS-tracked search teams (b above). The good news is that they found no new hawkweeds in the dreaded southern reaches, just a few extra plants to the north and east of the infestations they already knew about. While this was good evidence that they were close to delimitation, the search teams’ GPS practices were inconsistent – it was hard work for Kate and Michael Rigby to clean up the spatial data, and we had little idea how much time and effort the search teams had put in at each site.
In our new article, my co-authors and I document the process of designing, implementing and evaluating this delimitation survey. I’ve even put together a wishlist for future delimitation work. While minimum convex polygons describe infestations that we know about, probability maps can tell us where else our weed population might be lurking. The maps are ripe for Bayesian updating as we collect new survey data. They can also be aggregated into a delimitation score developed by Mark Burgman, Dane Panetta and colleagues to track progress from survey to survey.
Based on what my co-authors and I achieved in this study, I’m optimistic that these measures can be taken in real eradication programs.
Hauser, C.E., Giljohann, K.M., Rigby, M., Herbert, K., Curran, I., Pascoe, C., Williams, N.S.G., Cousens, R.D. & Moore, J.L. (in press) Practicable methods for delimiting a plant invasion. Diversity & Distributions. DOI: 10.1111/ddi.12388
The program funding my summer field project has been in the news this week! It’s a public introduction of Missy, the detector dog, and her trainer Steve Austin. With the help of several dozen government staff, researchers and volunteers, I’m evaluating Missy’s capacity to detect Hawkweeds in a variety of conditions.
Last month José and I ventured back to Wyperfeld National Park to explore monitoring options for the threatened pine-buloke woodlands. Here are a few of my photos taken along the way. Elsewhere, you can read more about…
Recently José, Guru and I returned to Wyperfeld National Park for the annual VMRG training weekend (you can read José’s account of our trip here and my summary of last year’s gathering here). It was great to reconnect with many familiar faces, receive updates on the monitoring program and get acquainted with the data logging devices.
We stuck around Wyperfeld for an extra 24 hours to get to know the park better in the context of our kangaroo-vegetation management project. We were privileged to have acting Ranger-in-Charge Dave Christian as our guide. He’s worked in the Mallee Parks for almost 30 years and I’d wager that what he doesn’t know about Wyperfeld and its management isn’t worth knowing! It was incredibly informative to ‘meet’ the buloke and slender Cypress pines that Parks Victoria are working to regenerate and to get a feel for the management operations on ground.
While I didn’t capture any photos of the Major Mitchell’s cockatoos or the regent parrots that we spotted, I’ve got plenty of other images to share.