Building tools to spot invasive weeds before they spread

As ecologist Keiko Hashiba walks through native bush, she is not only looking at what belongs there. She is looking for what might arrive next.

Some invasive weeds in Aotearoa New Zealand are already well known. Others are only beginning to escape garden fences and establish themselves in native ecosystems. By the time those garden escapes are recognised as ‘problems’, they are often already widespread and costly to manage.

Her PhD research at Waipapa Taumata Rau, University of Auckland focuses on how birds disperse non-native plant seeds into native forests, and how researchers and conservation agencies might identify emerging weed threats earlier, before they become entrenched.

The scale of the challenge is significant. A recent Department of Conservation review identified 386 environmental weed species already established in New Zealand ecosystems, while noting that many more potential “sleeper weeds” are likely to emerge in future.

For Hashiba, the issue is not abstract. Before beginning her doctorate, she worked directly in conservation and pest plant management, where she repeatedly encountered the difficulty of tracking how invasive species spread through landscapes.

Her research now examines the role birds play in transporting non-native plant seeds from gardens into native forests. Species with juicy, fleshy fruits that can survive in shaded forest interiors, such as non-native palms and figs, are particularly concerning. Birds such as kererū can spread their seeds after feeding on their fruit.

“Birds really do play a big role,” she says. “They can fly quite a long distance, not necessarily in one go but hopping, stepping and jumping using residential gardens, bush patches and shelterbelts.”

By identifying the scale and reach of how birds are spreading weeds and future weeds, Hashiba also hopes that the information could help councils, agencies, industries and communities make informed decisions about what risks particular garden plants may pose over time, and plant something that doesn’t risk becoming a threat to the Aotearoa’s biodiversity.

The work sits at the intersection of ecology, field research and practical conservation management. But one of Hashiba’s biggest challenges was not necessarily theoretical. It was physical.  

To answer her research questions, she needed specialised field equipment capable of collecting seed samples in difficult outdoor conditions. Commercial options did not exist in the form she needed, so she began designing and building prototypes herself.

That process led her to the Centre for Innovation and Entrepreneurship (CIE) and its Makerspace within innovation hub Unleash Space. CIE staff such as technology and prototyping manager Trevor McGurk and curious students, working on their own projects in the Makerspace, gave suggestions to help her refine the design.

The ability to prototype quickly inside a collaborative environment became central to progressing the project. CIE’s prototyping facilities and advisory and practical support allowed Hashiba to move from concept to workable field-testing equipment while continuing her research.

Part of the challenge was learning through iteration. Hashiba says prototyping helped her determine practical details that could only really be solved through making and testing.

As she tested designs, seemingly small decisions became critical. The equipment needed to be light, cheap and easy to make, while being durable. It needed just enough ground clearance to avoid rotting and prevent rats or mice damaging samples. Flexibility in the structure also mattered. Early prototypes have held up to storm conditions.

“It’s actually better to sway a little bit instead of being really solid, or rigid,” she says.

Through trial and iteration, Hashiba also discovered from literature that the way scientific equipment is presented can influence how people interact with it. Devices with a personable label with an attractive image reduce the chance of being vandalised. One of the students in the Unleash Space happened to be an amazing artist (as well as scientist) who offered her the kererū picture they designed to put on the label.

Hashiba is careful not to frame all non-native plants as harmful. Many are not invasive and may never be. But her research focuses on identifying the species with traits that allow them to spread beyond gardens and establish themselves in natural ecosystems.

The work is still unfolding. Early field tests have already collected seeds, although Hashiba says the devices likely need longer deployment periods to gather more data. She is working on building another 220 seed collection devices for her field research.

What happens next will depend on continued testing, refinement and analysis. But the broader ambition is already clear: building better tools to understand ecological change before it becomes ecological damage.

That starts with paying attention to the signals already moving quietly through the forest canopy.