How invasive plants use fire to overtake natives

Last summer’s horrific fires may have fundamentally changed Australian forests forever.
Alex Dook
Alex Dook
Freelance writer
How invasive plants use fire to overtake natives
Image credit: UWA

The bushfires of the 2019/20 summer were the most destructive Australia has ever seen. With more than 20% of Australia’s forests burned, traumatic scenes were broadcast all around the world. Not long afterwards, hopeful images of regrowth started to circulate through the news media.


View this post on Instagram


A post shared by Russell Crowe (@russellcrowe) on

The images of the forests seemingly making a rapid recovery from the bushfires offered the public a degree of hope. Unfortunately, certain invasive species of plants are much better than native species when it comes to recovering from a bushfire. As a result, the recent bushfires may have fundamentally changed many forest ecosystems.


According to Dr Mark Waters from UWA’s School of Molecular Science and the ARC Centre of Excellence in Plant Energy Biology, a plant’s ability to grow after a bushfire depends on how rapidly its seeds germinate.

“Most plant species around the world will germinate if they have light, water and warmth. But some native Australian plant species refuse to germinate until they are exposed to karrikins.”

Karrikins – named after ‘karrik’, the Noongar word for smoke – are a family of chemicals found in bushfire smoke. Following the first rain after a fire, karrikins soak into the soil and stimulate the germination of buried seeds.

“Before a seed germinates, there are proteins in the seed that actively stop the germination process, effectively putting the brakes on,” says Mark.

“The karrikin works chemically by degrading those proteins, which allows the seed to begin germinating.”


From an evolutionary perspective, this makes perfect sense. If a seed falls from a longstanding tree or plant, there is little point in trying to grow and compete for resources. The seed wouldn’t stand a chance. But if a bushfire burns everything down, a more level playing field is created. And it’s suddenly the perfect time to start sprouting.

For millions of years, Australian forests have survived this way. But thanks to Mark and his team, we now know that certain invasive species are especially sensitive to karrikins, allowing them to compete with natives.

Seeds respond to karrikins because of special receptors called KARRIKIN INSENSITIVE 2 (KAI2). While most plants carry only a single type of KAI2, some species have more receptors. One plant Mark worked on was the Brassica tournefortii, an introduced species of wild turnip.

A spindly, green weed grows out of a clump of foliage
View Larger

Brassica tournefortii, an invasive weed

Image credit: UWA
Brassica tournefortii, an invasive weed

“We found that Brassica tournefortii had three KAI2 receptors,” says Mark.

Due to its greater number of KAI2 receptors, Brassica tournefortii has an advantage over many native plants in germination after a bushfire.

So when vegetation grows back after a fire, it can grow back differently.


“The risk is that there will be a change in the species because of how some invasive species have improved karrikin receptors,” says Mark.

But with Mark’s research, scientists can take pre-emptive steps to mitigate these problems.

“You have to go through a large area and physically remove invasive species. This is difficult, but if you know there is a local population of invasive weeds, you can focus your efforts there.”

Mark’s research into karrikin receptors is also being used to bolster revegetation efforts for degraded land like closed mine sites.

“If a mine has closed after a long period of operation, nothing will be growing there. It makes sense to replant with natives,” he says.

Obviously starting a bushfire is not a practical or safe first step in a revegetation strategy. Luckily, the germination process can be kickstarted in safer ways like treating the seeds with karrikin water solutions before planting. However, the research isn’t conclusive on whether this is the best approach.

Alex Dook
About the author
Alex Dook
Raised by a physics teacher and a university professor, Alex had no choice but to be a science nerd. He has worked in science communication in both Perth and Melbourne, mainly setting things on fire for delighted children. Alex is now a freelance science writer and content creator.
View articles
Raised by a physics teacher and a university professor, Alex had no choice but to be a science nerd. He has worked in science communication in both Perth and Melbourne, mainly setting things on fire for delighted children. Alex is now a freelance science writer and content creator.
View articles


We've got chemistry, let's take it to the next level!

Get the latest WA science news delivered to your inbox, every fortnight.


Creative Commons Logo

Republishing our content

We want our stories to be shared and seen by as many people as possible.

Therefore, unless it says otherwise, copyright on the stories on Particle belongs to Scitech and they are published under a Creative Commons Attribution-NoDerivatives 4.0 International License.

This allows you to republish our articles online or in print for free. You just need to credit us and link to us, and you can’t edit our material or sell it separately.

Using the ‘republish’ button on our website is the easiest way to meet our guidelines.


You cannot edit the article.

When republishing, you have to credit our authors, ideally in the byline. You have to credit Particle with a link back to the original publication on Particle.

If you’re republishing online, you must use our pageview counter, link to us and include links from our story. Our page view counter is a small pixel-ping (invisible to the eye) that allows us to know when our content is republished. It’s a condition of our guidelines that you include our counter. If you use the ‘republish’ then you’ll capture our page counter.

If you’re republishing in print, please email us to let us so we know about it (we get very proud to see our work republished) and you must include the Particle logo next to the credits. Download logo here.

If you wish to republish all our stories, please contact us directly to discuss this opportunity.


Most of the images used on Particle are copyright of the photographer who made them.

It is your responsibility to confirm that you’re licensed to republish images in our articles.


All Particle videos can be accessed through YouTube under the Standard YouTube Licence.

The Standard YouTube licence

  1. This licence is ‘All Rights Reserved’, granting provisions for YouTube to display the content, and YouTube’s visitors to stream the content. This means that the content may be streamed from YouTube but specifically forbids downloading, adaptation, and redistribution, except where otherwise licensed. When uploading your content to YouTube it will automatically use the Standard YouTube licence. You can check this by clicking on Advanced Settings and looking at the dropdown box ‘License and rights ownership’.
  2. When a user is uploading a video he has license options that he can choose from. The first option is “standard YouTube License” which means that you grant the broadcasting rights to YouTube. This essentially means that your video can only be accessed from YouTube for watching purpose and cannot be reproduced or distributed in any other form without your consent.


For more information about using our content, email us:

Copy this HTML into your CMS
Press Ctrl+C to copy