(MUSIC PLAYS),
(MUSIC ENDS).
ZOE XIROCOSTAS: Living in the 21st century is proving to come with a lot
more challenges than we ever could have expected.
We're facing global pandemics, still confronting systemic inequality,
and trying to turn back the clock in the race against climate change.
Some would say the odds are against us,
but I work with the perfect role models
that we can look to to change that.
And they've already shown us that by making
ourselves more adaptable to change,
taking advantage of our surrounding resources,
and doing both of these things in a timely manner,
we can see ourselves thriving.
Now you might be thinking to yourself,
who can we model these traits off?
And to that, I'd say not who, but what.
Now, you probably thought I was gonna start listing
off amazing changemakers or Nobel Prize winners.
But in actual fact, my answer is a bit less conventional.
The things I think we could model these traits from are weeds.
Yes, I'm talking about those pesky plants with the flimsy leaves that
always seem to be growing out of the cracks of concrete footpaths.
And no matter how meticulous you are in your efforts to remove them,
you can just never quite seem to get them all.
And even if you think you did, it wouldn't matter,
because in two weeks time they reappeared out of seemingly thin air.
It's no wonder we spend our appreciation for them.
It's also not just our gardens that they're affecting, either,
weeds wreak absolute havoc on so many
of the world's precious ecosystems.
Invasive vines, for example, can entirely suffocate whole understories
of rainforest by growing an entirely new canopy on top of them,
using the already established plants as supports for them to grow on.
From there they'll shade anything underneath
them from all sources of light,
which, if you didn't know is how plants make their food to survive.
These effects can cascade up the food chain,
affecting the herbivores that would have eaten the suffocated plants
and then the predators that would have eaten the herbivores
that would have eaten the plants, and so on and so forth.
But can we even blame them?
I mean, these so-called evil weeds didn't historically
evolve in the ecosystems they now inhabit.
They're just making the best out of a situation
that they never should have been exposed to.
Now, there's some debate about the official definition of a weed.
But the scientist Bible Wikipedia tells us that
a weed is simply a plant in the wrong place.
And they can get to these places in a multitude of ways,
like being shipped overseas as a garden ornamental,
which then escapes into nearby bushland,
or by having their seeds stuck to the fur of exported animals,
which will then later drop into new territory.
Historically, weeds have some sort of vector involved,
like humans or animals that allow them to inhabit these new areas.
But with the onset of climate change,
these weeds are finding even more ways to push
their natural range limits on their own.
As global temperatures get hotter,
plants in warmer regions are being shown
to stop moving and dispersing away
from the equator so that they can function at temperatures
that are cooler and more optimal for them.
So this really begs the question,
what makes these invasive weeds so much better
at survival than all the native plants that they're competing with?
And the answer is it's really complicated.
If we look at weeds through a scientific lens,
you'll find that the most successful ones are those that grow quickly,
reproduce early, and compete fiercely.
You find this is true for those that have
been displaced by climate change,
but overcome it by moving poleward,
their fast life-history strategies
and resistance to the effects of warmer
temperatures allow them to keep up with
the quick pace of climate change.
Unfortunately, though, for the slow growers that take
years to flower produce seeds, and disperse,
they simply wouldn't have stood any chance in fleeing
their warming environment before it was too late.
But these traits alone aren't always the reason that weeds do
better than the native plants that they're competing with.
In about half of all invasive plant species,
the reason that they're so successful is because
they've run away from all their problems,
specifically the things that are trying to eat them.
One of the target spaces in my research is the Oxeye daisy.
It's a humble little plant that's native to most of Europe,
and it produces a spectacular sea of white petals
when it's flowering in large clusters.
Because of its beauty, this daisy was shipped
across the world as a garden ornamental.
And one of the places it ended up was right here in Australia,
where it probably escaped someone's garden
and continued to disperse further into nature.
Now you might be thinking to yourself,
how could a small flower encroach into already established
communities of native plants that had
evolved there over millions of years?
It should be practically impossible.
But the advantage that this small daisy has over all the other plants
is that nothing that would usually eat it leaves in Australia.
All the insects and herbivores that would usually
target this small plant are still over in Europe.
So while the native Aussie plants are busy
putting their energy into repairing damage
and growing new leaves when things try to eat them,
our humble daisy worries about nothing.
It's able to grow faster than it would in its native territory
because those herbivores aren't here to slow them down,
which means it can then reproduce quicker
and spread further into the new habitat.
Our daisy may have been able to seize its opportunities to spread.
But that's only possible because it was able to
be pollinated by the insects that live here.
No pollinators mean no reproduction, so this story would have ended
much sooner had they not been able to overcome that hurdle.
But did you know that some plants can do exactly that?
They can change the ways in which they reproduce in order to overcome
the barriers of not having the specific pollinators around,
or even if they just don't want to wait
for their pollinators to show up.
They do this by self-fertilizing,
and it's been shown to happen at higher rates when
a species reaches its native range edges
to promote them to expand further.
Now, I mentioned before that about only half of
invasive plants are succeeding because they're
eating less in the introduced environment
in comparison to their native habitat.
But this leaves some explaining to do for the other 50% of plants.
What makes them succeed?
For some, it could be that they fix nitrogen in their
roots better than all the other plants around them,
meaning they can attain more nutrients from the soil,
grow quicker and spread further.
For others, it could be that they fit a very specific niche
that no other plant in the ecosystem was able to exploit,
like exotic parasitic mistletoe that literally
drill their roots into the sides of trees
and suck the water and nutrients right out of
them like they were a giant wooden straw.
Now, I'm in no way suggesting that we all go are leeching off of
those around us and exploit them for our own personal gain.
But I think we can all appreciate the innovation of these mistletoes.
I know they're bad for our ecosystem
and they're really causing problems.
But if we want to get metaphorical here,
aren't they just thriving on the support of those around them?
Well, if that hasn't got you convinced,
then perhaps this will because they're known to seize any opportunity.
Weeds are best at rapidly invading disturb sites, including farmland,
logged areas, parks, and bushland with altered fire regimes.
In agriculture, weeds run wild across fields.
And this is a massive problem because farmers
are seeing a reduction in their crop yields.
These weeds are so successful that
the engineers even had to get involved.
And as of this year, they've created a robot that can kill 100,000
weeds per hour with lasers.
Essentially, these weeds have taught us to
learn from our mistakes by showing us that
prevention is better than treatment in almost
any scenario they're involved in.
What I'm really trying to get out here
is not that we should be like weeds,
but that we should learn from them because unlike weeds,
we can't run away from all our problems.
We can't.
Or rather, we shouldn't parasitize the people closest to us,
and we're definitely not having so fertilized babies anytime soon.
The 21st century couldn't be further from what anyone envisioned.
Unlike weeds, we too are now stuck in the wrong place.
But for us to have the chance to turn
the 21st century into the right place,
we should all take a leaf from a weed's book
and learn to thrive no matter the circumstances.