Of weeds and habitat

Natives are good, weeds are bad

 This is the mantra of the bushland manager.

I first learnt this mantra when I started in the industry about 13 years ago. I can’t remember exactly where I learnt this, but it can be explained by the plot of Independence Day, or pretty much any other alien invasion movie:

Alien invasion of Earth: It starts off with humans hanging around being awesome.

Weed invasion of Australia: It starts off with Australia’s bushlands hanging around being awesome (plants and animals from Australia are also referred to as ‘native’ or ‘indigenous’).

 

Alien invasion of Earth: Then aliens arrive in huge spaceships.

Weed invasion of Australia: Weeds arrive in huge ships, brought by European settlers.

 

Alien invasion of Earth: Everyone is like “Oh crap! Aliens!”

Weed invasion of Australia: Everyone is like “Oh crap! Weeds!”

 

Alien invasion of Earth: Aliens start to invade and mess shit up.

Weed invasion of Australia: Weeds start to invade and mess shit up.

 

Alien invasion of Earth: Humans fight to conquer the aliens.

Weed invasion of Australia: Bushland managers fight to conquer the weeds.

 

Alien invasion of Earth: Pew! Pew! Pew!

Weed invasion of Australia: Pew! Pew! Pew!

 

Alien invasion of Earth: Lives are lost.

Weed invasion of Australia: Native plants are lost.

 

Alien invasion of Earth: The human race survives, but is changed forever.

Weed invasion of Australia: Bushland in Australia survives, but is changed forever.

 

Australia is full of awesome plants and animals, and some bat-shit crazy ones too (we do have the most dangerous animals in the world!)  Most of these species can be found nowhere else, and our ultimate goal in bushland management is to conserve this weird and wonderful mix of species and environments.

And so bushland managers arm themselves with knapsacks, loppers and chainsaws to fight the weeds and save the natives from destruction.

This approach assumes that removing weeds will benefit our bushland. However, some weeds have been in Australia for a long time, and our native animals have started to adapt and use them as habitat.

Some examples include:

  • Blue Wrens and other little bush birds use Blackberry and/or Boxthorn as a food source and as shelter
  • Yellow-tailed Black Cockatoos eat seeds from Pine Trees
  • Golden-sun Moth use Chilean Needle Grass as habitat and potentially the larvae feed off the grass
  • Southern Brown Bandicoots use Blackberry as shelter
  • Gang Gang Cockatoos eat Hawthorn berries
  • Corellas eat Onion Grass bulbs
  • Sacred Kingfishers make nests in Willows and Date Palms

If you have any other examples, please post them in the comments below.

So…should we declare that the war on weeds over?

Shall we hang up our loppers and knapsacks, and return home to our loves ones and families?

Should we start to use that dirty ‘N’ word to describe our former foes? Naturalised?

Or will this type of thinking lead to a dystopian future – where ‘weeds’ run rampant and compromise the integrity of our bushland – the same integrity for which we have fought so hard to conserve? Will this lead to the bushland mantra being twisted into some sort of Orwellian propaganda slogan?

Animal Farm_2
Natives are good, weeds are better?

I don’t think that the war on weeds is over.  Weeds definitely do encroach on native plants and threaten ecosystems. However, weed control needs to be done in a way that doesn’t negatively impact the animals that use them as for habitat.16f2ui

Rather than removal, think replacement

When we come along to fight the war on weeds, we may be removing the last stronghold of our native animals.

Too often we assume that whatever remains is better than a weed-infested landscape.

The main reason that native animals use weeds as habitat is because there are not enough native plants around. Vast areas of bushland have been wiped out, and the only place that some animals can hide is in the weedy blackberries and boxthorns.

From my interview with Brian Bainbridge, I’ve learnt that it is vital to monitor your bushland to see what plants and animals you have (both weeds and natives). With this information, you can start to see how your management might impact these species (in both good and bad ways).

Instead of just looking at your bushland in terms of ‘weeds’ or ‘natives’, you can think in terms of habitat. Brian has a keen interest in birds, and observed that small bush birds like dense, shrubby vegetation. This is the exact type of habitat that blackberries and boxthorns provide. By replacing these weeds with suitable native substitutes, Brian was able to keep the bush birds in the landscape.

The ‘war on weeds’ idea is not defined in terms of what is being created, but by what is removed.

What about other types of animals and habitats?

If you have a keen eye and are very patient, you can spend time observing your bushland to see how it is being used by native animals. But since this takes time, here’s something that we prepared earlier (click on table for a larger view).

Well, actually this was put together by Chris McElhinny and co, who wrote a fantastic review of 56 studies in south-eastern and western Australia to identify animal-habitat relationships in forests and woodlands. Since most bushlands can be described as forest or woodland, it’s a great study that can help us identify which habitats are used by different animals. If you have other types of bushland,  (e.g. grasslands or shrublands), then check out the vegetation layers that are relevant for you.

image17
Habitat that animals use in forests and woodland in south-eastern and western Australia, with ways to increase habitat. (Excerpt from McElhinny et al. 2006. The ways to increase habitat are my own suggestions). Click on table for a larger view.

Any bushland can be grouped into several layers from the ground all the way to the tree canopy.

Within each of these layers are several habitat attributes – these are things that animals use as food, shelter or breeding.

Generally, when there is more of an attribute, there are more of the animals that use it for habitat. But just because you have a lot of one attribute, it doesn’t guarantee an increase in that particular species. They may not be able to reach your bushland, or there may be other factors at play.

Ecosystems are complicated, and increasing habitat attributes will only increase the likelihood of certain species occurring. It’s no silver bullet.

In the far right column of the table, I’ve added a few suggestions on how to increase these types of habitat in your bushland. If you have any other suggestions, please post them in the comments below.

The following describes three different ways you can use this table to identify and manage the habitat in your bushland.

  • Look at your weeds – what type of habitat do they provide? If you have animals that use these weeds as habitat, are there suitable native species you can introduce while you stage the weed removal?
  • Look at your bushland – what habitat is there and what can you do to improve the habitat? More shrubs? More logs? Are your trees too small for hollows? Maybe you need some nest boxes in the meantime?
  • Look at your bushland – based on the habitat you already have, what animals should be there? Maybe some animals can’t reach your patch of bush?

Creating habitat is a much more fulfilling goal than just removing weeds

 

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11 thoughts on “Of weeds and habitat

  1. Invasive coastal wattle on my Healesville property seem to be favoured by sugar gliders, ringtails ness in bamboo and palm trees, spinebills feed from agapantha flowers, great blog John

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  2. As long as people don’t read this and think “oh well, I may as well leave the weeds as they’re helping” then this blog is all good.
    Gang Gang Cockatoos using Cotoneaster as a food source… and for that matter, any cockatoo or member of the parrot family on fruit trees would apply here!

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    1. Thank you Brett for the examples. I think we still need to remove weeds, but we need to make sure we are not negatively impacting species that currently use it as habitat. Best wishes John

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  3. I love the images. It’s true I sometimes lie awake at night fantasizing about killing weeds/aliens. We’ve learned the hard way about leaving especially the thorny weeds (sweetbriars and blackberries in our area) as a bird habitat. I’m working my way through blurry old photos trying to find evidence for what I think is true – that when we pulled out and burned all the briars and blackberries in the 1960s, the big trees began to die back. The same thing happened when my parents bought the second farm, started clearing the prickly weeds, and the trees began to look worse and worse. Luckily we retained some areas of tea-tree because our stockman persuaded my Dad that “the little birds need somewhere to be.”
    The table of benefits looks like a really useful set of principles to work from.

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    1. After a day of hand weeding Broom seedlings all I see when I close my eyes at night is Broom seedlings.

      That’s an interesting observation about tree dieback. Maybe the ecology of having weedy shrubs brought in certain birds and insects, which maintained the trees in the landscape. Are the trees dying back due to insect damage? Or is there something happening with the soil/hydrology/erosion?

      If you haven’t checked it out already, I recommend digging up some of the old aerial photography of your bushland. Some of these photos go back to the 1930s and it gives you a great idea of what the land was like back then. You can try here first https://www.nla.gov.au/research-guides/aerial-photographs

      Best wishes John

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