Have you ever seen a kookaburra in a palm tree? It’s not a classic image, but it happens – and it’s important. Here Professor Chris Daniels our Presiding Member of the Green Adelaide Board explains why.
As we work together to preserve Australia’s environment and biodiversity it’s easy to focus on our native plants, but we shouldn’t neglect exotic or introduced species that have, over time, become a part of the landscape.
It’s pretty accurate to say that “any tree is better than no tree” because all trees can have something to offer. In fact, if they attract native animals and birds, then they are already offering at least one of three things – food, shelter or a place to breed.
You’ll find kookaburras, koalas and possums in pine trees, oaks and elms as well as in Aussie eucalypts. As long as there’s a branch to sit on, or a hollow to rest in, they’re happy.
Similarly, much-maligned blackberries provide shelter to help bandicoots avoid predators just as well as native thorny acacias do.
In a perfect world, all plants in Australia would probably be Australian natives; but we can’t turn back time. What we all need to do now is recognise that every plant can play a role in supporting wildlife.
Introduced species are usually only a problem if they were introduced in the wrong place (olives are a classic example) or have gone feral.
Ash trees were heavily planted in the Adelaide Hills in the 1970s because it was thought they would slow down bushfires and now all they do is choke creeks. Similarly, the majestic Aleppo pines at Glenelg may feed cockatoos, but their needles fall into the creek and smother it.
Aleppo pines were introduced around Adelaide primarily as wind breaks and now are among the worst of the “woody weeds”.
And no discussion about weeds is complete without mentioning soursobs. Believe it or not, they were being imported as desirable ornamental garden plants as recently as the start of the 20th century.
Of course, there also can be Australian natives that are out of place. Cootamundra Wattle, for example, was brought in from NSW as a popular garden plant but is now a problem in many areas.
The bottom line is that we have to assess introduced trees and plants in terms of the benefits and problems they bring – but that’s no different to any other form of vegetation.
If a koala is happy sitting in a palm tree but going elsewhere for its dinner, then that palm tree is better than no tree.
What scientists need to do is keep assessing the long-term impact of introduced species.
Pine trees provide food for yellow-tailed black cockatoos, for example, but do they offer the same level of nutrition as a native tree?
What we all can do is simply stop and observe what is happening around us. What could be planted or removed, encouraged or dissuaded, to create an even healthier and diverse environment?