Short and sweet: height-limited bloodwoods offer refuge to urban koalas and reduce risk to city dwellers
by Joanna Horsfall | APRIL 4, 2018
If I asked you to picture an important koala habitat area, a bustling suburban street wouldn’t likely come to mind. City living presents a number of unique challenges to Australian wildlife. As development in our population centres intensifies, human-induced threats like vehicle strikes and domestic dog attacks become all too common for our vulnerable urban koalas. As a consequence, for koalas that persist in the big smoke, the presence of mature trees that offer food and shelter amongst a complex urban maze is vital.
Although the idyllic backdrop for many an Aussie tale, gum trees can pose threats where they decorate heavily populated areas. Often reaching above rooves and powerlines, the danger of a fallen branch to people or infrastructure is considerable. This presents a difficult trade-off between ensuring human safety and protecting wandering koalas.
Last year, researchers from the University of the Sunshine Coast came upon a potential solution to this trade-off. On the adjacent coastal headlands, Stephen Trueman and colleagues identified a population of mature Corymbia intermedia trees, or ‘pink bloodwoods’, that were distinctly shorter than their inland counterparts. Trees growing in coastal settings can be height-restricted by environmental factors like soil salinity, strong winds and ocean salt spray. But interestingly, the researchers found that the short stature of these particular trees was, in fact, a genetic trait. Seeds collected from the short coastal bloodwoods were grown in cultivation and reached mature heights of only five to seven meters after eight years.
But what do the koalas think? Whether or not a koala makes use of a tree depends in part upon the palatability of its leaves. When the foliage of the short ecotype C. intermedia was used as koala fodder at Wildlife HQ on the Sunshine Coast, koalas ate the leaf just as readily as that of the tall bloodwood.
We need to enact creative strategies for people and wildlife to co-exist peacefully if we wish to preserve one of our most adored national icons. The importance of revegetating of urban areas with koala trees has already been recognised by many, and short ecotype bloodwoods could make possible the win-win scenario that local planners and decision-makers seek. Height-limited C. intermedia trees present a far lesser risk to city dwellers than taller gums and also provide much-needed refuge for koalas on the move. This novel approach also serves to illustrate a more far-reaching notion: for Queensland koalas, ‘conservation’ isn’t exclusively synonymous with preserving – it’s also about creating.
This article is based on the findings of the following publication: Trueman, SJ, McMahon, TV, Grant, EL, Walton, DA, Elliott, BB & Wallace, HM 2017. Designing food and habitat trees for urban koalas: identifying short ecotypes of Corymbia intermedia, Australian Journal of Botany, vol. 65, no. 1, pp. 384-388. http://www.publish.csiro.au/bt/BT16235