Large old trees are valued and protected in many of Australia’s city and suburban landscapes because of the environmental and economic benefits they provide. These include wind reduction, shade, storm water management and landscape improvement. The biodiversity benefit of old trees, however, is often forgotten and rarely quantified.
In a recent study I looked at what vegetation features make our neighbourhood parks suitable habitat for a range of different birds. I found that the number of large eucalypts with a trunk diameter larger than 0.5 metres (equivalent to a circumference of 1.5 metres or greater) was an important factor.
With increasing numbers of large eucalypts, parks supported more bird species – in particular woodland-dependent species, some of which are declining in south-eastern Australia – had higher bird abundance and a greater probability of breeding birds. Parks with the largest trees (with a trunk diameter more than 1 metre) had up to three times the number of woodland-dependent species than parks with only smaller trees. Moreover, large eucalypts affected the mix of species found at the parks, and parks with low numbers of large eucalypts harboured more exotic species.
Clearly, these findings show that large old trees provide a significant biodiversity benefit, and this value should be factored in by governments when protecting...
