Last month Clare Gover said “Habitat is what it is all about!” in trying to keep our wild Koalas. However, we need to understand more about how Koalas fit in the ecosystems where they live, and what makes those eco-systems work. Just planting food trees without understanding the soil, soil bacteria, role of organic matter and the insects and fungi in there, as well as the relations between the food trees and the other vegetation in the relevant ecosystems, may not produce the best result.
Dougal Johnston sees the environment with the eyes of a geologist. His time scales are measured in millions of years; while ours are measured in months and years and maybe decades. The world around us is changing at all time scales, from the housing developments each year around Toowoomba, to the cropping of the Downs over decades, to land clearing over a couple of centuries, and the coming and going of ice ages (and sea level rise) and the movement of continents over millions of years. Maps from 1945 of Highfields and Cabarlah are barely recognisable as the land we saw in 2005 and what of today? Invasive weeds such as lantana and Chilean needle grass (a weed of national significance) might not have taken such a hold on our environment if it had not been for intensive land clearing for crops and housing.
Throughout Queensland we can see many types of ecosystems: Mitchell Grasslands to the north-west of Toowoomba, tropical rain forest of North Queensland, and arid lands to our west - with different soils, different rocks, different vegetation, different climates. Such regions have their own distinct flora and fauna. To conserve and sustain our ecosystems and dare one say, to manage them, it is necessary to describe them in detail. We see such descriptions in The Conservation Status of Queensland’s Bioregional Ecosystems (Sattler P. & Williams R. editors, 1999). This was the first comprehensive description of regional ecosystems for Queensland.
The editors divided the state into 13 regions (mostly on catchment, climate and vegetation/soil similarity). These were then divided by physiographic type and on each type the vegetation based ecosystems numbered. The area of each ecosystem remaining (compared to the estimate of pre-colonial settlement) was used to classify the ecosystems as ‘no concern’, ‘of concern’ and ‘endangered’.
The most prominent local endangered ecosystem, 12.5.6, is, according to Sattler and Williams, tall eucalypt forest of Eucalyptus siderophloia, E. propinqua, E. microcorys and/or E. pilularis with E. saligna or E. grandis (in open forest) along the lateritic flat range tops from Toowoomba to the north (Laterite is a soil and rock type rich in iron and aluminium). Nearly all laterites are of rusty-red coloration, because of the high iron oxide content. They develop by intensive and long-lasting weathering of the underlying parent rock.
Adjacent to the tall forest (mostly on the upper slopes) are tiny pockets of endangered vine scrub (microphyll rainforest). Franke Scrub is at RE12.8.21. TFNC are active in the maintenance of this precious remnant scrub. Dougal emphasised the misuse of fire regimes in 12.5.6. Much too high fire frequency (and clearing for farming which also utilises fire regimes) has massively reduced the tall forest and almost wiped out some of the vine scrub ecosystems from Cunningham's Gap through the Toowoomba area, up to the Bunya Mountains and well north. Hopefully by observation we can learn (like the geologists – the present is the key to the past) how to better manage and conserve the ecosystems around us.
By Dougal Johnston with additions from Linda Mangubhai