We all know an old paddock tree when we see one: broad, deep, canopy; sagging, tangled branches; broken boughs full of hollows. The classic woodland tree. But how do you recognize an old tree that grew – not in the open – but in a closed, dense stand? It won’t have a big, wide canopy nor a thick, wide trunk if it’s growth was suppressed by neighbors. Continue reading
Everyone sees something different in a patch of bush. I usually wonder: were these patterns that we see created by natural forces (such as soils and geology) or by a hidden mosaic of past disturbances?
Most times, I work in ecosystems with a long history of human disturbances, such as clearing and felling, grazing and burning. Their imprints can be both indelible and invisible, but more often, just plain forgotten. Yet we need to know how disturbances have altered natural ecosystems, so we can predict how our activities will alter ecosystems in the future.
The best way to see the imprint of past disturbances is by combining field evidence and archival documents, like old reports and maps. But we often have to rely solely on field skills. Just as the science of geology required the law of superposition – which simply states that sediments were laid down sequentially, so lower strata are older than upper strata – so historical ecology requires the ability to see key juxtapositions. By observing how things are arranged in space, we can develop a chronology of past events and an informed narrative of ecological change. Continue reading
Stock grazing has reduced the conservation value of many native grasslands and woodlands in southern Australia. Not surprisingly, we often remove stock to help restore degraded areas. But how well does this work? Can damage caused by past grazing be reversed, or will the removal of stock create new, unexpected communities? Continue reading
They say one dog year equals seven human years. If so, one internet year must equal half a dozen dog years, everything changes so fast. After two and a half years of blogging, and over 30,000 page hits – a day in the life of a Gangnam YouTube clip – it’s time to spruce up my blog site with a new template (or theme) from WordPress.
If you are reading on a smart phone or tablet, you probably won’t see the change, but for those reading at a PC or laptop, I hope you like the new look. I’ve used a simpler theme, so it’s less cluttered and shows off the text and photos better than the old style did. Hopefully it’ll still look fresh in another year or two on internet time. Continue reading
The woodlands of Dunkeld are among the most beautiful in the world. Stately old trees, scattered across grassy paddocks, frame the rugged Grampians Ranges in the distance. In another continent they could be oaks or olives, but in Dunkeld the trees are River Red Gums. Eucalyptus camaldulensis. Century old giants.
The woodlands don’t go on forever, but peter out in the grasslands to the south and west. Sandy out-wash soils from the ranges allow trees to prosper. On the heavy clays further afield, grasses prevail. The boundary between the woodlands and the grasslands – the edge of the treed lands – is strikingly clear on air photos. Google Earth shows a ring of woodlands to the west, south and east of the Grampians, with farmed grasslands beyond.
But how stable is this boundary? Is it moving over time? In many regions, paddock trees are gradually dying out, creating a ‘tree regeneration crisis’. If this was the case at Dunkeld then the boundary would creep slowly in towards the ranges. Continue reading
A recurring theme in Australia’s environmental history is the quest for the Grand National Narrative. The desire to create the universal ‘big picture’ story that is everywhere relevant, everywhere important. This theme dominates many popular environmental histories, from Eric Rolls’ A Million Wild Acres to Tim Flannery’s Future Eaters and Bill Gammage’s recent book, The Biggest Estate on Earth.
The quest for over-generality isn’t new, and can be traced back to Thomas Mitchell’s famous quote from the mid-1800s:
“Fire, grass, kangaroos, and human inhabitants, seem all dependent on each other for existence in Australia; for any one of these being wanting, the others could no longer continue. Fire is necessary to burn the grass, and form those open forests…. But for this simple process, the Australian woods had probably contained as thick a jungle as those of New Zealand or America, instead of the open forests in which the white men now find grass for their cattle.” (Mitchell 1848).
It’s a unique and perceptive observation. But it certainly stretches the geographical imagination. A thick New Zealand jungle? In Adelaide, Wagga Wagga and Canberra. Really? Would you buy a used car from Mitchell Motors? Continue reading