Rain pounds on the roof and thunder shakes our house. A nearby tree is shattered by lightning. Just 100 metres away the Hobart Rivulet rages so powerfully that it will soon flood Hobart’s CBD. In just 24 hours we’re receiving a third of our annual average rainfall. The insurance council will later declare this storm event a catastrophe.
In the midst of all this I find myself recalling an old university debate. But given that part of our house is flooded too, it feels far from academic. In my student days I majored in geomorphology (literally “the study of the shapes of the earth”), and we keenly debated two theories on what it was that shaped our landscape. On one side were the catastrophists, led by a New Zealander-born lecturer. The catastrophism theory posited that the shapes we see in our landforms are largely the result of sudden, short-lived catastrophic events. The contrasting theory, uniformitarianism, put it down to gradual, bit-by-bit processes.
We could see why someone from a country prone to earthquakes, volcanic eruptions and avalanches might be a catastrophist. But as Australians we were more inclined towards uniformitarianism. It simply better suited to our “wide brown land”. The severe storm in May 2018 shook my easy, Aussie uniformitarianism, and brought that academic debate very close to home.
The morning after the storm it was still raining, though it had eased enough for us to check out The Patch. Before we’d even gone out our gate, we were stunned to see that whole tree trunks had washed out of the bush and down the neighbour’s back yard – and this across open ground, not down any recognised watercourse!
Further up the bush the flooding was equally fierce. As we sloshed along the track we realised we were witnessing one of the primordial shapers of the earth in action. Everywhere we looked water was still gushing downslope, tearing tonnes of soil and rock from the earth, uprooting trees and shrubs, pooling deep and dirty anywhere vaguely flat. It was not difficult in that situation to be persuaded by catastrophism.
Months later it’s spring. Having wrought their changes, those primordial forces have gone back to wherever it is they lurk. Now on my walks I find myself slowly, gradually, leaning back towards uniformitarianism. The lead persuaders are some of the bush’s smallest creatures. Initially you might laugh at the thought of comparing the might of rushing water with the puny lifting power of ants. But strength isn’t always blatant.
Take the small Iridomyrmex ants we observe swarming in the trees. We walk past perhaps twenty trees that have hundreds, thousands of ants ascending and descending their trunks, following lines of pheromones laid out by scouts who have found food. My mind swims at the sheer number of ants that must be active in the bush right now. I wonder how substantial their impact might be, and decide to follow my own trail of enquiry.
Iridomyrmex ants usually nest underground, where they hollow out large tunnels and chambers to house the colony. All of this is virtually invisible to us as we walk on our bush tracks, but millions and millions of ants shifting soil for their nests must involve the relocation of staggering amounts of earth. Their influence on the landscape doesn’t end with shifting soil. The ants we see on the tree trunks forage in the tree-tops, seeking out nectar, honeydew, and other invertebrates. And crucially they carry plant seeds back to their nest, to feed to their larvae. The antlings consume only the fleshy parts of the seeds. The rest remains viable underground, and in the perfect place to germinate.
We’re familiar with plants propagating from seeds that drop unaided to the ground, or when new shoots come up from the root system of the parent plant. But this gardening behaviour of ants offers another intriguing path to plant propagation. When I consider how particular plant species have been favoured by the presence of ants over maybe 60 million years, I realise the profound, long-term effect ants must have on the look of the landscape.
Just as the bit-by-bit industry of the ants is turning me uniformitarian, the catastrophic rears its head again. An echidna (Tachyglossus aculeatus) has been hibernating, snoozing through the coldest parts of winter under piles of sticks and leaf litter. But the spring activity of the ants has awoken it, the scent of formic food in the air making its appetite as sharp as its spines.
We watch as it does its bow-legged, gun-slinger shuffle through the bush. It may be amusing to us, but I doubt it is to the ants. This echidna is packing: powerful front claws, a prodigious snout, and that fast tongue (as Tachyglossus translates). It scratches, snuffles and sniffs out ants. But it doesn’t simply hoover up every single ant. In what could be even more catastrophic for the ants, it will selectively eat queen ants if it can, given their higher percentage of fat. And a colony without a queen may well be doomed.
Catastrophism and uniformitarianism – right here in The Patch, over just a few months, we have witnessed both. Has one of them come out on top? Rather than being persuaded by one or the other, as though they were binary opposites, I begin to think there’s another way of seeing it. Perhaps we always have both at work, variously chipping and bludgeoning away at the world around us. And sometimes at us as well.
Peter Grant lives in the foothills of kunanyi with his wife. He worked with the Tasmania Parks and Wildlife Service for 24 years as manager of interpretation and education. His passion for the natural world led him to write Habitat Garden (ABC Books) and found the Wildcare Tasmania Nature Writing Prize. More of his writing can be seen at naturescribe.com.
Click here to read more from Peter Grant's column, The Patch.
