OVERSEAS they are described as the cathedrals of the natural world, ancient trees that reach for the heavens.
It’s no wonder that oaks and elms like the ones we see in Hobart’s Franklin Square and St David’s Park are said to have inspired Gothic architecture, their thick boughs arching above our heads, forming a natural roof to shelter us from wind, hail and rain.
Ancient trees are also vital for wildlife. Many animal and bird species could not live without them, especially in view of the nesting cavities they produce. This is especially so in Tasmania, home to the largest flowering plants on earth, and some of the oldest.
I have two favourite trees, the European oak and the blue gum of Tasmania. They may originate at different ends of the earth but they share one thing in common – in their own environment they are the ones most favoured by birds.
I was interested to learn in recent weeks that a fabled oak tree in England had been voted “tree of the year”, in a competition to promote trees and their place in both human and natural history.
The oak in question, the Major Oak, is believed to be more than 1000 years old and its hollow trunk – it has a girth of 10 metres – is reputed to have once been the hiding place of the famed outlaw Robin Hood. The tree stands in Sherwood Forest near the city of Nottingham.
As a child in Britain with a growing interest in natural history, I soon learned that if I wanted to see woodland birds, the oak was the place to find them. From woodpeckers, to crows and jays all birds found food and nesting places there. In fact the oak’s acorn seeds were so popular with jays that they hid hundreds of them in holes, forgetting to collect many of them during the winter and giving the ancient trees new places to grow.
The blue gum fills a similar niche in the Tasmanian environment. Its wide boughs support the nests of strong-billed honeyeaters and grey currawongs, and its hollows give homes to swift parrots, sulphur-crested and black cockatoos, and musk lorikeets, among many other birds and animals, including bats.
Like the jay in Britain which is largely associated with oaks, the swift parrot relies on the blue gum not only for nesting cavities but for the pollen and nectar produced by the towering tree’s fluffy white blooms in spring. The swift parrot is so reliant on the blue gum that the bird’s threatened status is attributed to the clearance of the trees.
If I was to nominate my own tree of the year it would be the biggest of two blue gums that stand, appropriately, at Two Tree Point at Adventure Bay on Bruny Island. The trees greeted Captain James Cook when his vessel, the Resolution, watered there in 1777, and are still flourishing to this day.
There are those, though, that maintain the stately blue gum is overshadowed by another eucalypt in Tasmania, the swamp gum (or mountain ash as it is known in Victoria), the tallest flowering plant in the world. Some of these trees have been found to be at least 500 years old.
Researchers trying to gauge the age of trees in the Styx Valley at few years back devised ways of accurately dating both tree stumps and standing trees.
Improved techniques for assessing the age of trees, including radiocarbon dating of stumps, had established that some swamp gums (Eucalyptus regnans) regenerated after a fire somewhere around the year 1500 to 1510 AD.
Bushfires aid swamp gum regeneration because they clear undergrowth, and allow seeds to grow without competition. If fire does not come through forests for several hundred years, the trees grow to a great age. At the same time, wear and tear on these trees, and the work of parasites, creates rotting timber which is a food source for birds, among them the strong-billed honeyeater, a species only found in Tasmania.