Saturday, 21 February 2015

Arboreal habitat

What could be nicer than seeing a pigmy possum or beautiful bird curled up in a nest, high in a hollow in a tree? But, isn't it a good thing trees don't whimper.

How would we enjoy watching all those birds and cute animals snuggled in their tree hollow nests if we also heard the trees crying over their wounds? Trees that stand proud with thick protective bark defending against damage do not provide the hollows for colourful birds. Trees that stand tall with branches still limber enough to defy gravity without breaking do not provide the nests for our cute arboreal mammals. Insects and spiders may shelter in the fissures of bark, but as far as a house for those birds and animals, such healthy and strong trees are worthless.

Hollows for nests are formed when the defensive shield is breached and the inner wood exposed. Trees will fight to seal the breach with kino, gum or resin, but when decay fungi or insects get a breach head established then the rot sets in (literally). Unfortunately, the rot doesn't stop when a cavity big enough for a nest is created - the decay can extend into the very Heartwood of the tree and ultimately lead to its collapse.

A tree that could manage to never suffer the loss of a branch or a wound in its defensive shield of bark might actually live forever. It would look majestic too, at least to the humans it would tower above. But it would not provide a home for many birds and animals. 

Foresters of the 1940's, 50's and 60's thought their job was to grow majestic trees. They cleared away the wounded trees that had lost the fight against rot and damage. They ensured the offsprings of those trees had room to soar without breaking themselves against older neighbouring trees. They kept the fires away or allowed them to burn so cool that the bark barriers were not breached. The trees grew: healthy and undamaged. But increasingly now we realise that they also grew without the hollows. In Victoria, the possum emblem of the State is increasingly homeless as the trees with hollows collapse when their hearts rot away but the new generation stays too solid. 

Do we need now to wound these majestic trees to make the homes for our cutest animals? Should the foresters of the 1900's have been more careless and ensured trees were damaged to help ensure future habitat for birds and animals? Or did they do the right thing and expect only to make future homes for humans out of a half century of healthily growing trees?