I thought I'd put up a few more posts about what I learned at the 2nd International Urban Tree Diversity Conference in Melbourne this week apart from:
- there are some very talented people around the world working on this issue
- the City of Melbourne is probably leading the way in Australia
- the University of Melbourne is a great partner to have on your doorstep
- you never know who you're talking to at the conference breakfast table*
The big takeaway is diversify, diversify, diversify. Unsurprising I guess given the title of the conference :)
What was surprising however (to me at least) was what "diversity" actually means. I went in thinking "native", I came away thinking "native, exotic and anything else you can possibly lay your hands on!" Because not being dependent too much on any one thing is the key to creating a truly resilient urban forest, one that has the best possible chance of withstanding whatever the future might throw at it.
Some have this idea that the best thing you can do is simply put back what was here before we came along. Bad idea. Why? Well, firstly, because the conditions that were here before 'aint here no more! I talk about that here.
But there's another reason, one I hadn't really appreciated until Melbourne. And that is that climatic conditions here are about to get a whole lot different again and the native vegetation that lived here before may well not be able to deal with it. The whole flora of our region could change and by replicating the forest that was here 150 years ago, we could be setting it up to fail.
We have to hedge our bets, cover our bases, not put all our eggs in one basket. However you want to put it, the principle is clear: we simply don't know how things are going to pan out so maximising our diversity minimises our risk.
There are a number of formulae being used around the place to achieve this diversity. The City of Melbourne for example uses the 5/10/20 rule: no more than 5% of one species, 10% of one genus and 20% of one family. Others use a 10/20/30 rule and others a different one again. It probably doesn't matter which one you choose as long as you choose. We just gotta mix it up!
* I sat down and introduced myself to a lady who told me her name was "Anne". It was only later I realised it was this Anne. Wow. She spoke for an hour - I wish it had been two.