Thursday, August 11, 2016

The NOW game

The dog in the foreground is us while we continue to ignore tree mortality rates

Let's say your council has 5,000 street trees. 

If their average life span is 25 years, you're going to have to replace 1/25th of them every year just to stay even.

That's 200 trees a year.

Now you will also be losing street trees to building construction activity - plenty of them in fact - so lets bump that number up to 250.

And then we should make allowance for street trees removed by people who just don't want them there. And losses due to storm and vandalism. Lets make it 300.

This is the number we need to plant every year just to maintain our current canopy cover. If we're serious about substantially increasing our cover we need to plant many more than that. Lets make it 500.

And here's the rub: we have to keep them ALL alive.

If we're prepared to keep losing half of them, we need to be planting 1,000 street trees a year. If we don't, we'll measure our canopy cover 20 years from now and realise we cooked it. And we'll also realise that's 20 years we can't get back!

Measuring canopy cover is all the rage at present - and yes, it's the big game and yes, we need to do it to have a baseline to work off - but changes to it is something we'll only be meaningfully measuring decades from now because trees grow slowly.

What we should be measuring right now is the number of trees we're planting but also the number that survive. That's the NOW game.

Get that right and canopy cover will take care of itself.

Tip: click the photo to bask in the ambience of this well-treed street. See the spacings? That's the key to it. Ours are usually way too wide because we still think in terms of one tree per property. Tree spacings need to be determined by the size of the tree, not the dimensions of the lot.

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