Monday, September 16, 2019

Climate Change: Trees, aviation, and offsets

With crunch time for new Zealand climate policy approaching, most of the New Zealand media have got on board with a global reporting effort to cover the issue. There's one strand of stories today about polling and what it shows about changing public attitudes to the crisis, but the strand I'm most interested in is the one about trees.

First in that is an excellent in-depth piece by Charlie Mitchell in Stuff about what trees can and can't do to address the climate change crisis. It looks at the different carbon uptake of pine vs native forest, and in passing mentions how much carbon we've got locked up in our existing native forests: 6.5 billion tons of CO2-equivalent, or about 80 years of emissions. That's on one-third of our total land area, but it give an idea of what serious native reforestation can do, and how important its going to be for eventual drawdown: sucking the carbon out of the atmosphere and undoing the damage we've done. But the downside is that its going to take a thousand years to do it. Pine is less efficient in the long-run - 800 tons stored per hectare on good land, rather than 1300 to 1700 - and its a monoculture, with all the problems that entails, but it can do it in thirty years rather than a thousand. And because we only have thirty years, or less, and certainly not a thousand, then if we're serious about solving this problem we're going to have to shoot some cows and plant trees in their place (or, less violently, remove the ETS price cap, let carbon price rise, and let the market do the equivalent - something that is already happening to sheep and beef farming even at current carbon prices).

(Its actually not an either / or choice. We can apparently use pine as a nursery crop for native forest in the same way we currently use gorse. So that might let us combine short and long-term solutions. But low-value, high emissions farming is doomed either way the moment we stop subsidising it through the ETS)

The second piece is from the ODT, about the problem with offsetting. Unfortunately there's an embarrassing problem with it, derived from this paper, which overestimates by a factor of 250 the area needed to soak up aviation emissions (short version: they calculated it using the 3 tons / hectare annually absorbed by regenerating native bush, rather than the 800 tons / hectare sequestered in total by pine. Alternatively, you could view it as a perpetual offset for aviation for the next few centuries, but neither the authors or the ODT piece talks about it like that). But mistakes aside, there is a good underlying point in there: international aviation emissions are large (7.89 megatons CO2-equivalent in 2005 for international tourists coming to New Zealand, and 3.95 megatons for kiwis travelling internationally), they are not counted in anyone's national accounts, and they are increasing. And if we're serious about climate change, we need to do something about them.

As for what that something needs to be, the article points out that international air travel is highly concentrated among the wealthy:

"The vast majority of the world population has never stepped on to an airplane. So, the growth in aviation is mainly among people who have a longstanding habit of flying.

"This huge environmental impact is basically arising from long-standing habits of the rich, or nouveau riche, who fly more and more."

And the most obvious answer to this, as with any other public bad, is to tax the living fuck out of it to change that dirty, destructive habit. Whether this is done at a flat-rate or an escalating "frequent flyer levy" depends on your taste for intrusiveness, but either way, we need to tax it and end the effective ~$200 million subsidy to the tourist industry of letting them have their pollution for free. As an added bonus, we can then spend some of those taxes on soaking up the carbon emitted, but the primary goal has to be behaviour change. The best offset is to not emit in the first place.