Tuesday, May 27, 2008

Climate change: some "benefit"

The Herald reports that climate change will benefit farmers, according to a new report from MAF. Except that, when you actually read the report, that turns out not to be the case at all. The EcoClimate report uses climate change impact projections from NIWA to predict changes in production. And the headline result - buried in section 5 of the summary, far beyond where any journalist would bother to skim - is quite clear:

For average years, the projections show no strong increase or decrease during the coming century in production when averaged over the whole country. Projected national dairy production ranges from 96 to 101%, and projected sheep/beef production from 91 to 96% of the 1972–2002 average.
(Emphasis added)

That's a long way from "benefiting farmers", particularly when you notice that most of that range is on the downside, i.e. there is in fact likely to be a slight decrease in average agricultural production.

As for why, a picture is worth a thousand words, though this one needs a little extra interpretation:

2080 expected drought frequency, low-medium (l) and medium-high (r) warming scenarios.

The scale on the bottom is drought frequency, calibrated against a one-in-twenty year scenario. So, in the low-medium scenario, which is likely to be an underestimate the way things are going, most of the east coast will suffer droughts between 2 and 4 times more often. In the medium-high scenario, that's most of the country, and Canterbury and great chunks of the North Island will be looking at what was previously a one-in-twenty year drought every 2 - 5 years. And those droughts will be much more severe; at the moment production in the worst years (like the one that cost us a billion-odd dollars off GDP a decade back) was 70% of average. That's going to drop to 50%. So, more regular, and more extreme.

Of course, its not so bad if you live in Otago, and if you live in Southland, Taranaki, or the King Country, climate change will indeed be beneficial. But what this report basically tells us is that farmers on the east coast of New Zealand are fucked.

The full report is here [PDF].