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Big changes to agriculture in warming climate -

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ELEANOR HALL: Scientists say a four to six degree rise in average temperatures would require a complete change in the world's farming practices.

A warming climate could be beneficial for some countries, especially those in the northern hemisphere, like Russia and Canada. But Australia may have to import more food than it produces.

CSIRO research scientist Dr Mark Howden, is writing the food security chapter for the next Intergovernmental Panel on Climate Change report.

He spoke to Will Ockenden.

MARK HOWDEN: Four to six degree rises, which are indicated in the report today, would put Australian agriculture into unknown territory. There's no conditions which are analogues or which parallel the sorts of conditions we'd experience under those sort of climate changes.

WILL OCKENDEN: So what would happen under a one degree change?

MARK HOWDEN: Well with a one degree change, that's effectively like taking the climate from somewhere like Wagga and putting it over Melbourne and we know that we can farm quite successfully at Wagga, we have, you know, appropriate farming systems that can adapt to that sort of change and with experience of the sort of droughts and floods that Australia has, we'd probably have the sort of tools and techniques to make the sort of adaptations needed to keep a viable industry.

WILL OCKENDEN: Would we be able to adapt on a four to six degree rise?

MARK HOWDEN: It's difficult to say. So there would be agriculture occurring across Australia, but it probably would look very different from what it is now. Simply there's no sort of simple analogue to say a four degree to six degree rise, we couldn't say we could take the farming, say, from Roma in Queensland and put it over Melbourne, simply because the seasonality in soil types and other conditions, you know, don't allow us to do that.

More importantly I think that we haven't got a good handle on the way in which extreme climate factors will change, it's the really big factors, the very long and extreme droughts, the really big floods, and all the indicators are that that sort of variability, the extremes are going to increase, along with the average temperatures.

WILL OCKENDEN: What crops would suffer the worst?

MARK HOWDEN: It's really the temperate crops, things which tend to grow in the coolest seasons of the year, like wheat and barley. Also in part potentially the horticultural crops and viticulture because they're so tightly tied to water availability and to temperature regimes.

And so those things which are fairly regionally associated with specific regions and with specific conditions like irrigation are the ones that are probably going to have to adjust most.

WILL OCKENDEN: Climate change is obviously a global issue. What about the food security in other nations with a four to six degree rise?

MARK HOWDEN: Well there's a fair bit of work been done on that, but it's still in a sense hard to paint out a really clear international picture or global picture. What we can say is that the places which already have struggles with food security are likely to get worse in terms of food security, so that's the equatorial and sub-tropical regions, particularly across Africa and parts of Asia - those areas which tend to have plentiful food production may in some cases even get more.

So at least temporarily or for a few decades, some of the northern hemisphere crop producing areas such as in northern Europe and Russia and parts of the US may actually increase in yields, but then possibly decrease after that.

WILL OCKENDEN: So climate change would be in their interest?

MARK HOWDEN: At least for the first few decades, but after that there's a big question mark. And in fact more recent analyses are indicating that in the longer term, even those places would start to suffer from, you know, excess in terms of heat, which we tend to experience on a fairly regular basis.

ELEANOR HALL: Dr Mark Howden from the CSIRO, talking to Will Ockenden.