CLIMATE change has a speed: about 420 metres per year. That's the average rate at which temperature zones will shift across global landscapes during this century, according to research led by the Carnegie Institute in the United States.
It is also an estimate of how quickly plants and animals will need to move to stay within current climatic zones, and an indication of the pressure on agriculture to adapt as seasonal conditions shift.
Recently published in the scientific journal Nature, the research attempts to predict "temperature velocities" as a way of expressing how climate change will influence plants and animals adapted to certain climatic zones.
Such work is not entirely new, according to Professor Barry Brook, who occupies the Sir Hubert Wilkins Chair of Climate Change at Adelaide University, but it does provide a useful picture of how climate change may advance across landscapes - including farmland.
Unlike plants and animals, which must move or evolve to survive climate shifts, agriculture can adapt relatively quickly on the spot.
The challenge, Prof. Brooks said, was in deciding when to shift enterprises or methods as a result of a climate shift. Moving too early, or too late, could be extremely costly.
"The decision framework about when to make those changes, how quickly, and how we adapt, will be very challenging," Prof. Brook said.
"I think there will be a lot of learning by doing and copying the experience of people who do it successfully."
Making a decision first requires acknowledgement that there is an issue to respond to. That might be the most difficult step of all, Prof. Brook observes.
"This kind of climate system has a lot of natural variability, so people don't recognise the change in one direction or another; or they may not identify it as a trending change, because change is detected over decades rather than years."
"It can be hard to make decisions on that basis, and I don't envy anyone who has to do so."
The scientists from the Carnegie Institution, Stanford University, the California Academy of Sciences, and the University of California who collaborated on the "temperature velocity" work don't make decisions any easier: they acknowledge that their interpretation, which combines current knowledge on global temperature gradients with climate model projections for the next century, contains a number of assumptions and caveats.
However, the scientists also say that the end result in several respects mirrors what is empirically known about recent and prehistoric climate-forced natural migrations.
Their Nature paper, "The Velocity of Climate Change", puts the global average temperature velocity at about 420 metres per year, but with extreme variations according to the landscape.
In hilly or mountainous areas, where species can stay within their climatic zone by gaining altitude, temperature velocities are low.
In flat regions, such as the deserts, grasslands and coastal plains that characterise much of the Australian landscape, temperature velocities may be more than a kilometre per year.
Prof. Brook suggests that despite the increased velocity of change on flat country, species in these areas may adapt to increased temperatures better than those adapted to cold conditions, who may have "no more cold to go to".
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