Science Interviews


Sun, 21st Mar 2010

Farming in a Changing Climate

Professor Brian Thomas, Warwick University

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Chris -   The human population is estimated to be about 6.8 billion right now, and it’s set to grow to over 9 billion by 2040.  Supporting a population that big is a really big challenge, but it could be made even harder if you factor in the effects of climate change.  Professor Brian Thomas is from Warwick University where he works on predicting how climate changes could affect future food production.  He’s with us now.  Brian, Hello.

Brian -   Hello.

Chris -   Welcome to the Naked Scientists.  Please tell us, if you would, in what sort of way, or how, do we think climate change will impact on agricultural production?

Brian -   I think the impact of climate change on production will be shown in a range of different ways.  We’re dealing with – first of all, the general changes in the climate, which you might think of increasing levels of carbon dioxide (which could be a key issue for agriculture), but also increasing temperatures and changes in water availability.  So at one level, we can look at those factors and make assessments of how they might affect crop production and food production.  And then, imposed on top of this, there are changes in particular types of weather conditions - sometimes thought of as extreme events, but when you get combinations of whether that in combination with a particular characteristic of the crop may lead to loss of production or crop loss in a particular year.  We see that, at the moment, in general, crops in the UK are well-adapted to the general UK climate, but when we have a particular set of unusual weather then that will then often result in a particular problem in a particular crop, and we see that in a particular way.  So, our work is really a combination of some general assessments of the impact of climate change on overall crop production, but also, trying to tease out which particular aspects might be changed, and therefore, really get some heads-up on the sort of research we need to do to modify crops to anticipate those problems.

Chris -   Is it just a question of saying, “some bits of the earth are going to become a lot less propitious for growing anything.  Some will become better suited to growing things that currently grow in different places”?  And so, what we need to do is to have a re-jig – move things around a bit and we’ll maintain productivity without actually having to sacrifice anything.  Or are we facing a situation where actually we’re not going to be able to feed everybody?

Brian -   Inevitably, there will be shifts in production – it will often be "the art of the possible", but there are some big challenges there.  For example, in some of the models I've seen for production, in China for example - which, obviously, in terms of its scale and its contribution to overall food production is quite immense.  If you go back one step and say that one of the big problems is maintaining or sustaining production when temperatures increase, so much of the staple foods for temperate countries, the cereals, the impact of increasing temperature is usually to decrease yield, and that is partly to do with the fact that you get an acceleration of the growth of the crops so they have less time to photosynthesise and accumulate resources.  The models suggest that a lot of that would be offset, or some models say fully offset, by the increasing fertilisation effect of carbon dioxide.  But really, I think that the estimates are probably subject to quite a lot of uncertainty.

Chris -   Could you just tell us, how is it you actually do what you do?  Have you got a giant computer program where you're able to change various model parameters, tweak things in order to say, “Well, if we tweak this, this is the likely effect on this bit of the climate and this part of the world, and crops that grow there would change in a following way.” And then you do that many, many times and look at many, many different bits of the world, and this gives you a global picture?

Organic cultivation of mixed vegetables on an organic farm in Capay, California.Brian -   Well, to be honest, we’re not looking at a global picture.  We’re looking very much at UK agriculture and this work really is funded by Defra who are trying to use this sort of information to set their policy, although many of the principles we come up with would be applicable very widely.  But the main approach we’re taking is to use what is freely available output from computer models from UKCP09 who make predictions of the UK climate over the rest of this century, and they will give estimates of changes in overall rainfall and average temperature.  But they also have the facility to take these averages and to deconvolute them into typical runs of daily weather.  That would include things like day temperature, night temperature, rainfall.  A lot of agriculture, a lot of production in agriculture, is sitting in quantitative models, and then you can use the output from the weather generator models, put it into the agricultural models and then say, “What is going to be the change in say, in 2030, or 2050, 2080?”

Chris -   Speaking of which Brian, what’s your prediction for the southeast corner of the UK in the next 30 years?

Brian -   Probably, it’ll be warmer, it’ll be wetter in the winter, dryer in the summer, crop production will probably hold its own just about, but crops that require a continual run of production are particularly vulnerable to periods of drought.  Crops that require real cold in the winter like fruit trees are quite vulnerable to the increasing temperature.

Chris -   Which is a worry because we’ve heard from Redlace Selene who’s listening in at Second Life and says, “I was looking forward to the olive tree and the lemons in the UK garden.”  Never mind - better luck next time!


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It is the possible consequences of global climate change upon food production that scares me the most. LeeE, Fri, 26th Mar 2010

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