Failed States Index 2009, with interactive map

August 17, 2009

The Global Campaign for Education – a model of international activism

August 17, 2009

When farmers and weather men disagree, who's right?

August 17, 2009
empty image
empty image

I recently blogged on an excellent new paper by Steve Jennings and John Magrath on the changing nature of the seasons across a range of developing countries. One of the interesting side issues that emerged is that, while in most countries farmers’ perceptions fit the meteorological data, in a few others, farmers say that seasons, and particularly rainfall patterns have changed drastically since their parents’ time, but the meteorological data insist that nothing significant has occurred. What explains the disparity and who should we believe?

Some useful ideas come in a 2004 paper on Ethiopia by Elisabeth Meze-Hausken, published in the ‘Climate Research’ journal. She sets up the problem as follows:

‘Statistical analysis of rainfall chronologies was performed and contrasted with qualitative data collected through a survey and questionnaires. Fieldwork studies showed that local authorities, farmers and pastoralists perceived regional climate to have changed during the last few decades. Farmers explained that they have been changing their farming strategies by shifting to more drought-resistant crops as well as to a shorter agricultural calendar. They attributed this to a loss of the spring rains since ‘their father’s time’ (20–30 yr ago), as well as a shorter main summer wet period. However, rainfall measurements do not show a downward trend in rainfall.’

Meze-Hausken asked the question ‘If there is no proven change, has the need for rainfall changed during recent decades?’  For example increased demand for staple food (due to population growth) can be met by intensification or extensification of agriculture. If that increased pressure on the land leads to a crop failure, farmers may attribute it to drought (the traditional explanation) even if the rain fell as normal.

An alternative explanation is that other natural and human factors such as soil fertility, vegetation cover can reduce water availability, which farmers then interpret as due to declining rainfall, even without any actual measured change in rainfall itself.

Moreover, increased competition for land with the local pastoralists may have led to higher needs for stable and sufficient rainfall.

Steve Jennings, one of the authors of the Oxfam paper on seasonality, summarizes as follows:

‘The Ethiopia paper seems to say that farmer perceptions were of a compound variable (such as temperature + rainfall pattern + rainfall amount = agricultural drought) rather than the simple variable (rainfall amount) measured by weather stations. (No prizes for guessing he’s an environmental scientist by training……) This very much chimes with what we’ve supposed about the discrepancies between perceptions and data in Uganda (but sadly only had time to allude to in our paper). So the question then becomes why do people in some places seem to perceive changes in rainfall alone, whereas in others they perceive a compound variable. Is it what we ask them? Or is it that in places like Ethiopia, rainfall is so variable and the historical record so poor that it impossible for meteorologists to detect subtle changes that are obvious to communities?’

So who’s right, farmers or weathermen? Answer both, but they are measuring different things.

And if course it would be nice to have a similar exercise from the 1950s. Did complaining about the weathertropical farmers back then say, ‘the weather hasn’t changed a bit since my granny’s time’, or did they too radiate nostalgia for the good old days? After all, it’s not just a British trait to complain about the weather.

3 comments

  1. Fascinating subject Duncan and important. As one of the authors of the Oxfam paper you kindly praised, I think though that it’s worth stressing that disagreement like this between farmers and Met data – at least on the scale of the Ethiopia example – seems fairly rare. Most often how farmers see their weather changing does chime with Met Office records. Uganda is actually a good example; farmers there told us how the long rains are no longer consistent, and rain data from 37 stations backs that up, especially that the growing season is becoming broken-backed with reduced rain in April, the middle month of three (see Drake Mubiru’s paper on the IDS seasonality website). Across the Southern Africa region trends at individual stations might not appear statistically significant but meta-analyses of regional data also support perceptions of later onset of rains and more extreme precipitation days (see New, Tadross, Suarez papers cited in our report on Malawi). The Ethiopia case does throw up fascinating issues but how generally pertinent those issues are is debatable if the Ethiopia case is exceptional.A forthcoming report by Oxfam America on climate change in Ethiopia – probably in November – may shed more light on this.

  2. While the climate has changed in some (many) countries, I have seen no investigation of why. The media and other sources imply that it is due to CO2 related global warming, but climatologists say that so far the globe hasn’t warmed up very significantly.

    Do you know if anyone has looked at the causes of the changed weather in Ethiopia and Uganda? Is it already due to global warming? Or is it mainly due to more local factors such as regional deforestation and increased grazing/agriculture. If the land heats more quickly once forests are gone, presumably this would change regional wind patterns. Similarly, floods are heavily influenced by speed of the run-off, which is affected by changes to land use.

    I don’t doubt that the effects of climate change due to CO2 will be huge in years to come and need to be tackled now, but I remain to be convinced that this is the main cause of all recent weather changes.

  3. Pete – good point. I’d say that definitely there are 2 processes at work, one global and the other land use change. I feel that some things are mainly/more due to one and some to the other and we need to try to distinguish (more). At the same time, they do interact just to make it even more complicated!

    Apropos I’ve just been re-reading the IPCC 2007 Fourth Assessment Report chapter on Africa and they do say that vegetation cover can increase – or decrease – temperature by 0.8 degrees i.e. yes, there are big land-air feedbacks. That’s more than current global warming-caused trends. But there’s also a real underlying upward trend (0.5 degrees since the 60s) irrespective of vegetation cover, that’s not insignificant either.

    Re. floods – I agree in most cases the main cause is land-use changes +/or bad water /land management but, more intense rain can set the ball in motion and I think that more intense rain is probably a global phenomenon.

    Having said that, Robert Chambers at the seasonality conference mentioned said this: “I recollect a story of two mission rainfall stations in Tanzania, some 20 miles apart with a forest in between. One station was upwind for the prevailing wind and the other downwind. The forest was gradually cut down. The total rainfall was not affected but for the downwind station it became more erratic and intense. This may be apocryphal, but could it be that changes in when rainfall seasons start and end is predominantly associated with warming and its secondary effects, but that erratic rainfall and rainfall intensity are partially, largely or wholly associated with changes in land use?”.

Leave a comment

Translate »