Carrying on from last week’s blog, in which I discussed the
applicability of models to realistic scenarios, I have begun to explore the utilization
of crop modelling in policy, in this case for climate change adaption. Gaun et
al (2015) argue the results of their recent study can aid the design of future
rain fed agriculture strategies in West Africa.
The paper, “What aspects of future rainfall changes
matter for crop yields in West Africa?”, discusses the relationships
between variable rainfall patterns (as a result of climate change) and Sorghum crop
yields in the region. A stochastic rainfall model (based on the CMIP5
predictions) was adopted to drive 2 crop models (2 models were used to reduce model
dependency and ensure confidence in the simulated results).
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| Figure 1: Crop Yield change for increased (+30%) and decreased (-30%) frequency of rainfall events |
The model ran scenarios under varying Mean Annual
Precipitation, intensity, and frequency to differentiate the effects of each
factor. There is a general academic consensus that, as a result of climate
change, rainfall patterns will change. However, uncertainty (associated with
gridded climate change predictions) creates a challenge when estimating which
aspect of rainfall patterns will have the most detrimental impacts on crop
yields (Sorghum in this case). The study’s results indicated that a reduction in
Mean Annual Precipitation will have the most widespread influence. In drier
areas (Bellow 600mm/year), however, intensity prevails over alterations to
frequency (Figure 1). Increased frequency, in rainfall events, showed a
reduction in the total volume of water reaching deep soil layers, causing
greater evaporation from surface and soil stores and thus reducing the amount
of water available for crops and reducing yields. An assumed reduction in
runoff, in this scenario, does not outweigh losses through evaporation in the
soil moisture, thus the paper concludes increased intensity could be more
beneficial for crop yields.
In relation to policy implication
and further academic research, this paper provides justification for the focus
on seasonal total rainfall in agricultural management, yet calls for attention
to be brought to intensity and frequency in regions of low rainfall (ie. West
Africa). Furthermore this is especially important in relation to adaption to
climate change, by prioritising which aspects of rainfall variability will
have the greatest impacts on crop yields and consequently food security (see my
previous post on the sustainable development goals for more details). This
subject is very topical at present, yet I have started to wonder about the
consistency in results from paper to paper… are academics in consensus about
the influence of climate change on crop yields? Or is this just another topic
with high levels of uncertainty? Stay tuned to find out.
I've never really heard much about crop models before, so this blog is great for me to learn more about them :). I look forward to seeing it develop.
ReplyDeleteWhy do you think there might not be consistency?
Yes please stayed tuned for more information, much more to come!
DeleteIn response to your question, this is something i have notice throughout my reading. Crop Modelling studies are often not very applicable to real life situations and therefore are not very successful in policy implications. This could be detrimental in terms of climate change adaption as acting now could save us in the future.
Due to large amounts of uncertainty relating to climate change scenarios a large range of results are being generated between crop modelling studies with limited consistency. I thought it would be an interesting focus to look at how consistent these results (looking the relationship of climate change and crop yield) and how well such results are integrated into climate change policies.
Hi Charlie! Great post, even with the complex crop model I could clearly understand what was going on. I was particularly interested in your discussion of which aspect of rainfall patterns will have the most detrimental impacts on crop yields. My own exploration tends to focus on mean annual precipitation, like you mentioned, but I think there certainly seems to be merit in looking at intensity, particularly in dry areas like West Africa. I think there should be a adapted approach to studying climate change impacts for different areas as what might fit one region, would not necessarily fit another, and this study proves different methods of understanding rainfall for crops.
ReplyDeleteThanks I'm glad you enjoyed the post! I completely agree with you there! This paper provides a great justification for the investment in climate change mitigation strategies in this region!
ReplyDelete