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Nina Pirttioja: Strength in numbers when modelling future crop yields

31.1.2017 Nina Pirttioja
Nina Pirttioja 172px
Nina Pirttioja

Population growth, land degradation and increasing competition for land, water and energy are some of the major challenges faced in feeding a global population expected to reach 9 to 10 billion by 2050. Climate change adds yet another dimension to the equation, with projections of future warming and changes in rainfall.

Models can be used to make sense of these complex challenges. In agriculture many different types of models are used to assess various aspects of the food system. Depending on the question at hand you may wish to use a model to look at agricultural trade or economics. Or perhaps you want to know more about health problems associated with livestock.

Crop models form an essential part of the assessments by providing estimates of crop yields and quality. Since future climate conditions are expected to be well outside our experience, statistical models based on the past are not reliable. Instead, researchers are on firmer ground when they use models that describe eco-physical processes affecting crop growth and reflect an understanding of the phenomena being simulated. Such models were first developed in the 1960s and applied for several decades to understand crop responses to various management strategies.

However, some years ago, researchers started to raise the issue that many of these models were badly out of date (e.g. Rötter et al., 2011). The latest knowledge about crop responses to climate change was not incorporated. High quality field data that were required to support modelling were lacking. The use of multiple models and their comparison were needed to improve our understanding of uncertainty. All in all, adequate attention was not being paid to rigorous development, testing and application of the models being applied.

A number of exercises dealing with these issues were launched, involving hundreds of researchers worldwide. One such effort, the Crop Modelling Theme (CropM) of MACSUR has now released a Policy Brief summarising some of the recent research to model climate change impacts and adaptation in crop production. Work that SYKE contributed compared the sensitivity of wheat yields to changes in temperature and precipitation using 26 wheat models at sites in Finland, Germany and Spain. Results appeared last year in the journal Climate Research as a 50-author publication.

So what have we learnt from this research? One finding is that using multiple models to project future crop yields under a changing climate is a more robust strategy than relying on a single model. Another is that with model improvements we can indeed have more confidence in projecting future crop yields and representing their uncertainties. These findings, in turn, should help us in designing appropriate adaptation strategies to cope with a changing climate.


Rötter, R.P., Carter, T.R., Olesen, J.E. and Porter, J.R., 2011a. Crop-climate models need an overhaul. Nature Climate Change, 1(4): 175-177.

Pirttioja,N., Carter, T.R. Fronzek, S., Bindi, M., Hoffmann, H. et al., 2015. Temperature and precipitation effects on wheat yield across a European transect: a crop model ensemble analysis using impact response surfaces. Climate Research, 65: 87-105.

I am Nina Pirttioja, a researcher in the Climate Change Programme at SYKE. In my work I focus on exploring the performance and application of crop models outside current climatic conditions. During my free time I head outside to explore the outdoors and enjoy the weather.

Nina Pirttioja, Tel: +358 40 197 4339, firstname.surname@ymparisto.fi

Please be advised that the opinions of blog contributors do not reflect the views and opinions of the Finnish Environment Institute.

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