What are the long-term effects from flash floods and heat waves on agriculture?

Most climate research focuses on the impacts of higher mean temperatures. But this may be limiting our understanding of how climate variability, which causes heat waves and flooding, will impact the farming system, both now and in the future.

At this stage, climate science is not able to tell us a great deal about how the agriculture sector will be affected by an increasingly variable climate. But despite little  progress, there are still a number of things scientists can do to advance the research on climate variability and also to support communities adapt to climate change. This was argued in a new review, “Climate variability and vulnerability to climate change”, published in Global Change Biology earlier this year.

By not being able to investigate both the effects, and combined impacts, of climate variability such as heat waves, intensified precipitation and flash floods and an increased global mean temperature, the full impacts of climate change on a biological and human system are seriously being underestimated, the review continues.

As an example, the authors mention that if  changes only in climatic means are taken into consideration and climate variability is ignored, projections for crop yields in parts of East Africa may be under estimated by between 4 and 27 percent, depending on the crop.

Why so little research on climate variability?

“Research on impacts and effects from climate variability is currently being constrained by lack of information and models. By outlining what we know, as well as the data we still need, we hope that this review will push the research community to reframe some of its research questions to better integrate climate variability,” says Philip Thornton, co-author of the review and Theme Leader at the CGIAR Research Program on Climate Change, Agriculture and Food Security (CCAFS) and researcher at the International Livestock Research Institute (ILRI).

One major challenge right now is to understand how to tackle the uncertainty around projecting variability and changes. This needs to be overcome, while strengthening the confidence in projecting climate extreme events and their magnitude. The fact that this is a highly complex and challenging area, with a lot of uncertainty, is likely the reason to why research hasn’t really progressed.

Prediction of extreme climate events and their long-term effects is an extremely complex field. Photo: World Bank

What do we know and what are we still searching for?

“What we still need to know is, how will changes in climate variability play out, i.e. will annual rainfall amounts become increasingly erratic, or will there be more extreme heat stress days? And the second is, how will increasingly erratic rainfall or more heat stress days affect crops and livestock? We know little about the first, and through physiology and modelling a few things about the second and not much if anything about how these things interact with each other,” says Philip Thornton.

”One major and immediate challenge is to use the information we do have, about climate variability and its impacts, to help us better understand extreme events. Our recent work for the IPCC identified extreme events as a major risk factor for agriculture under climate change," says Andy Challinor co-author of the review, as well as co-author to the chapter “Food Security and Food Production Systems”, included in the recently released IPCC report “Climate Change 2014: Impacts, Adaptation, and Vulnerability”.

Read: Climate change, food security and small-scale producers: Summary of findings of the Fifth Assessment Report of the IPCC.

The “Climate variability and vulnerability to climate change” review, also put together by Polly Ericksen, from the International Livestock Research Institute (ILRI) and Mario Herrero, Commonwealth Scientific and Industrial Research Organisation (CSIRO), gives a solid overview of some of the current insights on climate variability’s potential impacts on food and biological as well as human systems while outlining where more research is needed.

The authors mention that we do know that shifts between new extreme high and low temperatures, could impact how crops grow and under what timeframe. Earlier flowering and maturity of several crops have been documented in recent decades, often associated with higher temperature.

Also, increases in maximum temperatures can lead to severe yield reductions and reproductive failure in many crops, further affecting billions of people depending on farming as their main livelihood and food source.

research do indicate that climate variability can reduce crop yields, from maize to rice, worldwide. but there is still a lot we don't know how. Photo: N. Palmer (CIAT)

For example each degree-day maize spend above 30°C can reduce yields by 1.7 percent under drought conditions, and rice yields could be reduced by 90% with night temperatures of 32 compared with 27 °C. But exactly how such changes in variability will affect global crop production in the future is still unknown. Crop response to changes in temperature and photoperiod (length of day and night) at supra-optimal temperatures is not well understood either.

Climate variability and extreme events can also be important for yield quality. Protein content of wheat grain has been shown to respond to changes in the mean and variability of temperature and rainfall, specifically, high-temperature extremes during grain-filling can affect the protein content of wheat grain.

There is still much to be learned related to how crop quality might change as it is affected by new extreme temperature changes. Not taking quality into account could negatively impact human and livestock nutrition and health.

Unruly precipitation could have huge negative impacts

As precipitation may become more intense but less frequent and in some places bring about longer dry spells, flash floods and runoff are more likely to increase, which might result in increased soil erosion and diminish soil moisture, both impacting food production and livelihoods.

Changed precipitation might also impact spread and incidence of malaria, cholera and dengue fever, directly affecting millions of people in tropical regions. The linkages between variability in precipitation and its effects on biological system need to be further investigated.

Changes in climate variability and in the frequency of extreme events may have substantial impacts on the prevalence and distribution of pests, weeds, and crop and livestock diseases, including livestock productivity and growth, but how the effects of future changes in climate variability impact these areas are not well understood. 

Little is known on how climate variability will affect occurance of pests and diseases. In the photo: Red striga on green grams. Photo: C.Schubert (CCAFS)

Even if we don’t have all the answers, putting off adaptation is not an option any longer! 

Even if we have limited information and data as well as predictive capability, we cannot let that hinder us from adapting to climate change. Putting off adaptation for the future is not an option any longer. In the light of this regret-free approach towards climate adaptation, the review includes five areas that need increased attention if we are to successfully address the above-mentioned environmental, health and food security challenges:  

  • Through a re-prioritized research agenda, ensure that the knowledge and data gaps around the effects of climate variability and extreme events on biological systems are addressed.
  • Improve available impact models, especially on crops and livestock, at all scales
  •  Improve the monitoring of local conditions, to improve our understanding and models that will help guide effective adaptation. Improved models would also help feed in important data to yield early-warning systems and locally appropriate indices for weather-based crop and livestock insurance schemes.
  • Strengthen efforts being made to adapting biological and food systems to the increasingly variable climate and to increasingly frequent extreme events.
  • Generate synergies and improve the communication between scientists and decision makers, as well as between natural and social scientists. There is a great deal that can be done on the co-generation of information and its communication in appropriate ways, and in engaging meaningfully with decision makers at local and national policy levels.

Download article: Thornton P, Ericksen PJ, Herrero M, Challinor AJ. 2014. Climate variability and vulnerability to climate change: a review. Global Change Biology