Mike Rivington and Mohamed Jabloun of the James Hutton Institute talk about climate and crop yields.

Climate change will alter how much rain falls – where and when. For farming, this means an impact on crop yields with knock-on consequences for the food and drink sectors. One crop in particular, barley, is important to the farming, food, and drinks sectors here in Scotland, contributing particularly to the whisky industry and livestock sector. So, we’ve been researching what the impacts of climate change might be on barley yields.

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To set the scene, Scotland’s climate has already experienced substantial change since 1960, including changes comparable in magnitude to those previously projected for the future. February has experienced the largest increase in mean monthly rainfall, whilst the largest decrease has been in September. Meanwhile, the eastern arable crop areas have experienced rainfall decreases in the key months of March and May.

Looking to the future, analysis shows that August, September, and autumn are likely to become warmer and drier in the future. Spring shows large spatial and temporal variation, with risks of drought affecting both crops and nature. Winters are likely to get warmer and wetter, particularly in the west, resulting in higher risks of flooding.

Storms may be more intense with higher amounts of heavy rainfall. But lower rainfall and higher rates of evapotranspiration (evaporation from plants and soils) associated with higher temperatures are also likely to reduce water availability, affecting ecological processes and agricultural production.

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Climate extremes are projected to increase, with longer summer dry periods and heavier rain in winter. Snow cover will continue to decline further, but there may still be some winters with high snowfall; it will just stay on the ground for less time.

So what does this mean in terms of water availability? Using 12 projections from a Regional Climate Model, we created a Climatic Water Balance indicator (indicating meteorological drought, as opposed to hydrological drought), to show where there may be a shift from water surplus to a deficit.

During the winter there is likely to be plenty of surplus water available. The problem comes in the spring and summer in the east of Scotland, where there is an increasing risk of less water availability to crops from our soils. This is because there may be less rainfall, but higher rates of evapotranspiration.

For barley yields, this means likely increased annual variability, with some years potentially experiencing good yields when conditions are favourable but with an overall decrease in yields by the 2040s, which continues to worsen by the 2070s.

The 12 climate projections used suggest temperature increases ranging from 1-3.5°C and, for growing season rainfall, a range between a 7% increase and a 14% decrease.

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This points to lower barley yields in many parts of Scotland, most likely due to additional water stress, depending on a soil’s capacity to hold water, especially if precipitation is limited in the spring to early summer periods.

There could be potential increases when there are favourable weather conditions (adequate spring precipitation), but overall reductions, especially where soils have lower water holding ability and / or on degraded topsoil (for example due to erosion and compaction) with low carbon and hence low water retention ability.

This is likely to cause substantial challenges to the barley supply chain and end users. Earlier sowing when possible could be a practical adaptation choice.

Of course, barley isn’t our only crop or use of land. Many other types of what can be called natural capital will also be affected by climate change.

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Flooding events could also increase the risk of spreading invasive species, increased erosion, and concentrated diffuse pollution flushes. Reduced snow cover will also affect water flow rates into rivers, often used for water abstraction in times of low rainfall for irrigation, while warmer air temperatures and altered albedo (darker surfaces) will increase water temperatures.

This increased water excess and scarcity stress will impact multiple species and habitats, in turn affecting ecosystem functions and the provision of ecosystem services, from pollinators to peatlands, as well as creating a higher potential for fire risk.

These are challenges we need to think about now, to mitigate the causes and adapting to the impacts of climate change. Using approaches such as Nature Based Solutions and fair burden sharing, rooted in social justice aims, could ensure we have sustainable economies and environments.