The study, published in the scientific journal "Environmental Research Letters", warns that the effects of climate change on harvests can lead to food shortages and higher prices.
Teresa Armada Brás, the researcher who led the study, explained to Lusa that, although there are many investigations that show the increase in the frequency of extreme climate events, the losses in agriculture associated to these events have not been studied.
Those responsible, researchers from the Faculty of Science and Technology (FCT NOVA), joined by a researcher from the Potsdam Institute for Climate Impact Research ("Potsdam Institute for Climate Research", in Germany) and NASA (United States), combined agricultural data and extreme weather events between 1961 and 2018.
Droughts, heat waves, cold waves and floods were taken into account in the analysis. We divided the study period into two parts, one until 1990 and another from 1991 to 2018, "and we found that the losses in agriculture are much greater in the second part", said Teresa Armada Brás.
According to the document, which resulted from a year and a half of research, historical droughts and heat waves have reduced European cereal yields on average by 9 percent and 7.3 percent, respectively. In other non-cereal crops yields decreased by 3.8, and 3.1 percent during the same periods of droughts and heat waves.
Cold waves led to a 1.3 percent drop in cereal yields and a 2.6 percent drop in non-cereal yields, while the impacts of floods were marginal and negligible.
Titled "Severity of drought and heat wave crop losses tripled over the last five decades in Europe", the study included 28 European countries (current EU and UK) and concludes that cereals are the most affected crop and that the worst weather events are heat waves and drought. These two events in 2018 in Europe caused an 8 percent drop in cereal production compared to the previous five years.
Teresa Armada Brás points out that notably in cereals the losses in Europe tripled between the two periods (before and after 1990). If in the first period, extreme climatic events had an estimated impact on production of minus 3.6 percent, after 1990 the impact was minus 9.8 percent.
Taking into account all crops, and 130 crops were analysed, the impacts also tripled, from minus 2.2 percent in the first period to minus 7.7 percent in the most recent years.
The official, pointing out that the numbers result from officially reported data, adds that "the food system has been damaged with the occurrence of extreme climate phenomena", also alerting to projections from the Intergovernmental Panel on Climate Change (IPCC in the original acronym) that point to an increase in dry periods in the summer, with longer and more intense heat waves.
Over the years, according to the researcher, all of Europe has suffered "more or less in the same way" the effects of droughts and heat waves, although the impacts in the Mediterranean area have been smaller, due to the large percentage of irrigated crops, which mitigates the effects of droughts and heat waves.
"The work alerts to the need to understand which are the most resilient crops for Europe and highlights the need for the intelligent use of water".
And he provides other data, arising from the study just released: a drought, on average, causes a loss of 8.5 percent of cereal production. And if the crop is wheat, the loss is even greater (in cold waves the loss is less than 2 percent). And each year the droughts become more severe, with cereal losses increasing by an average of 3 percent with each new drought.
The European Union's food system is disrupted by extreme weather events, assessing the main impacts and vulnerabilities is important because it can contribute to a redefinition of risk reduction efforts, to adaptation and also to reviewing the European Union's food trade flows, which may conclude that it will be better to stop producing certain crops due to climate change, explains the researcher.
In addition to Teresa Armada Brás, FCT NOVA researchers Júlia Seixa and Nuno Carvalhais, and researcher Jonas Jägermey participated in the work.