The extreme heatwave in North America is posing a major threat to the global food supply chain according to leading scientists.
Dr Alexandre Koberle, Research Fellow at the Grantham Institute for Climate Change and the Environment at Imperial College London, warned the heatwave will have far reaching effects in the future of the world’s agricultural production.
“The extreme heat wave roasting Western North America is linked to a long-term drought affecting the region,” he said. “Hot droughts such as this compound the impact on agricultural productivity and have been shown to lead to deeper and wider yield losses. Actual impacts will depend on local conditions of soil moisture and crop health before the heat wave, but many areas are reporting extremely low sub-soil moisture conditions. Irrigation helps reduce the impacts, but wind and heat reduce the effectiveness of irrigation. While all crops suffer in these conditions, fruits and vegetables that require good moisture may particularly at risk. Raspberries are “baking on the vine” and strawberries are ripening too quickly before they reach size. Forage crops are also impacted, putting livestock at risk. This heatwave is an example of the type of events agriculture will have to adapt to in the coming years, not decades. If North American farmers are struggling, imagine what happens in other regions where equipment, insurance and finance are lacking. Climate smart agriculture needs to be scaled up in the most vulnerable regions of the world.
“This heat wave is also affecting US prairie crops, much of which is exported. Extreme drought in Brazil, the other large agricultural exporter, is also putting harvests there at risk. While these events are not directly linked, higher probability of extreme events globally also increases the risk that they occur simultaneously in several regions. The global agricultural commodities market may face shortages putting food security at risk.”
Dr Emma Lawrance, Mental Health Innovations Fellow at the Institute of Global Health Innovation at Imperial College London and Climate Cares lead, warned the human costs were already being felt.
“Climate change is bringing higher temperatures and more frequent extreme heat in many places around the world,” she said. “We are sadly seeing the impacts of extreme heat on physical health and deaths in Canada and the USA right now. Research tells us that it is not only physical health that suffers at such high temperatures, but also mental health. Instances of suicide and hospital visits for mental illness or extreme distress rise with increasing temperature. If climate change continues at its current rate, rising temperatures may lead to an estimated 22,000 extra suicides across the USA and Mexico alone by 2050.
“While the elderly are a well-known at risk group in extreme heat, it is less well known that people with diagnosable mental disorders – particularly psychosis, dementia and substance abuse – are also more at risk, and by some estimates are two to three times more likely to die in a heatwave. Heatwaves can increase violence in the community, reduce economic outputs, and disrupt sleep, as well as induce physiological changes affecting mental function. The result is that population mental health suffers. For example, depressive language on Twitter rises at higher temperatures, and self-reported mental health and wellbeing declines.
“The effects of extreme heat on mental health is another example of how climate change exacerbates inequalities – poorer communities and individuals with experiences of mental illness are more vulnerable to the impacts of heat and may be less likely to have access to the cooling effects of green space, air conditioning and appropriate housing.
“Health systems and public health must prepare now for the impacts of heatwaves to come. But the good news is that actions to reduce the impacts of heat in our cities, such as increased tree cover, more equitable green space access and improved housing, can also help reduce further climate change. This is a win-win opportunity to turn a vicious cycle into a virtuous cycle and policy makers and communities must act now.”
Dr Fredi Otto, Associate Director of the Environmental Change Institute and Associate Professor in the Global Climate Science Programme, University of Oxford added: “Every heatwave occurring today is made more likely and more intense by human-induced climate change. In some cases, local factors enhance or counteract this effect. In that part of the world there is nothing to suggest that the latter is happening, so climate change is definitely one of the significant drivers of the intensity. How big a driver it is, is a work in progress.”
Dr Paulo Ceppi, lecturer in climate science at Imperial College London, warned the heatwave was a sign of things to come.
“In terms of the causes of the North American heatwave, there are two key factors. First and foremost, the weather: the heatwave was associated with a very unusual weather pattern – a very strong anticyclone (area of high atmospheric pressure) causing the air to sink and warm up, described as a ‘heat dome’ in the media. Also, the winds associated with this anticyclone pushed hot air from inland areas toward the coast, displacing the cooler marine air that usually keeps this coastal region temperate.
“Then, there is the climate. Global warming is shifting the odds and making heatwaves increasingly likely, while making cold spells less likely. There’s no doubt that climate change has increased the severity of the current heatwave. If global warming continues amplifying, we can expect more and more of these unprecedented heatwaves to occur in different parts of the world.
“Humans have already caused substantial global warming (about 1.2°C since 1850). With current carbon emissions we expect this warming to proceed at a fast pace. The only way to stop this trend is by drastically reducing our emissions of carbon dioxide, ideally to net zero. If we are to comply with the Paris Agreement ambition to limit global warming to 1.5°C, we would need to take extremely rapid action. Scientists have calculated that we’d need to reduce emissions to net zero by 2050, so we only have 3 decades left. However, it’s also important to remember that it’s never too late to take action: every tenth of a degree makes a difference.”
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