Extreme droughts are here – but we aren’t powerless

+ Earth’s freshwater cycle bent out of shape ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌ ‌
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Somalia is suffering its longest drought in more than four decades, threatening millions of people with starvation. In the US, human remains are surfacing at Lake Mead near Las Vegas, where water levels recently reached a record low. Europe faces one of its driest summers in recent memory, while low rainfall has ruined thousands of acres of rice crops in Cambodia.
You’re reading the Imagine newsletter – a weekly synthesis of academic insight on solutions to climate change, brought to you by The Conversation. I’m Jack Marley, energy and environment editor. This week we’re examining what’s driving droughts and how the world can adapt to drier conditions.
“Droughts are *complex extreme events* <theconversationuk.cmail19.com/t/r-l-tyktujkl-ukjyiutthd-r/> that result from a combination of drivers,” say Friederike Otto and Maarten van Aalst, researchers who study extreme weather and disaster risk at Oxford University and Columbia University in the US, respectively. “In the atmosphere, these include regular climate variability – including day-to-day weather – and larger seasonal patterns related to cycles, such as El Niño and La Niña. There could also be human-induced drivers like greenhouse gas emissions, or events such as volcanic eruptions.”
The fingerprint of climate change on any single drought is difficult to discern. But scientists can estimate its role by examining how 1.2°C of global heating so far has influenced average temperatures in a particular region, and determining what contribution this has made to drought conditions there.
“In the same way that loading a dice can increase the likelihood of rolling a six, the presence of human-induced climate change can alter the likelihood that a drought will occur,” say Otto and van Aalst. “Beyond the atmosphere itself, the condition of water reserves, soil and vegetation are critical.”
In an assessment published earlier this year, scientists at Stockholm University declared that human disruption to *Earth’s freshwater cycle* <theconversationuk.cmail19.com/t/r-l-tyktujkl-ukjyiutthd-y/> – which moves moisture from the soil and plants into clouds and back again – had exceeded the safe limit.
“We found that since the industrial revolution, and especially since the 1950s, larger parts of the world are subject to significantly drier or wetter soil. This shift towards extreme conditions is an alarming development due to the indispensable role of water in maintaining resilient societies and ecosystems,” say Arne Tobian, Dieter Gerten and Lan Wang Erlandsson, who led the research.
“More frequent and severe dry spells mean prolonged and more intense droughts in many regions … Global heating and changes to how the land is used, especially deforestation, are among the biggest factors responsible,” the team say.
“Research shows that clearing forests reduces the flow of moisture to the atmosphere, dampening how efficiently the Earth system can circulate water and ultimately putting ecosystems like the Amazon at risk of collapse.”
Since greenhouse gas emissions and habitat destruction have made droughts stronger and more likely to occur, the most pragmatic response is to reduce and reverse both. Tom Ovenden is a PhD candidate at the University of Stirling who researches how forests in particular can ameliorate droughts.
“Different [tree] species have different strategies for dealing with this kind of stress, but how they deal with losing water is particularly important,” he says.
When faced with a dry spell, some trees close the holes on their leaves which absorb CO₂ to prevent water escaping. Anyone familiar with the basics of photosynthesis will understand that less CO₂ means less food. Some trees take a risk and continue absorbing CO₂ at the expense of being able to effectively transport water.
Ovenden describes the unique responses different species take to droughts in terms of “personalities”. He argues that restoring more diverse forests is a better bet for *improving the cycling of fresh water* <theconversationuk.cmail19.com/t/r-l-tyktujkl-ukjyiutthd-j/> than rolling out plantations:
“If every species relied on the exact same strategy it would be a bit like putting all of their eggs in one basket … With a greater variety of tree personalities, forests are likely to be more resilient to droughts … than those made up of a single species,” Ovenden says.
Deep underground where tree roots struggle to reach, vast *aquifers of fresh water* <theconversationuk.cmail19.com/t/r-l-tyktujkl-ukjyiutthd-t/> have traditionally helped people endure periods of low rainfall. By improving the management of this groundwater, more lives can be saved each time droughts strike says Evan Thomas, an associate professor of engineering at the University of Colorado Boulder.
“An estimated 400 million people in Africa use groundwater. In the past decades, throughout the Horn of Africa, millions of dollars have been spent on the installation of borehole pumps so people can access groundwater.
“However, evidence shows that local communities and regional governments are not yet able to manage the operations, maintenance and service delivery of groundwater. This is because they lack funding … maintenance training, asset management tools, supply chains, and financially viable service contracts,” Thomas claims.
“As a result, there have been a high number of water point failures. For example, in Kenya about 35% of rural water pumps were broken before the 2016 drought. This increased to over 55% during the drought because of mechanical failures or depleted groundwater.”
By using electronic sensors to monitor which pumps weren’t working and notify maintenance workers in Rwanda, Thomas’s research team was able to cut the duration of downtime in which parts of the water system were unavailable from 200 days to 20 days.
“We also use satellite-based rainfall estimates to predict if a non-used pump is either broken, or simply not being used because surface water is available,” he says.
“Our data is being used by local communities, regional governments, and national and international donors to reduce repair intervals. This means communities have more reliable access to water during dry seasons.”
*- Jack Marley, Environment commissioning editor*
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[image: A green stalk of corn is surrounded by dead stalks in a dry field.] <theconversationuk.cmail19.com/t/r-l-tyktujkl-ukjyiutthd-d/>
*Human disruption to Earth’s freshwater cycle has exceeded the safe limit, our research shows* <theconversationuk.cmail19.com/t/r-l-tyktujkl-ukjyiutthd-h/>
‘Green water’ is essential for healthy soils and a benign climate, but it’s under threat. Read more <theconversationuk.cmail19.com/t/r-l-tyktujkl-ukjyiutthd-k/>
[image: A wooden canoe lies on parched ground.] <theconversationuk.cmail19.com/t/r-l-tyktujkl-ukjyiutthd-u/>
*Droughts in East Africa: some headway in unpacking what’s causing them <theconversationuk.cmail19.com/t/r-l-tyktujkl-ukjyiutthd-o/>*
It’s very easy to assume climate change causes droughts, but they are complex extreme events that result from a combination of drivers. Read more <theconversationuk.cmail19.com/t/r-l-tyktujkl-ukjyiutthd-b/>
[image: Two trees with knotted roots.] <theconversationuk.cmail19.com/t/r-l-tyktujkl-ukjyiutthd-p/>
*Climate change: having the right combination of tree ‘personalities’ could make forests more resilient <theconversationuk.cmail19.com/t/r-l-tyktujkl-ukjyiutthd-x/>*
The species which surround a tree in a forest make up the character of its neighbourhood. Good neighbours can make forests resilient to climate change. Read more <theconversationuk.cmail19.com/t/r-l-tyktujkl-ukjyiutthd-c/>
[image: A person pours water into a plastic container.] <theconversationuk.cmail19.com/t/r-l-tyktujkl-ukjyiutthd-q/>
*Groundwater can prevent drought emergencies in the Horn of Africa. Here’s how <theconversationuk.cmail19.com/t/r-l-tyktujkl-ukjyiutthd-a/>*
Drought-driven humanitarian emergencies can be prevented if groundwater is reliably made available at strategic locations. Read more <theconversationuk.cmail19.com/t/r-l-tyktujkl-ukjyiutthd-f/>

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