More than three-quarters of Earth’s surface has become permanently drier, UN report says
Kate Helmore ([url]https://www.theglobeandmail.com/authors/kate-helmore/)Agriculture[/url] and food policy reporter
Matthew McClearn ([url]https://www.theglobeandmail.com/authors/matthew-mcclearn/[/url])
Published 5 hours ago
An area of Earth larger than India has transformed from humid lands to dryland over the past three decades, destroying food systems, driving poverty and leading to water shortages across the globe, according to a new UN report.
The report, prepared under the United Nations Convention to Combat Desertification’s Science-Policy Interface – the UN body for assessing the science of land degradation and drought – found that between 1990 and 2020, more than three-quarters of the Earth’s land became permanently drier. More than 40 per cent of the global land mass (excluding Antarctica) is now classified as drylands – up from 37 per cent in previous decades. Twice as many people worldwide live in drylands today compared with 1990.
The report found that an area larger than Canada – equivalent to 7.6 per cent of all land – had been permanently transformed, for example from humid landscapes to drylands, or from forests into grasslands. China saw the largest total area permanently transformed; as a percentage of their total area, South Sudan and Tanzania were hit hardest.
Ibrahim Thiaw, the convention’s executive secretary, called it “an existential threat affecting billions of people” in a written statement.
Should high greenhouse-gas emissions continue, the authors forecast further expansion of drylands, including throughout the entire Mediterranean region, northern Venezuela, northeastern Brazil and large swaths of southern Africa. They would also grow on this continent, in central Mexico and across the American Midwest.
Jonathan Overpeck, dean of the University of Michigan’s school of environment, said the report highlights the problem more comprehensively than previous efforts.
But he said that while the report is “sophisticated and impressive,” it understates the problem’s extent. That’s because it focuses on moisture available through precipitation, but overlooks water locked up in ice. In many regions, snow and ice allow “moisture in the warmer months, because instead of raining in the winter, you get the snow, which persists on the land longer. … It’s sort of like a natural reservoir.” But climate change is melting that ice in mountainous regions including the Himalayas, the Andes and the Alps.
Prof. Overpeck added that the report also didn’t take into account the role of melting permafrost, which causes soil and vegetation to dry out.
“That’s really devastating for forests in Northern Canada and other parts of the boreal forest around the globe,” he said.
Though aridity and drought are often conflated, they are in fact distinct: The main difference is that while droughts can persist for months or years, they eventually end, allowing people and ecosystems to recover. But rising aridity is a permanent change that can’t be waited out; the only option is to adapt.
“There’s no going back from aridity,” said Narcisa Pricope, one of the report’s authors.
Greenhouse-gas emissions lead to increased aridity through trapping more heat in the atmosphere. These increased temperatures exacerbate water evaporation, therefore removing moisture from soil.
Aridity is a vicious cycle. As the soil becomes drier it is less able to sustain ecosystems, which means fewer plants grow, so less dead plant matter is absorbed by the soil. Dead plants within soil – detritus vegetation – trap moisture, which in turn feeds the soil and the ecosystem.
However, agricultural practices can also contribute to dryness – notably the use of fertilizer, which robs the soil of moisture-rich biodiversity, or by tillage, whereby soil is fractured, leading to increased runoff, erosion and a surface crust that water cannot infiltrate.
When more than half the world’s agricultural land and its soils are degrading, UNCCD chief scientist Barron Orr said, “your risk goes up, you have less cover and you are exacerbating the aridity trend.”
However, while increased aridity is a worldwide crisis, it presents an opportunity for Canadian agriculture, said Evan Fraser, director of the Arrell Food Institute at the University of Guelph.
Canadian producers still have access to huge areas of arable land and water, alongside infrastructure and energy, such as solar and hydro, he said. Compared with other agricultural countries, production in Canada is also efficient and well regulated, with sustainable practices that have the capacity to carry into a drier and more arid future.
The Canadian resilience to dry conditions can be seen in arid landscapes within the Prairies, said Margot Hurlbert, a researcher at the University of Regina. Despite a four-year drought, farmers have nevertheless managed to maintain yields through practices such as crop rotation, minimizing tillage and allowing soil to recover during some growing seasons. Planting less water-intense crops are also a key part of the solution, she said.
However, simply because these measures have worked during past droughts does not mean they will continue to work, Prof. Hurlbert said.
“We know droughts will get more intense over the next few years. The key is balance and recovery and diversifying the risk.”
To Mr. Orr, sustainable, water-focused agricultural policies in Canada and elsewhere are key to fighting increased aridity on a global scale. By subsidizing and promoting practices that lead to healthy soil – which in turn sequesters carbon – overall worldwide emissions can be reduced.
“Aridity is resulting from cascading effects that stem from climate change,” he said. “But we could try and have a positive, enhancing feedback loop too, maybe not as rapid but nonetheless long-term.”
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Kate Helmore ([url]https://www.theglobeandmail.com/authors/kate-helmore/)Agriculture[/url] and food policy reporter
Matthew McClearn ([url]https://www.theglobeandmail.com/authors/matthew-mcclearn/[/url])
Published 5 hours ago
An area of Earth larger than India has transformed from humid lands to dryland over the past three decades, destroying food systems, driving poverty and leading to water shortages across the globe, according to a new UN report.
The report, prepared under the United Nations Convention to Combat Desertification’s Science-Policy Interface – the UN body for assessing the science of land degradation and drought – found that between 1990 and 2020, more than three-quarters of the Earth’s land became permanently drier. More than 40 per cent of the global land mass (excluding Antarctica) is now classified as drylands – up from 37 per cent in previous decades. Twice as many people worldwide live in drylands today compared with 1990.
The report found that an area larger than Canada – equivalent to 7.6 per cent of all land – had been permanently transformed, for example from humid landscapes to drylands, or from forests into grasslands. China saw the largest total area permanently transformed; as a percentage of their total area, South Sudan and Tanzania were hit hardest.
Ibrahim Thiaw, the convention’s executive secretary, called it “an existential threat affecting billions of people” in a written statement.
Should high greenhouse-gas emissions continue, the authors forecast further expansion of drylands, including throughout the entire Mediterranean region, northern Venezuela, northeastern Brazil and large swaths of southern Africa. They would also grow on this continent, in central Mexico and across the American Midwest.
Jonathan Overpeck, dean of the University of Michigan’s school of environment, said the report highlights the problem more comprehensively than previous efforts.
But he said that while the report is “sophisticated and impressive,” it understates the problem’s extent. That’s because it focuses on moisture available through precipitation, but overlooks water locked up in ice. In many regions, snow and ice allow “moisture in the warmer months, because instead of raining in the winter, you get the snow, which persists on the land longer. … It’s sort of like a natural reservoir.” But climate change is melting that ice in mountainous regions including the Himalayas, the Andes and the Alps.
Prof. Overpeck added that the report also didn’t take into account the role of melting permafrost, which causes soil and vegetation to dry out.
“That’s really devastating for forests in Northern Canada and other parts of the boreal forest around the globe,” he said.
Though aridity and drought are often conflated, they are in fact distinct: The main difference is that while droughts can persist for months or years, they eventually end, allowing people and ecosystems to recover. But rising aridity is a permanent change that can’t be waited out; the only option is to adapt.
“There’s no going back from aridity,” said Narcisa Pricope, one of the report’s authors.
Greenhouse-gas emissions lead to increased aridity through trapping more heat in the atmosphere. These increased temperatures exacerbate water evaporation, therefore removing moisture from soil.
Aridity is a vicious cycle. As the soil becomes drier it is less able to sustain ecosystems, which means fewer plants grow, so less dead plant matter is absorbed by the soil. Dead plants within soil – detritus vegetation – trap moisture, which in turn feeds the soil and the ecosystem.
However, agricultural practices can also contribute to dryness – notably the use of fertilizer, which robs the soil of moisture-rich biodiversity, or by tillage, whereby soil is fractured, leading to increased runoff, erosion and a surface crust that water cannot infiltrate.
When more than half the world’s agricultural land and its soils are degrading, UNCCD chief scientist Barron Orr said, “your risk goes up, you have less cover and you are exacerbating the aridity trend.”
However, while increased aridity is a worldwide crisis, it presents an opportunity for Canadian agriculture, said Evan Fraser, director of the Arrell Food Institute at the University of Guelph.
Canadian producers still have access to huge areas of arable land and water, alongside infrastructure and energy, such as solar and hydro, he said. Compared with other agricultural countries, production in Canada is also efficient and well regulated, with sustainable practices that have the capacity to carry into a drier and more arid future.
The Canadian resilience to dry conditions can be seen in arid landscapes within the Prairies, said Margot Hurlbert, a researcher at the University of Regina. Despite a four-year drought, farmers have nevertheless managed to maintain yields through practices such as crop rotation, minimizing tillage and allowing soil to recover during some growing seasons. Planting less water-intense crops are also a key part of the solution, she said.
However, simply because these measures have worked during past droughts does not mean they will continue to work, Prof. Hurlbert said.
“We know droughts will get more intense over the next few years. The key is balance and recovery and diversifying the risk.”
To Mr. Orr, sustainable, water-focused agricultural policies in Canada and elsewhere are key to fighting increased aridity on a global scale. By subsidizing and promoting practices that lead to healthy soil – which in turn sequesters carbon – overall worldwide emissions can be reduced.
“Aridity is resulting from cascading effects that stem from climate change,” he said. “But we could try and have a positive, enhancing feedback loop too, maybe not as rapid but nonetheless long-term.”
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