Two-thirds of Earth's Land Is On Pace To Lose Water As The Climate Warms

Two-thirds of Earth's Land Is On Pace To Lose Water As The Climate Warms
Cape Town residents queued up for water as the taps nearly ran dry in 2018.
Morgana Wingard/Getty Images

The world watched with a sense of dread in 2018 as Cape Town, South Africa, counted down the days until the city would run out of water. The region’s surface reservoirs were going dry amid its worst drought on record, and the public countdown was a plea for help.

By drastically cutting their water use, Cape Town residents and farmers were able to push back “Day Zero” until the rain came, but the close call showed just how precarious water security can be. California also faced severe water restrictions during its recent multiyear drought. And Mexico City is now facing water restrictions after a year with little rain.

There are growing concerns that many regions of the world will face water crises like these in the coming decades as rising temperatures exacerbate drought conditions.

Understanding the risks ahead requires looking at the entire landscape of terrestrial water storage – not just the rivers, but also the water stored in soils, groundwater, snowpack, forest canopies, wetlands, lakes and reservoirs.

We study changes in the terrestrial water cycle as engineers and hydrologists. In a new study published Jan. 11, we and a team of colleagues from universities and institutes around the world showed for the first time how climate change will likely affect water availability on land from all water storage sources over the course of this century.

We found that the sum of this terrestrial water storage is on pace to decline across two-thirds of the land on the planet. The worst impacts will be in areas of the Southern Hemisphere where water scarcity is already threatening food security and leading to human migration and conflict. Globally, one in 12 people could face extreme drought related to water storage every year by the end of this century, compared to an average of about one in 33 at the end of the 20th century.

These findings have implications for water availability, not only for human needs, but also for trees, plants and the sustainability of agriculture.


 Get The Latest From InnerSelf


Where the risks are highest

The water that keeps land healthy, crops growing and human needs met comes from a variety of sources. Mountain snow and rainfall feed streams that affect community water supplies. Soil water content directly affects plant growth. Groundwater resources are crucial for both drinking water supplies and crop productivity in irrigated regions.

While studies often focus just on river flow as an indicator of water availability and drought, our study instead provides a holistic picture of the changes in total water available on land. That allows us to capture nuances, such as the ability of forests to draw water from deep groundwater sources during years when the upper soil levels are drier.

The declines we found in land water storage are especially alarming in the Amazon River basin, Australia, southern Africa, the Mediterranean region and parts of the United States. In these regions, precipitation is expected to decline sharply with climate change, and rising temperatures will increase evaporation. At the same time, some other regions will become wetter, a process already seen today.

The map shows the projected change in terrestrial water storage by the end of the 21st century
The map shows the projected change in terrestrial water storage by the end of the 21st century, compared to the 1975-2005 average, under a mid-range scenario for global warming. A continuum of yellow to orange to dark red reflects increasing severity of loss of stored water; teal to blue to dark blue reflects increasing gains in stored water.
Yadu Pokhrel, et al, Nature Climate Change, 2021, CC BY-ND

Our findings for the Amazon basin add to the longstanding debate over the fate of the rainforest in a warmer world. Many studies using climate model projections have warned of widespread forest die-off in the future as less rainfall and warmer temperatures lead to higher heat and moisture stress combined with forest fires.

In an earlier study, we found that the deep-rooted rainforests may be more resilient to short-term drought than they appear because they can tap water stored in soils deeper in the ground that aren’t considered in typical climate model projections. However, our new findings, using multiple models, indicate that the declines in total water storage, including deep groundwater stores, may lead to more water shortages during dry seasons when trees need stored water the most and exacerbate future droughts. All weaken the resilience of the rainforests.

A new way of looking at drought

Our study also provides a new perspective on future droughts.

There are different kinds of droughts. Meteorological droughts are caused by lack of precipitation. Agricultural droughts are caused by lack of water in soils. Hydrological droughts involve lack of water in rivers and groundwater. We provided a new perspective on droughts by looking at the total water storage.

Water in the environment. (two thirds of earth s land is on pace to lose water as the climate warms)
Water in the environment.
U.K. Met Office

We found that moderate to severe droughts involving water storage would increase until the middle of the 21st century and then remain stable under future scenarios in which countries cut their emissions, but extreme to exceptional water storage droughts could continue to increase until the end of the century.

That would further threaten water availability in regions where water storage is projected to decline.

Changes driven by global warming

These declines in water storage and increases in future droughts are primarily driven by climate change, not land-water management activities such as irrigation and groundwater pumping. This became clear when we examined simulations of what the future would look like if climate conditions were unchanged from preindustrial times. Without the increase in greenhouse gas emissions, terrestrial water storage would remain generally stable in most regions.

If future increases in groundwater use for irrigation and other needs are also considered, the projected reduction in water storage and increase in drought could be even more severe.

About the AuthorThe Conversation

Yadu Pokhrel, Associate Professor of Civil and Environmental Engineering, Michigan State University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Related Books

The Human Swarm: How Our Societies Arise, Thrive, and Fall

by Mark W. Moffett
0465055680If a chimpanzee ventures into the territory of a different group, it will almost certainly be killed. But a New Yorker can fly to Los Angeles--or Borneo--with very little fear. Psychologists have done little to explain this: for years, they have held that our biology puts a hard upper limit--about 150 people--on the size of our social groups. But human societies are in fact vastly larger. How do we manage--by and large--to get along with each other? In this paradigm-shattering book, biologist Mark W. Moffett draws on findings in psychology, sociology and anthropology to explain the social adaptations that bind societies. He explores how the tension between identity and anonymity defines how societies develop, function, and fail. Surpassing Guns, Germs, and Steel and Sapiens, The Human Swarm reveals how mankind created sprawling civilizations of unrivaled complexity--and what it will take to sustain them.   Available On Amazon

Environment: The Science Behind the Stories

by Jay H. Withgott, Matthew Laposata
0134204883Environment: The Science behind the Stories is a best seller for the introductory environmental science course known for its student-friendly narrative style, its integration of real stories and case studies, and its presentation of the latest science and research. The 6th Edition features new opportunities to help students see connections between integrated case studies and the science in each chapter, and provides them with opportunities to apply the scientific process to environmental concerns. Available On Amazon

Feasible Planet: A guide to more sustainable living

by Ken Kroes
0995847045Are you concerned about the state of our planet and hope that governments and corporations will find a sustainable way for us to live? If you do not think about it too hard, that may work, but will it? Left on their own, with drivers of popularity and profits, I am not too convinced that it will. The missing part of this equation is you and me. Individuals who believe that corporations and governments can do better. Individuals who believe that through action, we can buy a bit more time to develop and implement solutions to our critical issues. Available On Amazon

From The Publisher:
Purchases on Amazon go to defray the cost of bringing you InnerSelf.com, MightyNatural.com, and ClimateImpactNews.com at no cost and without advertisers that track your browsing habits. Even if you click on a link but don't buy these selected products, anything else you buy in that same visit on Amazon pays us a small commission. There is no additional cost to you, so please contribute to the effort. You can also use this link to use to Amazon at any time so you can help support our efforts.

 

thirds
enafarzh-CNzh-TWnltlfifrdehiiditjakomsnofaptruessvtrvi

follow InnerSelf on

facebook-icontwitter-iconrss-icon

 Get The Latest By Email

{emailcloak=off}

FROM THE EDITORS

InnerSelf Newsletter: January 24th, 2021
by InnerSelf Staff
This week, we focus on self-healing... Whether the healing is emotional, physical or spiritual, it is all connected within our own selves and also with the world around us. However, for healing to…
Taking Sides? Nature Does Not Pick Sides! It Treats Everyone Equally
by Marie T. Russell
Nature does not pick sides: it simply gives every plant a fair chance to life. The sun shines on everyone regardless of their size, race, language, or opinions. Can we not do the same? Forget our old…
Everything We Do Is A Choice: Being Aware of Our Choices
by Marie T. Russell, InnerSelf
The other day I was giving myself a "good talking to"… telling myself I really need to exercise regularly, eat better, take better care of myself… You get the picture. It was one of those days when I…
InnerSelf Newsletter: January 17, 2021
by InnerSelf Staff
This week, our focus is "perspective" or how we see ourselves, the people around us, our surroundings, and our reality. As shown in the picture above, something that appears huge, to a ladybug, can…
A Made-Up Controversy - "Us" Against "Them"
by Robert Jennings, InnerSelf.com
When people stop fighting and start listening, a funny thing happens. They realize they have much more in common than they thought.