Of the eight planets and 293 moons that call our solar system home, only Earth has a surface that sloshes with liquid water. Roughly 71% of the face of our world is covered in seas, lakes, rivers, and oceans, serving as the elixir for more than three billion years of global life. But parts of Earth are not as wet as they used to be, and that’s thanks mostly to the highest of those life forms—us.
According to a just-released report by the United Nations Convention to Combat Desertification (UNCCD), human-driven climate change is leading to a permanent state of increased dryness on 77.6% of the Earth’s land masses, a steady desiccation that has been playing out over the 30-year period from 1990 to 2020. During those three decades, drylands expanded worldwide by 4.3 million sq. km (1.66 million sq. mi.), an area nearly a third larger than the nation of India. And when the UNCCD says dry, they mean for keeps.
“Unlike droughts—temporary periods of low rainfall—aridity represents a permanent, unrelenting transformation,” said UNCCD executive secretary Ibrahim Thiaw in a statement that accompanied the release of the report—published as nations gather in Saudi Arabia for the 16th U.N. conference of the parties to combat desertification. “Droughts end. When an area’s climate becomes drier, however, the ability to return to previous conditions is lost. The drier climates now affecting vast lands across the globe will not return to how they were before and this is redefining life on Earth.”
Indeed it is. According to the UNCCD, the transformation over the three studied decades is leading to loss of GDP, forced migration, increased mortality due to dust storms, worsening of wildfires, land erosion, vegetation degradation, salinization of water and soil, and more.
“Without concerted efforts, billions face a future marked by hunger, displacement, and economic decline,” said Nicole Barger, chair of the UNCCD’s science-policy interface in a statement. “Yet, by embracing innovative solutions and fostering global solidarity, humanity can rise to meet this challenge. The question is not whether we have the tools to respond—it is whether we have the will to act.”
For the purposes of the report, aridity was measured as a function of three variables: ambient rainfall, transpiration—or the rate at which water is transferred to the atmosphere via plants—and evaporation. Drylands were defined as places in which annual potential evaporation and transpiration are 45% greater than average precipitation. Areas that meet that definition now cover 40.6% of all land on Earth, excluding Antarctica. And an additional 3% of the world’s currently humid areas are projected to become arid by the end of this century.
Europe is feeling the current burn especially acutely, with a whopping 95.9% of the continent experiencing drying. Also hard hit are Brazil, parts of the western U.S., the Mediterranean region, central Africa, and eastern Asia. Water, of course, is neither created nor destroyed, merely relocated. As 77.6% of the planet has grown drier, 22.4% has grown wetter, especially in the central U.S., Angola’s Atlantic coast, and southeast Asia—regions that have seen increasingly powerful storms and flooding. But it is drying that is the dominant trend globally, and it’s coming at a steep price.
By century’s end, up to 20% of all Earth’s land could experience abrupt ecosystem transformation, such as forests becoming grasslands, with attendant extinction and collapse of ecosystems. Farming could suffer too. Across Africa, aridity has led to a 12% plunge in GDP, partly driven by degradation of arable land. From 17% to 22% of current crop production is projected to be lost in sub-Saharan Africa by mid-century at the current rate of drying. By 2040, 20 million tons of maize production per year will be lost, along with 19 million tons of rice, eight million tons of soybeans, and 21 million tons of wheat.
More than 2.3 billion people live in the footprint of increased drying and their health could suffer from the environmental change. Reduced food stocks are projected to result in a 55% increase in childhood stunting in sub-Saharan Africa according to UNCCD analyses. More than 620 million people—half the continent’s population—now live in drylands. Water supplies have fallen 75% in Africa as well as in the Middle East as a result of drying—leading not only to shortages of potable water, but also resources needed for sanitation.
In the U.S. desert southwest, experts expect to see a 57% increase in coarse atmospheric dust and a 38% increase in the more dangerous fine atmospheric dust by the end of the century. That, in turn, could lead to a 220% increase in premature deaths from pulmonary illness and a 160% jump in hospitalizations.
By its very nature, the permanence of the current drying belies easy fixes; curbing greenhouse emissions will, in the long term, help lower global temperatures, but the kinds of changes that aridification is causing—such as the spread of parched grasslands, and the loss of forests due to wildfires—will not be reversed for centuries, if at all. For now, the best humanity can do is adapt. The UNCCD recommends wastewater recycling and economical drip irrigation as a way to husband and conserve scarce water. Africa’s Great Green Wall initiative—launched by the African Union in 2007—aims to replant 250 million acres of currently degraded land with low-water-demand greenery by 2030, sequestering 250 million tons of carbon and creating 10 million new green jobs.
Other remedial measures include initiatives like the Beijing-Tianjing Sand Source Control Program, which is similarly regreening vast swaths of China, preventing sand storms and loss of water to evaporation. Independent and industrial farms need to adapt in other ways too, converting to drought-resistant crops like sorghum, okra, and fava beans—while taking care to rotate those and a variety of other similar crops to avoid establishing agricultural monocultures that are susceptible to disease. Livestock populations must change as well, with goats, for example, which are more heat resistant than cows, being swapped in for milk production. In industrialized countries like Saudi Arabia, seawater desalinization is an additional—powerful—way to compensate for increased drying.
None of these measures are perfect fixes; all of them and more will be necessary to clean up the environmental mess humanity has spent the entirety of the industrial age making. “As large tracts of the world’s land become more arid, the consequences of inaction grow increasingly dire,” said UNCCD chief scientist Barron Orr in a statement. “Adaptation is no longer optional—it is imperative.”
