The Sahara Desert Is Expanding and Slowly Encroaching on Green Lands

You find yourself in Africa, a continent renowned for its diverse wildlife, rich cultures, and languages, and home to the world’s largest hot desert: the Sahara.

It’s daytime, and you’re parched, seeking water and shade after days of trekking. The horizon seems endless, and the heat is relentless, with temperatures averaging around 100°F. This is to be expected in the Sahara Desert, the largest hot desert globally. However, the title of the largest desert belongs to the cold deserts of Antarctica and the Arctic. Antarctica’s icy desert is roughly the size of 1 million Los Angeles International Airports, while the Arctic desert is slightly smaller.

The Sahara stretches across Northern Africa from the Atlantic Ocean to the Red Sea, covering an area large enough to fit about 100,000 Disney World theme parks side by side. Scientists have observed that the Sahara’s boundaries are expanding, a process known as desertification. This occurs due to factors like Hadley circulation, where air rises at the equator and descends in the subtropics, creating dry conditions conducive to desert formation. Since the 1920s, the Sahara is estimated to have expanded by over 10%.

Historically, the Sahara was not always the arid desert it is today. Around 20,000 years ago, the region was lush and green, known as the Green Sahara. Evidence of this verdant past includes rock paintings depicting animals like giraffes and hippos, suggesting a more humid environment. Recent geological studies, including deep-sea sediment cores from off the coast of Mauritania, support the existence of a wetter Sahara. These cores indicate that less dust was carried into the ocean during periods of higher humidity.

This historical green period was influenced by Earth’s axial tilt, which affects the amount of sunlight each hemisphere receives. Around 20,000 years ago, increased sunlight in the Northern Hemisphere led to a more intense West African Monsoon, bringing moisture and creating a verdant landscape with lakes and extensive vegetation.

Archaeological findings reveal that vibrant societies thrived in the Sahara during this humid period, with evidence of tools, fishhooks, and remains of fish. The region experienced multiple green periods over the last 8 million years, driven by changes in solar radiation due to Earth’s orbital cycles. The Sahara will likely see another green phase in the distant future due to these natural cycles.

Currently, the Sahara is expanding into the Sahel, a semi-arid region. Since 1950, the population in the Sahel has grown from 31 million to over 100 million, contributing to land degradation through overcropping and deforestation. This expansion is part of a broader phenomenon of desertification, exacerbated by increased human activity and climate variability.

Similar desertification trends are observed in other parts of the world, such as the Atacama Desert in Chile, which is expanding towards Santiago. Santiago has experienced a significant reduction in rainfall since 2010, leading to severe water shortages and impacts on agriculture.

The situation in the Sahara and similar regions highlights the complex interplay between natural climate patterns and human activities. The ongoing expansion of deserts underscores the need for sustainable land management and climate adaptation strategies.