8 Ancient Environmental Disasters Caused by Humans

Mayan ruins against blue sky in Tulum, Mexico
The Mayans' slash-and-burn agricultural practices caused a megadrought that could have led to their demise.

DC_Aperture / Shutterstock

Over the past million years, it's true that the Earth has gone through periods of extreme warming and cooling and that at times throughout its evolutionary history, it has been almost entirely void of life—but it's also true that humans can cause environmental disasters, too. Long before the boons of modern industry and technology, homo sapiens were capable of wreaking planetary havoc, even without the complex weaponry that exists today.

Here are eight environmental disasters either believed to have or confirmed to have been caused by humans, including extinctions, civilization collapses, ecological collapses, and desertification.

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North American Megafauna Extinction

Museum exhibit featuring skeleton of giant ground sloth

Sandy__R / Wikimedia Commons / CC BY 2.0

During the Pleistocene Epoch, the Americas were inhabited by some of the largest mammals ever to have walked the Earth—giant ground sloths, woolly mammoths, horses, giant beavers, massive cave bears, and even American lions and cheetahs. While experts have long debated the cause of their collective demise, no one denies the eerie coincidence that all of them went extinct simultaneously around 13,000 years ago, just as stone tool-wielding human hunters first arrived from across the Bering land bridge. The common theory that humans wiped out North American megafauna is widely referred to as "overkill."

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Easter Island Ecological Collapse

Group of Moai statues lined up on Easter Island
Feifei Cui-Paoluzzo / Getty Images

Despite being one of the world's most remote islands, Easter Island was once home to a great civilization famous for constructing 887 giant stone statues (called moai) all across the island. The civilization collapsed in the 1860s on account of some of the worst environmental management in human history. Nearly every last tree was chopped down between the time the first Easter Island settlers arrived in 900 C.E. to 1722. They were likely used as tools to erect the stone structures. As a result, all the native tree species on the island were driven to extinction, destroying the soil and forever altering the ecosystem of the island.

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Gilgamesh and Ancient Sumerian Deforestation

Stone tablet with the Epic of Gilgamesh inscribed

Osama Shukir Muhammed Amin FRCP (Glasg) / Wikimedia Commons / CC BY-SA 4.0

The epic Sumerian tale of Gilgamesh inscribed on ancient clay tablets describes vast tracts of cedar forests in what is now southern Iraq. In the tale, Gilgamesh defies the gods by cutting down the forest, and in return, the gods say they will curse the land with fire and drought. In fact, the Sumerians themselves likely deforested the land, causing widespread desertification. Soil erosion and salt buildup devastated agriculture by 2100 B.C.E., forcing residents to move north to Babylonia and Assyeria.

Further evidence for this theory? Some of the first laws ever written to protect forests were decreed in the Sumerian settlement of Ur.

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Collapse of the Mayan Civilization

Aerial view of Mayan ruins on coast in Tulum, Mexico
Robert Landau / Getty Images

The Mayans—one of the mightiest civilizations in the Americas, known for their highly sophisticated writing system, architecture, and astronomical savviness, among other progressive proficiencies—may have collapsed on account of a smorgasbord of ecological problems. Their bloated population was sustained for such a short time due to an unsustainable system of slash-and-burn agriculture, which eventually destroyed the forests, causing a "megadrought" by eliminating the natural tree canopy water-capture system. Eventually, biological diversity dwindled and the Mayan civilization collapsed (around 900 C.E.) likely as a result of their own actions.

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Collapse of the Minoan Civilization

Minoan archeological site on the island of Crete
Dmitry Naumov / Getty Images

Archaeological evidence from the Minoan civilization of Crete (lasting from 3000 to 1100 B.C.E.) has shown proof of deforestation during the late stages of development, leading many scholars to suggest that environmental mismanagement may have been a chief culprit in its collapse. Since the Minoans were a mighty sea power, they likely needed large quantities of wood to construct their ships. They also used wood for economic transactions, and when the supply ran out, Crete was hit with detrimental soil erosion and flash flooding. The change in weather caused Minoans to relocate or close their production facilities. The social and natural challenges together could have been the reason for their gradual demise.

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Nazca Culture and Desertification

Giant Nazca geoglyph carved into coastal cliff
Mauricio Araya / Getty Images

Famous for constructing the cryptic "Nazca Lines," or geoglyphs, Peru's ancient Nazca culture (which flourished from 100 to 800 C.E.) likely perished because of the deforestation and subsequent desertification of the landscape. The land, which was once a vast riverside oasis with fertile soils capable of supporting thousands of people, was held together by the ancient root systems of trees called huarangos, which were systematically cut down by the Nazca people for fuel and wood. The loss of these trees made the Nazca people and their vital agricultural crops more susceptible to El Nino flooding, soil erosion, and drought. Today, the region they once inhabited is still among the driest, most arid in South America.

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Australian Megafauna Extinctions

Skeleton of giant diprotodon displayed in a museum

LadyofHats / Wikimedia Commons / Public Domain

Like the North American megafauna extinctions, Australia's disaster 45,000 to 50,000 years ago coincided with the arrival of humans. The ancient megafauna of Australia were unlike creatures found anywhere else in the world: They included giant marsupial lions, hippopotamus-sized marsupials called diprotodons (basically giant wombats), lizards that grew to as long as 23 feet, and huge flightless birds related to waterfowl. While the cause of their extinctions some 42,000 years ago remains unresolved, leading theories point to climate change, modified ecosystems caused by the spread of humans, overkill, or a combination of all three.

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Collapse of the Anasazi Civilization

Anasazi cliff dwellings in Mesa Verde National Park
www.fordesign.net / Getty Images

Like so many other civilizations and cultures, the Anasazi fell victim to environmental pressures. Overpopulation put a severe strain on scant water resources in the American Southwest, where the Anasazi lived. The problem was exacerbated by a period of extreme drought, which the Anasazi became incapable of managing because of overstretched agricultural irrigation technology. The Anasazi people wound up fleeing their magnificent cliff dwellings for the Rio Grande and the Little Colorado rivers toward the end of the 13th century.