The survival of a society or an organism is entirely dependent on the "carrying capacity" of its environment — that is, the amount of necessary resources available. If you drop a bunch of deer on a vegetation-covered island with no predators, the deer are going to eat as much as they can and reproduce like rabbits. Eventually they will eat all the vegetation available and hit the "carrying capacity" of the island, sending their population plummeting towards extinction as starvation and disease rips through their ranks. Usually Mother Nature keeps things in check, but humans have proven to be excellent at creating disturbances to the natural order. (Think cane toads in Australia or kudzu in the southern U.S.)
But what about humanity itself? Humans are subject to the laws of carrying capacity too. When human societies draw more natural resources from their environment than is organically replenished each year, they start accruing ecological debt, which can compound into society-ending totals. Globalization and the incredible rise of consumerism have increased the chance that ecological overexploitation will take down an entire society.
Most cities and regions are not solely dependent on one geographic area to provide the majority of resources. But on the other hand, globalization relies on a food system that is dependent on the availability of cheap fossil fuels. Take cheap oil out of the equation and you could be looking at the beginning of the end of life as we know it.
It's instructive to look to the past to learn from societies that drove themselves out of existence by hitting their environment too hard. Here are four exploitive societies that died out when their environments could no longer support them.
The nunnery quadrangle in Uxmal. (Photo: Mesoamerican/Wikimedia Commons)
The Mayan civilization was a highly developed and sophisticated society in Central America that peaked, in terms of both population and power, in the 8th and 9th centuries. The exact mechanism that caused the group's downfall is still not exactly clear, but most theories cast the blame on climate change.
Some theories hold that they were brought down by drought exacerbated by the overzealous conversion of rainforest to farmland (sound familiar?), while others put the blame on the Mayans driving animals, which they depended on for food, into extinction.
The central figure holds a were-jaguar in Altar five from La Venta. (Photo: Ruben Charles/Wikimedia Commons)
The Olmec civilization was centered around south-central Mexico (where Tabasco and Veracruz are today) and was the first Mesoamerican civilizations, forming as early as 2000 B.C. and dominating the region through roughly 400 to100 B.C. The Olmecs were able to build their civilization around the many rivers found in their homeland. The rich soils around the rivers were extensively farmed and supported a population of more than 70,000 people.
The Olmecs developed the concept of zero (also independently invented by the Chinese and Greeks), constructed large cities centered around enormous pyramid temples, and connected them together with a network of stone roads that doubled as a rainwater collection system, diverting runoff into community reservoirs.
The jury is still out on the reason for the sharp decline in the Olmec population — their cities emptied by around 100 BCE — but it's likely that it was because of the silting of their rivers caused by management of the waterway. Things like artificial channels and dams and dikes disrupt the natural flow of the river and can cause the buildup of current-choking silt. Changes in the water flow could have been too disruptive for the Olmec to adapt to, sending their agricultural harvests steadily downward.
The Easter Islanders
The exact history of Easter Island is shrouded in mystery. (Photo: Hbcreuz/Wikimedia Commons)
Easter Island, best known for its famous moai — the large iconic stone statues found spread throughout the island — sits in the Pacific Ocean between South America and Australia. The island, first discovered by European explorers in 1722, is thought to have been populated around the same time Hawaii was discovered and settled.
The exact history of the Polynesians who originally lived there is somewhat murky, but it is clear that the island was once the home to a diverse range of large trees, some as tall as 50 feet high. These trees were used by island inhabitants to build fishing boats. Trees also may have been used to build and move the huge stone statues.
By the time the first Europeans arrived, the island was devoid of trees and had seen the extinction of every species of native bird. The deforestation of the island resulted in a crash in the human population size, from an estimated peak of 15,000 to just 2,000 to 3,000 people by 1722. Without the trees that formed the backbone of the islands ecosystem, the whole system was thrown out of whack, taking down the birds and other animal species that depended on the trees for food and/or habitat. This had a devastating effect on the people living on the island and was the primary cause of their decimation.
Sumerians could do nothing about the rising salinity of their soil. (Photo: Hardnfast/Wikimedia Commons)
The Sumerian civilization sprung out of modern-day Iraq around 4000 B.C. and developed into an advanced society of city states ruled by priests and kings that supported a large population (some Sumerian cities had tens of thousands of citizens). Sumerian farming techniques, which would be familiar to contemporary farmers, included monocropping, large-scale irrigation and the use of specialized labor.
Agricultural prowess allowed for the development of a stratified social structure in which certain classes could pursue learning in the arts, sciences, mathematics and technology. Sumerians were the first civilization to find the area of a triangle and volume of a cube. They also invented the abacus to more quickly add and subtract numbers and developed early arithmetic, geometry and algebra.
For all of their societal sophistication, Sumerians could do nothing about the rising salinity of their soil. The arid climate meant that irrigation water left behind salts in the soil when it evaporated. The amount of salts left behind each season were relatively minute, but after hundreds of years, the salt levels ultimately led to dead fields. Without agriculture to support their population, the Sumerian people melted away from the area and into history.