The Ayalon Cave in central Israel was cut off from the surface for an estimated 5 million years before a bulldozer excavating a quarry in 2006 broke into one of its 1.7 miles of skinny tunnels. Originally over 320 feet below the surface, the lime quarry had already been dug nearly deep enough to collapse the cave system before it was discovered. When researchers descended into the cavern, they found an utterly unique ecosystem.
A layer of chalk above the limestone cave has protected it all this time from the intrusion of surface water. The water within, which fills a deep and narrow lake, comes from a nearby aquifer and is highly filtered by the limestone. It brings no nutrients from the surface, therefore the life existing in the cave was, until 2006, an entirely photosynthesis-free food chain, a concept nearly non-existent on Earth.
The lake hosts chemoautotrophic bacteria, which live in a film on its surface. They make energy by oxidizing the sulfides in the water, and build organic compounds out of the carbon dioxide in the air. These are fed upon by tiny crustacean and arthropod species living in the cave, which breathe out carbon dioxide to continue the cycle.
One discovery made within the cave was very sobering: less than a decade before the discovery of the cavern, a species of eyeless scorpion formerly native to this one tiny crack in the world had gone extinct. The remains of 10 specimens were found, intact enough for scientists to study them. Despite the extreme isolation of their ecosystem, their extinction was due to human activity – overpumping of water from the aquifer had already lowered the level of the lake, reducing the humidity in the cave and the available food.
Now only 15 years after its discovery, the cave faces another massive threat: Israel’s National Infrastructure Committee and Water Authority wants to use the quarry as a place to direct runoff in the winter to protect against flooding after future rail plans narrow the nearby Ayalon River. A single instance of surface water incursion would doom the fragile cave ecosystem, destroying it and its unique species forever.
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