Lake Baikal is the world’s oldest and deepest lake. It’s at least 20 million years old, and roughly a mile deep at its lowest point. The Siberian lake contains holds more water than all the North American Great Lakes combined, what amounts to more than one-fifth of all the water found in lakes, swamps and rivers. It was formed by the shifting of tectonic plates, which created a valley that filled with water. That shift continues today at a rate of around 1 to 2 centimeters a year, meaning the world’s biggest lake is only getting bigger.
What’s more, Lake Baikal — the name means “nature lake” in Mongolian — is rich in oxygen from top to bottom, meaning life can thrive in its furthest depths. In most deep lakes, the lower waters are absent of oxygen. The surfeit of oxygen helps support a rich diversity of life. Most of the species in the lake —often called the “Galapagos of Russia” — are found nowhere else in the world. UNESCO has designated Baikal a World Heritage Site, calling it “the most outstanding example of a freshwater ecosystem,” saying “its age and isolation have produced one of the world’s richest and most unusual freshwater faunas, which is of exceptional value to evolutionary science.”
So it seems especially tragic that Lake Baikal — like many critically important ecosystems around the world — is now under siege from climate change. Its wildlife face increasing dangers from rising temperatures and pollution. In some places, untreated sewage has fed the growth of green algae, which gobble up oxygen, leaving little or none leftover for other marine life.