This Small Canadian Lake Reveals How Humans Have Changed the Planet

Crawford Lake is around 50km southwest of Toronto. It’s so small it only takes 10 minutes to walk around but this tiny lake tells a story with a much wider sweep. Every year, particles in the air settle on Crawford Lake and every summer, these particles sink to the bottom. They form layers of sediment much like the rings of a tree. These layers provide a geological record of human existence. Researchers say this sediment acts as a narrative of humanity’s environmental impacts such as climate change and pollution. And that the sediment shows a sudden, irreversible shift that began in the mid-20th century.