The theme for Earth Day 2020 is climate action. The enormous challenge — but also the vast opportunities — of action on climate change have distinguished the issue as the most pressing topic for the 50th anniversary.

Climate change represents the biggest challenge to the future of humanity and the life-support systems that make our world habitable.

Earth Day was a unified response to an environment in crisis — oil spills, smog, rivers so polluted they literally caught fire.

On April 22, 1970, 20 million Americans — 10% of the U.S. population at the time — took to the streets, college campuses and hundreds of cities to protest environmental ignorance and demand a new way forward for our planet.

The first Earth Day is credited with launching the modern environmental movement, and is now recognized as the planet’s largest civic event.