April 22 we celebrate Earth Day. Even as the world returns to normal, people are taking a thoughtful look at the natural world around them and the consequences of human action (and inaction). Urban dwellers are hearing birds sing and the flapping of wings. Los Angeles has had the longest stretch of clean air in countless years. Less noise pollution in our oceans is a welcome relief to sea life. Research has shown that ambient noise from ship engines can increase stress-hormone levels in marine creatures.

Creating awareness and encouraging sustainable action to support a healthy environment is a major part of the Earth Day celebration. Here’s what you should know about the holiday and some ideas for how you might commemorate it.