Within a few years of the first Earth Day in 1970, the US Environmental Protection Agency had been set up, and several environmental laws – such as the Clean Air Act – had been established or significantly strengthened.

More recent events have included planting hundreds of millions of trees, supporting farmers with sustainable agriculture practices, and starting climate literacy projects around the world.

Some observers also cite the importance of Earth Day in pushing environmental issues back up national and international agendas.

“With a host of issues driving our environmental challenges down society’s priority list, events like Earth Day remind us of the long-term cost of short-termism,” said Yvo de Boer, former UN climate chief.

In 2016, Earth Day was symbolically chosen for the official signing of the landmark Paris climate accord, which had been agreed in late 2015.

It was the first time that countries of the world had collectively agreed targets to try to limit global warming.