Amazon CEO Jeff Bezos, the richest man in the world, announced in an Instagram post on Monday that he was donating $10 billion to combat climate change in a new initiative called the Bezos Earth Fund.

“Today, I’m thrilled to announce I am launching the Bezos Earth Fund,” the Amazon chief executive wrote in his announcement post, while also committing $10 billion to start.

Bezos said he will begin issuing grants this summer, and that the new global initiative will make charitable donations funding “scientists, activists NGOs — any effort that offers a real possibility to help preserve and protect the natural world.”

The new Earth Fund is Bezos’ largest philanthropic effort to date, though he’s previously been criticized for how little he donates to charity compared to other billionaires.

“Climate change is the biggest threat to our planet,” Bezos said. “I want to work alongside others both to amplify known ways and to explore new ways of fighting the devastating impact of climate change on this planet we all share.”

“Earth is the one thing we all have in common — let’s protect it, together,” Bezos wrote. “It’s going to take collective action from big companies, small companies, nation states, global organizations, and individuals.”

Amazon, which delivers over an estimated 1 billion packages per year, has subsequently been criticized for having a huge environmental footprint.

Bezos is the world’s richest man, with a net worth of $129.9 billion, according to Forbes. Bezos’ climate pledge of $10 billion amounts to nearly 10% of his overall net worth. He holds a 12% stake in Amazon, which he founded in 1994, as well as owns the Washington Post.