Amazon CEO Jeff Bezos, the world’s richest person, pledged $10 billion to combat climate change on Monday, calling the phenomenon the “biggest threat to our planet.”

In an Instagram post, the 56-year-old billionaire said he was launching the Bezos Earth Fund, an initiative to fund scientists, activists, and non-governmental organizations researching and fighting climate change. Bezos did not specify which groups he’d be funding, but he noted that the $10 billion fund would begin issuing grants this summer.

“We can save Earth,” Bezos wrote in an Instagram caption below a photo of the Earth. “It’s going to take collective action from big companies, small companies, nation states, global organizations, and individuals.”

Bezos, who has been criticized in the past for his lack of giving compared to his outsized wealth, has recently made strides to increase his charitable donations. In 2018, he launched the Day One Fund with a $2 billion commitment, though it’s only announced distributions totaling $196 million over two years to charities working on family and homelessness issues.

The Bezos Earth Fund pledge represents less than 8% of the Amazon chief’s net worth, which totaled $129.9 billion as of Monday, according to Forbes. The $10 billion commitment comes from Bezos’ own finances and is separate from the $2 billion he pledged to his Day One Fund.

“Amazon took a bold step when it announced the Climate Pledge, committing the company to meet the goals of the Paris Agreement ten years early, and we’re incredibly excited about the Bezos Earth Fund,” an Amazon spokesperson said in an email statement. “Jeff’s passion and this extraordinary personal contribution to the fight against climate change are going to have a huge impact.”