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.

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

Bezos’ announcement comes as Amazon has taken steps to address its role in contributing to global warming and as it faces internal pressure from its own employees. In September, the company unveiled the Climate Pledge, a commitment to meet the international Paris Agreement's goal of net zero carbon emissions by 2040, 10 years earlier than what most countries had previously agreed to. The online retailer's plan to achieve that goal included an order for 100,000 new electric delivery vehicles and a $100 million investment in global reforestation projects.

That hasn’t been enough for some of the Seattle tech giant’s workers, who formed a group called Amazon Employees for Climate Justice to call out their employer for working with oil and gas companies and funding a think tank engaged in climate change denialism. The group also organized a walkout and a confrontation of Bezos at a recent shareholder meeting. Last month, some of the employees involved in the group said that Amazon threatened them retribution for their criticism of the company’s stance on climate issues.

“We applaud Jeff Bezos’ philanthropy, but one hand cannot give what the other is taking away,” Amazon Employees for Climate Justice said in a statement on Monday. “The people of Earth need to know: When is Amazon going to stop helping oil & gas companies ravage Earth with still more oil and gas wells? When is Amazon going to stop funding climate-denying think tanks like the Competitive Enterprise Institute and climate-delaying policy?”

In an email, an Amazon spokesperson chose to commend its CEO and founder. The company declined to respond to the Amazon employees’ questions.

“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,” the company said in a statement. “Jeff’s passion and this extraordinary personal contribution to the fight against climate change are going to have a huge impact.”

The Bezos Earth Fund will come from the Amazon CEO’s personal accounts, not from Amazon’s balance sheet. The $10 billion commitment represents less than 8% of his net worth, which totaled $129.9 billion as of Monday, according to Forbes.

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, and it’s announced distributions totaling $196 million over two years to charities working on family and homelessness issues. The Bezos Earth Fund will be separate from the Day One Fund and the Bezos Family Foundation, a foundation set up by the Amazon chief’s parents Jackie and Mike Bezos to focus on education issues.

A person familiar with the Bezos Earth Fund said that the $10 billion would not be used for investments and would be doled out as charitable giving to existing institutions and researchers.

“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,” Bezos said on Instagram.