Amazon founder and CEO Jeff Bezos speaks at the new Amazon Spheres opening event at Amazon's Seattle headquarters in Seattle, Washington, U.S., January 29, 2018.

Amazon founder and CEO Jeff Bezos on Monday announced the launch of a new Earth Fund that the e-commerce chief plans to use to combat the effects of climate change.

He said in an Instagram post that he's pledging $10 billion to start the fund, which will be called the Bezos Earth Fund, and will issue grants to scientists, activists and other organizations in their efforts to "preserve and protect the natural world."

"We can save Earth," Bezos wrote in his post. "It's going to take collective action from big companies, small companies, nation states, global organizations, and individuals."

"Climate change is the biggest threat to our planet," he added. "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 added in his post that he expects the Earth Fund to begin issuing grants to climate-oriented causes as soon as this summer. News of the new fund, though unexpected, comes as Amazon seeks to address criticisms that its e-commerce and shipping business fuel global carbon emissions.

More than 340 Amazon employees risked termination earlier this year after signing a Medium post published by advocacy group Amazon Employees for Climate Justice. The post criticized the company's external communications policy, which bars employees from speaking about the company's business without approval from management.

Amazon Employees for Climate Justice said Monday that while they support Bezos's move, it's still concerned about the company's support of the oil and gas industry.

"We applaud Jeff Bezos' philanthropy, but one hand cannot give what the other is taking away," the group said in a statement. "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?"

The company, hoping to address similar criticisms, has in recent months launched initiatives designed to help curb its environmental impact.

Last year, Bezos unveiled an ambitious plan to tackle climate change and committed the seller to honoring the goals of the Paris Agreement 10 years early despite President Donald Trump's withdrawal from the landmark climate accord earlier in his term.

As part of those plans, Amazon said in September it would buy a fleet of electric vans to start delivering packages to customers in 2021, with 10,000 of the new vehicles operating by 2022 and all 100,000 operating by 2030.

Bezos added at the time that the seller of everything from textbooks to lawnmowers will report its emissions metrics on a regular basis and introduce decarbonization strategies. Amazon expects 80% of its energy use to come from renewable energy sources by 2024, up from a current rate of 40%.