Amazon revenue to restore the Amazon rainforest? A political war chest in the US to counter the pernicious influence of big oil? Or research funding for “moonshot” technologies to suck carbon dioxide out of the atmosphere?

The world’s richest man is never going to be short of suggestions for how to spend money, but Jeff Bezos’s announcement of a new $10bn (£7.67bn) Earth Fund to fight global heating has raised the question of what is the best bang for a climate buck.

In an Instagram post to his 1.4 million followers, the Amazon founder said he would start distributing funds this summer and hoped to work alongside scientists, activists and NGOs to “amplify known ways and to explore new ways of fighting the devastating impact of climate change on this planet”.

The fund is controversial. Some campaigners believe Bezos – whose personal net worth is almost $130bn – should have used the money to pay more in taxes, or higher wages.

Others suggest the creation of a political fighting fund to counter the influence of lobbyists in the oil and gas industry, who have delayed climate action for decades. The top five petrochemical companies spend about $200m a year on advertising, briefing and campaign donations aimed at blocking carbon taxes, extolling the benefits of their industry and misleading the public about the risks.

“At this point, I think confronting the fossil fuel industry head-on – and the financial industry that supports it – is what is required,” said the US author, environmentalist and founder of 350.org, Bill McKibben. “If a plutocrat was willing to do that, it would be an interesting battle of titans. I’m not holding my breath, however.”

Counterintuitively, the high-tech multibillionaire is urged to invest in natural solutions. Studies have shown one of the most cost-effective ways to reduce carbon dioxide is to protect forests and support indigenous and traditional community land rights.

“Strengthening the Amazon and other rainforests is vital if the world is to have any chance of stabilising the climate. When healthy they are the biggest terrestrial carbon sink. When attacked by fire, they are a huge source of emissions,” said Marcelo Salazar of Brazil’s biggest environment NGO, Instituto Socioambiental.

He said “Amazon for the Amazon” funding could be used to shift the rainforest towards a new model of business and governance that relied less on destructive practices like deforestation and mining, and more on the renewable use of biodiverse fruits, nuts and natural oils that would allow indigenous people and other forest guardians to thrive.

Another proposal is to develop game-changing technologies that are too risky for business or too expensive for governments. “Many emerging technologies, like carbon capture and storage, need a financial shot in the arm to get them scaled up fast. Other solutions, such as the expansion of climate-smart farming or universal wastewater treatment, may be less eye-catching but they are no less crucial in terms of cutting emissions and providing greater resilience to the impacts of climate change,” said Prof Dave Reay, executive director of the Edinburgh Centre for Carbon Innovation.

Prof Richard Templer, director of innovation at the Grantham Institute, said his “cheeky suggestion” would be that the money be committed to areas where science demands action but markets do not yet exist, such as removing carbon dioxide from the air and restoring habitats – including forests and wetlands – that can reduce emissions.

New technology should not be necessary. Bob Ward, also of the Grantham Institute, suggested Bezos use the fund to overcome societal obstacles to net zero emissions through a global programme of research, analysis and engagement. “Some of this money should be targeted at the United States, Canada and Australia to, for instance, support local media to report and counter misinformation about the local impacts of climate change, and to build support for climate action among centre-right politicians and their supporters. The money should also be targeted at exploring options for managing a just transition among workers and communities around the world that are currently dependent on high-carbon industries,” he said.

Owen Gaffney, an analyst and strategist at the Potsdam Institute for Climate Impact Research and the Stockholm Resilience Centre said the key was to instil trust in liberal democracies to allow them to make big long-term decisions for the benefit of most people. “This means investing in solutions to reduce inequality and pricing carbon fairly,” he said.

Climate economists said more support for carbon pricing had the greater potential to trigger a wave of positive developments. “Carbon pricing can do three things: make fossil fuel use less attractive, make clean technologies more profitable, and generate income for governments to give back to their citizens by means of tax cuts or infrastructure investments,” said Ottmar Edenhofer, the director of the Potsdam Institute. “That’s no easy thing. Yet this is why it needs some push.”

McKibben said the world’s richest man would probably never have taken this step without pressure from a staff organisation, Amazon Employees for Climate Justice. This advocacy group has criticised their boss for supporting the oil and gas industry and for donating money to business groups that have lobbied against climate action. Earlier this year, 340 of them risked being fired by signing an online petition against Amazon rules that bar employees from speaking about the company’s business without approval from management.

In response to Bezos’s announcement of the new fund, the group called for action as well as money.

“We applaud Jeff Bezos’s 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?”

One idea is for Bezos to channel the $10bn through this group of climate justice advocates inside his company. “The mere fact that he thought it necessary to do this is because so many people – including his employees – have been organising so powerfully. So, in the end, I’ll put my faith in movements, not money,” McKibben said.