Some of the world’s largest asset managers and institutional investors called on companies in an open letter Wednesday to tackle the risks associated with deforestation, spurred by international outcry over wildfires in the Amazon rainforest.

The signatories represent a collective $16.2 trillion assets under management, and include some of the world’s largest institutional investors, including Legal & General Investment Management, Amundi Asset Management and APG.

“It is with deep concern that we follow the escalating crisis of deforestation and forest fires in Brazil and Bolivia,” the letter said. “As investors, who have a fiduciary duty to act in the best long-term interests of our beneficiaries, we recognise the crucial role that tropical forests play in tackling climate change, protecting biodiversity and ensuring ecosystem services.”

The letter said the investors see deforestation and the associated impacts as “systemic risks” to their portfolios, while warning that companies who have business exposure to deforestation in Brazil may face future difficultly accessing international markets.

To address the risk of deforestation, the investors “urgently” requested companies implement policies ranging from public, commodity-specific no-deforestation policies to establishing transparent systems for monitoring deforestation risk across the entire supply chain, and reporting annually on the company’s progress, among others.

Wildfires in Brazil and Bolivia that have destroyed vast swathes of the Amazon rainforest this year—although the exact amount is still unclear—were started in part by humans clearing land to farm lucrative agricultural exports like beef and soy. Now, the worst wildfires in years are also burning in Indonesia, and officials say 80% of the fires were set intentionally to clear the land for palm plantations to produce palm oil, a consumer oil found in everything from pizza to toothpaste.

The statement was coordinated by non-profits PRI and Ceres, who push for strengthened sustainability and responsible investing principles among institutional investors.

But rather than empty promises of corporate responsibility, the letter comes at a time when the needle appears to finally be shifting: investors and banks are increasingly seeing climate change, and associated risks like deforestation and water shortages, as serious financial risks to businesses and warming that businesses who do not act to limit their exposure will see their access to financing and insurance affected.

This spring, a group of central banks, including the central banks of England, France, and China, issued a dire warning that climate change represents a systemic risk to financial stability, and therefore falls under the remit of the world’s central banks.

That approach has begun to hit industries like coal particularly hard. Earlier this month, a top executive from ICBC, China’s largest bank and the world’s largest bank by assets, said that climate stress tests that began in 2015 are restricting financing to the coal industry and pushing it toward the renewables sector.