"We believe that the importance of the environmental factor will continue to increase as new, previously unanticipated environmental risks start to materialise," said Fitch.
Norilsk's spill, which Greenpeace described as one of the biggest oil product accidents to ever have occurred in the Russian Arctic, saw about 21,000 tonnes of fuel leaked into rivers and subsoil near the city of Norilsk on May 29.
Fitch said the scale of Norilsk's damages, which it estimated would equate to a quarter of the company's 2020 EBITDA, was comparable only with Vale's tailings dam collapse in 2019. Vale paid out US$1.4 billion and had US$3.4 billion of provisions outstanding at the end of June.
The fact that Norilsk pointed to thawing permafrost as the trigger for the accident bodes ill for other commodity-focused companies operating in Russia, said the ratings agency.
"Almost two-thirds of Russian territory is in permafrost areas, and this is where many commodity companies operate (including gas producers Novatek and Gazprom).
Global heating will require "significant spending on infrastructure and stricter focus on environmental controls and safety".
"While Novatek's Yamal LNG mega project has propelled the company from a niche Russian natural gas producer into a global LNG player with a 5% share of the global LNG market, it cost the company US$27 billion and required unique technical solutions. It was built on a large number of piles of different sizes and shapes not used on such a scale before to support its stability in permafrost," said Fitch.