SYDNEY, Australia — Australia’s biggest mining company, BHP, announced on Tuesday that coal output was down at one of its large mines. The reason? Smoke from the country’s ferocious wildfires — a crisis fed by climate change, which is caused in no small part by the burning of coal.

The reduced air quality in New South Wales, the country’s most populous state, has helped slow the company’s production of electricity-generating coal by 11 percent there, BHP said in a review of its midyear financial results.

“We are monitoring the situation, and if air quality continues to deteriorate, then operations could be constrained further in the second half of the year,” said the company, which ends its fiscal year on June 30.

The irony was not lost on many in Australia.

The country, which just endured its hottest and driest year on record, has been dealing for months with bush fires that have killed at least 29 people, ravaged tens of millions of acres, and left residents in its largest cities wheezing from the most polluted air in the world.