Document also shows US miner had been unlawfully clearing land for 15 years despite warnings from department

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The Australian government’s decision to allow the US mining giant Alcoa to continue clearing swathes of Western Australian jarrah forest despite past illegal clearing practices was made in part due to a critical minerals deal reached between Australia and the Trump administration last year, a new document shows.

The document also reveals Alcoa was unlawfully clearing land for its bauxite mining practices in the area south of Perth for 15 years, despite warnings from the federal environment department.

Conservationists have expressed outrage that an “unprecedented” $55m penalty announced by the environment minister was only applied to a six-year period in which the illegal clearing was alleged to have occurred.

Murray Watt said on Wednesday that the penalty – known as an enforceable undertaking – was for clearing that occurred from 2019-2025 in known habitat for nationally protected species without an approval under the Environment Protection and Biodiversity Conservation (EPBC) Act.

When announcing the penalty, Watt said he had granted Alcoa a national interest exemption to allow it to continue clearing in the northern jarrah forest for 18 months while the government considered a proposal for an expansion of the company’s Huntly and Willowdale mining operations to 2045.