The King's Speech star is fronting a new human rights campaign to save the lives and land of the Awa people, a hunter-gatherer tribe based in Brazil's rain forests.
In a video filmed for Survival International, Firth explains, "When the loggers see them, they kill them. Their bows and arrows are no match for guns. Another people wiped out."
He adds, "One man can stop this: Brazil's Minister of Justice. He can send in the federal police to catch the loggers, and keep them out for good. But we need enough people to message him. This is our chance, right now, to actually do something. And if enough people show they care, it will work."
Thousands of emails have been sent to Minister Of Justice Jose Eduardo Cardozo since Firth's appeal debuted.