The Bosawas Biosphere Reserve on the border of Nicaragua and Honduras, considered by the United Nations a global biological treasure, teems with wildlife.
But the Mayangna and Miskito people who live in the region and hold title to the land say 75,000 acres a year are being deforested by the invaders, representing a serious threat to the future of the forest.
"The problem is that in the parts of our territory that we have zoned to be conservation forest, they are being invaded by settlers," Arisio Genaro, president of the Nacion Mayangna, told BBC News.
The reserve is Central America's largest tropical rainforest.
"Even we the Mayangna don't touch these forests, that's where the animals we hunt reproduce," Genaro said. "If they destroy that, they will destroy our people."
The Mayangna have urged U.S. President Obama, meeting with regional leaders in Costa Rica, to support their battle against invaders.