The indigenous peoples of the Amazon rain forest are the shock troops in the struggle against climate change. “We are the first ones to be affected,” says Sônia Guajajara, one of Brazil’s best known indigenous leaders.

“We’re seeing floods that last longer, we’re seeing droughts that are longer, we’re seeing a reduction in fish with the drying out,” she recently told The Times’s editorial board. “And so it affects our food security. It also affects our culture.”

The Amazon rain forest, an environmental treasure of more than two million square miles across Brazil and eight other countries, is sometimes called “the lungs of the planet” because the trees release so much oxygen and absorb so much carbon dioxide, mitigating the effects of climate change. It is also home to an unparalleled diversity of animal and plant species as well as roughly one million indigenous people in Brazil alone.

Although long imperiled, the forest is at greater threat now under the presidency of Jair Bolsonaro, a polarizing populist leader in the mold of President Trump who took office in January and will meet Mr. Trump at the White House on Tuesday .