Cows, dust and smoke. That was what greeted me on my return home to Altamira, after several weeks on the road. An unusually fierce dry season has taken a horrific toll on the Amazonian landscape, swathes of which are already denuded by cattle ranches. Together, they threaten the integrity of the world’s biggest tropical forest. I will get to the science behind that horrifying statement shortly. But first, let me describe what is happening on the ground, in and around my home in Altamira, in Pará