Nearly a quarter of all plant species on Earth—or roughly 55,000 unique flora, by some estimates—currently call Brazil their home. The United Nations, in fact, classifies Brazil as the globe’s leading “mega-biodiverse” nation, “unmatched by any other.” And, while one might attribute this staggering ecological richness solely to Brazil’s 60% chunk of the Amazon, the fact remains that the nation owes much of its mega-diversity to another, lesser-known, rainforest along its eastern coast: Mata Atlantica.

Earlier this year, an international team of biologists, immunologists, and pharmaceutical chemists discovered something interesting about a plant endemic to this region.…