Sandra Díaz

by

Elizabeth Maruma Mrema

2025 Time 100 Sandra Diaz
Daniel M. Cáceres

Good teachers not only know the number of children in their nursery, they also understand the traits of every individual child and the dynamics of interactions in class. What a good teacher does in a classroom, ecologist Sandra Díaz does for the natural world.

Counting what is out there in the natural world seems simple, but it’s an important endeavor for scientific research and protecting biodiversity around the world. A professor of community and ecosystem ecology at Argentina’s Córdoba National University, Sandra uses her research to assess and quantify functional biodiversity, helping to lift our understanding of this crucial project from simply counting species to a complex examination of their roles in different ecosystems.

Yet Sandra’s work resonates with me not only as a fellow lover of nature. She is an indefatigable diplomat on the front lines of the triple planetary crisis of climate change, biodiversity loss, and pollution. With 1 million of the planet’s 8 million plant and animal species at risk of extinction and scarce funding to protect nature, the world needs many more leaders like Sandra.

Mrema is deputy executive director of the U.N. Environment Programme