ALERCE COSTERO NATIONAL PARK, Chile — Dr. Toby Kiers, 45, an evolutionary biologist based at the Free University of Amsterdam, is on a novel mission. She is probing a vast and poorly understood universe of underground fungi that can be vital in the era of climate change. Some species of fungi can store exceptional levels of carbon underground, keeping it out of the air and preventing it from heating up the Earth’s atmosphere. Others help plants survive droughts or fight off pests. …In short, they are what she called “levers” to address the hazards of a warming climate. …Dr. Kiers wants to know which fungi species are where, what they do, and which should be immediately protected. …Dr. Kiers’s expedition to southern Chile aims to fill in some of the gaps in knowledge about fungi, specifically the mycorrhizal fungi… That is what gives them such an urgent role on a hotter planet.