On this week’s show: Climate change is killing critical soil organisms in arid regions, and early evidence for the Maya calendar from a site in Guatemala.

Staff Writer Elizabeth Pennisi joins host Sarah Crespi to discuss how climate change is affecting “biocrust,” a thin layer of fungi, lichens, and other microbes that sits on top of desert soil, helping retain water and create nutrients for rest of the ecosystem. Recent measurements in Utah suggest the warming climate is causing a decline in the lichen component of biocrust, which is important for adding nitrogen into soils.

Next, Sarah talks with Skidmore College anthropologist Heather Hurst, who directs Guatemala’s San Bartolo-Xultun Regional Archaeological Project, and David Stuart, a professor of art history and director of the Mesoamerica Center at the University of Texas, Austin, about their new Science Advances paper. The study used radiocarbon dating to pin down the age of one of the earliest pieces of the Maya calendar. Found in an archaeological dig in San Bartolo, Guatemala, the character known as “seven deer” (which represents a day in the Maya calendar), was dated to 300 B.C.E. That early appearance challenges what researchers know about the age and origins of the Maya dating system.