Tropical beetles confirm 1967 forecast that mountain habitats become climate traps

In the UNESCO-listed Guanacaste Conservation Area of Costa Rica, scientists tested the heat tolerance of over a hundred rove beetle species collected along Volcán Cacao’s 1,500-meter elevation span. Using controlled temperature experiments and DNA barcoding for identification, they discovered that beetles inhabiting the cool cloud forest possess the lowest upper thermal limits, rendering them highly susceptible to incremental warming.

Conversely, lowland beetles operate close to their maximum tolerances yet can survive modest temperature increases. These results provide empirical support for Daniel Janzen’s 1967 hypothesis that tropical mountain species, accustomed to stable climates, lack the flexibility to cope with rapid warming. The work builds on two decades of biodiversity surveys and continuous climate monitoring in the region, highlighting the broader threat climate change poses to richly diverse but understudied tropical ecosystems.