A community of small mammals in the western United States has changed more in the past century than in the past 13,000 years, thanks to human activities.

Rebecca Terry at Oregon State University in Corvallis and Rebecca Rowe at the University of New Hampshire in Durham analysed the skeletal remains of small mammals dating back to 12,800 years ago from a large cave in Utah. They found that energy flow — a metric combining the number, size and metabolic rates of animals — in this community was largely stable up until about the late 1800s, even during periods of rapid natural climate warming. But in the past 100 years, energy flow has dropped significantly, indicating a population surge in small animals that thrive in grassy habitats and a loss of animals in desert shrublands.

The authors suggest that this is a result of the replacement of shrublands with invasive grasses, owing to human activity, in this desert region.

Proc. Natl Acad. Sci. USA http://dx.doi.org/10.1073/pnas.1424315112 (2015)