Paleo Slide Set: Packrat Middens: Vegetation & Climate Variability in the Southwestern United States
Packrat middens in the western U.S.

This map shows locations where middens have been collected, dated, and analyzed. 
The coverage is uneven because middens tend to be preserved in some environments better 
than others, and researchers have mainly focused on areas where questions about past ecosystem 
change and climate variability were pressing. Of these locations, the Nevada Test Site near Las Vegas 
is an important staging ground for midden research and its application. One of the more pressing questions 
for the licensing of the Nevada Test Site as a facility for storing nuclear waste has been the spectrum of 
past climate change in this region. Because climate change is a driving force behind variations in the 
hydrological cycle, the future possibility of ground water contamination can be determined by the past 
range of climate change. By using midden research to reconstruct the past 40,000 years of ground water 
levels in this region, the potential for ground-water contamination and transport of radionuclides away 
from the burial site can be established. 

Photo Credits:
Julio L. Betancourt 
U. S. Geological Survey & NOAA National Geophysical Data Center