Tales of the Packrat: The Legacy of Early Grazing on Utah’s Rangelands

Tales of the Packrat: The Legacy of Early Grazing on Utah's Rangelands: Pack Rat Midden,  Photo Courtesy and Copyright 2009 Ken Cole - All Rights Reserved
Pack Rat Midden
Copyright © 2009 Ken Cole

One of the best storytellers in Utah’s national parks is not a ranger, but the lowly packrat. Their stories of past plant communities are written in their middens. The midden is a heap of leaves, twigs, seeds and fruits the packrat discards outside its nest. Protected in a desert cave or rock crevice and preserved by a rat’s own urine, this heap is a detailed and accurate time capsule of the past local flora.

Ken Cole with the US Geological Survey is a fluent translator of the packrat’s stories. Ken and colleagues sampled old packrat nests around Glen Canyon National Recreation Area and Capitol Reef National Park. By carbon-14 dating, the nest ages are known to span the last 10,000 years. As controls, they also collected nests from mesa tops inaccessible to livestock. Ken and colleagues then carefully translated these packrats’ stories by identifying and counting the plant fragments in these fossil nests.

Reaching for a Pack Rat Midden, Click to Zoom, Photo Courtesy and Copyright 2009 Ken Cole - All Rights Reserved
Reaching for a Pack Rat Midden
Copyright © 2009 Ken Cole

At both Capitol Reef and Glen Canyon, old packrat nests revealed pre-settlement plant communities that were rich in diverse grasses, wildflowers and shrubs. Then these floras changed. Beginning 150 years ago, vast herds of sheep and cattle tromped and chewed their way across the unfenced rangelands of Utah in numbers unimaginable today. We know that palatable plant species and those susceptible to trampling suffered declines, because they are absent from middens from that time period. Unpalatable shrubs multiplied. Despite curtailed grazing in subsequent decades at Capitol Reef and Glen Canyon, packrats show us that the flora still has not recovered. Like Aesop’s fables, this cautionary lesson of the packrat’s ecological tale remains clear and relevant today. We should all listen.

This is Linda Kervin for Bridgerland Audubon Society.

Credits:

Photos: Courtesy and Copyright Ken Cole

Text: Jim Cane, Bridgerland Audubon

Additional Reading:

Betancourt, Julio L., Thomas R. Van Devender, and Paul S. Martin, eds. Packrat Middens: The Last 40,000 Years of Biotic Change, University of Arizona Press, 1990 http://www.uapress.arizona.edu/books/BID40.htm

Pack Rat Middens, Colorado Plateau in Land Use History of North America, Ken Cole, USGS/Northern Arizona University, http://cpluhna.nau.edu/Tools/packrat_middens.htm

Introduction [to Carbon 14 Dating], Tom Higham, Radiocarbon Laboratory, University of Waikato, New Zealand http://www.c14dating.com/int.html

Tales of the Packrat The Legacy of Early Grazing on Utah’s Rangelands

Tales of the Packrat: Pack Rat Midden,  Photo Courtesy and Copyright 2009 Ken Cole - All Rights Reserved
Pack Rat Midden
Copyright © 2009 Ken Cole

One of the best storytellers in Utah’s national parks is not a ranger, but the lowly packrat. Their stories of past plant communities are written in their middens. The midden is a heap of leaves, twigs, seeds and fruits the packrat discards outside its nest. Protected in a desert cave or rock crevice and preserved by a rat’s own urine, this heap is a detailed and accurate time capsule of the past local flora.

Ken Cole with the US Geological Survey is a fluent translator of the packrat’s stories. Ken and colleagues sampled old packrat nests around Glen Canyon National Recreation Area and Capitol Reef National Park. By carbon-14 dating, the nest ages are known to span the last 10,000 years. As controls, they also collected nests from mesa tops inaccessible to livestock. Ken and colleagues then carefully translated these packrats’ stories by identifying and counting the plant fragments in these fossil nests.

Reaching for a Pack Rat Midden
Copyright © 2009 Ken Cole

At both Capitol Reef and Glen Canyon, old packrat nests revealed pre-settlement plant communities that were rich in diverse grasses, wildflowers and shrubs. Then these floras changed. Beginning 150 years ago, vast herds of sheep and cattle tromped and chewed their way across the unfenced rangelands of Utah in numbers unimaginable today. We know that palatable plant species and those susceptible to trampling suffered declines, because they are absent from middens from that time period. Unpalatable shrubs multiplied. Despite curtailed grazing in subsequent decades at Capitol Reef and Glen Canyon, packrats show us that the flora still has not recovered. Like Aesop’s fables, this cautionary lesson of the packrat’s ecological tale remains clear and relevant today. We should all listen.

This is Linda Kervin for Bridgerland Audubon Society.

Credits:

Photos: Courtesy and Copyright Ken Cole

Text: Jim Cane, Bridgerland Audubon

Additional Reading:

Betancourt, Julio L., Thomas R. Van Devender, and Paul S. Martin, eds. Packrat Middens: The Last 40,000 Years of Biotic Change, University of Arizona Press, 1990 http://www.uapress.arizona.edu/books/BID40.htm

Pack Rat Middens, Colorado Plateau in Land Use History of North America, Ken Cole, USGS/Northern Arizona University, http://cpluhna.nau.edu/Tools/packrat_middens.htm

Introduction [to Carbon 14 Dating], Tom Higham, Radiocarbon Laboratory, University of Waikato, New Zealand http://www.c14dating.com/int.html

Utah’s Recent Pinyon Migrations and the Prospects for Climate Change

Packrat Fossil Midden City of RocksCourtesy and Copyright 2009 Julio Betancourt - All Rights Reserved
Packrat Fossil Midden
City of Rocks
Copyright © 2009 Julio Betancourt

In the late 1970’s, springtime in the American West warmed abruptly by 2 degrees Fahrenheit in the valleys, double that higher up. Our average onset of Spring now comes a week earlier across the West. If these are the first signs of climate change, even longer growing seasons will trigger not just earlier blooms but also northward plant migrations.

The past provides us with lessons about plant migrations. A thousand years ago, one-needle pinyon hopped from the Raft River Mountains in Utah to City of Rocks, Idaho. Across Utah, two-needle pinyon leaped over the Uintas to Flaming Gorge. We know this from radiocarbon dates on pinyon pine needles taken from ancient nest heaps of packrats preserved in caves. According to Dr. Julio Betancourt of the U.S. Geological Survey, who uses these packrat middens and tree rings to reveal past plant migrations, these recent advances by Utah’s two pinyon pines followed the Medieval Climate Anomaly, a period from 900 to 1300 AD marked by warming in Europe and severe drought in Utah.

Packrat 7000 year old Midden Joshua Tree Natl Park, Courtesy and Copyright © 2009 Julio Betancourt - All Rights Reserved
Packrat 7000 year old Midden
Joshua Tree Natl Park
Copyright © 2009 Julio Betancourt

Droughts figure prominently in Dr. Betancourt’s view of tree migrations. Droughts trigger bark beetle infestations, wildfires, and tree dieoffs, opening up niches for regeneration. When the drought abates, the resident tree species typically return. With long-term warming, however, other species can move in from lower elevations or further south. Dead trees now abound on Utah’s landscape, and Dr. Betancourt thinks that we are on the verge of a new spate of tree migrations.

This go around, which species retreat or advance will depend on new factors, including human fragmentation of the landscape and accelerated dispersal of native and non-native species that hitch rides with us. To conserve ecological goods and services associated with some species, Dr. Betancourt argues, we will have to manage for these plant migrations.

This is Linda Kervin for Bridgerland Audubon Society.

Credits:

Photo: Courtesy and © Copyright 2009 Julio Betancourt

Text: Julio Betancourt USGS NRP Tucson: Biotic Response to Climate Variability

Faculty and Staff > Julio Betancourt

Additional Reading:

USGS National Research Program: Tucson AZ
http://wwwpaztcn.wr.usgs.gov/home.html

Climate Change and the Great Basin, Jeanne C. Chambers, USDA Forest Service, Rocky Mountain Research Station, Reno, NV, 2008,

A Database of Paleoecological Records from Neotoma Middens in Western North America, USGS/NOAA North American Packrat Midden Database, http://esp.cr.usgs.gov/data/midden/ (Accessed 27 August 2009)