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Past, Recent, and 21st Century Vegetation Change in the Arid Southwest

The purpose of this research project is to document vegetation change in the arid lands of the southwestern United States. The project compiles data on past and present plant distributions.  These plant distributions are combined with data on past, present, and future climates to predict future plant distributions. The project requires four major research efforts:  

Macrobotanical Digital Library

Identification and verification of plant macrofossils

Digitized Range Maps for Modern Plants of the Arid Southwest

Documentation of modern plant distributions

Fossil Packrat Midden Database

Compilation of existing paleoecological data

Modern Climates of the North America

Extrapolation of 20th Century climates to a 1 km2 grid

Much of this research is based upon the past distributions of desert plant species as recorded in fossil packrat middens, These databases are the building blocks for modeling the climate tolerances for plant species (paper describing methods) and the dynamics of their response to past climatic changes.  Future plant distributions will be modeled using climate output from General Circulation Models and plant migration models in the final stages of the project.  

Background Information: Late Pleistocene and Holocene Vegetation Change

Horseshoe Mesa in Grand Canyon National Park as it appears today (left), and as it may have appeared during the Pleistocene (right) based upon paleoecological reconstructions using packrat middens.

Climate changes expected during the 21st century are far larger than any experienced during historic time. In order to study the effects of such large climatic shifts, data is needed on climate changes of similar magnitude during the last 50,000 years. The study of environmental changes of the past is known as paleoecology.  Paleoecology is the science of reconstructing past environments using fossil materials of plants, animals, or other indicators of past environments.  Rather than reconstructing the past of a specific type of plant or animal, the goal of paleoecologists is to combine all the types of data to obtain insights into the structure and function of past ecosystems.  Frequently, paleoecological studies focus on environments of the Quaternary Period (the last 1.9 million years) because older environments are less well represented in the fossil record.  There are many instances of older ecosystems being reconstructed, but research at the Colorado Plateau Field Station is typically on the the Holocene (the last 10,000 years), or the last glacial period of the Pleistocene (the Wisconsinan period of the ice age; ~70,000 to 10,000 years ago).  These studies are useful for understanding the dynamics of ecosystem change and for reconstructing conditions that existed before the impacts of industrialized societies on natural ecosystems.

Project Scientists:

Non-technical Project Summary

For questions or comments concerning this website, contact Kyle McGinn at: kmcginn@usgs.gov