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  How Do We Know?    
 
Introduction
Present Day Forests
Recent Forests
Ancient Forests
Conservation
How Do We Know?
Dating
Fossils
Buried Forests
Pollen
Tree Rings
Land Surveys
Human Inspiration
Tree Guide
Glossary
Resources
Credits
Teacher Orientation
      At many points throughout this Web exhibit, we discuss past environments and landscapes. How do Illinois State Museum scientists know what past landscapes looked like? This section of Illinois Forests is about how scientists learn about the climate and forests of the past.

There are a variety of records that tell scientists what happened in the past. 

  • One source is historical records. These are written accounts made by people who witnessed events and wrote them down in what scientists consider the 'recent' past. Historical records in the United States have been made over the past 300 years. This section will include land survey records and journal entries made by surveyors in the field.
    • Land surveys show a 'snapshot' look at the landscape as it was when the surveyors were there.
    • Journals offer descriptions of the same landscape, and descriptions of events that changed the land, like fires, settlement, and cultivation.
  • Tree rings are another source of information about the recent and ancient past. Because trees produce rings yearly, rings provide information about fires, droughts, and general growth conditions, and give us a time frame in which to place these events. 
  • Fossils are preserved original remains or preserved evidence of plants and animals. Sometimes trees and forests are preserved. Fossils are preserved in a variety of places, from lake-mud and peat bogs to very dry environments. Illinois State Museum scientists use fossils to learn what ancient landscapes looked like. They also use fossils to learn about past climate. 
The following pages describe the resources and methods scientists use to reconstruct the prehistoric plant communities. It also covers relative dating, radiocarbon 14C dating, and what these tell us about the timing of past climate changes. 

   
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