April: Archeology and Our Environment
April is full of good reasons to turn our attention to the great outdoors.
Celebrate National Park Week (April 19-27) by visiting a national park. Earth Day is April 22! Some States have declared April as Archaeology month. Go to the Society for American Archaeology's state archaeology month page to find out when your state celebrates archeological discovery.
Archeologists don't just dig into the earth, they dig into the earth's history. Archeology provides a long-term perspective on changing climate, land and water forms, soils, plants, and animals.
Ecologists, archeologists, and other researchers often work together to understand Historical Ecology, or the ways in which people interact with and affect their natural environment through time. Changing climate and other ecological changes affect peoples' lives, including native Alaska communities today, who find their traditional means of subsistence challenged.
Be sure to explore the video and audio links on this site about current research on Kenai Fjords in Alaska. Researchers are examining ancient cultural sites and consulting living descendants of these cultures in Alaska to better understand long-term human use of the area.
Archeologists' reports, soil samples, pollen analysis, geophysical studies, plant and animal remains, and artifacts all help ecologists learn about the ripple effects of ecological change. Detailed investigations such as those of chemical and grain-size characteristics of soils provide insight on the ecological past. Archeology helps ecologists to investigate ecosystems and reveal the elusive story that only the Earth can tell.
Case Study: Paleobotany on Steens Mountain,
Special thanks to Scott Thomas, Bureau of
Steens Mountain in southeastern Oregon offers scenic and recreational experiences on over 400,000 acres of public land. Its plant communities are well known, but until about 6000 years ago there were no juniper trees on Steens Mountain. How do we know this?
Because plants respond to climate change, scientists can study climate change by examining plant species in a particular place over a long period of time. Species may vanish from a plant community altogether or expand into a new one. The number of species also may change.
Paleobotanists study ancient plants. Archeologists and paleobotanists often work together to reconstruct ancient environments and the ways that they changed over time. Environmental Archeology seeks to understand the ways that humans interact with, impact, and are affected by the natural environment.
Paleobotanists use drills to extract sediment cores from bottoms lakes and ponds and examine them for plant pollen and charcoal. Flowering plants produce distinctive pollen when they bloom. The lightweight pollen grains blow far and wide in the wind. When they fall on the surface of a lake, they sink to the bottom and become incorporated into the mud on the bottom. Charcoal can be carried in the wind or washed into a lake by a stream. Eventually the waterlogged charcoal sinks to the bottom of the lake and joins the pollen in the mud.
Not only can the charcoal be identified to the species of wood but, more importantly for purposes of studying climate change, it can be dated using the Carbon 14 dating method. The pollen layers tell the story of the plants and changes in the composition of a plant community over time.
When paleobotanists sample sediment cores, they are examining the evidence for changes in the plant communities over time. When the charcoal taken from the core is dated, researchers can figure out how long it took for plant communities to change.
For example, in southeastern Oregon, the pollen record covers the last 13,000 years. Plant history indicates that the climate in the Steens region has changed a number of times since the end of the Pleistocene. We know this because the pollen record has changed dramatically in that time. Generally, when there is more grass pollen in comparison to sagebrush pollen, the climate is wetter than now and vice versa. When saltbush and greasewood replace sagebrush in the pollen record we deduce that the climate is warmer and drier than before.
From the Steens sediment cores we know that Wildhorse Lake was under ice until 9,000 years ago because its pollen record did not begin until then. Fish Lake was ice free and started collecting pollen 13,000 years ago while Diamond Pond at Diamond Craters was not collecting pollen until about 6,000 years ago.
These changes in vegetation over time affect animals and humans. Archaeologists can use these data to help explain changes such as site use and abandonment, increased population, increases and decreases in site density and shifts in the type of plants and animals species important to people and essential to their survival.