by Daniel B. Botkin, originally published by Perigee Books, a division of Penguin/Putnam, 1999.

This book, originally published as “Passage of Discovery“, is an ecologist’s guide to the first half of the Lewis and Clark trail, their travels up the Missouri River from St. Louis to Three Forks, MT.  I have decided to share this book with the readers of my website, and I am going to present the entire book here, one chapter at a time, with a new chapter appearing each week.  There are more than 40 chapters.  If you follow along and read all of them, you will learn about the entire Missouri River as seen by Lewis and Clark at the beginning of the 19th century, and as I visited it during the 1990s to see what they had seen, and to learn how the countryside had changed.  Comparing what Lewis and Clark saw with what we see today is one of the best insights we can get of how nature and environment in American has changed since European settlement.   I hope you enjoy it and find it rewarding.

- Daniel B. Botkin

All of the chapters published thus far can be found in the Passage of Discovery category. Please note that they are listed in reverse order of date posted.

More books by Daniel Botkin are available for purchase from the Center For the Study Of the Environment bookstore.

19. Ledges State Park: Reading Ancient History in Tiny Grain of Pollen

From Ames, Iowa follow Route 30 to Route 164, just south of the town of Boone.  Take this route south to Ledges State Park.  From DeSoto Bend National Wildlife Refuge, take Route 30 east to the same junction with Route 164.

Although the main body of the expedition traveled by boat on the Missouri or along side  it by foot and horseback, Lewis and Clark took turns exploring the land back from the river.  Often they sent a few men out to hunt for food.  Those who hunted often roamed widely and sometimes – not too infrequently – became lost and returned to the expedition after a long enough hiatus to cause some concern.

Because the river and the surrounding land are intimately linked, exploration away from the river was necessary for the expedition to understand the natural history of the newly purchased lands.  So it is today.  The best way to get the feel of the Missouri River as countryside is to go back from it into the prairie and woodlands.   With this in mind I set out from Ames, Iowa to explore the countryside between that city and the Missouri River with two ecologists from Iowa State University, David Glenn-Lewin and Tom Jurik.

From Ames, Iowa we took State Route 30 west to Ledges State Park where there were beautiful sandstone ledges thrust out of soils deposited by the great continental glaciers more than 14,000 years ago.  The Pease and Des Moines Rivers sculptured these ledges through sandstone on their way to the Ames.

We walked through the park on trails to admire the view of bottomland woods; even on a cloudy, cold day the scenery was dramatic as we stood on the ledges and looked at the Des Moines River beyond.  This was not the Iowa of urban stereotypes, not miles upon miles of flat fields of corn, but a steeply rolling countryside of water, hills and forests.  The scenery was all the more striking because the forests on the hills obscured the steep descents along the bluffs until we walked out to an edge to make a sudden discovery of flowing water below and sandy cliffs beneath our feet.

Tom and David told me the ancient history of this landscape.  All that we saw from these bluffs was under hundreds of feet of ice 14,000 years ago and for many thousand years before that, the time of the last great continental ice age.  Those masses of ice bull-dozed the landscape, tearing rock and stone, pebble and crystal with an awful force and momentum, grinding rock to stone and stone to soil, tumbling clays and sands and pebbles and rocks together into a jumble that we call “glacial till”; sandpapering the hills and filling the valleys with masses of this till.

Then the climate changed and the ice melted back and torrential rivers began to flow, cutting through the till and into the bedrock sandstone that had resisted the icy mass for thousands of years.  Warmer and warmer it became; by 10,000 years ago elm and ash grew near these rivers, floodplain species then just as now.  For several thousand years, the landscape must have looked quite as we saw it this April day.  But then the climate grew even warmer, too warm for trees, and the climate and winds pushed the prairie ever eastward.  By 7,000 years ago the climate was the warmest it would become after the ice ages, and prairies pushed their way through these ledges and east, all the way to the Atlantic coast.  Then the climate cooled again and the prairies retreated westward and about 3,000 years ago the forests had fully returned, to cloak the hills as we saw them that day.

The history of the vegetation is learned from the study of one of the unlikeliest products of plants: their tiny pollen grains.  From them scientists have painstakingly reconstructed an ancient history, never available before. This knowledge of the countryside is something new; it is a late twentieth century item, the result of medium and high technology.  The people who uncovered the history of the migration of trees and grasses needed fine microscopes to examine pollen grains.  Each pollen grain has a hard outer coating of silicon; the grains, under a microscope, are elaborately patterned, like Victorian Christmas tree ornaments.  Each genus has its own characteristic pattern and overall shape and, for many plants, each species within a genus can be distinguished.  The patterns seem as various as snowflakes.  Cores taken with long metal tubes driven into mud on the bottoms of lakes and bogs provide the primary material.  This is subjected to strong acid washes to clean out everything but the resistant casings of the pollen.

But how to date the deposits?  That had to await the nuclear age and the invention of carbon dating.  Organic material in the muds, with the pollen casings, are removed and the amount of radioactive carbon counted.  This decreases over time at a rate that is calculated and carefully calibrated.  It is the ticking of the Pleistocene clock.  From this knowledge of the atomic age, scientists date the layers of pollen grains and then know what was growing when.  With these technologies, we have a moving picture of natural history not available to Lewis and Clark nor to any people before.  It is a grand cinema, deepening our understanding of nature.

Standing on these lovely ledges, we were awed by the history revealed to us, a time before civilization and agriculture, before Babylon.  Learning this history of the land and vegetation has changed the way that I look at countryside and the way that I feel about countryside.  Now I see this land as clothed in glacial till, its bare bones of bedrock arching in a few places above the fill, the deep, u-shaped glacier cut valleys hidden beneath rock and stone, silt and clay, the product of climate changes, migrations of species, and great forces beyond our imagination acting over thousands of years.