Laboratory of Tree-Ring Research

Why the past matters

Freshman Colloquium Arts and Sciences 195A, section 16, Spring 1996

Day of week:

Friday.

Time:

From 10:00 to 10:50 a.m.

Location:

West Stadium (Building #58) Room 104G, plus site visits on campus.

Instructors:

Malcolm K. Hughes (Laboratory of Tree-Ring Research)

It is no accident that insurance companies use past records when figuring out how much to charge for insuring a particular risk, as do civil engineers when deciding how secure a house site is from flood or landslide. What has happened can happen. We will take several journeys into the past that will teach important practical lessons about our natural environment, and how people interact with it. In some cases we will meet the scientists or other scholars doing this work and you will have the opportunity to talk with them about the social usefulness of their work, as well as their other reasons for doing it. Some examples of the topics we will discuss are:

• ``Old man river just keeps flowing along'', or does he? Water supplies are essential to the development of the West, and at the heart of many economic and political issues in this region. Where does our water come from, and what can we learn about the security of those supplies from the study of the environmental past?
• Some of our most important laws designed to protect nature are, at least partly, based on the idea that, before Europeans arrived, nature was stable and hence changeless for long periods of time. From studying natural records of the past as unlikely as the mud at the bottom of lakes, or the urine-soaked middens of long-dead rodents, we now know this to be hopelessly wrong. For example, not so very long ago, mammoths and other large mammals roamed a Southern Arizona landscape devoid of giant saguaro cacti. What do findings like this mean for our current attempts to protect nature?
• For ninety years the U.S. Forest Service, private landowners, state, local and Federal governments have been fighting forest fire, often at considerable financial and human cost. Now there is talk of fire as an inescapable, and often useful, aspect of the forest, with proposals to abandon the old policies of fire prevention and control. A new policy of the intentional introduction of fire has already been adopted in some cases. A large part of the scientific basis for this, sometimes unpopular, policy change comes from the study of the history of forest fire over many centuries, using natural records such as the scars fires leave in living trees. Is this strong enough evidence to make such a risky change of policy?
• Almost five hundred years ago, the early Spanish explorers in the Southwest found impressive abandoned buildings. They had no idea whether the people who built and lived in these buildings had left them recently or thousands of years earlier. It took until 1929 for this mystery to be solved by the UA's Andrew Douglass, who used tree rings to provide a detailed calendar of the development and changes of Native American societies in this region for the thousand or so years before the Spanish invaders came. Why should this matter to us now?
• Fears of the threat of very sudden climate change (``global warming'') that could disrupt agriculture, water supplies and energy use stem from evidence that human activity has led to a rapidly increasing concentration of carbon dioxide in the atmosphere. How do we know that there is more carbon dioxide in the air now than in the past? How much and how rapidly had this changed before humans were around to affect it (we have to use naturally preserved samples of ancient air to answer this)? What can we learn from these natural variations about the significance of the increases caused by human action? Do they tell us anything helpful about how best to respond?

Each student will write two short position papers, each stating, and giving good reasons for supporting, their personal view of the value of knowledge of the past in answering one of the questions ending each of the bulleted paragraphs (above). These papers, and the quality of the student's contribution to class discussions, will be the basis of letter grades.

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