Can You Read a Tree?

Cover page for Can You Read A Tree?

by Jessica Fries-Gaither

Narrated by John Croyle


Sun and clouds
Sun. Photo courtesy of stock.xchng.

What's the weather  like today? Sunny? Rainy? Snowy? What about yesterday? Was it the same or different? You probably know that weather changes from day to day. Sometimes it even changes from hour to hour!


Polar bear lying on ice
Polar bear lying on ice. Photo courtesy of iStockphoto.

Climate can change, too. It just happens over long periods of time. A place might have been very different long ago. A cool place might have been warm. A warm place might have been cool. How can we know what the climate was like long ago?


Journal Entry.
Journal Entry. Photo courtesy of JoelMontes, Flickr.

Scientists have kept records of the weather for the last two hundred years. To learn what the climate was like before that, they might have read old diaries or journals. A farmer might have kept a journal about when he harvested his crops each year. Another person might have written in a diary about when trees bloomed in spring.


Looking up at trees
Trees. Photo courtesy of stock.xchng.

But diaries and journals can only help so much. What about hundreds of thousands of years ago, before there were people at all? The secret to learning about Earth's climate can be found in surprising places, like giant trees.


Bristlecone pine forest of the White Mountains in California
Bristlecone Pine Forest of the White Mountains in California. Photo courtesy of Rick Goldwaser, Flickr.

The World's Oldest Tree

In the White Mountains of California, a gnarled  and twisted tree grows on the steep side of a mountain. Its name is Methuselah (meh-thoo-se-lah). It isn't an ordinary tree. You see, Methuselah is nearly five thousand years old. It is the oldest-known living tree in the world.


Ancient bristlecone pine
Ancient bristlecone pine. Photo courtesy of Clinton Steeds, Flickr.

Methuselah is a bristlecone pine tree. These long-living trees are found in only six states in the western United States. Their trunks are smooth from wind-blown sand and ice. They have yellow-green needles, like other pine trees. Bristlecones aren't very tall. They grow to be only about sixty feet. Most of the tree's energy is used to survive, instead of growing big. 


The Giza Pyramids
The Giza Pyramids. Photo courtesy of Tommy Wong, Flickr.

Scientists think that Methuselah has been growing since 2832 B.C. Imagine all the things that have happened during this time. The pyramids were built in Egypt. The first Olympics were held in Greece. The Roman Empire ruled a large part of Europe. Christopher Columbus discovered America. America won its independence from Britain. And so on!


Ancient bristlecone pine forest
Ancient Bristlecone Pine Forest. Photo courtesy of Bran Schalcosky, Flickr.

Why are trees like Methuselah important? They help scientists learn about the Earth's climate long ago. Here's how.


Tree rings
Tree Rings. Photo courtesy of Garry Knight, Flickr.

Have you ever seen the inside of a tree? If so, you know that a tree's trunk is divided into many circular sections, or rings. These tree rings can tell scientists how old a tree is. Each ring equals a year, so a tree with five rings is five years old. A tree with fifty rings is fifty years old, and so on.


A person counts the rings of a tree.
Counting the rings. Photo courtesy of Sam Beebe, Flickr.

Scientists also measure how wide the rings are. The width of the rings helps them understand what the climate was like during that year. A wide ring tells scientists that there was plenty of water and warm temperatures during the year. A narrow ring means that there wasn't enough water or the temperatures were too hot or too cool.


Counting tree rings
Count the rings. Photo courtesy of Bertie Mabootoo, Flickr.

Scientists don't just study one tree's rings to learn about the climate. Instead, they will study the rings of many trees in the area. The rings of all the trees will be similar. Scientists compare the rings to draw conclusions about what the climate was like for that place in the past. Scientists have done this in many places in North America and Europe. They know what the climate was like thousands of years ago.


Large tree
Tree. Photo courtesy of Andy Beecroft, Wikimedia Commons.

Go outside and look at the trees near your home or school. What can they tell you about the past?