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Determining Climate Change Through Sediment Cores

Introduction

Pollen are microscopic particles that plants distribute through insects, wind, etc., to other plants of their own species for fertilization and sexual reproduction. Pollen is unique to the type of plant it comes from, so pollen from different species are often different in appearance. Even though pollen particles are really small, we can look at them under a microscope and identify the plant species they came from.

Part 1: Plants, Pollen, and Climate

Some scientists collected pollen from different plant species across the United States. Your Pollen Identification Guide shows a pollen particle and the plant species it came from. Each plant species (identified by number) was only found in a particular place.

1. Why do you think that often particular plant species are found in certain areas? (Hint: look at the maps)

Using the maps, work individually and fill in the climate sections of your Pollen Identification Guide for each plant.

Part 2: Pollen from Sediment

Sediment (particles such as dust) from the air and surrounding areas is continually and slowly deposited into lakes. This sediment settles on the bottom of the lake and builds up over time. Other particles, such as pollen, can travel through the air and eventually settle on the lake bottoms, getting trapped in the muddy sediment. Scientists can take cores from lake bottoms, sample the sediment, and sieve out the pollen to determine the identity of plants growing near the lake.

With your group, look at the core diagram with the samples.

2. Which sample has the oldest pollen? Which has the newest pollen? Why?

Part 3: Sample Examination

Your group will receive a “sample” from the core. Work together to identify the pollen grains.

3. What plant species are present in your sample?

4. What do you think the climate was at the time when the pollen was deposited? How did your group decide this?

5. In a sample, if there’s more pollen from one plant than another, would that mean the climate at the time was closer to the first plant’s ideal climate?

Once you have determined the climate for your sample, put your answer on the core diagram at the front of the room. Fill out your own core diagram with the class results and discuss them with your instructor.

Part 4: Deductions About Climate

6. Given what you know about plants and climate, what happened over time to the climate where the core was taken?

7. Is this a reasonable conclusion? Explain.

8. Are ecosystems stable through time? Why or why not?

9. If certain plants only grow in certain climates, where do they go when the climate changes?

10. Some people believe in "assisted migration," that is, moving plants to areas that will be suitable habitats for future climate changes. Do you think this is a good idea or a bad idea? Discuss with your classmates.