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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?
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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.
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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.