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Name ________________________
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)
Plants have adapted to grow best in certain climates. Those that are adapted to
grow best in conditions with abundant water will not be found in areas where
there is little water.
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?
New sediment falls into lakes and is deposited on top of older sediment which
settled before. Therefore, Sample E has the oldest pollen because it is on the
bottom of the core and Sample A has the newest pollen because it is at the top of
the core.
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Name ________________________
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?
Answers vary
4. What do you think the climate was at the time when the pollen was deposited? How
did your group decide this?
Answers vary, but should reflect the fact that the common two types of pollen
grow in relatively similar climates.
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?
No, because some plants produce more pollen than others. However, for this
activity, we can assume that all of these plants produce relatively the same
amount of pollen.
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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Name ________________________
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?
Generally, the temperature moves from warm to cold to hot (this generally follows
climate change patters from the Medieval warm period, to the Little Ice Age, to
current temperatures). Precipitation varies within that trend—see “Core diagram
answers” for more details. There are varies reasons for variation with
precipitation (heterogeneous landscapes, etc.)
7. Is this a reasonable conclusion? Explain.
Yes
8. Are ecosystems stable through time? Why or why not?
No, because ecosystems are closely tied to climate. When general climate trends
change, the type of ecosystem in an area may change as well.
9. If certain plants only grow in certain climates, where do they go when the climate
changes?
Gradually, plant populations can move to more suitable climates via seed
distribution. They may also go extinct.
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.
Answers vary. A famous example of this is the Torreya Guardians—their website
is at <http://www.torreyaguardians.org/recruit.html>.