What is a range shift and why do they happen?

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Clip Guide

: Here you will find clear descriptions of what you just saw, how they know what they said they knew, why they know it to be trustworthy information. Finally we will ask the question, "So what!" and explore why the information is important.

WHAT

In this clip from the 2005 presentation “Impacts of Changes in Extreme Weather and Climate on Wild Plants and Animals,” biologist Camille Parmesan describes shifts in location for Edith’s Checkerspot Butterfly as a consequence of extinctions occurring in some populations and not in others. She explains that the extinctions occurred along a shift in the temperature isotherm--a shift where higher temperatures occur further north and at higher altitudes than was previously the case. Further investigation, however, revealed that the butterfly die-offs were not directly related to the isotherm shift but instead were driven by extreme events such as false springs, droughts, or changes in snowpack.

HOW

Because she wanted to study population changes over the past 100 years, Dr. Parmesan needed to select a species that had been studied in the past and also lives in a range that had experienced climate changes over the past century. Edith’s Checkerspot Butterfly fulfilled both qualifications. Next, Dr. Parmesan needed information on current butterfly populations. Because the data she needed did not yet exist, Dr. Parmesan obtained this information by performing field studies of her own.

WHY

When determining whether or not two variables influence one another, it is important to perform observations to see if the relationship exists or not in real life. The exact cause of population extinctions in Edith’s Checkerspot Butterfly was unknown, so Dr. Parmesan used observations and fieldwork to test the truth of a hypothesis. Initially, it appeared that the isotherm shift was causing the extinctions because the two occurred in the same area. When Dr. Parmesan performed on-the-ground research, however, she discovered that die-offs were in fact driven by extreme events such as droughts leading to a timing mismatch.

SO WHAT

Scientific data suggests that the climate is warming. In both apparent and subtle ways, these changes in average temperature will impact where certain species are able to survive. Studies such as Dr. Parmesan’s can help people to understand the relationship between climate change and population extinction, allowing us to make better decisions about how to preserve valued species.

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Printable Companion Guide:

FTHM Guide PDF--Parmesan II.pdf

Active Listening Questions

Active Listening Questions:

Where did most of the population extinctions occur?

What were some of the challenges to gathering data faced by Dr. Parmesan in her butterfly population study?

Is the relationship between climate change and population extinction direct or indirect?

Taking the Reins

taking the reins

Clip Discussion Questions

Reflect on the clip using these questions. Then, record your thoughts in a science journal or discuss them with a friend.

Based on Dr. Parmesan’s observations and conclusions, where does it seem likely that there will be populations of Edith’s Checkerspot Butterfly in the future?

Dr. Parmesan’s study involves a type of bioclimate modeling. Based on what she talks about in this clip and on the word itself, what do you think bioclimate modeling is, and why do you think scientists might want to study this topic?

Clip Discission Question Printable Companion:

Discussion Questions-Parm II.pdf

Clip Activity:

Go Beyond:

Imagining Extremes In this clip, Dr. Parmesan explains that climate-related extreme events or years with conditions considerably above or below average have led to the extinction of some butterfly populations. Use your science journal to record your thoughts, sketches, and ideas about one type of extreme event.

Scientific studies project that if current trends of carbon emissions and global warming continue, the United States will see an increase in the number of days per year with a temperature of over 100 degrees F.
- Look up the average number of days per year above 100 F in the area where you live. Days above 100 deg F are considered an extreme event.
- If the number of days above 100 deg F increased by 20 or more days per year, how would that impact social and economic conditions where you live?
  - Is there food grown in your area?
  - What are your water resources like?
  - What would this mean in terms of energy use?
  - What would this mean in terms of popular activities?
- At what point would climate changes cause you to be no longer be willing to live in an area?