Resource Type
Completion Time
Less than a week
High school and Up
Download and Share
Julia West
Repeat Photo Pairs (Available in PDF)
Earth System, Structure, and Processes
Snow and Ice Science
Climate Change
General Polar Science


It's All About Repetition!

In this lesson, we will learn what repeat photography is, and discuss how it can be used in scientific analysis.


What is repeat photography? It is the taking of photographs from the same location, over time, to document changes. This tool has become extremely useful in science, as a qualitative way to document the effects of humans on an area, succession in vegetative communities, seasonal changes, and much more.

Why do landscapes change over time?

  • Human activity (deforestation, development, agriculture, pollution)
  • Animal activity (beaver dams, overgrazing, insect or fungal infestation)
  • Fire
  • Natural events (floods, hurricanes, volcanoes, etc)
  • Climate change

What can we look for when observing change using repeat photography?

Landform changes
  • rivers changing course
  • lakes or ponds changing size
  • beaches eroding
  • landscaping and development (such as roadbuilding)
  • glacial retreat or advancement
  • effects of landslides or avalanches
Vegetation changes
  • presence of vegetation
  • size of vegetation
  • types of vegetation
  • location of vegetation types

Some of these factors will be discussed as we take a look at some repeat photography. As you look at the photos pairs available in the lesson, consider the questions that follow them, and jot down notes. You will get a chance to analyze some photos yourself and answer a few questions, and then experiment with creating your own repeat images.

Repeat Photography and Connections to Your Area

The lesson PDF offers documented photo pairs from various places, and questions linked back to your local area.

Photo: You can use repeat photography to show human development in an area. McKinley Village, Alaska.
Question: Can you think of any vantage points in your area where you could document increased development over time?

Photo: Reclamation and restoration of a riverbed in the Kantishna Hills area of Denali National Park, Alaska.
Question: Are there any new parks in your area, reclaimed mines or industrial sites, or other places where nature has been restored?

Photo: Natural areas where human effects have changed vegetation at Enchanted Mesa near Albuquerque, NM.
Question: Are there any areas near where you live where the vegetation has changed because of animal grazing, farming, or fire suppression?

Photo Evidence of major environmental/climate change in Grinnell glacier in Glacier National Park, Montana.
Question: Have you ever seen glaciers? If you live where there is snow, can you think of opportunities to document changes in snow depth or drifting through images?

When examining repeat photography, it is extremely important to not make assumptions, especially when you are exploring landscapes that are naturally changeable (for example, changing riverbeds or areas that flood frequently). There are usually several microclimates depending on local topography, and one area might show change while another nearby area doesn’t. This tool is useful for making generalizations and documenting large-scale changes. Using these, we then design more detailed studies and specific site analysis.

It is also important to recognize that the photos are not telling us why the change is happening, nor the effects of the changes. This is what additional quantitative investigation is for.


Examine the photo pairs in the lesson PDF and answer the following questions for each one.

  1. Describe changes that you see, considering the factors on page 3.
  2. Consider any known factors that might have contributed to the change, and write these down as hypotheses for further study.
  3. Using your knowledge of food webs in ecosystems, along with background information that is given to you with each photo pair, state some possible effects on animal and plant communities that might result from the change.
  4. Consider any possible effects this change might have on the physical environment or the microclimate of the area (wind, snow accumulation, frequency of fire, etc)

Note: As you consider the effects of the changes in the next photo pair, think about the animals that live in Denali National Park in Alaska. Caribou is an important species that feeds mostly on lichens and small tundra plants. Moose are also very common, and are usually found in low-lying areas where there are plenty of shrubs and small trees to feed on. Snowshoe hares’ habitat is mainly brushy areas with abundant shrubs for protection and food. Wolves prey on caribou, moose, hares, or any other small mammal or bird. Lynx eat almost exclusively snowshoe hares, but will prey on other small animals when the hares are at the low point of their 8-11 year population cycles. Some birds need open tundra to nest, and others thrive in shrubby or forested areas.

In general, also remember that fire is a natural part of many western U.S. landscapes. Consider the increase in woody vegetation combined with either drier weather or, in the north, drier ground as a result of thawing (and draining) permafrost. What might be the effects on wildfires?


  • Create your own repeat photography project to explore the change of seasons. Over a period of as many months as possible, take photos of a landscape every week, and describe what you see. Since this is a short term project, you will need to get closer to your subject area, unlike many of the large scale photos presented above. You will want to capture the growth of herbaceous vegetation.
  • Predict the future! Find a good vantage point in your area, and take a photo, draw, or paint what you see. Imagine a future, 10, 20, or 50 years down the road, and create an image that shows what you think the area will look like at that point. Do you live where there are forest fires? Will there be increased development – suburbs, road building, towns? Is a cleared area growing back to forest? Is there a dam and reservoir affecting the area? You can either choose by researching current and past trends in human activity, or create a scenario that you would like to see happen there. Add a description of your project and intentions.
  • Choose an area close to home, where you can compare old photos (from many years ago) to current photos. You don't need to find repeat photography examples. Create your own! Find old photos and see if you can determine where they were taken from. Try to capture the scene as it exists now, and create your own photo pairs. Include descriptions.
  • Research another area of the world where repeat photography has been done, and create a presentation about it, explaining the changes.
  • Consider the applications of repeat photography in park management. Very often, small incremental changes go unnoticed, and over time result in a large change from the original. Examples could be the number of signs along a road, increased erosion from foot traffic on a trail, etc. Choose either a national or state park that you have visited, or a local natural area. Make a list of human impacts on the area, and the possible applications of repeat photography to capture incremental changes over time. Describe the implications each could have in management decisions.

Teacher Notes

  • This lesson is intended either to stand alone for independent student work, or used in a class situation with a discussion.
  • For this lesson, it is assumed that the students have covered some environmental science topics, including biomes, succession, human impact on natural environments, ecosystems and food webs, and microclimate.
  • See the resource list for better resolution on some of these photos. These websites have excellent descriptions of the changes, along with explanations. In this lesson, the photos are isolated so students can come up with their own conclusions.


Denali Repeat Photos
NPS Land Change Virtual Tour
Allen, Betencourt, Swetnam, 1997. Southwestern US LUHNA pilot project
USGS Repeat Photography Project
AK Dept of Fish and Game


Teacher Julia West created this lesson plan as a capstone project for the 2013 teacher training course entitled: Climate Change: Seeing, Understanding, and Teaching, held in Denali National Park. The course is facilitated by the Arctic Research Consortium of the U.S. (ARCUS) in partnership with Alaska Geographic and the National Park Service.

Thanks to: Dave Shirokauer, NPS, Denali Nat’l Park; Sarah Bartholow, PolarTREC; Nan Eagleson, Murie Science and Learning Center; and Susan Steiner, PolarTREC teacher, who together provided a fantastic learning experience in the 2013 “Climate Change: Seeing, Understanding, and Teaching” course in Denali National Park.


Content Standard A: Science As Inquiry: a. Abilities necessary to do scientific inquiry b. Understandings about scientific inquiry Content Standard C: Life Science: d. Interdependence of organisms Content Standard E: Science and Technology: b. Understandings about science and technology Content Standard F: Science In Personal and Social Perspectives: b. Population growth c. Natural resources e. Natural and human-induced hazards f. Science and technology in local, national, and global challenges
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This program is supported by the National Science Foundation. Any opinions, findings, and conclusions or recommendations expressed by this program are those of the PIs and coordinating team, and do not necessarily reflect the views of the National Science Foundation.