As part of a recent study about historic changes to Michigan’s coastal dunes, a Michigan State University research team documented landscape change through the use of repeat photography, which is the practice of taking multiple photographs of the same subject from the same location, at different times.
Repeat photography is a common and effective method to assess the rate and characteristics of landscape change. For example, repeat photography is an excellent way to observe glacial retreat in western alpine settings resulting from climate change. Figure 1 provides an example from Glacier National Park illustrating this phenomenon. Without repeat photography, researchers may not have fully realized these examples of broad landscape change.
|Figure 1. Repeat photography of the Boulder Glacier in Glacier National Park. Top image: photograph of the Boulder Glacier in ~ 1910. Bottom image: photograph of the Boulder Glacier in 2007. Note the significant reduction in size of the glacier due to melting due to ongoing climate change (source: USGS).|
The coastal dunes of Lake Michigan provide an excellent opportunity to utilize repeat photography to evaluate landscape changes. The dunes are an ideal research location because: 1) the shoreline is relatively open and accessible; 2) coastal dunes are dynamic and change easily; and 3) vegetation coverage on dunes reflects relative dune stability at any given time.
Figure 2 illustrates the application and benefit of repeat photography within the context of dune morphology. Note the sequence of exposed organic (dark) layers which represents prehistoric periods of stability and soil formation compared with the expanded vegetation in the repeat photograph. This photographic evidence indicates the dune is in the process of stabilizing due to expanded plant cover and demonstrates the sensitivity of this landscape.
|Figure 2A: Taken in Van Buren State Park in 1997.||Figure 2B: Same site taken from the same place in 2014|
Here is the protocol the team used to create repeat photographs of historic photos for this project:
1) Select location – In order to achieve accurate repeat photography, the exact location of the original image must be known either through GPS coordinates or utilizing a permanent, fixed structure or landscape feature. Both Google and Apple Maps on your smartphone have the ability to easily show you the GPS coordinates of a location. With your map application open, simply press and hold on the location, and Google and Apple Maps will come up with the coordinates. For more detailed instructions, click here for Google Maps (Androids) or here for Apple Maps (iPhone).
2) Image antiquity – Ideally historic and repeat photos should span the greatest time period. Images acquired in the late 19th and early 20th centuries are especially useful for research efforts.
3) Focus on larger dune landscapes – for the purpose of this study, the photo's main focus had to be the dune and not any figures that may or may not be present (see Figure 2A & 2B).
Acquisition of Modern Photograph
If a suitable photograph (see Site Selection) is available, the following protocol should be followed when acquiring the modern photograph of the image couplet:
1) Make a copy of the original photo or take a picture of it with a high quality smartphone - You'll need to bring a copy of the original photograph to the site for comparative purposes.
2) Travel to site – Identify the location where the original photograph was taken and travel to it. Helpful tip-- If you are able to obtain the GPS coordinates of the original photo using Google Earth or a smartphone application it may save time when you’re out in the field. Record these coordinates and then find that location along the dune.
3) Find exact location - Attempt to find the exact location where the original photograph was acquired. In order to accomplish this task, attempt to align any modern landscape features, such as trees, bluffs, and built structures, visible in the original photograph with the modern view. See Figures 1 – 2 for examples of the desired similarities in view between the original and modern photo.
4) Equipment - Citizens scientists are encouraged to collect as high quality of a photo as possible. Photos may be collected using a tripod-mounted, large camera (4x5in sheet or 120 roll film), a high-quality digital camera, or by a using a high-quality cellphone camera.
5) Tracking the location - Cataloging the location of the repeat photograph is important. For best results turn on the location/GPS coordinate feature on your camera (if available); or, activate the GPS feature on a cellphone or other device and record your position. If this is not feasible, record the description of the site as detailed as possible (i.e. approximately 100 ft east of the boat launch, facing SE).
6) Shooting the scene - To the best extent possible, scientists should attempt to match the field view of the original photograph with the repeat photo. To ensure as close of a match as possible, take several shots of the repeat image with subtle adjustments between each photo.