Written by J Kelly Cluer, Director of Business Development, Kinross Gold Far East, Magadan, Russia, and Carson City, Nevada, USA; in collaboration with Dr M Saandar, Monmap Engineering, Ulaanbaatar, Mongolia

The centennial of Roy Chapman Andrews’ brainchild, the Central Asiatic Expedition (CAE), is just around the corner. The idea of rephotographing the CAE’s amazing 1910s and 1920s views of Mongolian landscapes and cityscapes was conceived in 2012, on a sultry August evening session in an Ulaanbaatar pub. Since then, my long-time colleague Dr M Saandar and I have clocked many kilometres throughout the Gobi Desert, hunting down the location of photographic scenes preserved in the American Museum of Natural History (AMNH) archives. Key players at AMNH have been instrumental in the project: Mike Novacek, Mark Norell, Mai Reitmeyer, Suzann Goldberg; and it is an honour to acknowledge their help and support. Each field season yields more compelling new visual evidence of change, often at a surprising tempo. Now comprising a significant body of work, the nascent idea has evolved into the CAE II 100th Anniversary Rephotography Mission.

To date we have completed field missions during 2016, 2017 and 2018 resulting in 35 rephoto views. If the global pandemic situation and travel restrictions ease, a 2021 mission will target Flaming Cliffs, Red Mesa, Tsagaan Nuur, Choir and other points along the old CAE routes.

‘Camp with lava-capped red mesa in background’ August 1923 by Walter Granger is inset on a re-photo captured in August 2018.

Only a few years ago we did not know the exact camera location for any of the AMNH photographs. Every rephoto has been a journey and, by finding the old positions and collecting precise GPS coordinate and view direction data, the task for future rephotographers will be vastly simplified; perhaps even to the point where the future photographer is a mission-programmed drone.

Preliminary results from the Gobi locations show dramatic landscape changes including spectacular cliff retreat at Flaming Cliffs. Our current ideas are that intense wind, freeze/thaw action, and possibly even seismic tremors combine to undermine the cliffs and eventually topple them over. In recent times with tourism on the uptick there is also a human element of erosion as this popular destination gets crowded and is virtually unregulated.

A fine example of landscape change is visible at the Twin Towers of Flaming Cliffs where the CAE made many photographs during several missions to the productive fossil locale, the site of the world’s first dinosaur eggs preserved in nest form. In 2017 we noticed the change after the frustration of trying to find the view in the old photos – the view was so dramatically changed and it took time to understand that part of the famous cliff face was missing!

Measurements revealed that approximately five metres of the cliff had disappeared. Approximately five meters per century, five centimetres per year. Another way to visualize the cliff retreat is about the width of your smartphone every year. The change is rapid. But cliff retreat is punctual, as sudden whole-column collapse, not grain-by-grain disintegration. We are still looking for local people that may know when this happened. An exact date of collapse is an important element refining the rate of change. Our best illustration of this change is the rephoto looking north-easterly from the egg nest ledge, "Shackelford Point 4” (above), staged right at the cliff edge, where period movie footage was shot (see youtu.be/t0B0bgvUu1E). The thoughtful placement of the donated Dodge at left made us consider placing a Land Cruiser there for the rephoto, but we’re waiting for Toyota to sponsor that.

There is currently discussion about how to protect and preserve the Flaming Cliffs. It brings up important questions about natural versus man-made erosion and landscape changes. Certainly the toppling sandstone columns at the cliff face is a natural geomorphic response to local erosion processes. This seems to be how the cliff retreats and is surely one of the reasons why new paleontological finds can be counted on year after year – new strata are continually being exposed at the unstable cliff face. However, it is disconcerting when you watch tourists trying to topple them over! I hope the stakeholders can come up with a workable solution that allows people continued access to this natural wonder while preserving its untamed characteristics. Education has to play the leading role here, and rephotography can clearly show people how natural change happens and provide context and a view of what the future may bring.