A botanical journey through time

“A photograph is the closest thing to a time machine we have,” says Professor Timm Hoffman, director of the Plant Conservation Unit (PCU) in the University of Cape Town’s (UCT) Department of Biological Sciences. “It takes only a second, and in that second you capture an image that is so rich in information, it can be mined again and again to understand changing landscapes.”

Hoffman, who started the southern African citizen science repeat photography project, rePhotoSA, has been working with historical photographs of landscapes since he was a postdoctoral researcher in 1989.

Today, a doyen of repeat photography, a recent paper published in Ecological Informatics, revealed he is the world’s most prolific researcher in the field in terms of papers published on the theme. His work has also been recognised through two major awards: the WWF Living Planet Award in 2020 and the 2021 Silver Medal by the South African Association of Botanists.

A picture worth a thousand words

Repeat photography is used globally to document landscape change and is becoming an increasingly relevant field as the world experiences accelerated global change. While there are several web-based repeat photography research projects that focus on environmental change in the world, these are primarily in the Global North. rePhotoSA is the only one documenting change in southern Africa, and only one of three to incorporate citizen science.

rePhotoSA is an open access website which provides an online platform for citizen scientists to search for existing historical images from the southern African region, and to find, through the photograph’s metadata, the exact location where the photograph was taken and then repeat the photograph and upload that new image.

The project, which was started in August 2015 as a collaboration between the Plant Conservation Unit and the Animal Demography Unit within the FitzPatrick Institute of African Ornithology, houses over 6 000 historical images uploaded to an interactive map.

“The number of historical images on RePhotoSA are only about a quarter of the entire collection which has been scanned by the Plant Conservation Unit,” says Hoffman. “There is a lot of work that goes into putting an image onto the site, you have to know exactly where the photograph was taken which is usually quite tricky. Many of the images come with captions that just say, ‘the Karoo’, for instance.”

The earliest pictures in the collection date back to 1876 and then run all the way into the 2000s.

“Each image is just so rich in information,” he says. “You can look at the images and see what species were present then, how abundant they are, and how this has changed over time. Of course the question of why these changes have occurred is really tricky. So many factors influence the changes one sees in the landscape over time, from climate change, to land use, to the dynamics that exist naturally between plants.”

The resilience of the succulent Karoo

The photographs have revealed some interesting findings. The collection has a number of images for the Succulent Karoo biome, which has been described as the richest desert in the world because of its phenomenal diversity of plants, reptiles and insects.

“In this region we have about 300 photographic sites where we have taken the same photograph as the original photographer, and through this have built up a very interesting, and surprising story,” says Hoffman.

A key discovery to come out of this work is that the impacts of climate change are difficult to discern from those that have occurred because of changes in land use. Crop and livestock production have declined in the region, as farmers shift to more commercially oriented practices. Thus fewer animals graze the veld which in turn has less impact on the land. What the repeat photographs suggest is that for large areas there has been an improvement in plant cover.

“What we are also seeing is the return of acacia trees to the rivers, because people now have access to electricity and are not living off the land and relying on firewood for fuel anymore,” explains Hoffman.

The area was, however, impacted by the recent drought, which seems to have killed entire plant populations. Hoffman notes climate scientists are predicting many more of these more extreme climate events, noting that we have yet to see what the longer-term impact of these events will be, though the collection of repeat photographs for the area will provide important monitoring sites for documenting such changes in the future.

A lifetime relationship with historical photographs

Hoffman’s work with historical photographs began when he was a postdoctoral researcher at the Jornada Basin Long Term Ecological Research programme in New Mexico in the United States.

Here he met with Raymond Turner, a big name in repeat photography, who inspired him to take his fledgling interest in the field more seriously. When Hoffman returned to South Africa he joined what was then called the National Botanical Institute (today the South African National Biodiversity Institute) which had been supporting botanists and ecologists to conduct botanical and ecological surveys of South Africa, and this involved taking photographs of landscapes. Hoffman found these photographs and began to scan and collect them.

“When I joined UCT in 2000 I already had several thousand images,” says Hoffman. “A friend of mine who worked in the UCT Libraries, Paul Weinberg advised me to approach Humanitec for support to build my collection.”

Humanitec was an initiative within the UCT Libraries to preserve and make available the many rich collections, such as photographs and audio recordings, housed at UCT.

“We received a great deal of support from Humanitec,” says Hoffman, “and the few tranches of funding we got from them played an important role in helping to kickstart the rePhotoSA vision. Many colleagues, students and a team of dedicated staff have helped enormously to build the collections over the years since.”

Things we lost in the fire

In April 2021 catastrophe hit, as the PCU offices from which Hoffman worked, and which housed not only all his equipment but the entire collection of photographs, was completely destroyed in the fire that started on the slopes of Table Mountain and tore through UCT’s Upper Campus.

While Hoffman was devastated at the fire and the loss, the digitisation project of the photographic archive was the silver lining, albeit a slight one. Around 30 000 images of his total collection had been digitised and he had at least one image for 90 percent of his most important sites. But, he says, only 10 percent of another collection of 35 000 slides had been digitised.

What next

He is determined not let the devastation caused by the fire unravel the hard work he and his colleagues have put into repeat photography and the work of rePhotoSA.

“I am lucky to have a wonderful group of colleagues and staff who have provided such support and encouragement in the period after the fire,” he says.

He has already repeated 78 photographs taken at Cape Point Nature Reserve in 1966 and began scanning major new slide collections.

“These historical images will continue to build the PCU’s photography collection to be used by current and future generations in their teaching and research endeavours.”