Repeat photographs show changes in the landscapes of southern Africa

 What is their history – and what are the changes they are undergoing in response to climate change and human pressure?

Photographs of historical landscapes are a good way to measure this. These photographs show how things looked at a particular moment. It is possible to document changes by standing in the same spot and taking a new photograph of the same scene. Researchers can sometimes measure the rate and extent of change in different landscape elements.

This and other historical data, such as climate or fire records, can provide insight into the reasons for change. These data can be compared to the information written about environmental changes using different approaches and models. Researchers can determine if the environment has reached critical thresholds and how to respond.

Repeat photography is a great way to capture images.

Growing field

Since the 1950s, repeat photography has been used in Africa to document the change in vegetation. In the last 30 years, there has been a surge in interest. The technique is used all over the world. Major projects have been undertaken in the drylands of North America, Ethiopian highlands, and the southern African region.

The historical landscape photos were compared with the modern images to analyze changes in alpine ice, soil erosion, and hydrology, as well as changes in populations of desert succulents, savanna trees, and long-lived desert trees.

Repeat photography is increasingly being seen as an important tool for monitoring the impact of climate change on vulnerable species and threatened ecosystems.

Landscape in Venterskroon, in South Africa’s North West Province. Photographed in 1919 (left) and again in 2017 (right). I. B. Pole Evans (1919); repeated L. de Speville (2017)/Images are copyrighted by rePhotoSA, under a CC-BY-NC 4.0 Creative Commons license.

In southern Africa, we have produced over 2,000 photos that repeat all of the major ecotones within the region. In a recent summary of this work, we provided a realistic assessment of the long-term impact of climate and land-use change on the African subcontinent. In contrast to our expectations, we discovered that the vegetation cover and biomass increased in most locations as a result of changes in land use, climate, and CO2.

The accumulation of such a high number of repeat photos was the result of many research projects conducted by researchers over a long period. Repeat photography is necessary to gain a holistic view of the changes in southern Africa’s terrains. But it would also require a lot of travel and time, which we don’t have. Citizen science is the answer.

Citizen science

In August 2015, the rePhotoSA Project launched. The goal is to get interested people involved in re-photographing historic locations. It has two advantages. Participants add to the total number of images. The public is made aware of the changes in the landscape.

The website contains over 6,000 images of southern African landscapes dating from the 1800s up to the 2000s. The interests and passions of the original photographers heavily influence geographic spread. These photographs are often donated by family members or institutions that the original photographers were a part of, and sometimes even by the photographers themselves.

The website uses a grid with quarter-degree squares to help narrow down possible photo locations. Users can browse through the QDSes color-coded and then download a high-resolution copy to print, along with a field data form where metadata can be recorded. Users must register for the project after repeating a photo to upload it to the website. We also have Facebook and Instagram pages.

Citizen scientists repeated and uploaded more than 280 photographs of landscapes between 2015 and 2020. These photos were mostly taken around South Africa’s Cape Peninsula and in the eastern Karoo region.

It is not surprising that the density of repetitions increases nearer to cities. These areas have seen changes such as increased urbanization, infrastructure like power transmission lines, and the introduction or removal of alien vegetation.

Read more: Tracking Science: A Way to Include More People in Producing Knowledge

In more rural locations where urban expansion is less visible, we often see other ecologically interesting trends: increased woody vegetation cover – bush encroachment – and denudation of large areas as a result of fire or overgrazing.

The quality of the data obtained through citizen science initiatives is not always consistent. Inferences regarding the causes of observed changes are partly dependent on the quality and metadata of a repeat photograph. The benefits outweigh any costs, especially when data collection is large.

Long-term monitoring

Recently, the project reached an important milestone when a peer-reviewed article describing its activities was published. Both bringing a South African project of repeat photography into the international research arena and highlighting the importance of citizen science and Open Data are significant contributions.

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