Further comments on analysing trajectories of vegetation and landscape change in southern Africa from historical field photographs

Abstract

The comparison of matched historical and repeat photograph pairs provides an important tool to assess historical trends in vegetation and landscape change. An analysis of repeat photographs is invaluable for ground-truthing and augmenting an understanding of trajectories of vegetation change derived from other methods such as aerial photographs, remote sensing and models. In this article, we comment on some of the methodological strengths as well as limitations associated with using historical photographs to understand vegetation change. Strengths include the long time period covered by some images and the level of detail contained in the photographs. Limitations relate to the patchy and potentially biased temporal and spatial coverage of a region. We suggest ways to overcome these limitations while also addressing the important issue of how best to interpret changes observed between two repeat photographs. We suggest that researchers should be open to a wide range of interpretations that may draw on climate models, ecological theory, other historical sources, and the evidence available in the images themselves. Historical photographs, where available, nevertheless provide an indispensable record of change in the landscape useful for anticipating future changes.