Old images record landscape change through time

Historical photographs are a powerful tool for examining and understanding the distribution of surficial processes, both physical and biological, on the timescale of decades and centuries. Such imagery is particularly valuable for understanding human-landscape interaction. Here, we present several examples of quantitative, image-based, landscape-scale analyses made using hundreds of different images, each taken at a different place. This analysis takes advantage of a large, searchable, Web-based image archive that contains enough images to allow testing of specific hypotheses regarding landscape change over time. For example, analysis of Vermont landscape images dated between 1860 and 1990 demonstrates that erosion is more common in clear-cut areas than in partially or wholly forested sites. We find that the quality of riparian buffers increased slowly over the past 184 years, with a dramatic improvement after 1980. Oblique aerial imagery taken after the 1927 flood of record and recently rephotographed demonstrates the frequency of near-channel land-use change over the past century. Together, these examples show the value of readily searchable image archives in allowing scientists, planners, and land managers to approach problems of significant societal relevance.