Repeat photography of Lake Michigan coastal dunes: Expansion of vegetation since 1900 and possible drivers

Abstract

Coastal dunes are prominent features along the Lake Michigan shoreline, especially along Michigan’s Lower Peninsula. Numerous studies in recent years have reconstructed the geomorphic history of these dune systems, from their initial formation in the mid-Holocene to about 300 years ago. These studies have suggested linkages between past dune behavior and climatic variability and fluctuating lake levels. Less is known, however, about how these dune systems change on shorter-temporal scales in the modern era and the potential drivers of that change. Using repeat photography, this paper attempts to demonstrate how the coastal dunes of Lake Michigan’s eastern shore have changed since the 19th century. We collected hundreds of photographs of these dunes, taken between the years 1885 and 2018, from archives and citizen scientists. In the spring and summer of 2019, we took ∼70 new photographs replicating the original images. The changes between coastal dune conditions in the original photographs and in the 2019 photographs show a general expansion of vegetation across formerly barren and active surfaces along the entire shoreline. Although human development has also played a role in reshaping the coastal dune systems, the most pronounced difference between historical and current dune conditions where repeat photography was conducted is the expansion of vegetation – grasses, shrubs, and even trees. Here, we present the 20 photograph pairs most representative of these trends, explore these changes, and discuss the likely causes, including the increase in precipitation in Michigan in the past ∼80 years.