Using land-use history to better understand biodiversity patterns in agricultural landscapes: case study of roadside vegetation.

Recent historical ecology studies have highlighted the over-riding influence of land-use history in creating past, present and future patterns of biodiversity in fragmented agricultural landscapes. Many landscape elements may still be experiencing major community changes as a consequence of recovery from intense historical land use. An historical ecology approach can enhance our understanding of why different species and ecosystem states occur where they do, and explain variations in ecological conditions within remnant ecosystems, too often casually attributed to the ‘mess of history’. Understanding the history of the land, its biota, and its anthropogenic interrelations must be treated as an integral aspect of any landscape ecology study (Lunt & Spooner 2005).
The rural road network is an important social component of agricultural landscapes; it facilitates transport of people, is an infrastructure corridor and is important for movements of outputs and inputs of agricultural production (Spooner 2015) . Present day landscapes are dominated by road networks, which are a historical vestige of past land-use decisions - a collection of farm boundaries, stock routes, laneways, railway reserves and other land administration boundaries, all of which contribute to present day spatial patterns. In this paper, I will discuss the use of land-use history to better explain patterns of biodiversity in roadside environments. In many regions, surveys of roadside habitat and vegetation variables are used to calculate an overall ‘conservation’ ranking of low, medium or high, to which appropriate management actions are directed.
Historical information on road development was collated from archived 19th and 20th century cadastral maps, such as road age, road width, as well as data relating to heritage (e.g. county or parish boundaries, stock routes, old fence lines; Spooner 2005) to evaluate the extent to which roadside conservation values and key vegetation structural attributes were influenced by historical variables.
Ordinal regression analyses showed that road age and road width was significant predictors of roadside conservation values (Spooner et al. 2004; Spooner & Smallbone 2009). Significant differences (p < 0.05) in the density of mature trees in roadside vegetation were found for roads in different road age classes. The oldest roads (<1870s) were characterized by having the greatest density of large hollow-bearing trees. By contrast, the youngest roads (post-1900s) had few shrubs or large trees (Figure 1). These findings highlight the influence and prevailing imprint of historical land-use on current roadside vegetation composition and structures. By understanding the history of roads, and developing the story of their development, can (i) provide a critical tool to enrich our understanding of present day biodiversity patterns, and (ii) aid in successful landscape conservation and restoration activities with land managers.