Research into and related to trees, a particular group of woody plant species, has contributed significantly to human knowledge about the environment at large. In the nineteenth and twentieth centuries, trees were not only objects of study themselves, but also scientific instruments, helping early scientists to understand the environments and ecologies they inhabited. This talk addresses several cases in which scientists, sometimes with the contributions of laypeople, used trees to generate knowledge about the environment that was, in turn, also shaped with the help of trees.

Discussing the role of trees in nineteenth and early twentieth century medical topographies of deadly fevers, as well as in the documentation of the urban heat island effect, reveals how trees were incidental and intentional vehicles for better understanding human-environment relationships. The interest in the instrumental knowledge about trees and their effects on human health and wellbeing was related to urbanization and, by extension, to colonial expansion and wider geopolitics. Arboreal knowledge-making both informed and was instigated by considerations about population growth and the acceleration of human settlement. Regardless of the phenomenological, mythical, and therefore hypothetical and proto-scientific nature of much early tree knowledge, it had a significant impact upon how early design professionals conceived of and shaped the built environment. In addition to being informed by cultural paradigms, aesthetic fashions, and political ideologies, the parks and tree-lined streets that characterize many urban environments today were based upon both mythical and scientific nineteenth and twentieth-century ideas about trees vis-à-vis human wellbeing.