Measuring the Arboretum

How large is the Arnold Arboretum? For decades, staff reported the size of the Arboretum landscape as 265 acres—a historical figure derived from an early and outmoded survey of the property. Now, through the precision of global positioning tools, new mapping technologies, and a more inclusive assessment of property maintained through the institution’s Landscape Management Plan, we are able to share the more accurate calculation of 281 acres, representing all areas managed by the Arnold Arboretum. This corroborates a figure previously calculated by the City of Boston.

Parcels comprising the Arnold Arboretum landscape can be categorized as land owned by the City of Boston and leased to Harvard University; City land managed by Harvard but not included in the lease agreement; and land owned by Harvard University. To determine the extent of all of these properties, Leon Croizat surveyed the landscape in 1937-38, and reported the Arboretum’s total area as 265 acres in the May 16, 1938 issue of the Arboretum’s Bulletin of Popular Information (Series 4, Vol. VI, No. 5) [pdf]. Even by the standards of the time, Croizat’s tools for measuring the Arboretum—magnetic compass, alidade, and chain—were archaic and susceptible to error. Nevertheless, his results proved long lasting, as staff continued to describe the Arboretum’s area as 265 acres even after the 1996 addition of approximately 18 acres of City property lying to the east of South Street, now known as the Bussey Brook Meadow.

A more accurate assessment of the Arboretum’s dimensions became possible with the development of a geographic information system (GIS) for mapping the living collections. The Arboretum’s GIS provides a powerful tool for staff to plot individual plants in the landscape, while facilitating a more precise understanding of the total extent of properties managed by the Arboretum. These enhanced capabilities have played a critical role in facilitating comprehensive and consistent care for the collections as part of the Landscape Management Plan (LMP).