Tracking Changes to Urban Trees over 100 Years in Ithaca, NY, USA

Abstract

Municipally managed urban trees provide environmental, social, and economic benefits. Continued provision of these benefits depends on the health and sustainability of these trees, which depends in turn on tree managers having the type of information usually found in a tree inventory. The city of Ithaca, New York, USA possesses 7 inventories of its street and park trees dating back to 1902. This paper uses the data contained in these inventories to assess the health and sustainability of the city’s street and park tree populations. Attention is given to the structure of these populations with emphasis placed on species and genera diversity and DBH size class distributions. Prior to 1987, the city’s municipal tree population was dominated by a few species, such as Norway maple (Acer platanoides), and genera such as maples (Acer) and elms (Ulmus), and the DBH size class distribution was skewed unsustainably towards older trees. From 1987 onwards, new plantings have significantly increased species and genera diversity, and the DBH size class distribution suggests sufficient younger trees to account for tree mortality and removals. These changes did not occur quickly due to the persistent legacy effect of past planting preferences and practices, but required a consistent effort by municipal tree managers over many years. As a result, based on an analysis of the most recent tree inventory conducted in 2019, the city’s street and park trees and the benefits they provide look to be on a more sustainable footing, although challenges still remain.