Data from urban tree surveys of the 19th–21st centuries as input for planning the maintenance of historical tree stands: A case study of Kaarli boulevard in Tallinn, Estonia

Greenery plays a crucial role in shaping the urban environment and its resilience to climate change. Urban trees are the most noticeable and long-living part of urban greenery, but poor management decisions or negligence pose a significant risk to the health of urban tree stands. To successfully plan the maintenance and renewal of urban trees, we need to be able to assess their condition. In this study, we examine what data on urban trees are available in Estonia to date, as well as the quality of these data. The study aims to determine whether the available data are sufficient to plan future maintenance and renewal of urban tree stands. As a case study, we examined the available dataset on Kaarli puiestee and assessed its usability. Kaarli Boulevard (Kaarli puiestee) is one of the most researched historical urban tree stands in Estonia. After examining the available materials, the following concerns emerged: 1) data retrieval is difficult; 2) retrieving the necessary information from the materials is time-consuming; 3) different methods have been used in the surveys, which means that there is no systematic longitudinal study that could be used to monitor changes in the condition of the trees and to assess the impact of different factors. Planning of future maintenance cannot solely rely on using this existing material as input, because the data is not uniformly comparable. It is therefore essential to improve the quality of the data by making it readily available, ensuring data harmonisation and keeping it up to date. Keywords: urban trees; historical boulevards; tree surveys; greenery; dendrology