Historic urban tree canopy cover of Great Britain

Abstract

Research Highlights: Historic trend analysis of urban tree canopy cover change, while growing in popularity, remains uncommon and concentrated to just a handful of countries. Background and Objectives: Tree canopy cover is a relatively quick, easy to obtain and cost-effective urban forestry metric. It is used to provide insight into not only the coverage of a defined area but also an urban forest’s potential to provide benefits to those who live and work in the locality. On-going delivery of benefits is reliant on a sustained healthy canopy, and knowing how canopy coverage is changing over time can be informative for strategic urban forestry management planning. Materials and Methods: Changes in tree canopy cover is assessed for ten urban areas across Great Britain since the 1940s using a random point-based assessment of paired aerial imagery. Results: The study reveals a predominance of increasing trends over the long term, with just one town displaying a long-term decrease and two revealing “flat lined” trends. Over the past two decades, however, the trends are more variable, with six towns displaying no statistically significant change, one declining and just three increasing in canopy cover. Conclusions: The results indicate a need for ongoing research to broaden the geographic spread of trend analysis and investigation into the drivers of changes, but also to increase the number of time points considered.