Tree removals as socioecological experiments in cities

As keystone structures in urban ecosystems, trees are critical to addressing many of the current livability, health, and environmental challenges facing cities. Every day, trees are removed from urban landscapes as part of routine management. These tree removals are an opportunity for implementing manipulative experiments to directly measure the social and ecological functions of trees. Here we review the kinds of tree removals that commonly occur in cities, assess the relevant opportunities that arise for research-practice partnerships, and discuss the challenges posed when implementing experiments of this nature. We argue that experimental studies on the routine removal of urban trees will improve and expand the mechanistic understanding of how trees support biodiversity and human well-being in cities beyond current knowledge, which is largely based on correlative studies. Finally, we highlight the opportunity for experiments to be co-designed by scientists and urban land managers, and how "learning while doing" can generate tangible research impacts and improve urban forest decision making.