The Urban Forest. Cultivating Green Infrastructure for People and the Environment

This book is a collaborative effort among academics and practitioners who have developed an appreciation for the value of trees in cities. Its focus is on urban “green infrastructure” (GI) – the interconnected web of vegetated spaces, ranging from street trees and private gardens to neighborhood parks and peri-urban forests, which provide essential ecosystem services in densely populated areas. The concept of green infrastructure embodies the view that biotic systems are just as vital to the functioning of a modern city as any other type of infrastructure, be it roads, water, sewage, power, or communication. At the same time, green infrastructure is different – more dynamic, more heterogeneous, and often more fragile – because it is alive. The services provided by this sort of infrastructure are more varied than those delivered by a system of roads or pipes. These services may have an immediate benefit, such as providing shade to a pedestrian on the street, or benefits which are longer term and somewhat removed from plain sight – like mitigating climate change or providing habitat for wildlife. In fact, the role of urban trees is tied up with the many other natural and man-made systems in the city, and their value lies in their mutual relationships with the soil, the atmosphere, and the people with whom they come in contact. What is provided, then, by the entirety of the “urban forest” (UF) is an array of ecosystem services – things like preventing damage from storm-water runoff, filtering dust and pollutants from the air, and providing an outlet for outdoor recreation – whose necessity often becomes most apparent when they are missing or insufficient. The challenge of ensuring that these ecosystem services are indeed delivered, and that they may be enjoyed by the population in an equitable and sustainable way, is a multidimensional undertaking. It requires knowledge of the physical attributes of urban greenspace, including the biological and hydrological processes underlying the growth and viability of trees and other plant species. It requires a broad view of the environmental interactions between the built and the unbuilt and a solid base of knowledge on which strategic decisions can be made regarding the planning and maintenance of green assets. Furthermore, it requires a set of tools for coping with the social and cultural dynamics that can determine success or failure in a landscape that includes human actors. And finally, it requires an understanding of how the totality of these environmental and social factors can be integrated in better policy and in more effective “governance” of urban green infrastructure. In this volume, we summarize the collaborative efforts of researchers and practitioners from across Europe to address these challenges. Its chapters convey the findings and recommendations of three working groups that were established within the framework of the European COST Action FP1204 GreenInUrbs, whose mandate is to develop a “green infrastructure approach, linking environmental with social aspects in studying and managing urban forests.” The three groups set as their task the compilation of “best practices” in three respective realms: the environmental, social, and governance-related aspects of urban forestry and green infrastructure. Members of the working groups represent some three dozen countries and embody a wealth of experience and expertise in fields ranging from plant physiology to landscape architecture to actor-network theory. By bringing together individuals from such diverse geographical and disciplinary backgrounds, the COST Action aspires to promote a common language – one which not only recognizes the distinctive needs of each country and region but informs a larger, more integrated approach to the cultivation of green cities. We hope and expect that this book will be of value to a broad and diverse audience. While many of the topics are technical in nature, the presentation of these topics is geared toward a nonspecialist audience. This is to ensure that the information and insights gathered by the working groups will be accessible to citizen activists as well as scientists – and while rigorously grounded in empirical evidence, the lessons offered will find a receptive audience among those who can truly “make a difference” in the way that resources are managed and policies are made. In addition, we foresee that the findings presented here will stimulate renewed dialogue between practitioners and theoreticians, each of whom brings invaluable knowledge to the discussion of the role that trees, forests, and green infrastructure play in our urban life.