Authors: Clive Davies (EFI), Diana Tuomasjukka (EFI), Rik De Vreese (EFI)
Forests and trees contribute to climate-smart cities in two ways: by providing renewable, bio-based products (particularly for construction and renovation), and by providing ecosystem services important for climate management and well-being.
As 70% of the global CO2 emissions are from cities, wood can play a crucial role in the construction and renovation of their built infrastructure by storing carbon and substituting other, more climate unfriendly materials, such as concrete, cement and steel. This shift is being driven by urban designers and architects who are looking to make their developments carbon neutral or carbon negative. Indeed, there is plenty of scientific evidence that using wood products instead of e.g. concrete, steel, synthetic textiles, oil or coal, helps to reduce CO2 emissions. Moreover, by integrating wood-based products e.g. in buildings and furniture, carbon is stored over longer periods.
This role is likely to increase further as most cities are growing. With their high concentration of resources and people spread over a relatively small geographic area, cities are uniquely positioned to drive modernization including the use of renewable bio-based products in a circular economy.
Forests and trees in and adjacent to cities and towns, including individual trees and smaller urban woods, are fundamental components of the urban fabric. They provide a variety of ecosystem services of importance in sustainability, climate management and the well-being of urban dwellers. For instance, urban and peri-urban forests and trees improve air quality, protect against flooding, and moderate extreme climate events as well as urban heat islands. Even in the densest parts of cities, urban trees and woodlands are a resource that facilitates nutrient cycling and groundwater management.
There are notable indirect benefits as well: due to their cooling and shading effects during summer, urban forests and urban trees reduce the use of electricity for air conditioning, hence avoiding carbon emissions. Shade provided by trees leads to lower indoor temperatures in summer. Combined with a decreased urban heat island effect, this may lead to up to 90% less cooling energy needed. The windbreak effects of urban forests and urban trees can lead to energy need reductions of 20% in winter times.
Urban forests also provide places for sports, recreation and mental restoration, thus improving human health and well-being. In that role, urban forests and trees strongly influence a city’s attractiveness and resilience. Finally, trees are an important part of the ecological networks and green infrastructure that connect urban, peri-urban and rural regions. However, potential disservices have to be duly considered, for example allergenic reactions to tree pollen and risks associated with falling trees or branches.