by Deniz Korman
Global ambient temperatures keep rising year by year, and urban areas specifically experience higher temperatures compared to rural areas due to lower vegetation coverage and increased emissions. An effective strategy to counteract this problem is to expand green spaces and improve urban forestry. However, it is important to ensure that the greenery that we integrate into our cities can withstand changing climate conditions as ambient temperatures keep increasing at a rate faster than ever. Lanza and Stone (2016) focus on how global warming has affected the climate conditions around 20 highly populated metropolitan areas in USA, and the impact that this has had on present tree species. They have identified the metropolitan cities that have experienced the greatest rate of temperature increase in the past 10 years, and looked into how the climate conditions around these metropolitan areas have changed between 1961 and 2010. Using these data, they have tested whether climate changes have made the regions unlivable for previously present tree species, and created a future projection that looks into how much species loss would occur if the historical climate shifts re-occurred. They found that within the past 50 years, 6 of the 20 metropolitan areas studied lost one or more tree species. All six of these cities were located in the southeast region of US, which they have attributed to disproportionate growth of metropolitan areas within this region. However, their future projection predicts that 5 more metropolitan areas be added to this list if climate changes follow a similar trend, and these additional cities are spread across the country, rather than being limited to a region. These findings suggest that southeastern metropolitan cities should be our priority for improving heat management, as they are the ones that are experiencing the most biological loss due to climate changes. In addition to this, the climate projections and tree species presented in the study act as a valuable reference in order to ensure that our new urban green spaces survive ambient temperatures that are expected to increase in the following decades. While the scope of the paper was limited to tree species, the climate projections can be used when planning different kinds of green spaces such as vertical or rooftop gardens or urban agriculture.
While introducing resistant trees is a smart idea, we should keep in mind that we need to balance between introducing non-native species and trying to preserve the existent ecosystem as climate conditions keep drifting away from their historical states. Overall, this study touches on a problem that has yet been explored or taken into account within urban greenery planning, and is bound to become more important as global temperatures keep increasing exponentially.
Lanza, K., Stone Jr., B., 2016. Climate adaptation in cities: What trees are suitable for urban heat management? Landscape and Urban Planning 153, 74–82. http://www.sciencedirect.com/science/article/pii/S0169204615002443