Green infrastructure and other nature-based solutions such as parks, greenbelts, and natural stormwater treatment swales could reduce carbon emissions in European cities by an average of 17.4%, according to a new study.
The findings represent a far more sweeping assessment of nature-based solutions (NBS) than has been undertaken in the past. Previous studies have generally looked at how green infrastructure can absorb carbon emissions generated elsewhere in the economy, by storing carbon in vegetation and soils. The new study also considers the indirect benefits of these features, finding that they can actually contribute to reducing carbon emissions in their own right.
For example, a tree-lined path may encourage people to get out of their cars and walk or bike instead, reducing transportation emissions. The vegetation may also help keep nearby buildings warmer in winter and cooler in summer, thus reducing building energy use.
Past studies have also tended to consider the effect of individual nature-based solutions in isolation, while the new analysis looks broadly at features ranging from parks, street trees and other plantings and roof gardens to urban farms, permeable pavements, wildlife habitat, narrower roads, and walking and biking paths, among others.
Researchers combed through studies of nature-based solutions conducted around the world to assess their potential to save resources, reduce urban sprawl, promote eco-friendly behavior, moderate temperature extremes, and sequester carbon.
They mapped where different nature-based solutions would be most effective in 54 different cities in the European Union, based on the source of carbon emissions in a given spot and the existing built environment in a particular city. For example, street trees are most helpful along busy roads in urban centers, while habitat preservation is most effective on the urban fringe and green stormwater treatment does the most good in industrial areas.
“Due to the limited land resources in cities, the spatial allocation and configuration of urban NBS need to be optimized to achieve maximum carbon emissions reductions,” the researchers write in the journal Nature Climate Change.
Maximum implementation of the various nature-based solutions could reduce carbon emissions in European cities by up to 25%, the researchers found. The most effective distribution of features as mapped in the study would reduce carbon emissions in a given city by 17.4% on average. Carbon sequestration in these locations would also soak up an additional 5.6% of a city’s remaining carbon emissions.
“Compared with carbon sequestration, the indirect effects of NBS in carbon emissions reduction through human behavior interventions were shown to play a much larger role in reducing urban carbon emissions,” the researchers write.
The largest reductions in carbon emissions would occur in the industrial sector, where nature-based solutions could cut a city’s carbon emissions by an average of 14.0%. Emissions reductions would average 8.1% in the residential sector and 9.6% in the transport sector, the researchers found.
The researchers also analyzed the potential for nature-based solutions in different scenarios of future development for the EU cities. They found a kind of virtuous cycle of climate action, in which scenarios with more ambitious climate policies also yield more potential for applying nature-based solutions, for example by limiting sprawl and promoting high-density urban development.
“Thus, pioneering cities that have created the best opportunities for NBS to be effective should extend their climate action plans to fully incorporate NBS implementations, which would maximize their chances of achieving city carbon neutrality,” the researchers write.
Source: Pan H. et al. “Contribution of prioritized urban nature-based solutions allocation to carbon neutrality.” Nature Climate Change 2023.
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