Effects on heat mitigation, energy use, and carbon savings in urban-scale implementations of nature-based solutions

Extensive changes in land cover and energy use resulting from urbanization lead to an imbalance in urban thermal conditions, making cities more susceptible to the impacts of climate change. Nature-based solutions (NbS) that leverage the cooling effect of green spaces to mitigate urban heat are gaining attention as a way to improve urban sustainability in the face of climate change. The study evaluated the urban-scale application of NbS’s impacts on heat mitigation capacity, air temperature, cooling energy, carbon emissions, and carbon sequestration, as well as the resulting economic benefits using the Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST) Urban Cooling Model (UCM). Green roofs as building adaptations, land use adaptations such as the expansion of urban parks and roadside green space, forest restoration, and multiple adaptations, which are combinations of building and land use adaptations, were considered applicable NbS. Cool roofs were also studied to compare their effects with other urban green infrastructure. The results showed that simultaneously implementing the multiple adaptation methods is the most effective if the applicable areas are sufficient. Considering the implemented area ratio, urban parks are the most effective single adaptive measure, with energy savings of 14.75, 8.63, and 1.98 times higher than those of 100 % green roofs, cool roofs, and 20 % roadside green space expansions, respectively. Restoring forests (21.29 km²) can yield 4.7 times higher energy savings than installing 100 % green roofs (62 km²). In contrast, deforestation loses more energy and carbon than cool roofs can save. This study can help provide an appropriate strategy for achieving urban carbon neutrality by reducing carbon emissions and increasing carbon sequestration through NbS in addition to relieving urban temperatures.