Maintaining human thermal comfort (HTC) is essential for pedestrians because people outside can be more susceptible to heat stress and heat stroke. Modification of street microclimates using tree canopy cover can provide important benefits to pedestrians, but how beneficial and under what circumstances is not clear. On sunny summer days, microclimatic measures were made in residential streets with low and high percentages of tree canopy cover in Melbourne, Australia. Streets with eastwest (E-W) and streets with north-south (N-S) orientation were repeatedly measured for air temperature, relative humidity, wind speed, solar radiation, and mean radiant temperature on both sides of the street between early morning and midafternoon. Physiological equivalent temperature was estimated to indicate HTC throughout the day. In streets with high-percentage canopy cover, air temperature, relative humidity, solar radiation, and mean radiant temperature were significantly lower than in streets with low-percentage canopy cover. The reductions in air temperature under high-percentage canopy cover were greater for E-W streets (2.1°C) than for N-S streets (0.9°C). For N-S streets, air temperature, mean radiant temperature, and solar radiation were greater on the east pavement in the early morning and greatest on the west pavement in the midafternoon. The midday thermal benefits are restricted to E-W streets, which are oriented in the same direction as the summer sun's zenith. High-percentage canopy cover reduced wind speeds but not enough to offset the other microclimate benefits. These findings can assist urban planners in designing street tree landscapes for optimal HTC in summer, especially in areas of high pedestrian density.
Low- and middle-income countries in Southeast and East Asia face a range of challenges related to the rapid pace of urbanisation in the region, the scale of pollution, climate change, loss of ecosystem services and associated difficulties for ecological restoration. Possible pathways towards a more sustainable future lie in the applications of nature-based solutions (NBS). However, there is relatively little literature on the application of NBS in the region, particularly Southeast Asia. In this paper we address this gap by assessing the socio-ecological challenges to the application of NBS in the region – one of the most globally biodiverse. We first provide an overview and background on NBS and its underpinnings in biodiversity and ecosystem services. We then present a typology describing five unique challenges for the application of NBS in the region: (1) Characteristics of urbanisation; (2) Biophysical environmental and climatic context; (3) Environmental risks and challenges for restoration; (4) Human nature relationships and conflicts; and (5) Policy and governance context. Exploiting the opportunities through South-South and North-South collaboration to address the challenges of NBS in Southeast and East Asia needs to be a priority for government, planners and academics.
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