Page 256 - Çevre Şehir ve İklim Dergisi İngilizce - Özel Sayı

Footprints of the Nature in Cities; Urban Heat Island Effects
and the Role of Afforestation Efforts in Reduction of These Effects

According to research, shading can reduce surface temperatures by up to
20% (Luber, G. and McGeehin, M., 2008). Studies have shown that when the
canopy closure is 5%, the cooling effect in the area is 0.5 ℃; at 30% closure,
the cooling effect increases to 4℃; and 50% closure, the cooling effect rises to
6℃ (Yin, Y., et al., 2024).
The main benefits of afforestation, an effective method for reducing the
UHI effect, are listed below.
• Providing Shade: A study compared the temperature difference
between an urban afforestation area and a nearby area without any tree
cover; as a result, it was found that temperatures were up to 9 °F (5 °C)
lower due to the combined effects of evapotranspiration and shading
(Akbari and Davis, 2012).
• Natural cooling through evapotranspiration: Trees create a cooling
effect in the surrounding air by evaporating water through their leaves
(Demirbaş, 2009). Intensive afforestation can help reduce temperatures
by 2-8 ℃ (Matzarakis and Endler, 2010).
• Improving air quality: Trees absorb carbon dioxide from the air and
improve air quality (Dwyer et al., 1992). Additionally, a large tree can absorb
approximately 22 kg of carbon dioxide per year (Nowak et al., 2014).
However, the temperature reduction can vary depending on factors such as
tree species, density, placement, and climate conditions. To achieve effective
results in efforts to reduce the Urban Heat Island effect, it is important to
consider the following factors in afforestation practices:
• Selecting native tree species that are adapted to the climate of the area
to be afforested (Yıldız and Avdan, 2023),
• Instead of planting a single species, establishing mixed stands by using
various species together and planting at appropriate spacing intervals
and planning maintenance processes (Üstündağ et al., 2023),
• Due to their high capacity for providing more shade and cooling the
environment through transpiration, fast-growing and broad-leaved
species should be preferred (Akpınar and Külekçi, 2017),
• As the sun moves to the west and south in the afternoon, these facades
of buildings are exposed to the most sunlight during the hottest
hours of the day. In densely urbanized areas, placing trees primarily
on these facades to naturally shade the buildings and reduce surface
temperatures is an important factor to consider in such applications
(Akpınar and Külekçi 2017).
Therefore, alongside other preventive measures in urban planning,
encouraging green belt afforestation activities around and within cities as
much as possible has great potential not only in preventing the formation

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Special Issue / 2024