**2. Review of literature**

#### **2.1 The importance of microclimate**

Microclimate has been defined as the suite of climatic conditions measured in localized areas near the earth's surface [9]. Microclimate includes environmental variables such as temperature, light, wind speed, and moisture. It has been critical throughout human history, providing meaningful indicators for habitat selection and other activities [10]. Regardless of the global biomes in which we live, it is specifically microclimate that our bodies respond to, and not to the descriptors of the respective climatic region as a whole. For example, farmers have long used localized seasonal changes in temperature and precipitation to schedule their agricultural activities. Microclimate directly influences ecological processes and reflects subtle changes in ecosystem function and landscape structure across geographical scales [11].

As an example related to human health, microclimate in urban areas affects our thermal comfort [8]. However, relationships between microclimate and biological processes are complex and often nonlinear. For example, plant distribution can be perceived as a function of light, temperature, moisture, and vapor deficit [10]. Therefore, just a subtle change in microclimate could cause detrimental effects on human emotions and health, aside from just thermal comfort.

## **2.2 Effects of urbanization on microclimate**

Rapid urbanization, especially in developing countries, has led to large flows of migration to urban areas [12]. According to a 2021 report authored by the market research firm Statista, the degree of urbanization worldwide was at around 56% in 2020 [13]. With rapid urbanization, changes to the urban environment and climate are inevitable [14]. The rate of urbanization is very high and anthropogenic effects on the climate of Earth are difficult to predict.

At local scales, activities associated with land use and land cover changes and urbanization induce impacts such as changes in atmospheric composition in water and energy balances and changes in the ecosystem [15]. By definition, ecosystems are interconnected, therefore a small change in any component can result in non-linear effects elsewhere. For example, according to a study conducted by Xiong et al. [16] in 2015 on the influence of different air temperature step-changes on human health and thermal comfort, perspiration, eye-strain, dizziness, accelerated respiration and heart rate were all sensitive self-reported symptoms.

Due to global climate change and intensifying urban heat island effects, urban living environments have deteriorated, becoming increasingly detrimental to human thermal comfort and health, not only psychologically, such as in terms of thermal sensation, mood, and concentration, but also physiologically by way of, for example, sunburn, heat stroke, and heat cramps [7]. They also cautioned that "global climate change and intensifying heat islands have reduced human thermal comfort and health in urban outdoor environments". Other studies on re-naturing cities have found that changes to urban microclimate can potentially exacerbate the risks of meteorological hazards such as heatwaves. Heat-related issues pose an impact not

only to the environment but also lead to heat-related human health problems and in extreme cases, cause deaths [15]. This is only one aspect of how microclimate can affect humans.
