The population has increased rapidly in the last five decades globally which has led an enormous pressure on the environmental conditions of the world (Meerow et al. 2016; Meerow and Newell 2019). The urban areas have been facing more pressure than the rural areas due to the increasing population (Elmqvist et al., 2019). Shifting the population to other areas for safety, religious practices, and political practices were very common in the 19th and 20th centuries. Recently the internal migration rate has been the biggest issue in the world. The people have migrated from rural to urban due to better facilities including health, education, and economic resources. Urban expansion has been leading to simultaneously rising temperature of Earth's atmosphere (Grimm et al., 2008, Seto et al. 2012, Mishra et al. 2015). Nowadays, approximately 55% of the global population lives in urban areas that are expected to reach 68% in 2050 (UN, 2018 and The Economist, 2012). The urban areas have played a fundamental role and brought inextricable changes in living standards. However, it has also brought some negative environmental consequences such as UHI. Urban heat island (UHI) is one of the major issues attributed to rapid urbanization and is a major concern for the geo-environmentalists of the world (Sadashivam and Tabassu 2016). Urban Heat Island reveals the rising of temperature significantly in urban areas than rural areas (Phelan et al. 2015 Stewart et al., 2021; Li et al., 2023). Urban Heat Index (UHI) is the rise in temperature which is due to the absorption and storage of sun energy by man-made impervious surfaces. It also has a direct effect on the wind speed in urban areas (Phelan et al. 2015). Air rising temperature of the cities is linked to high air pollution and heat-related health issues such as heat cramps, heat exhaustion, heat rash, and heat stroke that can aggravate heat-associated mortality (Brauer and Hystad., 2014; Zhao et al. 2016; Qian et al., 2022; Irfeey et al., 2023). The UHI exacerbates health impacts by upsetting rainfall patterns (Collier 2006). The European heat wave of 2003 can be the best example of the UHI that caused thousands of deaths (Robine et al. 2008; Schwaab et al., 2021; Phelan et al. 2015) It is reported by various authors that the rising level of temperature of major cities of the world from 2010 to 2015 city which is assessed UHI by satellite and ground measurement techniques for the estimation of temperature. South Asian countries have been facing urban sustenance challenges including poverty, rising air pollution with GHG emissions, and mounting energy demands. Around 45% of the world's population in South Asia has been living below the poverty line (earning less than $2 a day) (Sumner 2012) which leads to more vulnerability to climate impacts. According to the World Health Organization (2017), 11 cities have having high concentration of pollutants out of 20 big cities. Energy utilization in the south Asia is 64% between 1994 to 2002 (Lahiri-Dutt 2006). The forthcoming issue in South Asia is increasing temperatures in the winter and increase of extremely hot days and nights during the summer (Jacobs et al., 2019; Chan et al. 2012; Suresh et al., 2023) It has been reported that the cities including Hong Kong (China), Bangkok (Thailand) and Delhi (India) mortality rate increased from 4.1–5.8% with per over 1°C a temperature threshold of approximately 29°C. UHI is going to be a vital problem in South Asia including extensive environmental, and climate deterioration. Major cities in South Asia inhabited around 15% of the global urban population. In South Asia, the research work on UHI has increased to three folds since 2000. Delhi (India), Chennai (India), and Colombo (Sri Lanka) are frequently studied for HUI with satellite imagery.
Pakistan is also facing the UHI problem, a Pakistan-specific heat wave study (2018). It is reported that Pakistan has experienced 126 heat waves from 1997 to 2015. However, more than 2000 people died in the country due to the heat wave of 2015, most of the deaths occurred in the cities/ urban areas. The country will have to experience around 12 heat wave events annually by 2030, 20 such events by 2060, and 26 events by 2090 which will be the very alarming situation and need more attention (Khan et al., 2020). Sadiq Khan., et al. 2020 estimated changes in LULC from 1993 to 2018 at Islamabad for warming and cooling effect using a random forest (RF) classifier, and LST was retrieved by a standardized radiative transfer equation (RTE). He reported that impervious surfaces have increased by 11.9% on the cost of declining barren land, forest land, grass/agriculture land, and water bodies in the last 26 years. They reveal that LULC conversion contributed to warming effects of 1.52°C. The long-term variability in minimum and maximum temperature trends in Lahore City found that the minimum temperature is increasing more than the maximum temperature (Sajjad et al. 2015; Zuo et al., 2022; Wang et al., 2023. (Rizvi et al. 2021) conducted the effects of UHI and extreme heat wave (HW) events in Karachi for a period of 10 years in two phases i.e. from 1998 to 2002 and ii from 2012 to 2016. They reported that UHII for nighttime in summer during 1st phase was 1.9°C, and in 2nd phase, it increased by 0.6°C. They agreed that UHII has increased significantly in Karachi during the HW period which caused more than 800 deaths in Karachi between 17th June and 24th June 2015.
Recently much of the work is conducted on the urban heat Island Intensity in different cities of Pakistan using satellite data /remote sensing however, no work on the same has been conducted in Larkana, Sindh. This research is therefore evaluating the UHI in Larkana using satellite data from 1990 and 2023, collected from USGS, Landsat 5 and 8. Furthermore, the population was also collected to understand that what is the rate of urbanization in Larkana over the last 34 years and see whether these changes or not. This study also evaluates the impacts of urban heat islands on the Environment; and correlates urban expansion with the effects on the LST in Larkana. The overall goal of this research is to analyze the urbanization scenario in Larkana using Landsat data for 34 years and to examine urban expansion and its impact on urban surface temperatures using Landsat images.