The scale of the transformation is striking. In 1989, settlements occupied just 5.18 percent of the study area. By 2019, that figure had climbed to 36.51 percent, meaning more than a third of the landscape had been converted to urban fabric within a single generation. This is not merely a change in what the land looks like from above; it is a change in how the land behaves. Natural vegetation and soil, which once absorbed rainfall, shaded the ground, and released moisture back to the air, have been replaced by impervious surfaces that store solar energy during the day and radiate it slowly at night, driving the phenomenon scientists call the urban heat island.

To quantify these changes, the researchers drew on three generations of Landsat sensors: the Thematic Mapper, the Enhanced Thematic Mapper Plus, and the Operational Land Imager with its Thermal Infrared Sensor. By classifying land cover across multiple epochs and applying geographic information system techniques, they constructed a time series of land surface temperature, vegetation greenness, surface albedo, and evapotranspiration. The thermal record tells a clear story. In 1989, land surface temperatures across the region ranged from roughly 14 to 40 degrees Celsius. Thirty years later, the observed range had widened to between 12 and 42 degrees Celsius, with the hottest surfaces concentrated precisely where the newest development had spread.

The study’s most technically ambitious component was its use of the Surface Energy Balance Algorithm, known as SEBAL, to estimate evapotranspiration, the combined flux of water evaporated from soil and transpired by plants. SEBAL works by solving the energy budget at the land surface: incoming solar radiation is partitioned between sensible heat, which warms the air, and latent heat, which drives water vapor upward. By computing this partitioning pixel by pixel from satellite-derived radiometric temperature, albedo, and vegetation indices, the model converts thermal imagery into maps of daily water use across the landscape. The results revealed a substantial intensification of the water cycle, with evapotranspiration rising from 5.81 to 6.70 millimeters per day in the earlier period to 8.14 to 8.56 millimeters per day by 2019.

That increase may seem counterintuitive. Cities are usually associated with drying, not with more vigorous water fluxes. But the authors point to two interacting mechanisms. First, the Normalized Difference Vegetation Index, a standard satellite measure of green vegetation, actually increased over parts of the study area, reflecting both afforestation efforts and the expansion of irrigated gardens, lawns, and roadside plantings within the growing city. Second, changes in surface albedo, the fraction of sunlight reflected by the ground, altered the amount of energy available for evaporation. Where vegetated and irrigated surfaces expanded, more energy was channeled into latent heat, pushing evapotranspiration upward even as the surrounding built environment grew hotter and drier.

The spatial fingerprint of the urban heat island expanded accordingly. Heat island zones, identified where surface temperatures persistently exceeded those of the surrounding rural and vegetated landscape, spread across the urban cores of Islamabad and Rawalpindi, tracking the growth of housing schemes, commercial districts, and transport corridors. In a mountain and plateau setting, this pattern carries particular risks. Cool air drainage from the Margalla Hills once moderated nighttime temperatures in the valley settlements; as the urban footprint climbs the slopes and fills the basins, that natural ventilation is disrupted, and heat that would have escaped accumulates over neighborhoods with limited tree cover.

The consequences extend well beyond discomfort. Elevated land surface temperatures increase cooling energy demand, strain electrical grids during summer peaks, and worsen air quality by accelerating the photochemical reactions that produce ground-level ozone. Reduced infiltration on sealed surfaces diminishes groundwater recharge in a region already drawing heavily on its aquifers, while intensified evapotranspiration from irrigated urban greenery raises water demand in a semi-arid catchment. Public health researchers have repeatedly linked urban heat exposure to heat stroke, cardiovascular stress, and excess mortality among elderly and outdoor-working populations, and the developing cities of South Asia are among the most vulnerable because adaptive infrastructure, from shaded streets to reliable cooling, remains unevenly distributed.

What makes this study especially valuable is its setting. Most urban heat island research concentrates on large lowland megacities, where the signal is easiest to isolate. Mountain and plateau cities present a more complicated picture because topography, elevation, and aspect already create strong temperature gradients before urbanization adds its own. By demonstrating that settlement growth in such terrain produces measurable, decadal-scale shifts in both the thermal and hydrological regimes, the authors highlight a class of rapidly growing cities, from the Himalayan foothills to the Iranian plateau and the Andean valleys, whose climate dynamics are poorly captured by models and monitoring networks designed for flat terrain. The findings suggest that these effects remain largely unrecognized in developing regions, contributing to a gradual atmospheric degradation that policy has yet to confront.

The authors argue that neither prevention nor cure can wait for perfect data. They call for coordinated action on demographic planning and institutional capacity-building, and they advocate incorporating geo-artificial-intelligence approaches, in which machine learning applied to satellite archives can forecast land cover change and its climatic consequences before development decisions are finalized. Such tools could allow planners in Islamabad and cities like it to test scenarios, locating green corridors where they will deliver the greatest cooling, protecting recharge zones from sealing, and steering growth away from the most thermally sensitive slopes. The study speaks directly to urban planners, policymakers, and climate specialists aiming to build climate-compatible cities, and its message is blunt: in semi-arid mountain ecosystems, the link between urban expansion and atmospheric stress is now measurable, and the window for affordable adaptation is narrowing with every hectare of land that disappears under concrete.

Subject of Research: Impacts of land cover change on the urban heat island effect and evapotranspiration in the mountain and plateau region of Islamabad and Rawalpindi, Pakistan

Article Title: Assessing the impacts of land cover changes on urban heat island effect and evapotranspiration patterns in mountain and plateau regions

Article References: Islam, A., Ali, S. M., Kanwal, A., Zaman-ul-Haq, M., Tariq, A., Ali, I., Adnan, S., Faqeih, K. Y., Alamri, S. M., Alamery, E. R., & Bokhari, S. A. (2026). Assessing the impacts of land cover changes on urban heat island effect and evapotranspiration patterns in mountain and plateau regions. Theoretical and Applied Climatology, 157(9), Article 607. https://doi.org/10.1007/s00704-026-06544-w

Image Credits: AI Generated

DOI: 10.1007/s00704-026-06544-w

Keywords: urban heat island, land surface temperature, evapotranspiration, SEBAL, Landsat, land cover change, Islamabad, Rawalpindi, remote sensing, urbanization, NDVI, surface albedo