A city built in a forest, now a city of asphalt

Islamabad was designed in the 1960s as a green, low-density capital nestled against the Margalla Hills, its master plan built around generous green belts and tree-lined sectors. That vision has been steadily eroded. As one urban planner associated with NUST has put it, the city has effectively turned from a city built in a forest into a city of asphalt. The scale of that shift is now measurable, not just anecdotal.

Joint studies by NUST and the PMD in 2025 recorded temperature differentials of up to 3 to 5 degrees Celsius between densely built sectors such as I-10 and G-9 and the greener Margalla foothills nearby. This is the Urban Heat Island effect: built surfaces absorb and radiate heat far more than vegetation and open ground, and the more concrete a sector accumulates, the hotter it becomes relative to its greener neighbours.

The drivers of the heat trap

The scale of Islamabad's physical growth explains much of the change. CDA and Suparco satellite data show the city's built-up area expanded by more than 30 percent over the past decade, largely at the expense of green cover, according to 2024 figures. The Islamabad Capital Territory's population now exceeds 2.3 million, per Pakistan Bureau of Statistics census projections from 2024, straining a master plan designed for a fraction of that number.

Traffic adds to the pressure. Over 2 million vehicles are registered in the capital, according to 2024 Excise and Taxation Department figures, contributing significantly to localised heat and emissions. Meanwhile, EPA Pakistan reported in 2024 that canopy cover in residential sectors has diminished as paved driveways and multi-storey construction replace what were once shaded, permeable plots. Surface temperatures on commercial asphalt in areas like Blue Area can exceed ambient air temperature by 10 to 15 degrees Celsius, according to Ministry of Climate Change mapping from 2024, turning some of the city's busiest commercial districts into genuine heat traps for pedestrians and outdoor workers.

Who feels it most

The Urban Heat Island effect does not distribute its costs evenly. Construction and municipal workers face acute heatstroke risk during peak summer hours, often with limited protection. Low-income settlements, or katchi abadis, such as those in Sector I-11, experience the worst conditions, with tin roofing and virtually no tree cover, while wealthier, greener sectors like E-7 remain comparatively cool. Urban residents more broadly face rising cooling costs and frequent power outages precisely when demand for air conditioning peaks, while reduced safe outdoor playtime is becoming a routine summer constraint for children across the city.

The public health impact is measurable. The Ministry of National Health Services recorded hospital admissions for heat exhaustion spiking by roughly 25 percent during the May and June heatwave period in 2025, with pressure particularly evident at PIMS and Polyclinic. Heatwave days, defined as periods where temperatures exceed normal by 5 degrees Celsius for three or more consecutive days, have doubled in frequency across the ICT and Rawalpindi region over the past fifteen years, according to 2025 PMD data.

A master plan under pressure

Much of this is not simply the product of a warming climate but of governance failing to hold the line on its own rules. The original CDA master plan set aside green belts precisely to prevent this kind of heat accumulation, but those provisions have frequently been bypassed. Natural nullahs have been paved over for parking and commercial use, and road expansion projects in 2024 and 2025 that cut down mature trees drew public outcry and legal challenges, reflecting growing awareness that Islamabad's canopy is not a decorative feature but functional infrastructure.

It is worth being precise about what the evidence actually shows here. Background global warming has added roughly 1.2 degrees Celsius, but the localised UHI effect is what makes specific sectors feel 3 to 5 degrees hotter than their green neighbours. These are related but distinct phenomena, and conflating them risks overstating what can be attributed to global climate trends alone.

Early signs of a response

There are signs of institutional recognition, if not yet full correction. The CDA launched an initiative in 2025 to plant Miyawaki forests, a dense, fast-growing afforestation technique, in specific sectors as a targeted counter to the UHI effect. The Islamabad Nature Conservation and Wildlife Management Act has seen updates in 2024 and 2025, alongside MoCC urban forestry guidelines aimed at protecting remaining canopy.

Margalla Hills forest fires during recent heatwaves have added a further, visible reminder of how heat, vegetation loss and air quality are interconnected around the capital, with fire risk itself rising alongside drier, hotter conditions.

Reclaiming the green capital

Islamabad's founding premise, a capital designed around its landscape rather than in spite of it, has not disappeared, but it has been steadily crowded out by unchecked expansion. Reversing that will require more than isolated tree-planting schemes. It will mean enforcing the master plan's original green belt provisions, protecting the katchi abadis with the least capacity to cope with heat, and treating urban canopy as core infrastructure rather than an afterthought. The city's cooler, greener identity is still recoverable, but only if planning failures of the past two decades are not allowed to continue unchecked into the next.

Key Facts

•Urban Heat Island effect creates temperature differentials of up to 3 to 5°C between dense sectors and the Margalla foothills (2025, NUST/PMD).

•Islamabad's built-up area expanded by over 30 percent in the last decade, largely at the expense of green cover (2024, CDA/Suparco).

•Heatwave days have doubled in frequency in ICT/Rawalpindi over the past 15 years (2025, PMD).

•Hospital admissions for heat exhaustion spike by roughly 25 percent during May to June heatwaves (2025, Ministry of National Health Services).

•Surface temperatures on commercial asphalt can exceed ambient air temperature by 10 to 15°C (2024, MoCC mapping).

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