Pakistan is home to some of the hottest cities on Earth. In May 2022, Jacobabad reached 51°C, and scientists found that climate change made that heatwave around 100 times more likely. In June 2015, a heatwave in Karachi and southern Sindh killed around 2,000 people, as temperatures hit 45°C in the city and power cuts shut down fans and water pumps.
Heat is now one of the deadliest climate risks for Pakistan’s cities. And one of the simplest defences is growing on our streets, or should be.
Why cities are hotter than the countryside
Concrete, asphalt and brick soak up sunlight all day and release it at night. Traffic, generators and air conditioners add even more heat. The result is the urban heat island effect: city centres stay several degrees hotter than surrounding areas, and nights don’t cool down enough for bodies to recover.
When cities lose trees to road widening and construction, the effect gets worse.
How trees cool the air
- Shade. A tree canopy blocks sunlight before it hits roads, walls and people. Shaded surfaces can be 11 to 25°C cooler than surfaces in direct sun.
- Evaporation. Trees release water vapour through their leaves, which cools the air around them, like a natural air cooler.
- Cooler air. Studies across many cities find tree canopy typically lowers daytime street-level air temperature by about 1 to 2°C, and more in dense green areas. Places with no trees nearby are several times more likely to hit dangerous heat.
A drop of 1 or 2°C may sound small, but during a heatwave it can be the difference between uncomfortable and dangerous, especially for labourers, street vendors, children and the elderly.
Where trees help most
- Bus stops and markets, where people wait and work in the sun.
- School grounds, where children play at midday.
- Along the south and west sides of homes, to shade walls from the afternoon sun and cut cooling costs.
- Dense low-income neighbourhoods, which usually have the least green cover and the least access to air conditioning.
The best trees for shade in Pakistan’s heat
- Neem. Dense shade, very drought tolerant, and suits Karachi and Sindh.
- Pipal and Bargad. Enormous canopies for parks and open ground.
- Jaman. Evergreen, so it shades all year.
- Sheesham. A classic shade tree for Punjab’s roads.
Avoid thirsty or problematic imports. Read why Conocarpus is a poor choice, and see the full native tree guide.
Trees are part of a heat plan, not all of it
Heat action plans also need early warnings, cooling centres, reliable power and water, and safe working hours for outdoor workers. But trees keep working every day, for decades, without electricity.
Help cool your city: sponsor a shade tree or join a plantation drive.