One of the first things that Pakistan’s Prime Minister-elect Imran Khan wants to implement when he takes office this week is an unprecedented reforestation drive – planting 10 billion trees to reverse the effect of extreme weather crippling the country. He has already announced plans to revive his “Billion Tree Tsunami” dream project that forested 350,000 hectares in the northwestern Khyber Pakhtunkhwa territory between 2014 and 2017, when Khan led the canopy call to build a green armour against incessant flooding, extreme temperatures, prolonged droughts and unpredictable rainfall in many parts of Pakistan.

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Khan’s decision to deal with the ecological disaster head on – way before attending to the festering political issues of Kashmir or terrorism – is grounded in alarming projections by his ministry of climate change that estimates extreme weather will cost Pakistan up to US$14 billion every year, besides hundreds of lives and millions of livelihoods.

Pakistan has been scalding under an intense heatwave followed by a season of erratic rainfall. The country’s southern city Nawabshah burned at 50.2 degrees Celsius (122.4 degrees Fahrenheit) this summer, making for the hottest April day ever recorded in the history of the planet. Surging temperatures have spawned new glacial lakes in the remote mountain valleys. Of the 3,000 glacial lakes in the high reaches of northern Pakistan, 52 could burst anytime, according to the government, resulting in large-scale flooding sweeping away hundreds of thousands of mountain dwellers, their homes and agricultural lands.

These weather extremes have become the new normal for much of South Asia, home to a fifth of the world’s population. Last year, the region saw more than 1,400 people succumbing to extreme heat alone.

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A World Bank study released in June estimates that 800 million people – almost half of South Asia’s population – living in “hotspots” of high temperatures and erratic rainfall will be affected if the governments do nothing to reduce greenhouse gas emissions. The World Bank’s lead economist Muthukumara Mani says the cost of such inaction would see incomes drop by 14.4 per cent in Bangladesh, 9.8 per cent in India, and 10 per cent in Sri Lanka by 2050.

“When we talk about global climate change, South Asia is always at the epicentre,” Mani said. “Combined with poverty, this is a serious threat for South Asia’s future growth and developmental aspirations.”

The signs of a future malady are beginning to show – whether it’s in the muggy, sweltering heat of Delhi, where schools remained closed past summer holidays this year, or in the scorching daytime temperatures of Karachi, accentuated by massive power outages that left at least 65 people dead.

The World Bank study showed seven out of the top 10 so-called hotspots projected to be the worst affected in future were in the Vidarbha region of Maharashtra. “We were surprised. India is such a vast country.

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How could these hotspots be concentrated in one small region? Digging into anecdotal evidence, the researchers linked this to an socio-economic anomaly – that of Vidarbha’s spate of farmer suicides in recent years. Similarly, in Sri Lanka, the north and northwestern parts such as Jaffna, just emerging out of civil war but still reeling under social upheavals, were projected to be the most affected. The Chittagong division in Bangladesh, specifically the port city of Cox’s Bazar housing the world’s largest refugee camp of Rohingya, also emerges as a future hotspot.

Heightened urbanisation in South Asia has seen a significant increase in the number of urban poor. “My suspicion is that the urban poor is actually the largest single hotspot as far as climate change is concerned,” says Anand Patwardhan, a professor of public policy at the University of Maryland in the US.

Elfatih Eltahir, a professor of civil and environmental engineering at MIT, says South Asian cities will become uninhabitable in the next few decades. He predicted in the journal Science Advances this month that the worst heatwaves are staring South Asia in the face. In the absence of measures to reduce carbon emissions, these heatwaves could strike regions in India, Pakistan and Bangladesh as early as 2050. The most affected would be the densely populated agricultural regions in the Ganges and Indus river basins.

“There seems to be no solution in sight,” says Sushil Kumar Dash, a professor at the Centre for Atmospheric Sciences, Indian Institute of Technology Delhi. “The heat is killing – and for the urban poor with no access to air conditioning, the consequences of heat extremes are going to be miserable.”

Subhra Priyadarshini is Chief Editor of Nature India