Experts in India believe that the next ten years could see a sharp increase in the urban population for which the country is not prepared, while climate change will make the situation worse.
According to the French news agency AFP, Mumbai, one of the largest cities in India, has grown by about 8 million people in the last 30 years. The population of the city has reached two crore and is predicted to increase by another seven million by 2035.
Like other major cities in India, Mumbai's housing, transport, water and infrastructure have not maintained their standards and around 40% of the population is forced to live in slums.
Those living in the suburbs of Mumbai travel hours for work. Many people are seen hanging out of the doors of overcrowded trains while others travel by car or motorcycle on roads that are inundated by floodwaters during the monsoon.
Mohammad Sartaj Khan came here as a teenager from rural Uttar Pradesh to Dharavi, a sprawling slum in the western Indian city of Mumbai, home to a million people.
Sartaj Khan, 35, told AFP, "I had a wonderful childhood in the village." Unlike the crowd, there was a peaceful atmosphere here.
"When I came here, I saw people running like ants," he said. Just as ants keep walking in their streets despite the crowd, no one cares about others.'
"But people don't have money," he added.
Sartaj Khan said that he used to earn Rs 6,000 a month in Mumbai, but now he earns four times more, a large portion of which he sends to his wife and children, whom he rarely sees.
The United Nations has estimated that India's population will surpass China's from the current 1.4 billion and reach 1.7 billion in the 2060s.
According to the International Energy Agency, 270 million more people will make it their home by 2040, while the use of steel and concrete for power generation, transportation, and home construction will increase carbon emissions.
The capital, New Delhi, home to 20 million people, is engulfed in toxic air pollution every winter. Air pollution caused nearly 17,500 premature deaths in 2019, according to a Lancet assessment.
Scientists believe that the monsoon season is becoming more erratic and more powerful, causing more floods and more droughts.
Rising temperatures are making summers more severe than ever. March was the hottest month for India this year.
"Poor people, especially urban migrants, are the most vulnerable to climate change," said Poonam Mitreja, an official at the Population Foundation of India.
"Instead of complaining, we have to do something," he said.
