Over 800,000 people planted saplings along forests, highways, along railway tracks and country roads on Monday 11 July. Officials in Uttar Pradesh handed out millions of plants across India's most populous state in an effort to increase its green areas.

Planting 50 million trees would enhance enthusiasm and educate about environmental conservation, said Chief Minister Ahilesh Yadav. "The world has realized that serious efforts are needed to reduce carbon emissions to mitigate the effects of global climate change. Uttar Pradesh has made a beginning in this regard," Yadav said in an AP report.

Pakistan's Sindh Forest Department holds the previous record of 8,47,275 for maximum trees planted in 24 hours in 2012.

All 29 states in India are being spurred on in forestation initiatives as part of commitments made at the climate change summit in 2015.More than $6.2bn for tree-planting has been allocated across the country, in a pledge to increase the country's woodlands and forest areas to 95m hectares (235m acres) by 2030.

The saplings planted will be monitored carefully as only around 60% of saplings survive, with the rest falling victim to disease or lack of irrigation, officials said.

A local tree called a peepal has important properties, according to Shashwat Rai, who planted the tree, also known as Ficus religiosa, in Lucknow's Kukrail Reserve Forest. "I've read in a book that this tree releases maximum oxygen," he said. "There is so much pollution in the city, we need trees that produce oxygen."

Anonymous auditors from Guinness World Records were travelling around Uttar Pradesh to do a tally on the numbers. "We are trying to maintain full transparency," senior forest official Sanjeev Saran said.

"They are out in the field and are supervising the plantation drive," he said. "We do not know who they are or where they are at this point in time. They are working incognito, and this suits us."

Outdoor air pollution in India is contribuing to over 500,000 premature deaths ever year, costing the country billions of dollars, according to a study in Geophysical Research Letters. Researchers concluded that exposure to fine particulate matter in India translated to about 3.4 life years lost.