Residents in a district of the Indian state of Punjab who want to buy a gun face an unlikely new hurdle: to secure a firearm licence, they must plant at least 10 trees.

Applicants in Ferozepur district are required to send photos of themselves with their saplings to officials, as well as follow-up pictures a month later to prove they are caring for their trees.

“The people of Punjab are really crazy about the big cars, mobile phones and guns – so let them be crazy for the plants also,” said Chander Gaind, the district’s deputy commissioner.

More than 100 applications have been received since the rule was introduced last month, with residents planting kikar and neem trees across the district.

The northern state of Punjab, which was engulfed by a violent insurgency throughout the 1980s and 1990s, has a well-established tradition of gun ownership. There are almost 360,000 active gun licences across the state, among the highest in the country, according to government figures.

Gaind hopes that the new rules imposed on licence applicants could lead to 12,000 saplings being planted each year, helping to boost the district’s green cover and replenish its water sources.

Depleting groundwater – driven by poor water management, expansion of cities and unpredictable monsoon rains – is a concern across Indian. The country is dependent on groundwater, but environmental experts say that for decades government policies have failed to replenish or protect supplies.

In Punjab, groundwater depletion in some districts is occuring at an especially rapid rate, according to a study by researchers from the department of civil engineering at the Indian Institute of Technology Gandhinagar.

Many trees have been felled in Ferozepur to allow for road-widening, while water-intensive rice fields have also exacerbated the depleting water table, said Gaind.

“[By planting] these saplings in the monsoon weather especially, the growth will be very fast,” he said.

The district is also considering imposing the rule on the renewal of licences, for which there are 500 applications each month.