Street vendors in India are suffering from lower earnings and ill health as they lose access to shade in cities where trees are felled to make way for construction, researchers said on Thursday.

As deadly heatwaves become more frequent in tropical countries such as India, loss of shade can severely affect those who live and work on the streets, according to a study by researchers at Azim Premji University.

The study of the southern Indian city of Hyderabad showed that women and new migrants, as well as vendors in poorer neighbourhoods are at greater risk of being denied shade.

"As the primary day-time occupiers of urban streets, in hot cities the importance of wooded streets becomes fundamental in ensuring a comfortable, liveable work environment," co-authors Sukanya Basu and Harini Nagendra wrote.

But "street vendors are largely left out of considerations of urban ecological planning, despite being among the most affected by the availability of shaded streets," they said in the study published in the Landscape and Urban Planning journal.

Green spaces help reduce the so-called urban heat-island effect - under which cities are often several degrees warmer than nearby rural areas, help clean the air and replenish groundwater, according to environmentalists.

City dwellers in leafy neighbourhoods also tend to live longer, according to a study last year by the Barcelona Institute for Global Health.

But booming Indian cities are losing green spaces rapidly as more land is needed to build metro lines and apartment blocks.

The scarcity of urban green spaces worldwide became clear as the coronavirus pandemic forced lockdowns, triggering a rush to parks for exercise and to improve well-being.

In Hyderabad, where summer-time temperatures routinely soar above 40 degrees Celsius (104 degrees Fahrenheit), construction often results in the felling of trees and clearance of vendors, as does the beautification of public spaces.

For street vendors, trees help extend the life of the products they sell and draw more customers, besides offering respite from the heat, Basu said.

"Access of street vendors to public green spaces and their right to shade is critical in the context of the right to the city," she told the Thomson Reuters Foundation.

But gentrification results in unequal access to shade, she added.

Wealthier, residential neighbourhoods in Hyderabad, a technology hub, had fewer vendors and more trees on the streets, while low-income and congested neighbourhoods with more vendors had fewer trees.

"A public green space should be equitable - going beyond aesthetics," Basu said.

"It is important for planners to understand that these green spaces are the workspace for vendors, and in some instances their residence, as well."

In cities across developing nations, authorities often view street vendors as a hindrance to progress and target them for forced evictions, despite evidence that they contribute to the local economy and the city's character.

"The city can be conceptualised and designed as a place where formal and informal co-exist," said Shalini Sinha, India representative for WIEGO, a non-profit that advances the rights of women informal workers.

"But the very concept of a city currently undermines vendors and their right to the city," she said.