Bangladesh's capital, Dhaka, once a city of lush forests and grass fields, has suffered drastic environmental changes due to rapid urbanization, experts say.

Now home to more than 15 million people, Dhaka began to lose its trees, lawns and areas of open space to accelerating and unplanned urbanization since the country became independent in 1971 and is now considered one of the least livable cities in the world, environmentalists said.

Urbanization without taking into account protection of the environment has taken its toll on the ecosystem of the 400-year-old city.

"Population boom coupled with unplanned industrialization and urbanization spoiled the urban vegetation of Dhaka," Mohammad Shakil Akther, an urban environmental expert, told China's Xinhua news agency.

There should be at least 10 square yards of green space in every residence in the city to ensure a healthy life, said Akhter, who teaches at the Bangladesh University of Engineering and Technology.

Sustainable urban development must consider a healthy living environment, Akther said, adding that "trees aside from its aesthetic function can also greatly improve the people's quality of life."