Designers have unveiled Asia's largest rooftop farm which represents cities of the future - helping to fight climate change.

The 75,000 sq ft (7,000 metres) farm is built on top of the Thammasat University in the sprawling concrete metropolis of Bangkok, Thailand.

It mimics the layered rice terraces in the rural north of the country and is open to any residents who want to grow rice and vegetables, the region's staple food.

Designers, who unveiled the project this month, believe that rooftop farms will become the green cities of the future as urban populations grow and land becomes scarce.

Major cities including Paris and Singapore are adding similar rooftop farms to shopping malls and office blocks.

Kotchakorn Voraakhom, the landscape architect behind the project in Bangkok, believes the farms are more environmentally friendly - while also being resilient to floods said to be caused by climate change.

She said: ''We tend to make a distinction between buildings and green spaces but green spaces can be part of building design in cities like Bangkok, which has few green spaces

''Rooftops are usually under utilised but they can be green spaces that reduce the urban heat-island effect, the environmental impacts of buildings and land use, and also feed people.''

Bangkok suffers regular flooding during the monsoon season because of the amount of concrete covering the city. The World Bank estimates that extreme weather will cause 40 per cent of the city to be flooded by 2030.

However, due to their height, urban farms can avoid flooding while