A solution to the problem of lost urban wildlife habitats could be found right above our heads, according to English Nature.
Canary Wharf has one of the existing English green roofs
It wants developers and homeowners to turn roofs into meadows, to provide an environmentally friendly alternative to "drab" asphalt or traditional tiles.
It says the idea could help replace many of the habitats lost in the push to regenerate derelict land in Britain's towns and cities.
Early "green roof" projects have already seen rare species of insect normally found well away from the city turn up in central London, the UK Government's conservation body said.
The roofs are constructed with a waterproof layer and barrier to stop water and invasive roots, then topped with materials like brick dust and soil to encourage plants to take seed.
English Nature said green roofs were already popular in many European countries, particularly as a way of soaking up water in flood prone areas.
In Britain they are still few and far between, but some have started to sprout at locations including Canary Wharf, the Horniman Museum in south-east London and a Devon zoo.
The green roofs replace existing structures and are then planted
English Nature spokesman Pete Massini told BBC News Online: "The reason they're not widely used in this country is that perhaps we're quite traditional and conservative with a small 'c' in terms of our notion of what a roof should be."
But he said there were many benefits for those willing to make the change.
"They can cool down cities in summer, filter dust out of the air and regulate the temperature of buildings," he said.
"One of the other reasons that we're suggesting this is for aesthetic quality.
"With the need for denser and more high-rise developments more and more people are going to be living in tall buildings and at the moment they will be looking out at quite drab views."
Developers had the best opportunities for creating green roofs because they could feature in the original plans for little more than the cost of a standard roof, Mr Massini said.
But he expects the current cost of £15 to £30 a square metre to convert existing roofs to drop as they become more popular.
The idea is popular in Belgium and other European countries
Homeowners could cheaply convert garage, shed and extension roofs, he said - as long as they took advice on the weight bearing properties of the structure.
"We should be seeing them everywhere - they are very valuable," Mr Massini said.
Bugs and beetles
Exactly what species of plants and animals turn up on roofs depends on what they are made of and the local area.
He said: "Some very rare bugs and beetles have been found so far.
"They are species which are normally found on sand dunes and shingle beaches, but are now turning up in urban areas."
In other areas, species of bumble bees, whose numbers have declined, have been attracted by the abundance of plants.