A survey to assess the condition of trees in Golf Green, where a large branch of a tree fell and killed a rickshaw-puller last month, has found that at least five more trees could topple.

The Kolkata Municipal Corporation (KMC) conducted the survey in Ward 95 (the Golf Green area) following a request from the local councillor, who said residents were afraid after the death of the rickshaw-puller.

Tree surveys are not common in Calcutta, though instances of trees falling and injuring people, at times fatally, are not unheard of. Sources in the civic body said there was no plan for a pan-Calcutta survey to identify vulnerable trees.

Environmentalists have often blamed concretisation of pavements that leaves very little soil for surface roots, unscientific pruning that shifts the weight of the tree to one side and heavy cables resting on branches for toppling of trees in the city.

The survey, conducted earlier this month, also found that many of the trees needed trimming. The civic body has begun work for trimming.

"We conducted a survey in Ward 95. Of the 72 trees examined, six need to be felled as they can topple. The rest need trimming," said Sarbani Roy, a botanist with the KMC.

Four Krishnachura, one Debdaru and one Kadam trees need to be felled, Roy said. Two of the Krishnachura trees are dead, she said.

"The tree whose branch fell and killed the rickshaw-puller will also have to be felled. The trees that need to be hacked down have become very weak. The trunks have become hollow. Strong winds can topple them," she said.

Some of the trees surveyed have tilted towards the road and can topple any time.

Roy and two more botanists from the KMC, Avik Mukherjee and Suvoprasad Bhattacharya, conducted the survey.

Rickshaw-puller Alok Kayal, 42, died after a huge branch of a tree fell on his rickshaw on June 28. The rickshaw and Kayal were crushed under the combined mass, which a veteran horticulturist put at around 2 tonnes (2,000kg).

Tapan Dasgupta, the councillor of Ward 95, told Metro residents of Golf Green became frightened after the tree fell on June 28 and killed Kayal.

"I requested the KMC to do a survey of the condition of the trees in the area. The civic body is trimming some of the trees but felling has not started yet," said Dasgupta.

KMC officials said felling would take some time as permissions from the higher authorities of the KMC need to be obtained.

Environmentalists have often complained that tree trimming in the city is done unscientifically — all sides are not cut uniformly. That results in the shifting of the weight of the tree to one side, as a result of which the tree can topple during a storm.

Concretisation of pavements, which leaves no space for surface roots of a tree to grow, is another reason for toppling of trees. Surface roots play the role of anchor. If their growth is stopped, the trees weaken, they said.