The tree that killed a woman and injured four others when it uprooted last Saturday was unlikely to have failed owing to a lack of space, said a former senior arborist at the Botanic Gardens.
The 270-year-old tembusu tree had already been there when the Gardens were established in 1859, said Mr Lahiru Wijedasa. "It has been standing in the Gardens for more than a century. If its roots had not been able to adapt to the development, we would have seen tree failure ages ago," said Mr Lahiru, who worked at the Gardens between 2006 and 2009.
Mr Lahiru, who is now pursuing a doctorate at the National University of Singapore, was responding to speculation that the tree fell owing to a lack of space for its roots.
He urged members of the public to await the results of the final investigations and not jump to conclusions, saying he decided to speak up to clarify some speculations.
On suggestions that the tree might have been affected by recent wind and rain, Mr Lahiru said the weather conditions could cause a "compromised" tree to be uprooted.
"But like a chair with four legs, one of which has been hollowed out by termites, there may not have been visual clues.
"The point is, even if measures are taken to reduce the risk by 99 per cent, there is always a 1 per cent chance of something happening," Mr Lahiru said, adding that the National Parks Board (NParks) has done its due diligence to ensure tree health.
On the suggestion of having mature trees inspected monthly, he said this may not help if there are no visual symptoms such as a receding crown, leaves turning colour, or more leaves falling off than usual. There is already a system to look out for such red flags.
NParks does detailed, twice-yearly routine inspections of mature heritage trees, in addition to the daily visual checks by arborists on the ground, he said.
NParks had determined the tree to be healthy in its last routine inspection, conducted last September.