The National Parks Board (NParks) of Singapore said on Wednesday that the process of inspection and care of trees is in line with global standards, and in some areas exceed the best practices of the International Society of Arboriculture (ISA).
While speaking at a media briefing after two separate incidents where trees toppled, causing injuries and killing one person, Oh Cheow Sheng, the group director said NParks takes an "adaptive approach" to tree management. He added that the group has implemented more stringent inspections over time in response to unpredictable and severe weather patterns.
Last Saturday, a woman was killed and four others were injured when a large, 270-year-old heritage tree toppled at the Singapore Botanic Gardens. After two days, another woman was taken to intensive care after a tree at Yuan Ching Road fell on her.
In the first case, the Tembusu tree that stands at 40m tall with a girth of 6.5 metre was last inspected in September 2016. According to reports, the tree receives two checks a year, which is more frequently than other trees in the Gardens, due to its heritage status.
When questioned about the accident, NParks said it could not discuss the reasons for the Tembusu tree toppling as police were still investigating the case.
Oh said: "Trees react to changes in environmental, site and soil conditions. Tree care can mitigate risks but healthy trees can be affected by strong wind gusts and rainfall."
"On top of mitigation, a preventive measure against poor weather is to plant the right tree species in the right place - for example, some are not suitable to be planted in waterlogged areas. Another possible measure is to increase the drainage around an area which is prone to being waterlogged by rainfall," he added.
However, in the case of the Yuan Ching Road incident, the Singapore Land Authority, which manages the area where the tree fell, said: "trees and greenery on state property are maintained on a regular basis".
The trees along expressways and major roads are inspected once every six to 12 months, according to NParks. While the trees, which are more than 4 metre in girth are also subject to yearly detailed second-level inspections.
The authorities also said that proper measures are taken to improve the general health of trees, including routine mulching to supplement the regular fertilisers and pruning techniques to better their structure and balance.