There are about seven million trees in Singapore and at least another million will be added by 2030, thanks to the OneMillionTrees movement launched by the National Parks Board (NParks) in April last year.

With about six million of these trees currently under NParks' care and the tree population's growth gradually adding to the workload of arborists here, new ways of using old technology have emerged to ease the physical burden of tree inspections.

Since 2019, NParks has been looking for ways to incorporate Light Detection and Ranging (Lidar) technology into its tree inspection regime, by using a software called the Remote Tree Measurement System (RTMS) to interpret the data that such scans produce.

Lidar scanners primarily use reflected laser beams to determine the distance of target objects.

The technology has been around since the 1960s and was first used to take measurements for military purposes. Today, scanners are also placed on aircraft to examine and map the earth's surface.

The eventual inclusion of Lidar scans in NParks' tree inspection regime will grant its more than 230 certified arborists some reprieve from the physical demands of the job.

In January, NParks began a year-long trial of the technology for tree inspections. The board is hoping that by the end of the trial, about a quarter of more than 80 data fields that arborists have to manually enter on its tree inspection checklist can be completed automatically using the RTMS.

Currently, inspections - including measuring the height and girth of trees and checking for open cavities - are carried out by people in the field. Inspecting each tree takes about 15 minutes, something NParks hopes the RTMS will help to cut down by more than half.

Apart from using Lidar scans to measure trees, visual checks in the future may also be conducted remotely, thanks to wide-angle images that are captured simultaneously with the Lidar scans using an attached camera, allowing officers to perform a visual scan of the trees from their offices.

As a result, trees that require immediate attention can be identified earlier to avoid potentially fatal tree failure incidents.

NParks director for streetscape and operations technology Ow Siew Ngim said that the number of tree incidents - which include tree falls and branch snaps - yearly has fallen from about 3,100 in 2001 to about 420 in 2019 and 340 last year.

She said such incidents have decreased due to NParks' increased reliance on technology to manage its trees over the years.

Ms Ow added that with more adverse weather conditions to come, NParks will continue to tap technology and incorporate new methods - such as Lidar scans - to ensure timely intervention and mitigate tree failure risks.

Poor weather conditions have caused several trees to collapse this year. Last month, a 24m-tall West Indian locust tree in Malcolm Park off Whitley Road fell onto Tanglin Community Club amid intense rainfall, damaging the roof of its ceramics room.

The board is also trialling using the RTMS to pre-empt such incidents by putting the trees under simulated stress tests.

Using data from Lidar scans, 3D models of individual trees can be produced. Arborists can then simulate wind speed to see if the tree structure can hold up against harsh weather.

For instance, while trees here are exposed to average wind speeds of about 5kmh to 10kmh, wind load simulations can go up to 80kmh to mimic thunderstorms.

Despite such efforts, Ms Ow said it is impossible to eradicate tree incidents.

She said: "Our trees are given due care according to the prescribed regime... but trees are living things, and they are also subject to various environmental conditions."

As trials continue and new methods of interpreting data are adopted, more improvements to the inspection regime will follow, said NParks deputy director for streetscape Taufik Mohamed Ibrahim.

"We are just starting to collect data - a lot of it. So hopefully over the next decade, we will know better how to use it, and how it will add to our existing capabilities," he said.

Besides using technology for surface-level checks, the board is working on research projects that use technology like ground-penetrating radar to detect and model tree roots.

Developments in these projects will be shared when ready, said an NParks spokesman.