NParks' Tree Inspection Regime

Mr Shawn Huang Wei Zhong asked the Minister for National Development (a) what is the current inspection routine and procedure to ensure that trees in public areas are safe from tree rot, infestation and tree failure that can potentially cause a loss of life; (b) whether there are sufficient resources allocated to conduct these inspections; and (c) what are the scenarios that will cause a healthy tree to fail within nine months after its inspection.

Thank you, Sir. Ms Hany Soh and Mr Shawn Huang have raised questions about NParks’ current tree inspection regime and I will address them together.

The National Parks Board (NParks) has a tree inspection and maintenance regime that is aligned with the Best Management Practices of the International Society of Arboriculture (ISA). Regular tree inspections are carried out by trained inspectors every six to 24 months, depending on the location and size of the tree. Trees that are close to areas with high pedestrian or traffic activity are inspected more frequently.

During a tree inspection, NParks’ inspectors conduct a comprehensive visual examination of the tree crown, branches, trunk and roots to assess the tree’s health and stability. Trees that are found to have possible defects are subject to an additional in-depth inspection, which involves the use of diagnostic equipment to assess the internal condition of the tree. Since November 2016, such in-depth inspections are also conducted annually for trees of more than four metres in girth. This is a precautionary measure in response to changing weather conditions, and is over and above the Best Management Practices of the International Society of Arboriculture.

Beyond inspections, NParks has put in place other measures to reduce the risk of tree failure. First, NParks carries out targeted arboriculture treatments to improve general tree health and their ability to withstand severe weather conditions. It prunes trees regularly to remove weak, dry or overgrown branches, and to improve their structure and balance.

Second, NParks is also progressively replacing storm-vulnerable tree species with hardier species.

Third, NParks uses technology to analyse risks and improve inspection processes. For instance, NParks is piloting modelling techniques to understand the impact of adverse environmental conditions, such as strong winds, on the structural integrity of trees. This will help NParks to better determine the pruning required to improve tree stability.

To ensure that there is sufficient expertise to perform tree inspections, NParks has built up a pool of certified arborists in Singapore by offering professional training courses and seminars. These courses are conducted by both international and local arboriculture experts, for NParks staff, as well as tree care professionals in the private sector and other public agencies that manage trees. There are currently more than 620 arborists in Singapore who are accredited with the International Society of Arboriculture. Apart from its in-house arborists, NParks also requires its tree maintenance contractors to have certified arborists in their teams.

With this comprehensive tree management programme, NParks has reduced the number of tree failure incidents by almost nine-fold, from 3,100 in the year 2000, to 339 in 2020. However, it is not possible to completely prevent tree-related incidents because trees are living organisms that can be affected by pests and diseases, as well as environmental conditions. Even healthy and structurally-sound trees can fail during storm events due to exceptionally strong winds or heavy rainfall.

Lastly, Ms Hany Soh has asked whether NParks has a safety check regime in place for its parks. Beyond trees, safety inspections are also carried out for park infrastructure and facilities. NParks appoints registered professional structural engineers to inspect the structural integrity of buildings and structures in its parks, such as shelters, bridges and monuments, once every five years, in accordance with statutory requirements under the Building Control Act. Regular and systematic checks of park facilities are also conducted by NParks staff and external inspectors. For example, all playgrounds are inspected monthly by NParks staff, and every six months by external Certified Playground Safety Inspectors. This allows NParks to detect and rectify defects in a timely manner and to keep our parks safe for users.

In conclusion, Sir, the questions raised by Members are in relation, I probably assume rightly, to the recent Marsiling Park death. We deeply regret the loss of life, every one death or injury as a result of tree-fall incidents is one too many. My colleagues at NParks and the arborist community work hard day after day to keep our streetscape, to keep our parks and our nature areas safe for Singaporeans to enjoy.

We will continue to press on to keep up the work and to ensure that our City in Nature is safe and enjoyable for everyone.

Thank you, Speaker. I thank the Minister for his response to my question. Indeed, the victim of the recent Marsiling Park fallen tree incident is actually my Woodgrove resident. Like the Minister, I agree with him, that every of such unfortunate incident is one too many.

I have two clarifications to make. Firstly, I understand that some countries do adopt methods such as cabling and bracing by placing or threading steel cables between tree branches or trunks to limit its movement and to provide more structural support to the trees, thereby minimising the damage caused to trees in windy or stormy conditions.

Another practice of tying back trees, on the other hand, as practiced by countries such as Japan, is to ensure that if trees were to fall prematurely, it will fall towards a pre-determined direction, away from human traffic.

In this regard, I would like to seek the Ministry's clarification, whether they will consider implementing these measures for trees that are within parks or high human traffic areas.

My second clarification is whether NParks will consider to do more public education on safety at parks, sharing tips on how to recognise potential hazard in parks and what to do when a park-related accident occurs.

I thank the Member for her questions. On behalf of my colleagues at NParks, we extend our deepest condolences to the family of the deceased. We stand by them and have offered the support that they may need at this difficult time.

In regard to the Member's first question on the use of restraints on trees. NParks does use tree support systems for trees that have reached maturity or have known structural weaknesses, among others. For example, there is a heritage tree I am told, the Lychee Tree atop Mount Rosie in the Novena neighbourhood. It is supported by permanent galvanised steel structure built to withstand elements. This tree is more than 100 years old.

NParks also uses cabling methods in selected situations such as the tree, a Palaquium tree at the Evolution Garden at Singapore Botanic Gardens (SBG). This method is used as a precautionary measure to restrain the tree from falling in a direction of the footpath.

Tree support systems can constrain, however, young and semi-mature trees in the ability to grow. This could also constrain them in their ability to make natural swaying movements in order to buffet the impact of strong winds, and in fact, may inadvertently weaken the structure of the tree – because the crown gets the full impact and the tree structure is constrained from some degree of natural movement.

NParks will study carefully what more situations we can use it, but we also have to recognise that these structures can also pose safety issues if used without care in park settings where people frequent.

To ensure that park users can enjoy our parks safely, NParks has installed advisory signs on various safety related issues across our shared spaces. This includes signs to guide the appropriate use of play and fitness equipment; as well as what the public can do when they encounter wild animals in our parks, or hazards like falling branches in forested areas. NParks will continue to engage and educate our community on public safety tips in our parks by putting out advisories and safety messages onsite and on NParks' website.

Recognising potential tree hazards in our parks, requires assessing the health and structural integrity of trees and is best carried out by trained personnel with the requisite experience and expertise. Members of the public with feedback on public trees or park facilities can contact NParks via its hotline at 1800 471 7300 or through the OneService app.

For park-related accidents or incidents, public should contact the Police or the SCDF immediately, if there is an emergency or NParks' hotline otherwise. Members of the public may also approach NParks officers who are stationed onsite at some of our parks during office hours.

Thank you, Mr Speaker. I thank the Minister for his reply. Besides trees in parks, many trees are actually in HDB estates managed by Town Councils. Can the Minister share how does NParks work with and coordinate with the Town Councils for tree inspection and how does NParks share their expertise with the Town Councils?

I thank the Member for his question. NParks manages some 6 million trees in Singapore, whilst in Town Council areas, if I recall right, about a million trees managed in areas under Town Council management. There are, of course, trees managed by private property owners, by MCSTs, by other agencies as well.

And so, the first thing is to ensure that the arborists in Singapore, as I said earlier in my reply, that we have a community of arborists numbering more than 620, who are trained and accredited by the International Society of Arboriculture. They have to undergo regular training and upgrading in order to upkeep their standards and they are then certified by NParks. NParks offers professional training courses and seminars, both by international and local experts, and that raises and supports the standards of arborists, who are then deployed not only under NParks' regimen but also that of Town Councils, the private sector as well as other agencies as well.

In addition, in relation to trees under Town Councils, NParks works closely with agencies that manage trees, Town Councils and landowners to advise them on tree care standards. NParks also provides professional training courses and seminars for tree care professionals in the private sector and other public agencies which manage trees. For example, NParks provides training for the staff of Town Councils or managing agents administering landscaping contracts, in various plant health and maintenance topics.