Furthermore, NParks was on an exercise to remove/replace storm-vulnerable trees and advising other public agencies, such as the Singapore Land Authority (SLA) and Housing and Development Board (HDB), to do the same. The only storm-vulnerable species publicised was the Albizia tree (Falcataria moluccana), which is fast-growing and could easily exceed 20m in height. But its wood is soft and prone to breaking during storms. In addition, they are shallow-rooted and thus susceptible to uprooting. There should be other storm-vulnerable species listed, but unfortunately, they were not shared in the article.
Photo by Shin Min Daily News
Almost 4 years ago (27 Sep 2012), a NSman on in-camp training was crushed by a tree and was subsequently pronounced dead at the hospital he was taken to [2]. The incident took place at the entrance of the Ama Keng Training Area in Lim Chu Kang. If a certified arborist (CA) were to have carried out tree inspection on that tree, the CA could have recommended the removal of the offending tree. Based on the photo, the tree appeared to be an African tulip tree (Spathodea campanulata), detailed further below.
In an "after" photo where SLA selectively removed Albizia trees at Jalan Anak Bukit, (near Bukit Timah Hill), African tulip trees were observed to be left behind and intact. [1] The site of the "after" photo was visited last week and it looked very different due to road expansion works.
"After" photo after an exercise by SLA to remove Albizia trees. Probably taken in 2012, from NParks website [1].
Road widening in the target area of storm-vulnerable trees, which include Albizia and African Tulip trees. Photo taken on 11 Sep 2016.
African tulip trees near the edge of the road expansion.
Land Transport Authority (LTA) notice on the road widening.
There are nine tree species identified as being invasive in Singapore. A common attribute of these invasive tree species is that as compared with non-invasive species, they have only 54% of the mean wood density. It should be noted that other than Falcataria moluccana and some outlying individuals of Cecropia pachystachya, "no attempt has been made to control the other species." [3]
The following are four of the invasive tree species that could be considered "storm-vulnerable", which could be removed from roadsides, forest edges, parks and high-traffic areas:
a. Acacia auriculiformis (Ear-leaf acacia)
It could grow in nutrient poor soil as it has nitrogen-fixing bacteria associated with its roots. Fast-growing and drops a lot of leaves. Roots grow shallow, spreading and densely matted, which makes it suitable to stabilise eroding land.
b. Cecropia pachystachya (syn. Cecropia peltata) (Trumpet tree)
In Singapore, this tree is viewed as a weed and is short-lived [4]. It has hollow stems, which is inhabitaed by ants.
c. Falcataria moluccana (Moluccan albizia)
Perhaps the fastest-growing tree in the world [4]. Like the Acacia, it is capable of fixing nitrogen from the air. Considered a weed and hazard due to its soft, brittle wood, and shallow roots.
d. Spathodea campanulata (African tulip tree)
Similar to the Albizia tree, the wood of the African tulip tree is soft, tends to become hollow, and drops their branches over time. The roots grow shallow and is more likely to uproot during storms.
Table 1. Invasive tree species in Singapore with their common names
Acacia auriculiformis Ear-leaf acacia
Cecropia pachystachya Trumpet tree
Falcataria moluccana Moluccan albizia
Leucaena leucocephala Lead tree
Manihot carthaginensis Ceara rubber tree
Muntingia calabura Jamaican cherry tree
Piper aduncum Spiked pepper
Spathodea campanulata African tulip tree
Table 2. Potentially invasive tree species (not necessarily storm-vulnerable) identified in the paper [3]
Hevea brasiliensis Para rubber tree
Andira inermis Brown heart tree
Ptychosperma macarthurii Macarthur palm
Elaeis guineensis Oil palm
Ficus religiosa Bodhi tree
Reference:
1. National Parks Board Tree Management Programme (https://www.nparks.gov.sg/news/2013/1/nparks-tree-management-programme), 1 Jan 2013, Last updated on 20 Nov 2014,
2. Jalelah Abu Baker and Lim Yan Liang, NSman's death: Tree was checked in April, Asiaone (http://news.asiaone.com/News/Latest+News/Singapore/Story/A1Story20120929-374484.html), 29 Sep 2012
3. Nghiem, L. T. P., Tan, H. T. W. and Corlett, R. T. 2015. Invasive trees in Singapore: are they a threat to native forests? Tropical Conservation Science Vol.8 (1): 201-214
4. Tee et. al., Trees of Our Garden City, 2nd ed, 2009
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