Critically endangered trees: Hope for the Hopea Sangal

Despite its size, Singapore is teeming with animal and plant species. Conserving them is an ongoing challenge. In this five-part series leading up to the National Parks Board's Singapore Biodiversity Week starting on May 20, The Straits Times highlights some which have been saved from the brink of extinction. Today, we look at the inspiring story of the Hopea sangal, and efforts to save other critically endangered trees.

SPH Brightcove Video
At the Pasir Panjang Nursery, a ray of hope is growing slowly, but surely. There, on the braches of a 15-year-old Hopea sangal tree, lie the responsibility of repopulating Singapore with the once common forest giant.
National Parks Board's (NParks) Mr Ang Wee Foong (left) and Dr Adrian Loo are among staff responsible for increasing the long-term survival chances of critically endangered plants in Singapore. For instance, NParks staff salvage seeds from plants and
National Parks Board's (NParks) Mr Ang Wee Foong (left) and Dr Adrian Loo are among staff responsible for increasing the long-term survival chances of critically endangered plants in Singapore. For instance, NParks staff salvage seeds from plants and propagate seedlings in nurseries. PHOTOS: NG SOR LUAN, ANG WEE FOONG

In a quiet corner of southern Singapore, a ray of hope is growing slowly. A Hopea sangal in Pasir Panjang's Hort Park is only 15 years old - a mere infant of a tree.

But on its branches and those of its few "siblings" lies the responsibility of populating the country with the forest giant, which can grow up to 40m tall. They are descendants of what was believed to be the last tree of its kind here, a 150-year-old specimen felled illegally in 2002.

However, in a fortunate turn of events, five more have been found since then - three in Bukit Timah Nature Reserve in 2005, and two others in Nee Soon Swamp Forest in 2014. All are believed to be more than a century old.

Yet, there are still fewer than 20 known mature Hopea sangal trees in Singapore. But with more young specimens being nurtured, they could one day help fill forests here.

At first glance, though, the 4m-tall plant in Hort Park, with its scrawny trunk and sparse foliage, looks nothing like the towering sentinel it will one day become.

But it will not have to depend solely on the winds to spread its seeds (pictured below). The National Parks Board (NParks) is lending a hand, with some tender loving care in its nurseries.


NParks' efforts have borne fruit.

Seeds salvaged from the Hopea sangalin Changi have been nurtured into saplings and some have taken root in various places. For instance, visitors to the Singapore Botanic Gardens' Learning Forest may spot two Hopea sangal saplings along the SPH Walk of Giants.

  • What happened to the Changi tree?

    SEPTEMBER 2002

    •Botanists find an old tree growing in a tree conservation area in Changi, where permission must be sought from the National Parks Board (NParks) before it can be cut down. It is identified as the Hopea sangal, once thought to be extinct here.

    NOVEMBER 2002

    •Mr N. Sivasothi - a research officer at the Raffles Museum of Biodiversity Research in the National University of Singapore (NUS)- discovers the tree has been felled when he comes across its stump.

    •DTZ Debenham Tie Leung Property Management Services claims it chopped down the tree in view of public safety as it was termite-infested and had been struck by lightning.

    •Botanist Shawn Lum, then vice-president of the Nature Society (Singapore), refutes DTZ's claims, saying the tree had still been healthy.

    •NParks takes DTZ to court for flouting the Parks and Trees Act as well as for failing to secure a permit to fell a rare tree in a gazetted conservation area.

    MARCH 2003

    •DTZ is ordered to pay $76,035 to the state as compensation for the loss of the Hopea sangal tree. The company is also fined another $8,000 for illegally felling the tree.

    APRIL 2003

    •NParks sets up a volunteer group to decide how the wood from the tree can be used.

    •The committee decides nine pieces of wood will be sculpted into artworks by artists from the Sculpture Society.

    APRIL 2004

    •Sculptures find a home at the Singapore Zoo.

    NOVEMBER 2004

    •Then Minister Mentor Lee Kuan Yew plants a 1m-tall Hopea sangal sapling in his Tanjong Pagar constituency. This sapling is one of several presented to NParks' Pasir Panjang Nursery by the Nature Society (Singapore) after the tree is felled.

    JANUARY 2005

    •Amendments to the Parks and Trees Act to introduce stiffer fines to protect trees are passed in Parliament. Those found guilty of cutting down any tree with a girth exceeding 1m in a designated tree conservation area, vacant land, national parks and nature reserves, could be fined up to $50,000, up from $10,000.


    •Sculptures made from the logs of the original Changi tree can still be seen at the zoo entrance. Cross-sections of the trunk can also be viewed at the Lee Kong Chian Natural History Museum in NUS and at the Changi Museum.

    •Sources: Infopedia, ST Archives, Habitatnews

The Hopea sangal is a critically endangered tree usually found in pristine forests, said Dr Adrian Loo, director of the terrestrial division at NParks' National Biodiversity Centre. It has been found in peninsular Malaysia, Myanmar and Thailand. In 2002, Singapore was added to the list - botanists found one tree growing in Halton Road in Changi.

Before scientists had time to study the tree, which was 35m tall with a girth of 3.3m, it was chopped down by DTZ-Debenham Tie Leung Property Management Services. The reckless act had members of the public, as well as nature and heritage groups, up in arms.

Known commonly as chengal pasir or chengal mata kuching, the tree is believed to have given Changi its name.

"Luckily, some of the seedlings and fruits were collected from where they had sprouted and fallen around the tree, and passed to Pasir Panjang Nursery, where we managed to propagate them," said Dr Loo. Before the tree was felled on Nov 20, 2002, botanists had collected some seeds from the ancient tree, without knowing they would be among the last.

One of the seedlings grew. Late last year, about 15 years after it was "rescued", it bore fruit - marking the beginning of a third generation of Hopea sangal trees in Singapore.

Its seeds were sown again in Pasir Panjang Nursery. They have now grown to become 30cm seedlings. In a way, these are the "grandchildren" of the original Hopea sangal tree at Changi, said Mr Ang Wee Foong, deputy director of nursery management at NParks.

He hopes there will be many more generations to come.


The Hopea sangal is one of the plants for which NParks is carrying out recovery efforts to increase their long-term survival chances.

Many trees in Singapore have become critically endangered due to habitat loss, said botanist Wee Yeow Chin. "During the years immediately after Raffles founded Singapore, large tracts of rainforests were cleared by immigrants for the cultivation of pepper, a spice, and gambier, which was used for leather tanning," he said.

High diversity of trees, but many are last of their kind

Nanyang Technological University's Asian School of the Environment botanist Shawn Lum said the situation remains critical.

Dr Lum has been monitoring trees with diameters of more than 30cm in the Bukit Timah Nature Reserve over the past decade. While species diversity is high, many appear to be the last of their kind, he said.

"Of the roughly 500 different species of large trees in Bukit Timah, about 60 have but one individual. This is not good," said Dr Lum, who is also president of the Nature Society (Singapore).

While many crop plants, such as corn, for example, can self-fertilise, many of the critically endangered native species are "self-incompatible". This means that one tree can only be pollinated by a different tree.

"If two trees of the same species are too far apart to be effectively pollinated, then that tree's future is not bright," added Dr Lum.


That is why habitat protection, or "in-situ" conservation, is a key strategy for NParks. This entails making sure the whole habitat is protected and unaffected by developmental works, said Mr Ang.

"For instance, a dead branch hanging over a plant could potentially damage it. So we will arrange for the branch to be removed."

Growing plants in nurseries - or "ex-situ" conservation - is another strategy. This involves collecting seeds or taking cuttings from plants in parks and nature reserves.

Said Dr Lum: "For most animals, you can't cut off a piece to grow a new one. However, you can sometimes chop off part of a tree to propagate another tree. The cutting is a clone of the plant from which it was taken, but it can keep a species going, at least in the short term, to keep it from disappearing."

But prolonged inbreeding in plants could expose genetic weaknesses in that population, just like in animals. So the longer-term strategy would be to introduce genetic variation into a population, said Dr Lum.

One way to do this is to facilitate cross-pollination across the island, by connecting habitats with groves of native endangered trees that have been carefully selected to minimise inbreeding. This would allow pollinators, such as insects, to move between natural and planted populations of native trees, linking them up and enhancing their genetic resilience, said Dr Lum.

On the ecological value of native trees, NParks' Dr Loo said they contribute to the structure of Singapore's forests and provide food for rare animals such as the Raffles' banded langur - a shy, black and white monkey.

Agreeing, Dr Wee noted how trees - part of the Republic's rich natural heritage - fit into the complex food web that exists in local forests. Insects feed on plants and, in turn, they are eaten by other predators. This is why growing exotic trees from far away countries will not help much in drawing in biodiversity, he said. "We only import the tree but not the fauna associated with it."

Correction note: In an earlier version of this story, we said that the National Parks Board's Singapore Biodiversity Week starts on May 22. It will be starting on May 20 instead. We are sorry for the error.

Join ST's Telegram channel and get the latest breaking news delivered to you.

A version of this article appeared in the print edition of The Straits Times on May 05, 2017, with the headline Critically endangered trees: Hope for the Hopea Sangal. Subscribe