IN the heart of a verdant urban forest in Kuala Lumpur, plant physiologist Dr Elizabeth Philip is trying to answer an important question about Malaysia’s forests.
She’s in charge of the Environment and Climate Change programme at the Forest Research Institute (FRIM), Kepong, researching and helping to estimate greenhouse gas emissions, and their removal from sectors such as forestry and agriculture.
It’s hard to talk about the impact of heat in the cool shadows of a leafy oasis like FRIM, but according to Philip, this is already an inevitable feature of a warming world. Pointing out the news articles about droughts and floods that she has collected, she declares: “Actually, all this shows that our forest plays an important role. The role of the forest, whether in adapting to climate change or mitigating it, is important and cannot be overemphasised.”
The Intergovernmental Panel on Climate Change’s (IPCC) Sixth Assessment Report, released in 2023, cautions that there has been an increase in the frequency and intensity of extreme events as the planet warms.
According to the report, weather modelling shows that a 1.5°C increase in average global temperature would see a previously once-in-decade heatwave occur 4.1 times more often, and at 2°C warmer, 5.6 times more often.
But it’s not just the heat that Malaysians have to worry about: it’s also the higher volume of rain that warming brings, and thereafter, the inevitable floods.
The same report warns that a global average temperature that is 1.5°C warmer would result in a once-in-10-years heavy precipitation event happening 1.5 times more often, and at 2°C warmer, 1.7 times more often.
At these temperatures, conditions would also be between 10.5% and 14% wetter.
In 2025, the World Meteorological Department confirmed that 2024 was the first calendar year with a global mean temperature of over 1.5°C above pre-industrial levels – it was, in fact, 1.55°C.
This is what Philip is trying to figure out: How will all this impact our forests – forests on which we depend for ecosystem services such as temperature regulation, wildlife habitats, landslide prevention, water catchment systems, and biodiversity survival, among others?
In short, with more frequent flooding and more intense and prolonged heat, will our forests change in tandem with climate change – or can they even cope?
Challenging times
Some of Malaysia’s most expensive and premium timber species, including our national tree, the merbau, are found in lowland dipterocarp forests in Kelantan, Pahang, and Terengganu.
Philip says while climate change impact on forests is not yet clear because fragmentation and human activities also contribute to species loss, they are already facing challenges.
“There is a need to understand if episodes like El Nino are getting more regular due to global warming,” she says.
The El Nino-Southern Oscillation (Enso) is a global climate phenomenon that sees changes in winds and sea surface temperatures over the tropical Pacific Ocean, which will affect rainfall patterns in this part of the world.
Scientists have yet to determine how intense the so-called super El Nino forecasted this year will be; it is expected to peak between November and January.
“When you have prolonged drought from El Nino, studies have shown that in some forests, the big trees, those with a 60cm diameter or those measuring some 45m tall, die,” Philip says.
This is because large trees rely on a combination of root pressure, capillary action, and transpiration pull to move water from their roots to their leaves. During prolonged droughts lasting months, such as during an El Nino season, this water transport system can come under increasing stress – and “You tend to have more mortality,” says Philip.
Though the forest will continue to grow, the loss of large trees may reduce the balance of the forest’s sequestration of carbon, she says.
Large trees naturally sequester and store more carbon. However, when they die, gaps open up in the forest canopy, allowing more sunlight to reach the forest floor and letting smaller trees and other plant species thrive. Hence, the forest continues to grow – but at the price of losing carbon storage.
“El Nino or the drier seasons will induce this kind of mass flowering because this is a tree’s response to water stress,” explains Philip.
“That’s good because you will have the next generation. But we also see that after El Nino, you have La Nina.”
Seen as a cooler phase of Enso, La Nina often follows El Nino and usually brings wetter than normal conditions to parts of the world, including Malaysia.
One concern that Philip has is the flooding and ponding that result from the heavier precipitation during this time.
“From my previous observation among some urban trees, especially with some species, with three days of water ponding, there would be some depression in the growth.
“During flooding, if it’s for one or two days, it’s OK as the trees can recover. But what if the flood lasts for two or three months? We have not experienced that yet,” she says.
What could happen was demonstrated during an episode of severe inundation in Taman Negara in 2014: Understorey plants like young saplings, shrubs, and ferns could have been lost as seedlings will be choked due to submersion.
The forest understorey is the layer of vegetation beneath the canopy that plays a crucial role in regeneration and the survival of light-demanding species.
“So then you would have problems with the regeneration of the forest. That could be impacted, and that’s something that we need to consider,” Philip says.
She points out that while these are all naturally occurring climate events, the question is whether they are becoming more frequent due to climate change, and whether our forests can cope and adapt.
“At the moment, our forests are recovering from all these setbacks, such as El Nino and La Nina. But if El Nino happens too frequently due to the increase in global warming, that might impact our forests in the long term,” she says.
On higher ground
In a world that heats up by 2°C or more, flora that have adapted to cooler temperatures may not survive, while those from the warmer zones might even ‘migrate’,” says Philip.
Researchers, she adds, are already seeing this trend in the Mediterranean and parts of Southern Europe, as well as the phenomenon of pests and diseases “migrating” north.
“So what we see on Mount Kinabalu or Gunung Tahan, such as stunted and slower growth species, mossy forest, and lichens, you may not see in the future,” she says, referring to flora growing in cooler climes at higher altitudes.
While many studies in cooler countries have shown that flora is increasingly “moving” towards the poles as temperatures rise, the 2008 study “Global Warming, Elevational Range Shifts, and Lowland Biotic Attrition in the Wet Tropics” suggests that in Costa Rica’s tropical forests at least, species are more likely to move uphill.
This is because near the equator, temperatures do not change as much as you move north or south; they change as you go uphill, where it’s cooler.
In their last study of Malaysian forests, Philip and her colleagues had not seen any climate-induced change in disease or pests – not yet, anyway.
“But we don’t know what would happen because pests and disease would come when the trees are weaker.
“If you have El Nino, then after that, La Nina and followed by El Nino, it’s very difficult for the ecosystems to recover,” says Philip.
The 2008 study mentioned above also found that unlike forests in temperate regions, tropical forests in Costa Rica may simply lose species as the climate warms because there are few cooler places for lowland species to “move” to.
Incidentally, that IPCC Sixth Assessment Report also projected that regions like Sumatra and Borneo would suffer biodiversity loss of between 16.8% and 17.6% in tandem with a 2°C rise in temperature.
Building resilience
FRIM researchers will be keeping a close eye on this year’s so-called super El Nino to document its impact on Malaysian forests and whether there will be bush or forest fires triggered.
“What we have seen is that when a fire happens, it usually doesn’t burn the whole forest.
“What we see is that about 20% to 25% of the biomass catches fire, depending on the wind’s speed and direction. So if this year is going to have a strong El Nino event, will this go up to 30%?”
The government, she adds, has already put protective measures in place, such as having waterways, check dams, and tube wells in places where there are likely to be wildfires, such as peatland.
But it still needs to look into measures to make Malaysian forests more resilient against climate change, such as storing seedlings or getting communities to start nurseries of tree species in the country.
“If our forests are not resilient, the impact is on us,” Philip says, adding that this will include effects on, among others, our water, biodiversity of important agricultural elements such as pollinators, food sources, and wildlife.
“And when all this is impacted, humans are the first to go as we are the least resilient.”
