SINGAPORE - Halfway across the globe, the world's largest tropical rainforest is in flames. Closer to home, swathes of green in Sumatra and Kalimantan are feeling the heat.

In the tale of two burning rainforests, there is one common fear: as the flames roar through the Amazon and South-east Asia, hopes of limiting greenhouse gases are going up in smoke.

Assistant Professor Kelly Andersen from Nanyang Technological University's (NTU) Asian School of the Environment, explains that tropical rainforests help to take up planet-warming carbon dioxide from the atmosphere, locking the carbon in tree biomass such as trunks and roots.

When they burn, the stored carbon is released into the atmosphere, and the planet loses its natural defence against climate change.

Adds Prof Andersen, who has worked in the Amazon for more than five years: "As the world's largest tropical rainforest, the Amazon has been acting as a buffer to increasing carbon dioxide emissions from human activity, protecting us from even stronger global changes than what we are already seeing around the world."

Already, multiple agencies, including the United States National Oceanic and Atmospheric Administration and the European Union's Copernicus Climate Change Service, have independently confirmed that July this year was the hottest month ever recorded.

"This means what happens in the Amazon will have far-reaching effects for people and places around the world," Prof Andersen said.

DISTANCE DOESN'T MATTER

For people in Singapore, the fires burning in Indonesia can be more keenly felt, especially when haze wafts in. This week, air quality here was a whisker away from crossing into the unhealthy zone for the first time this year .

Ms Aqeela Samat, palm oil demand specialist for the World Wide Fund for Nature, Singapore (WWF-Singapore), points out that Indonesia is currently experiencing its worst annual fire season since 2015, with fires this year razing an area at least two-thirds the size of Singapore.

The fires in the Amazon more than 16,000km away also affect Singapore, experts say.

And this is not just because of the Amazon's oxygen-producing abilities.

Associate Professor L Roman Carrasco from the National University of Singapore's Department of Biological Science, explains that most of the world's oxygen supply comes from the oceans. Phytoplankton, tiny marine organisms, produce the life-giving gas when they photosynthesise.

"The Amazon produces 16 per cent of the oxygen produced by plants worldwide, which is still substantial. But producing oxygen is only one of the many services that tropical forests like the Amazon provide for us," says Prof Carrasco, who studies tropical forests.

One of the main ways that the Amazon can affect the global climate lies in its ability to soak up carbon from the atmosphere.

Carbon dioxide is blind to borders - it has the same impact on the climate, no matter where it is emitted, says Singapore Management University's (SMU) Associate Professor Winston Chow, a lead author for the upcoming report by the Intergovernmental Panel on Climate Change.

As he puts it: "Molecules of carbon dioxide don't care where they're from. Whether from the Amazonian fires, or the smoke stacks in Jurong, or the oil fields in Texas, they all trap heat on Earth in the same way."

This means that carbon sinks like tropical forests, no matter where they are located, all help in the climate fight.

Prof Carrasco explains: "Tropical forests, by sequestering (removing) and containing carbon, represent one of our main hopes to prevent climate change. Their contribution is beneficial to all in the planet regardless of our location."

Human activity, such as the burning of fossil fuels for energy or land clearance, releases carbon dioxide into the atmosphere, where it acts like a blanket in trapping heat.

Data collected by scientists from the Scripps Institution of Oceanography in the United States showed that global carbon dioxide concentrations stood at 408.82 ppm (parts per million) on Sept 10 - a jump from the 280ppm recorded at the dawn of the Industrial Revolution, around the year 1780.

The excess heat throws the climate system out of whack, causing the climate to change. The symptoms are clear: rainfall patterns are changing, resulting in too much rain in some places and drought elsewhere; while melting ice sheets contribute to sea level rise. The warming also increases the likelihood of extreme weather events, such as heatwaves.

At 6 million sq km, the Amazon rainforest is more than 8,000 times the size of Singapore. But a huge swathe of it - 7,200 square miles, or more than 25 times the size of Singapore - has been set ablaze by farmers looking to clear land for agriculture, according to the National Geographic.

Professor Jean Yong, a botanist at the Swedish University of Agricultural Sciences, says: "The huge amount of carbon dioxide released from the Amazonian fires will increase the total concentration of carbon dioxide globally, exacerbating climate change-induced weather and environmental anomalies worldwide, including Singapore."

GLOBAL EFFECTS, LOCAL IMPACTS

The causes of the fires in the Amazon and Indonesia are similar, with land being cleared for agriculture, observers point out.

Dr Arief Wijaya, senior manager for climate and forests at think-tank World Resources Institute Indonesia, says that in South-east Asia, forests are cleared mainly for palm oil and pulp and paper; while in the Americas, land is cleared for soy or cattle ranching.

"From Brazil to South-east Asia, the role of human activity in the onset of these forest fires cannot be denied," says WWF-Singapore's Ms Aqeela, emphasising that solutions had to go beyond putting out fires to addressing the root cause.

"Robust forest governance, funding and legislation that support deforestation-free supply chains are essential."

Across the Pacific Ocean, death by fire does not just affect the trees of the forest and their ability to capture carbon from the air.

The short-term, local impact of forest fires is multifold, scientists say. This ranges from the health of people living near the fires, to the loss of biodiversity and ecosystem services.

Ecosystem services are the things essential to human life that nature provides. The Food and Agriculture Organisation of the United Nations put the estimated value of ecosystem services at US$125 trillion.

Forests, for instance, provide clean water, help cool the surrounding environment, prevent floods and enhance physical and mental well-being. They are also treasure troves of biodiversity.

Says NUS' Prof Carrasco: "From a practical standpoint, the future cure of cancer could be lost in those fires. From an ethical standpoint, losing the Amazon means a huge loss of natural history.

"Imagine losing half of all the great books, movies, paintings, sculptures and historical buildings of the world. Imagine they are lost forever, your children will never know about them. Losing the Amazon is the natural equivalent to that."

NOT ABOUT THE SIZE

But it is not just the large swathes of forests that are worth protecting.

Experts The Straits Times spoke to were unanimous in their belief that even tiny plots are worth saving.

Asked if this includes Singapore's fragmented forests, NTU's Prof Andersen says: "Absolutely! Take a walk along a big road and compare that to a stroll in Bukit Timah Nature Reserve. Forests, trees and green areas provide many ecosystem services - regulating the air we breathe, moderating temperatures by creating shade and taking up water rapidly during big rain events."

Singapore's forests are also remarkably rich, and are home to globally critically endangered species, including the Sunda pangolin and the straw-headed bulbul.

Says Prof Yong: "Singapore's last remnant and natural forests are amazing hubs of tropical biodiversity. Despite the small size of Bukit Timah, or the mangroves, these natural green areas represent the last bastions of Singapore's intangible and iconic natural heritage for the next generation."