Reforestation is a possible way to fight climate change. However, opportunities for reforestation, or tree-planting, are limited in South East Asia (SEA), especially with economic, land-use and operational constraints.
A study on reforestation was led by researchers from the National University of Singapore, which was published on Nature Climate Change on August 17.
How does reforestation address climate change?
Reforestation is regarded as a cost-effective nature-based solution, as tree and plants are able to take in carbon dioxide in the atmosphere through photosynthesis.
This ability to capture and store carbon makes planting trees a good way of addressing climate change.
In Singapore, the National Parks Board is working with various partners to plant one million trees in the next 10 years to reduce temperatures and improve air quality in urban areas.
Barriers to reforestation
According to the study led by Professor Koh Lian Pin, who is from the NUS Department of Biological Sciences, around 121 million hectares of land across South East Asia is suitable for reforestation.
This land area translates to about 1,677 times the size of Singapore.
If the suitable land was reforested, it would be able to capture and store 3.4 billion tonnes of carbon dioxide in a year.
That would translate to more than 10 per cent of the global carbon dioxide emissions of 36 billion tonnes.
However, due to limitations around land usage, not all of the suitable land can be reforested, said Koh, who is also Director of the NUS Centre for Nature-based Climate Solutions.
One practical constraint is that farmers use some pockets of "barren land" to grow crops for their own survival, or to sell in local markets.
Land suitable for reforestation
NUS postdoctoral research fellow Dr Zeng Yiwen, who is one of the authors of the study, explained that the amount of suitable land would drop from 121 million hectares to 76 million hectares if small pockets of land used for subsistence farming are taken into account:
“If we exclude these small farmlands, the available land for reforestation in Southeast Asia would be reduced to about 76 million hectares, and its climate mitigation potential would drop to 2.2 gigatonnes of CO2 per year.”
Another critical factor is that reforestation sites would need to be near mature forests, that could act as sources of seeds or seedlings for the reforestation site.
If this distance from mature forests is taken into account, the area of suitable land drops to 33 million hectares, according to another author of the study, Tasya Sarira:
“If we want to maximise the success of reforestation projects and restrict them to within two kilometres of existing intact forests, we would only be looking at about 33 million hectares of available land in the region, which would provide only 0.9 gigatonnes of CO2 sequestration potential per year."
Other factors include the protection status of the land and the cost of reforestation.
Overcoming constraints to reforestation
But the constraints can be overcome by involving smallholder farmers in the reforestation process, said Koh.
Doing this enables reforestation to offset up to 39 per cent of the region’s annual carbon dioxide emissions.
In addition to capturing carbon dioxide in the atmosphere, reforestation has other benefits, such as conserving habitats for other plants and animals, clean air and water, and helping to alleviate poverty.
However, efforts towards replanting vegetation requires strong government commitment, smart policies and financial support from private industries.
Koh added that a careful consideration of nature-based climate solution can help to inform climate policies and decisions:
“A more complete and nuanced consideration of both the potential and limits of nature-based climate solutions is needed to inform climate policies and decisions that are scientifically sound, economically feasible and socially acceptable."
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