- In the past few years, previously spotless air-conditioned icons of Singapore such as Changi Airport and the Apple Store have experienced infestations and diseases on indoor greenery.
- Experts say the rise in extreme temperatures as the city-state loses forest cover explains the migration of flies, bees, butterflies and rats into cooler indoor environments.
- Singapore’s pest control industry is booming as a result, with the country’s National Environment Agency mandating tougher rules to curb vector-borne diseases.
- Methods used to control pest species are being challenged by animal welfare groups concerned over the growing use of glue traps, which catch protected as well as target species.
SINGAPORE — Singapore’s reputation as one of the world’s cleanest cities is being put to the test by a surge in rodent and insect infestations that experts say is being fueled by climate change and heat stress.
At Changi Airport, famous for its indoor gardens that embody the “City in Nature” image Singapore markets to the world, lush plant displays have been succumbing to disease and insect attacks. In the last two years, swaths of greenery have had to be replaced.
It’s a similar story at the iconic floating Apple Store at Marina Bay Sands, where a circle of Chinese banyan trees lines the interior of its glass dome, encircling the latest iPhones, iPads and MacBooks. Last year, the trees had to be replaced because of insect infestations.
“The insects are coming inside — to escape the heat,” says Veera Sekaran, a botanist at the National University of Singapore and founder of Greenology, the firm that manages landscaping at both Changi and Apple’s flagship store. “Heat stress doesn’t just affect people.”
Biological markers for heat stress
Plants grown in artificial indoor environments are already vulnerable to disease. When insects move in to feed on sap or build nests, they become even more susceptible, Sekaran tells Mongabay.
“The best biological markers are the little creatures, because their tolerance to extremes is very low,” he tells Mongabay. “This is especially true in the tropics, where temperatures are usually stable. For a butterfly, a 1-degree [Celsius, or 1.8° Fahrenheit] temperature rise is very difficult. They either adapt or evolve, and evolution takes time. In the meantime, they seek shelter — as do wasps, bees and rats.”
That ecological stress is visible across the island. Singapore’s National Environment Agency (NEA) reported in August that it had detected an average of 5,400 rat burrows in the first half of 2025 — almost double the 2,800 recorded over the same period in 2024.
Local media have blamed poor hygiene in eateries and littering for the growing rats numbers, but Sekaran says the problem is climate-related: heat stress.
Singapore is fast approaching heat levels that threaten livability in a city that trades off its high standards of living. In 2023, the island nation recorded its joint-highest ever temperature of 37°C (98.6°F). In 2024, the annual mean temperature of 28.4°C (83.1°F) was the warmest on record, tied with 2019 and 2016. The government’s Third National Climate Change Study projects that by 2050, Singapore could experience between 47 and 189 “very hot days,” defined as those when the mercury exceeds 35°C (95°F), every year, compared with 21 today.
“Temperatures are only going to rise, so the problem is not going to go away,” Sekaran says.
Green city, thinning forests
Singapore is heating at twice the global average rate, due to a combination of global warming and the urban heat island effect — as concrete and glass trap heat and forests are lost to development.
Although the island is famous for its lush streetscapes and manicured gardens — 40% of its land area is covered by some form of greenery — only 16% is forested. Of that, just 0.3% is primary forest. The rest is secondary forest, which has grown back over abandoned kampongs and plantations but remains unprotected and vulnerable to clearance.
Under the government’s urban redevelopment master plan, an area of secondary forest larger than Singapore’s parks and nature reserves combined could disappear over the coming decade or so, mainly for public housing. Ecologists such as Emma Ramsay, an urban heating researcher at Nanyang Technological University, have warned that removing forests reduces the city’s natural cooling capacity and resilience against pest outbreaks.
The risks of Singapore’s pest control boom
Rising infestations are fueling the rapid growth of Singapore’s pest control industry. According to NEA data, there are now 439 licensed pest control firms — roughly one exterminator for every 1.6 square kilometers of the island, or 1.6 per square mile. The market is projected to nearly double in value by 2033, from $18.5 billion in 2025 to $36.6 billion, according to Deep Market Insights.
The industry has thrived under strict hygiene regulations, and a determined push to control vector-borne diseases like dengue, which are set to proliferate as the climate warms.
Regulatory pressure has created fertile ground for industry growth, says Victor Chan, general manager of EcoSpace Pest Management. Low barriers to entry — minimum education, training or startup costs are required, and a basic vector control course is all that’s needed to get certified — mean that firms can set up quickly.
But ecologists warn that the industry’s reliance on spraying chemicals carries risks for biodiversity. “The modus operandi is to go in and spray — which kills everything,” Anuj Jain, founder of biophilic design firm Biosea, tells Mongabay.
A 2023 study published in Proceedings of the National Academy of Sciences found that nearly half of Singapore’s butterfly species and two-fifths of its bees have gone extinct over the last two centuries, driven mainly by deforestation and land-use change. Jain, who co-authored the study, says the impact of insecticides on the city’s insect populations has yet to be researched, but almost certainly contributed to their decline.
Insecticidal fogging is routine across the island to combat dengue-carrying mosquitoes. While Singapore uses the biological agent Bacillus thuringiensis israelensis (Bti) to target mosquito larvae, the method also kills non-target insects such as bees and spiders, Jain says.
An alternative to pesticide use, Project Wolbachia, was launched in 2016. By releasing mosquitoes infected with a bacterium that prevents reproduction, the program aims to reduce populations of dengue-carrying Aedes aegypti mosquitoes. The initiative is set to expand across half the country in 2026. But Jain warns Wolbachia can spread to other insects, with potentially devastating consequences for native insect biodiversity.
“These interventions come at a big cost that no one talks about,” he says.
Expertise gaps
Singapore’s pest control industry boom has not only come at a cost to insect biodiversity. Numerous firms have been criticized for mishandling reticulated pythons (Malayopython reticulatus), whose numbers have been sustained by the growing population of rats, their preferred prey.
In November 2024, two uniformed men believed to be pest controllers set fire to a python trapped in machinery. In April 2025, another company drew condemnation after workers were filmed stomping on a python found in a drain.
Pest control companies are trying to capture a slice of the wildlife management pie by expanding beyond bug extermination, but many lack the skills to handle wild animals, says Joe Kam, founder of wildlife rescue group JKWildlife.
Animal welfare groups have also raised alarm over the widespread use of glue traps for rodent control. ACRES, a local NGO, receives about one call every other day about an animal ensnared in glue — often unintended species, from oriental-pied hornbills (Anthracoceros albirostris) and equatorial spitting cobras (Naja sumatrana) to common palm civets (Paradoxurus hermaphroditus) and stray kittens.
Of the 2,000 animals ACRES has rescued from glue traps between 2014 and 2023, one-quarter were protected species, and a quarter of the traps were laid by pest control firms, according to data from the group.
“Glue traps are still widely used in Singapore because they are effective, affordable, and provide a visible way to monitor rodent activity. However, I recognise the animal welfare concerns raised by ACRES,” Chan of EcoSpace wrote in a text message.
In May 2025, Singapore issued guidelines advising firms not to set glue traps outdoors, or to reduce their size and check them daily. But unlike the United Kingdom, New Zealand and parts of the United States, Singapore has not considered banning glue traps.
As climate change impacts intensify, experts say infestations may get worse, bringing about knock-on effects for biodiversity, public health and animal welfare.
While Singapore continues to market its “City in Nature” image to the world, ecologists warn that the city-state may pay the price for short-term fixes to warming-induced rat and bug problems as forests continue to make way for steel and concrete.
Banner image: The lime butterfly (Papilio demoleus malayanus), common in Singapore, is considered a pest as its caterpillars can defoliate and devour leaves of citrus trees and bushes. Image by Indrajit Das/Wikimedia Commons.
Citations:
Wu, Y. (2023). Study towards integrating secondary forests into future land use development in Singapore for biodiversity objectives. Sustainability, 15(4), 2916. doi:10.3390/su15042916
Chisholm, R. A., Kristensen, N. P., Rheindt, F. E., Chong, K. Y., Ascher, J. S., Lim, K. K., … Keita Sin, Y. K. (2023). Two centuries of biodiversity discovery and loss in Singapore. Proceedings of the National Academy of Sciences, 120(51), e2309034120. doi:10.1073/pnas.2309034120
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