Reports indicate that a resident of Forbes Park in Manila once imported a pair of Finlayson's squirrels (Callosciurus finlaysoni) from abroad and kept them as pets. One day, the small creatures escaped from their cage and began roaming the village. Today, Forbes Park and neighboring areas are plagued by squirrels running through their enclaves. With no natural predators in the tropics, the squirrel population has exploded, reaching Bonifacio Global City, Makati City, Quezon City, and even Batangas, Cavite, and Rizal.
Environmental Impact of Invasive Species
The Department of Environment and Natural Resources classifies the Finlayson's squirrel as an invasive alien species that competes with local fauna for food and breeding spaces. These animals also raid bird nests, damage trees, and chew on electrical cables. The lesson is clear: we must be cautious when raising invasive alien fauna. Often, people bring them into the country without considering the consequences for the local environment. Imagine, for instance, if a flood overruns a household keeping piranhas as pets.
Alien Tree Species Also Pose Risks
The same issue applies to trees. On one occasion, a security guard warned me while I was trying to park beside the office building of the Department of Economy, Planning and Development (DEPDev) 7 at the Ecotech area in Lahug, Cebu City. Pointing to the tall mahogany (Swietenia macrophylla) trees lining the parking area, the guard cautioned that hard fruits hanging above could smash my windshield. I ended up parking on the roadside below the DEPDev building, amused that a planning office had planted such trees in its parking lot.
Mahogany trees are also a highlight of a man-made forest in Bilar, Bohol, enticing tourists to stop and take selfies by the roadside. They also line the center island of Patalinjug Avenue in Lapu-Lapu City, although these are trimmed regularly to prevent seasonal fruiting. While valued for their premium wood, fast-growing mahogany trees are environmentally invasive, pushing out native plants and reducing overall forest diversity. Sometimes marketed as herbal medicines, their seeds contain ingredients that can cause gallstones and have mutagenic effects.
Gmelina Trees and Biodiversity Loss
Many more alien tree species are invading green spaces, outcompeting native hardwood varieties that take longer to grow. Gmelina trees (Gmelina arborea), originally from India and Myanmar, are widely popular in the Philippines as a fast-growing timber source. In the 1980s, these were cultivated in Negros Oriental as part of the government-run Central Visayas Rural Projects. In less than 10 years, many people in the area grew wealthy from harvesting the timber. However, nothing else grew under the trees. It was further observed that local birds left the area, along with insects that serve as pollinators, an essential element in the food production chain.
In fairness, there are gmelina species native to the country. Commonly called Parrot's Peak and Dadiangas, they are not highly invasive and do not smother indigenous vegetation. The native varieties also do not alter local soil properties or threaten local biodiversity.
Philippine Environment Month
June is officially celebrated as Philippine Environment Month, established by Proclamation 237, signed by the late President Cory Aquino in 1988. When planting trees or joining environmental activities, we must remember that alien species of flora and fauna must be strictly regulated due to their impact on native biodiversity, as called for by Republic Act 9147, or the Wildlife Resources and Protection Act.
