There’s a picturesque road in Bohol, an island province in the Philippines, that’s famous for the lush green trees lining the two-kilometer route through a dense forest.
This scenic spot is a must-see attraction for tourists, along with the famous Chocolate Hills, which are home to the endemic Philippine tarsier.
Driving along this road feels like a royal welcome from nature, with the arch of canopies overhead and the asphalt splashed with sunlight peeking through the crown spaces.
If you stopped by to take some photos, you’d agree that the temperature in the area feels noticeably cooler – thanks in no small part to the trees.
But while the forest feels undeniably serene, a deafening silence belies its enchantment: chirping birds and insects are nowhere to be heard or found.
This quaint road weaves through a reforested area called the Bilar Man-Made Forest – a reforestation project launched in the 1950s that aimed to revive the land denuded by illegal slash and burn or kaingin in the Loboc watershed.
The approximately 20,000 hectares of land were reforested with thousands of mahogany trees (Swietenia macrophylla), which is why it’s also named the Bohol Mahogany Forest.
More than half a century later, the once ash-covered land has survived and been regreened with vegetation, but the mahogany trees, which are a non-native species in the Philippines, have killed the local biodiversity.
And yet, mahogany continues to be the species of choice for reforestation projects in the country.
We already know about the threats posed by this tree and other invasive non-native species to the ecosystem. So, why does the planting of non-native trees remain the norm – and how can we ensure that future reforestation efforts prioritize native species instead?
Mahogany was first introduced to the Philippines in 1907 by Tropical America for reforestation due to its rapid growth and ability to tolerate environmental stresses.
However, the use of mahogany to restore forests has long been frowned upon, as research shows this non-native species is invasive. While not all non-native species are harmful, mahogany has an allelopathic effect on the environment, meaning it produces chemicals that inhibit the growth of surrounding vegetation.
What’s even more alarming is that this species has detrimental effects on native Philippine tree species, including the country’s national tree, narra (Pterocarpus indicus).
So, why is the Philippines continuing to plant non-native species like mahogany?
According to the Forest Foundation Philippines, past reforestation efforts were mostly led by the private sector and aimed to establish plantations for lumber production and harvesting rather than for environmental conservation.
Since most non-native species grow quickly, they can be used to speed up reforestation. These species have become valuable economic assets, turning large-scale plantations into profitable business ventures.
In 2013, mahogany contributed significantly to the Philippines’ gross value added, amounting to PHP 2.13 billion (USD 36.4 million).
While mahogany plantations bring in revenue, they also cast a shadow on the ecological landscape.
“Mahogany is a good lumber, but the problem with mahogany is that when you use it in reforestation, it will colonize the area because it grows so fast that it will dominate the local species,” says Basil Castaño, a farmer, environmentalist and administrator of the Philippine Native Tree Enthusiasts (PNTE).
Founded in 2013, PNTE is an environmental civic group that aims to bring together people with a passion for the promotion, propagation and protection of the country’s local flora, which are often overlooked in favor of more popular exotic species.
Though Castaño believes that not all exotic species thriving in the country cause harm to the ecosystems, he emphasizes that mahogany planting should be regulated.
After all, Castaño points out, trees multiply exponentially: in just one season, thousands of seeds can disperse from a single tree into the surrounding environment. Within a mere 30 years – a blink of an eye in forest terms – it can dominate the entire landscape.
In the 1980s, the government carried out several reforestation projects using non-native trees. This caused much of the native flora and fauna to die out, recalls Celso Salazar, president of the Pangasinan Native Tree Enthusiasts (PangNTE), one of PNTE’s regional sub-groups.
“What is left now are exotics like acacia because they grew fast, but for all you know, they destroyed the biodiversity,” Salazar says.
The silent, man-made mahogany forest in Bilar illustrates how the introduction of an invasive species can also impact native fauna. Local birds and insects do not recognize their fruits and canopies as edible or suitable habitats.
As another example, the African tulip tree (Spathodea campanulata), which originated in West Africa and has been introduced throughout the tropics, is now widespread across the Philippines. With their striking, fiery orange blooms, they have become popular as accents in both commercial and residential landscape designs.
A recent study found this species disrupting the habitats and food sources of native bees, with potentially far-reaching consequences for the pollination of native plants.
In other words, if we fail to manage the growth of invasive exotic species, we will see the extinction of native flora and fauna.
Many environmentalists say reforestation efforts should instead focus on the usage of native trees that have thrived in the land since time immemorial.
“We are planting native trees there so that we can bring back the biodiversity,” says Castaño.
Tree planting is one of the most popular conservation activities in the Philippines, especially on Arbor Day, an annual event encouraging the planting of endemic or indigenous species, particularly in protected areas.
However, for many years, mahogany has been the go-to species for tree planting projects due to its popularity and relatively low cost.
“It’s the supply and demand dynamics of the market,” says Castaño. “Mahogany is more popular – that’s why there are many seedlings available, some of which you can get for as low as five pesos [USD 0.09] apiece.”
“If you ask about narra or molave, sellers have a [misconception] that they won’t grow as fast, discouraging many from choosing native species.”
Native trees are also prized for lumber production due to their high-quality wood. However, most indigenous species, such as narra, are protected by law, which prohibits their harvest. This further pushes the market toward more readily available and less regulated species like mahogany.
Sadly, native tree seedlings are still not as mainstream as their non-native counterparts. “Some people think that mahogany is our native tree,” Salazar said.
Narra, one of the native tree species PNTE recommends for reforestation, is being exploited by middlemen who inflate its prices. As narra seedlings gain popularity, many sellers are capitalizing on growing demand.
This creates a false impression of limited supply, which isn’t all true: there are plenty of native trees available all across the country.
Salazar recalls that when PangNTE was officially registered as a civic environmental organization, it acquired a 20-hectare plot of land, where it has been growing 1,000 native trees.
Meanwhile, in the town of Natividad, the Victor O. Ramos Arboretum, one of the largest arboretums in the country, hosts over 305 Philippine native tree species.
For PNTE, community involvement is a key aspect of reforestation and conservation. Given that ecosystems encompass both environmental elements and human interactions, it’s crucial to focus on their stewardship.
The group has been particularly advocating tree growing to communities. Tree planting, for Castaño, is “just 10 percent of the deal. The number one important thing is tree growing – planting the correct species at the right place at the right time.”
In recent years, conversations around reforestation have gained momentum as more people have become aware of the long-term negative impacts of invasive non-native trees on biodiversity. And yet, despite knowing the risks, they continue to plant them, often for their perceived economic benefits.
Inez Ponce de Leon, a scientist and expert in risk and science communication, believes non-native tree planters are just a small part of a larger system that supports and promotes the growth of non-native species because there is an existing and thriving market.
“People will trust science, but at the end of the day, science is not going to feed them,” says Ponce de Leon. “What feeds them is a system, and you cannot punish the people that are oppressed by that system because there’s a system above them.”
Castaño says PNTE has been engaging with communities for years, encouraging them to exclusively plant native trees, and regularly communicating with the government, lobbying for policy recommendations to plant native trees in public lands and national parks.
But these efforts are often disrupted by changes in authority. For instance, when a new environment secretary or town mayor takes office, the dynamics between the community and officials shift, changing the decision-making process.
Ponce de Leon believes this goes down to one critical issue: trust.
In one of her studies on disaster risk communication and community response, she found that people don’t care about leadership change if it happens far away from them.
This means even when science speaks abundantly about the disadvantages of non-native species, trusted local figures can influence communities to continue these practices.
“We are a very close network of people. We trust people close to us. But when you use that reasoning, you also assume you do not trust people far away from you. That’s not it: they trust people far away from them, but they will listen to people close to them.”
“You have to know the community first for its merits rather than for what you want to do,” she adds.
Castaño believes that Philippine forestry laws are well written, but there are still gaps in the legislation and challenges in implementation. For instance, while there are already laws that protect native trees, which people follow, there’s a lack of strict rules related to the planting of invasive species.
He also suggests that penalties should be enforced – not necessarily for planting the wrong tree species, but for deliberately destroying a forest: “there should be stricter policies for environmental protection.”
Meanwhile, Ponce de Leon believes that for people to obey the law, it’s important to create an enabling environment, which may include changing the market dynamics to favor native species or incentivizing the planting of native trees.
And while these measures work, she says that a broader systemic approach is needed.
“There are greater changes that have to be made at a macro level in order to enable micro changes to happen. You can’t just impose on people to plant because you love the environment – that’s nice but it’s a luxury.
“We can’t expect people to obey an abstract notion when they have real concerns.”
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