environmental issues

[OPINION] Choose native trees over exotics for climate resilience and biodiversity conservation

Celine Murillo
[OPINION] Choose native trees over exotics for climate resilience and biodiversity conservation
'Despite its limitations, planting trees is a climate solution. The key to maximizing its impact is planting the right trees in the right place in the right way.'

The following is in response to an earlier Voices piece, “Small is beautiful: Ipil-ipil for a climate-challenged Philippines.”

Cruise along Sayre Highway across Bukidnon, and globs of reds will regularly interrupt the smudge of roadside greens: African Tulip (Spathodea campanulata) with its claw-like flowers.

This eye-catching tree, exotic and invasive, with a reputation for being a bee-killer, is widely cultivated here. It’s as prolific here as Golden Trumpet (Handroanthus chrysotrichus), a flowering tree, also exotic, that pops up in every town – notably in the capital Malaybalay where it is a focal piece in the city plaza.

This seeming preference for exotics is frustrating, especially with Bukidnon being home to some of the last old-growth forests of Mindanao.

Forests are good sources of seeds, particularly seeds of native species.

TAKE COVER. The underside of a Bangkal tree (Nauclea orientalis), one of the native species recommended by the DENR for streambank stabilzation. Photo by Celine Murillo
An epidemic of exotics

A species is native when it naturally occurs or originates in a place. For example, our national tree Narra (Pterocarpus indicus) is a native species. It has been found growing in very old forests, devoid of human interventions, in the Philippines.

Meanwhile, exotic species are anything that does not originally occur in a place. Anything that is brought from one place to another is an exotic even if it has been hundreds of years since it got there. One example is the ubiquitous Acacia (Samanea saman). Despite it being common, it is not native to the Philippines. This tree was introduced to the country during the American colonization.

Exotic species have a tendency to become invasive, taking over a habitat by hogging all the resources and outcompeting the locals. They can also bring in parasites and diseases, making local wildlife vulnerable to habitat loss or – worse – extinction. These are some of the reasons why many environmental and civic groups advocate for planting native trees.

Despite this, exotics like mahogany (Swietenia macrophylla) and gmelina (Gmelina arborea) continue to be in the limelight for being “fast-growing,” easy to maintain, having economic value, and – in the case of African Tulip and Golden Trumpet – having showy, attractive flowers.

Just recently, an opinion piece on this website encouraged the planting of Ipil-ipil (Leucaena leucocephala) in denuded slopes. It makes its case by noting the tree’s deep root system and ability to thrive in poor soil conditions.

While these characteristics are indeed ideal to stabilize landslide-prone areas, Ipil-ipil is an exotic species introduced by the Spaniards. It is cited by no other than the Department of Environment and Natural Resources as bio-invasive. Along with African Tulip, it is also listed as one of the 100 worst invasive species by the IUCN Species Survival Commission. When left to their own devices, Ipil-ipil forms pure stands that are difficult to eradicate, making land virtually unusable. And while it has economic and ecological value for being a source of firewood, cattle fodder, and fertilizer as well as containing high levels of nitrogen that “fixes” the soil, it puts our local biodiversity at great risk.

See, native trees have an intricate relationship with the land. They support other wildlife and are adapted to local environmental conditions. Preferring or replacing them with exotic species will break this relationship and will result in a whole host of other problems.

The good news is, there are many native trees that possess Ipil-ipil’s (and other exotics’) lauded properties.

TOWERING. Dao (Dracontomelon dao) is fast-growing. Its timber is also valuable. Photo by Celine Murillo

Bani (Pongamia pinnata), for example, can thrive in different soil conditions – even lahar – and can tolerate long dry spells. It has thick and deep roots, and is also nitrogen-rich, which means it can help “fix” the soil. Its leaves can also be made into “green mulch” for fertilizer. Additionally, Bani produces an oil with antiseptic and stimulant healing properties for skin diseases, scabies, sores, and herpes. It also has clusters of tiny, beautiful, fragrant flowers.

There is also the native Ipil (Instia bijuga) whose only disadvantage against the exotic Ipil-ipil is that it’s not as fast-growing. However, it is suitable for erosion control, especially along waterways and creeks, and has a high tolerance to wind damage and salt. Its delicate flowers also attract bees and other pollinators.

Indigenous solutions

Even after mentioning the perils of “mono-culture” (that is, planting just one species of tree or plant), saying that, in order for “plantations” to be healthy and self-sustaining, it must mimic natural forests that have “complex, balanced communities of plants, animals, and fungae,” the aforementioned opinion piece goes and suggests planting Ipil-ipil in 100-hectare plots!

The best way to go about any attempts at environmental rehabilitation is to first do a species-site matching. This is an important step that determines which species are suitable to a location, assessing properties, endemicity (whether native or exotic), growth rate, variety, and other requirements. If the goal is to prevent erosion and fix the soil while being as low maintenance as possible, a mixture of native species like Bani, Banaba (Lagerstroemia speciosa), Narra, Batino (Alstonia macrophylla), Tindalo (Afzelia rhomboidea), and Dao (Dracontomelon dao), among others, can be considered. These trees offer one or two, if not all, of the desired benefits, with the added advantage of supporting local wildlife like birds and insects, and having higher chances of surviving and mitigating the Philippines’ worsening climate.

VIBRANT. Aside from having a dense and deep root system making it suitable for erosion control, Banaba (Lagerstroemia speciosa) also has beautiful flower. Photo by Celine Murillo

Which brings us to trees as a climate solution. Despite its limitations, planting trees is a climate solution. The key to maximizing its impact is planting the right trees in the right place in the right way. The right trees are always native trees.

There are many individuals and organizations who are already doing this in the real world, offering proofs of concept of how planting native trees, when done right, is far more superior than planting exotics in all aspects across the board. There’s Daang Kalikasan in Pangasinan, the Nabunturan Native Tree Enthusiasts Arboretum in Davao de Oro, and the LGU-led Green Wall of Alcala project in Cagayan. Even here in Bukidnon, there are groups who are doing the work of cultivating more native trees. Malaybalay’s city government has also started consulting the same groups to temper the exotic epidemic here. Join the Philippine Native Trees Enthusiasts Facebook group and you’ll find many other real-world examples. (You may also find sources of native tree seedlings there.)

Speaking of climate solutions, the Ipil-ipil opinion piece also talks about the tree’s use in Dendro Thermal Plants during the time of Marcos Sr. The piece toys with the possibility of reviving this project for its potential in lessening the Philippines’ dependence on fossil fuel.

There is absolutely no doubt that, in order to get us off the brink of social and biological collapse, the most pressing climate action that we must take is to move away from fossil fuel. However, promoting a “solution” that could potentially lead to ecological suicide is dangerous and irresponsible, especially when we are facing species extinction left and right. Plus, there are more viable alternatives for biomass – rice husks, for one – but that’s another story.

We can let our ancestors and predecessors off the hook for giving exotics a pass in the past. The science was lacking back then. But now that there is ample information – studies conducted both by international and our own government and educational institutions, as well as many existing real-world applications – pointing to its detrimental effects, it is our responsibility to update our opinions and align it to the most holistic and most compassionate approach to a solution.

After all, humankind is not separate from nature. We, too, have a relationship with the land and our native species. If we are to thrive, we must ensure that they thrive as well. – Rappler.com

Celine Murillo is a conservation storyteller combining poetry, photos, film, and community to tell stories of wildlife, wild places, and the intertwining of nature and culture. She is a Young ASEAN Storyteller under the ASEAN Youth Biodiversity Programme of the ASEAN Centre for Biodiversity, and a 2022 fellow at Climate Tracker’s Digital Hub for Content Creators. 

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