Government Reforestation Efforts on Mahogany Plantations: Pushing Our Native Trees Toward Extinction

Originating from the Neotropics (southern Florida, the Carribean, Mexico and Central America), Mahogany, popularly known as either of the two, Big-leafed mahogany (Swietenia macrophylla) and the much smaller leaves as Mahogany (Swietenia mahogani) were introduced as early as 1907, then at Mt. Makiling forestry in 1913. Mahogany was one of the exotic species to be showcased by the government's reforestation projects in different parts of the country such as Ilocos Norte, Cagayan, Cebu, Bohol, Negros and Bukidnon. It is widely distributed throughout the archipelago that seedlings made its way to other places such as national parks and especially private lands.

I won't be surprised of this because DENR offices / nurseries throughout the country has been propagating mainly on exotic species which includes mahogany. I have even heard of a local telling me years ago (about 11yrs.) that the DENR officials in their area were telling them that if they planted mahogany in one hectare of land, they will be able to get an ROI (return of investment) of about 1 million pesos after several years until harvest time from the sale of the lumber of such trees. Who wouldn't be tempted to invest and embark on such ventures knowing that 1 million pesos is a great sum of money way back then.

Studies show that according to the FAO Corporate Document Repository entitled, The unwelcomed guests. Proceedings of the Asia-Pacific forest invasive species..... by N.T. Baguinon, M.O. Quimado and G.J. Francisco from the University of the Philippines, Los Banos that:

"Mahogany is successful at invading natural forests due to the following attributes of the species. The fruit of mahogany is a capsule and contains an average of 62 winged seeds (Anonymous, 1930). The number of seeds a mahogany mother tree can disperse is considerable. Assuming 50 capsules, 3000 seeds can be blown away from the mother tree. The seeds can be blown some 20 to 40 meters from the mother tree. The seeds, being recalcitrant, germinate in less than a month. Mahogany seeds contain food reserves and germinate hypogeal. This means that even if the initial light is relatively poor, the young mahogany plant develops even without initial photosynthesis. The first young leaves of mahogany are scale leaves and not green. True photosynthetic leaves come later and are adapted to sun-flecked shade and partial shade. Hardened mahogany seedlings can tolerate open fields as long as soil moisture is not limiting. The leaves of mahogany are rarely attacked by herbivores. Thus a mahogany plantation is like a "green desert" to wildlife. Dipterocarps fruit and seed irregularly in intervals of four to five years and therefore stand no chance competing with mahogany.

When mother trees shed their leaves during the months of February, they form a thick litter mat. Dry mahogany leaves are red and can be very rich in tannin. The leaves are intact during the whole length of the dry season. This litter mat could be one reason why very few seedlings are recruited under the mahogany plantation, including their own seedlings. Dispersed recalcitrant seeds rest on top of the litter mat instead of reaching the moist soil and hence die due to desiccation.

They may also be allelopathic (Thinley, 2002). Extracts from the leaves of mahogany were shown to retard the growth of narra (Pterocarpus indicus) test seedlings. Recruits increase away from the mahogany plantation and this increase is proportional to the competition offered by mahogany wildlings (Alvarez, 2001; Castillo, 2001). The importance of mahogany seedlings is negatively correlated with the Shannon-Weiner Diversity Indices of quadrats positioned from the mahogany plantation and away from it. In other words, diversity of the quadrats decreases as the importance of mahogany increases."

The disadvantages of introducing exotic species one after another is just being realized by our countrymen. Reverting the consequences of these actions may be too late because we might have damaged ecosystems that we have yet to discover. If only we learn to appreciate what we already have and tapping its full potential and managing it properly for future generations, then maybe we wouldn't be experiencing all these environmental problems that we are facing now.

Today, DENR's PAWB (Parks and Wildlife Bureau) is prohibiting such exotic species to be planted in the Integrated Protected Areas System (IPAS) within the Philippines. Defining such areas I have yet to see.

DISCLAIMER. I have posted this write-up about "Mahogany", which is an exotic and invasive tree species in order to further enlighten readers of its harmful effects and disadvantages towards our native Philippine flora. I am against planting and propagating this tree species, nor am I promoting it.