Having trees is not enough. Metro Manila needs closed canopy forest in its watershed to slow floods, expert says.

The presence of trees in the watershed above Metro Manila is not sufficient to significantly slow floodwater from reaching the capital region, Forest Management Bureau (FMB) Assistant Director Ray Thomas Kabigting said Friday.

What is needed is closed canopy forest, where trees are dense enough to form a continuous overhead cover that intercepts rainfall and slows its flow downward, he said.

Kabigting made the statement in an interview on DZRH News program The Situation Report on September 11, debunking a common misconception about the relationship between forest cover and flood mitigation in the Upper Marikina watershed.

The FMB official said the Philippines defines forest as any half-hectare area where at least 10% of the land is covered by trees five meters or taller, meaning that even a relatively sparse collection of trees qualifies as forest under the legal definition but does not provide the flood mitigation benefits that a dense, closed canopy forest would.

“Ang gusto po naming ipaalam sa mga kababayan natin na ang koleksyon po ng puno kahit hindi sila dikit-dikit at hindi po nagki-create nung canopy cover kung tawagin, na sarado po at madilim ang ilalim, hindi po ibig sabihin hindi na siya gubat. Ang ayaw po natin is yung wala talagang laman,” Kabigting said.

Kabigting said the Upper Marikina protected landscape is recovering its forest cover, and the area technically has forest by legal definition, but much of it is open forest where the canopy is not dense enough to meaningfully slow the impact of rainfall on the ground below.

“Okay pa kayo, may gubat pa kayo, pero ba’t kami binabaha? Dahil po yung tubig ulan mula sa taas kapag ibinagsak mo dire-diretso siya, at biglang may madadaanang kalsada na yung surface run-off po niya o yung pagdaloy po ng tubig over sa isang surface ay dire-diretso. Hindi po nababawasan,” Kabigting said.

The FMB official said what closed canopy forest does is intercept rainfall at the level of the tree canopy, slowing its descent and allowing soil to absorb more water gradually rather than having it rush immediately down slopes and into river channels.

“Ang gusto natin diyan ay closed canopy yung gubat mo, dahil doon ang nakakatulong para mabawasan ang impact o yung lakas ng pagbagsak ng tubig mula sa taas pababa para hindi dumaloy ng mabilis,” Kabigting said.

He said the continuous dependence of communities on natural resources, both regulated and unregulated, is one of the most persistent drivers of deforestation, because families that rely on forest land for farming, livestock, and shelter cannot be expected to stop simply because the government says so without viable alternatives.

“Katulad na lang po sa Upper Marikina, marami po diyang mga formal and informal settlers na kailangan po ng sasakahan, kailangan po ng tatayuan ng kanilang mga maliliit na bukirin at pangangalaga po ng mga hayop nila. Ang pamilya po ay lumalaki so lumalaki rin po ang kubo. Meron po tayong mga ganung factors na nagko-contribute po sa constant deforestation,” Kabigting said.

Kabigting said the encouraging reality for the Philippines is that it is a tropical country with rapid natural forest regeneration, and that if unsustainable activities are stopped and communities are given alternatives, the forest can recover on its own at a meaningful rate.

“Ang regeneration po natin naturally or by nature po, kung wala po tayong gagawing unsustainable activities, ay mabilis ho. Kaya po for example sa Quirino, sa Isabela, sa Mindanao, kahit po hayaan ninyo ang gubat na naputulan, hayaan niyo lang ho, wala pong gagawin, tutubo ho mag-isa yan,” Kabigting said.