DENR studies show roadside trees in urban centers alleviate airpollution

By all means, save every tree in the city.

They protect you from the ubiquitous air pollutants that abound in urban centers. Without the vegetation, those pollutants would go to your lungs and give you all sorts of ailments. Also, trees ameliorate air temperature, filter light radiation, and reduce dust pollution.

These surfaced in studies done by the Department of Environment and Natural Resources (DENR) in two urban centers -- Metro Cebu and Metro Manila.

In an 11-month study done in Cebu, eight tree species (raintree or acacia, rubber, banaba, Manila palm, talisay, macopa, mango, and ipil-ipil) reduced air temperature from a maximum of 1.6 degrees Celsius to a minimum of 1.1 degrees centigrade

Researchers J. Sumabon and C. Tura of the DENR-Ecosystems Research and Development Service (ERDS) in Central Visayas also observed that gmelina, talisay, rubber, macopa, duhat, raintree, narra, mahogany, jackfruit, and Japanese acacia filtered light radiation with 5,000 to 6,000 lux radiation in light intensity. (Lux is a unit of illumination on a surface that is everywhere one meter from a uniform point source of one candle intensity or equal to one lumen per square meter.)

In their joint DENR-funded research entitled "Biophysical assessment of tree species in the urban centers of Cebu," which was monitored by the Los Baños-based Philippine Council for Agriculture, Forestry and Natural Resources Research and Development (PCARRD), Sumabon and Tura reported:

"Based on statistical analysis, leaf area played a significant role in the amount of dust collected or trapped on the leaves. The bigger the area, the higher the capacity for dust particles to be trapped."

They further noted that presence of hair-like appendages or trichomes and the rough surface of leaves increased the dust-holding capacity and capability of leaves as compared to those with smooth surfaces.

Metro Manilans also benefit from the presence of trees in the metropolis as these are efficient absorbers of toxic compounds emitted by vehicles.

Attesting to this are two studies done by researchers of the DENR National Capital Region (NCR).

One study, entitled "Pollution uptake of Acacia mangium and Acacia airiculiformis in the National Capital Region," was conducted by I.V. Rammalosa, B. Castro, G. Pastofide, E. Agbay, E. Amor, and M.A. Epan, Jr. The other, "Survey and characterization of selected urban parks in NCR," was done by M. Uriarte.

In the NCR studies, the researchers collected leaves of A. mangium and A. auriculiformis along highways and busy intersections and compared them with those collected from trees at the UP Los Baños and at the La Mesa dam watershed in Novaliches, Quezon City.

The researchers noted high levels of lead in the leaves of the two tree species at EDSA corner Ayala Avenue and South Supermarket corner Gil Puyat, both in Makati City; EDSA Cubao and Visayas Avenue, both in Quezon City; and on R. Papa corner Rizal Avenue in Caloocan City.

"These were places where most jeepneys, vans, taxicabs, and cars using leaded gasoline pass by," the DENR-NCR team reported.

High sulfur dioxide levels were also observed in the leaves of the two acacia species found at Claro M. Recto corner Evangelista in Quiapo, Lerma corner España in Sampaloc, and Roxas Boulevard in front of the Manila Hotel, all in Manila; and on Wacat street corner A. Bonifacio in Caloocan City.

Vehicles that frequently pass these areas are jeepneys, buses, and taxicabs that use diesel-fuel and emit highly visible black smoke containing gaseous wastes of sulfur dioxide, the DENR team noted.

They averred that A. mangium and A. auriculiformis were efficient absorbers of sulfur dioxide and lead.

The other DENR-NCR study surveyed and characterized 12 national urban forest parks in Metro Manila. The most common tree species in the study were acacia, narra, mahogany, giant ipil-ipil, and talisay.

Fruit trees such as tamarind, mango, santol, duhat, and datiles also abound. Bunga de China, a palm, was present in 10 of the 12 urban parks.

The leaves of the trees in the park are discolored, evidence of the effect of pollution on the foliage, Uriarte pointed out.