DIVERSITY DEFICIT: Iloilo City Urged to Plant More Native Trees in Plazas

By Rjay Zuriaga Castor

A study by the University of the Philippines Visayas recommends that the Iloilo City government increase the planting of native tree species in public plazas to enhance urban biodiversity and reflect the region’s natural ecosystems.

Presented during BIO-ILOILO 2025, the city’s first urban biodiversity symposium organized by UPV, City Environment Office and the Department of Environment and Natural Resources (DENR), biologist Dr. Resurreccion Sadaba stressed the ecological and cultural importance of planting native trees, particularly in Arevalo and La Paz Plazas.

He warned that the dominance of non-native species poses ecological risks and weakens the resilience of urban green spaces.

The study, co-authored by Sadaba with Logroño, assessed biodiversity and carbon storage in tree communities across seven city plazas, revealing a “moderate” urban biodiversity level.

“The urban biodiversity is moderate. It’s not that poor or low […] More than half of our plants in our plaza are not native,” Sadaba said.

The study documented 183 plant species from 69 families, with the legume family (Fabaceae) being the most prevalent due to its roles in nitrogen fixation, soil erosion control, and biodiversity support, alongside its cultural and culinary value.

However, only 34% of the species were native, with the remainder comprising invasive (4%), naturalized (25%), cultivated (20%), non-native (15%), and cryptogenic (2%) species.

Of the 94 tree species identified, 43 were native, while 50 were non-native.

The study found that Arevalo Plaza had the highest proportion of native trees at 38% and was identified as a biodiversity hotspot.

La Paz Plaza, while hosting fewer native species, was notable for an endemic species unique to the area.

In contrast, Mandurriao and Jaro Plazas had more naturalized than native trees, while Bo. Obrero showed high species density but few native trees.

Plaza Libertad, despite its small size, maintained a respectable proportion of native species.

Sadaba highlighted that high tree density in Arevalo and La Paz improves air quality and cools the microclimate, enhancing urban livability.

He encouraged other districts to follow Arevalo’s example to improve urban ecological balance.

He noted that high tree density in Arevalo and La Paz enhances air purification and cooling, improving the microclimate in those areas.

However, he cautioned that the dominance of single tree species, such as mahogany, can suppress native tree growth and reduce overall biodiversity.

Sadaba called for a balance between native and non-native species in urban planting.

“We must balance native and non-native species through selective management, gradually replacing invasives,” he said.

To sustain ecological benefits, Sadaba urged the city to regularly monitor tree density and carbon stocks while prioritizing native species in future plantings.

He pointed to Arevalo’s replanting success as a model for other districts to follow, fostering a healthier, more resilient urban environment for Iloilo City.