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Along Urban National Streets and Roads in Cebu City, Philippines

Kristine Mae L. Jumonong1, Angela C.

Barliso1, Mariejayn C. Lempio1, Henry Clint D. Ricaborda1, Jake Joshua C.

Garces1 and Jay P. Picardal1,2*

1Biology Department, College of Arts and Sciences, Cebu Normal University, Osmeña Boulevard, Cebu City, Philippines 6000

2 Research Institute of Tropical Biology and Pharmacological Biotechnology, Cebu Normal University, Osmeña Boulevard, Cebu City, Philippines 6000

In urban landscapes, understanding the diversity of roadside vegetation is essential for better planning and designing of sustainable cities.

The city of Cebu, located in central Visayas Philippines, is considered an urban tree biodiversity hotspot due to threats from continuous infrastructure development, road widening, and anthropogenic activities.

To provide an update on tree diversity, as well as to determine the ecological status of the remaining trees thriving in Cebu City’s urban corridors, a floristic inventory and tree distribution survey (i.e. five national streets /roads) were conducted. Following a standard protocol for urban tree inventory, a tree distribution map was created using GIS, and information on urban corridors’ name, BDH of each tree, wire conflict, and tree condition were provided. Data showed 2,203 trees (45 genera and 27 families) were listed from these roadsides, with the proportion of alien trees higher (84.75%) than native trees (15.25%).

Among these trees, 12.94% were in excellent tree condition, with narra (Pterocarpus indicus) and Manila palm (Adonidia merrillii) as the most abundant native tree, and mahogany (S. macrophylla) as the most exotic species. The distribution of trees by DBH classes along the five national roads showed that most trees belonged to the range of

≥ 70 cm, suggesting that mature trees dominated five urban corridors.

In terms of tree protection and management, most trees in Cebu City were recommended for silvicultural treatment to salvage mother trees from further damage. Baseline data gathered in this study may serve as

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guide for urban planners for a responsible and sustainable urban tree conservation and management.

Keywords: floristic inventory; urban trees; alien trees; native trees;

Cebu City

INTRODUCTION

C

ultivation and conservation of urban trees is a global initiative (Pearlmutter et al., 2017). All over the world, major cities acknowledge that they are at the forefront of battle against climate change – as the most vulnerable area to feel its impact, but with the highest potential to mitigate its effect. Recent call from the United Nations’ Sustainable Development Goals [UN-SDG] Partnership Platform invites all mayors of major urban metropolis to undertake a “Trees in Cities Challenge,” whereby pledges on planting specific number of trees are recorded under a defined monitoring scheme (UN-SDG, 2019). This program has been instrumental in helping cities to attain most of the sustainable development goals established by the United Nations (Turner-Skoff & Cavender, 2019), particularly SDG 11 focusing on sustainable cities and communities (UN, 2015). In the Philippines, similar initiatives have already been implemented across regional scales since the start of the National Greening Program in 2011. These initiatives encouraged communities to establish and manage arboretum of trees, including those in highly-urbanized areas (DENR-FMB, 2015).

Urban trees comprise the most essential component of urban greenspaces (Wolf et al., 2020) where they are commonly distributed across public domains (e.g. national highways, parks, recreation areas and riverbanks) (Konijnendijk et al., 2006) and private properties (e.g., schools, residential areas, gardens and industrial zones) (Tyrväinen et al., 2005). Aside from shrubs and underground vegetation, trees in cities provide an array of benefits and various forms of ecosystem services to make cities livable to humans and other life forms. While various species of trees ensure that watersheds can provide a steady supply of fresh water for domestic and industrial use, prevent flooding, and cool the air, they also provide socio-economic, psychological, visual, and sensory benefits as well as symbolic functions valued by humans (Dwyer et al.,1992; Good, 2010). Most importantly, they provide habitat for urban wildlife, thus ensuring a relatively diverse ecosystem (Roy et al., 2012). However, various

J.J.C. GARCES, J.P. PICARDAL 51 anthropogenic activities in major cities have been noted to cause decrease of tree covers (Ejares et al., 2016), and as tree cover deteriorates in cities, so will the availability and access to associated ecosystem services, thereby affecting environmental quality and human health. Thus, it is imperative that current tree diversity status in major Philippine cities be assessed to address this urgent concern.

Cebu City is one of the six congested and polluted cities in the Philippines. In 2010, 93.5% of Cebu City’s total population lived in urban barangays, and these were localities where infrastructure development have increased rapidly in the last few years. Despite massive industrial developments, patches of tree vegetation still thrive in Cebu City where they are scattered among parks and recreation areas, building structures, street lanes and residential spaces (Flores et al., 2020). Cebu City is also home to an immense number of endemic trees that are considered indispensable for maintaining urban biodiversity (Cebu Biodiversity Conservation Programme [CBCP], 2017). As of 2014, trees in Cebu City were reported to cover an area of 15,674,341.8 m2, or 25.11% of the city’s urban barangays, citing Brgy. Talamban (37.95%), Lahug (31.29%) and Guadalupe (25.70%) to have the three highest percentage of tree cover among the lowland barangays (Ejares et al., 2016). However, current knowledge on the diversity of trees in the city is scant, and previous studies on Cebu city trees focused only on carbon sequestration (Pansit, 2019; Parilla et al., 2018) and tree canopy mapping using LiDAR (Ejares et al., 2016).

There is a need to assess whatever remaining old-age trees flourishing in Cebu City because the greatest challenge now is to focus on managing urban ecosystems, which may include direct and indirect ecosystem services that urban dwellers can avail freely. Trees located along the urban corridors such as street roads and highways are an important component of urban greening because the combined area is much larger than the green spaces and formal parks alone (Shackleton, 2016). It has also been noted that trees in urban areas are rarely monitored, are disappearing at alarming rates, and are not documented sufficiently (Babalola et al., 2013). Except for the inventory of trees to be cut down for Bus Rapid Transit (BRT) and other road widening projects, few tree inventories have been undertaken in Cebu City to date.

This study reports the current list of remaining trees on the selected urban corridors (national streets/roads) in Cebu City. A distribution map of each

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tree located along the selected urban corridors was also produced to show how each tree in the selected urban corridors of Cebu City is distributed, highlighting its abundance, conservation status, and tree condition. Wire conflict, tree protection initiatives, and tree management were also discussed.

MATERIALS AND METHODS Site Identification

The study was conducted in five selected urban corridors (national streets/

roads) that were densely populated by trees based on the researchers’ ranking of national streets/roads in Cebu City with their respective existing length:

(1) N. Bacalso Avenue: 2.472 km - (10.288838 and 123.866707 E), (2) Cebu South Road (C. Padilla-Bulacao) : 2.550 km - (10.279706 N and 123.855548 E), (3) Osmeña Boulevard: 2.035 km - (10.304312 N and 123.895168 E), (4) Rama V. Street: 3.050 km - ( 10.312346 N and 123.886167 E), and (5) Salinas Drive: 0.896 km - (10.312346 N and 123.886167 E).

Figure 1. Map of Cebu City (first box figure) and map of the selected national streets/roads, namely: (1) N. Bacalso Avenue, (2) Cebu South Road (C. Padilla- Bulacao), (3) Osmeña Boulevard, (4) Rama V. Street and (5) Salinas Drive

J.J.C. GARCES, J.P. PICARDAL 53

Data Collection and Analysis

The method for roadside tree inventory and tree risk assessment was based on the study of Sreetheran et al. (2011). The inventory was conducted from October 2018 to April 2019, following a descriptive survey design. Roadside trees were selected through purposive sampling, making sure that both sapling and mature trees were included in the inventory. Mapping of tree distribution was produced by using the handheld GPS, where the coordinates were inputted to a GIS-based software (Manifold System).

Data were collected as follows. Once a tree is encountered along the selected urban corridor, the following information were noted: GPS coordinates, local name/common name, diameter at breast height, wire conflict (e.g., presence and absence of overhead utility wires), characteristic vegetation and tree condition. Characteristic vegetation may either belong to (a) residential gardens, (b) grassland, (c) scrubland, (d) plaza/park area, or (e) near buildings such as schools, business edifices, residential houses, and churches. Meanwhile, tree condition was derived from a general observation from ground level up, and was rated either as excellent, good, fair, poor or very poor, following the criteria of Sreetheran et al. (2011). ‘Excellent’

trees are characterized by sound and solid tree structure and composition, absence of pests, and full and balanced crown development. ‘Good’ and

‘Fair’ trees, however, can be distinguished, by their missing bark sections one major/several dead, broken, or missing minor limbs, in terms of tree structure; presence of one or more pests, in terms of tree condition; and full but unbalanced crown development. ‘Poor’ and ‘Very Poor’ trees can be recognized by either an extensive decay or hollowness in terms of tree condition; two or more dead, broken, or missing major limbs, in terms of tree structure; presence of two or more pests; and full but unbalanced crown development. The conservation status of each tree species was determined based on International Union for the Conservation of Nature (IUCN) guidelines (“The IUCN Red,” 2021) .

Taxonomic identification of trees was done by utilizing primary reference materials for native trees, namely, Philippine Native Trees: Up Close and Personal Series 101, 202 and 303 published by Green Convergence for Safe Food Healthy Environment and Sustainable and Hortica Filipina Foundation, Inc. Philippines. Verification of exotic trees’ ID was done using

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Plants of the World Online (POWO), an online database maintained by the Royal Botanic Gardens, Kew, Richmond, UK as well as Co’s Digital Flora of the Philippines. Photos of each tree encountered were also taken, including the most essential parts such as leaves, trunk, whole stature of trees, flowers and fruits, if present. Initial identification suggested by parataxonomists and gardeners were also noted, especially for those trees that were not recognize on the spot. Data were collated, cleaned, and analyzed using descriptive statistics, such as means and frequency function of MS Excel.

RESULTS AND DISCUSSION Tree Composition

A total of 2,203 trees with 50 species under 45 genera from 27 families were encountered in the five selected national roads in Cebu City (see Table 1).

Natalio Bacalso National Road had the highest number of trees (654 trees) followed by Cebu South Road (591 trees), Osmeña Boulevard (583 trees), Vicente Rama national road (315 trees) and Salinas Drive (131 trees) (see

Figure 2). N. Bacalso had the most diverse tree composition with 35 genera (Fig.3), and this is reflected in the distribution pattern observed in the data of N. Bacalso Road (see Figure.4). Considering that Vicente Rama national road was the longest site in the study, the data may suggest that the length of a national road/street is not directly proportional to the diversity and number of trees planted.

Table 1

List of Urban Trees (Family, Species and Local Name), Abundance, Conservation Status and Origin in Five Selected National Roadside/s or Road/s in Cebu City, Philippines

Family Species Local

Name Abundance IUCN

Status* Origin Location/s

Anacardiaceae Mangifera indica L. Manga 5 DD Native

Cebu South Road, N. Bacalso, Osmeña Blvd, and V. Rama

Annonaceae Annona squamosa L. Atis 11 LC Alien

Cebu South Road, N. Bacalso, Osmeña Blvd, and V. Rama

J.J.C. GARCES, J.P. PICARDAL 55

Annona muricata L. Guyabano 11 LC Alien

Cebu South Road, N. Bacalso, Osmeña Blvd, and V. Rama Polyalthia longifolia

Benth. & Hook. Indian mast

pine tree 34 NE Alien All selected

national roads

Apocynaceae Alstonia scholaris L. Dita 1 LC Native Osmeña Blvd.

Cascabela thevetia L. Yellow

oleander 4 LC Alien Cebu South

Road and N.

Bacalso

Plumeria rubra L. Kalachuchi 7 NE Alien

Cebu South Road, N. Bacalso, Osmeña Blvd.

and V. Rama Arecaceae Adonidia merrillii

Becc. Manila

plam 117 NT Native All selected

national roads Wodyetia bifurcata

A.K. Irvine Foxtail palm 11 LC Alien Cebu South

Road and N.

Bacalso Arenga pinnata

(Wurmb.) Merr. Kaong 1 LC Native V. Rama

Cocos nucifera L. Coconut

tree 2 NE Alien Osmeña Blvd.

Corypha utan Lam. Buri 1 LC Native N. Bacalso

Roystonea regia

(Kunth) O.F. Cook Royal plam 13 NE Alien Salinas Drive

Asparagaceae Cordyline australis (G. Forst.) Endl.

zealand New cabbage tree

2 NE Alien N. Bacalso

Bixaceae Bixa orellana L. Achuete 2 LC Alien V. Rama

Caricaceae Carica papaya L. Papaya 6 DD Alien

Cebu South Road, N. Bacalso and Osmeña Blvd

Casuarinaceae Casuarina

equisetifolia L. Agoho 3 LC Native

Cebu South Road, N.Bacalso and Osmeña Blvd.

Combretaceae Terminalia catappa

L. Talisay 7 LC Native N. Bacalso and

Osmeña Blvd.

Cycadaceae Cycas rumphii Miq. Pitogo 1 NE Native N. Bacalso

Dipterocarpaceae Hopea plagata

(Blanco) S.Vidal Yakal 1 CR Native N. Bacalso

Euphorbiaceae Macaranga grandifolia (Blanco) Merr.

Binuñgang

malapad 1 VU Alien Cebu South

Road Melanolepis

multiglandulosa (Reinw. Ex Blume) Rchb. & Zoll.

Alim 5 LC Native N. Bacalso,

Salinas Drive and V. Rama

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Fabaceae Acacia propinqua

A. Rich Acacia 2 NE Alien Osmeña Blvd

and Salinas Drive Caesalpinia

decapetala (Roth) Alston

Mysore

thorn 4 LC Alien Cebu South

Road and N.

Bacalso Leucaena

leucocephala (Lam.)

de Wit Ipil-ipil 7 CD Native

N. Bacalso, Cebu South Road, Salinas Drive and V. Rama

Tamarindus indica L. Sambag 7 LC Alien

Cebu South Road, N. Bacalso, and Osmeña Blvd.

Lamiaceae Gmelina arborea

Roxb. ex Sm. Gmelina 31 LC Alien All selected

national roads Premna odorata

Blanco Abgaw 1 LC Native N. Bacalso

Vitex parviflora

A. Juss. Tugas 5 LC Native N. Bacalso

Lauraceae Persea americana

Mill. Avocado 1 LC Alien V. Rama

Leguminosae Pterocarpus indicus

Willd. Narra 1704 EN Native All selected

national roads

Malvaceae Ceiba pentandra

(L.) Gaertn. Duldul 4 LC Alien Cebu South

Road and N.

Bacalso

Meliaceae Azadirachta indica

A. Juss. Neem tree 5 LC Alien Cebu South

Road and V.

Rama

Swietenia

macrophylla King Mahogany 90 VU Alien

Cebu South Road, Osmeña Blvd, N. Bacalso and Salinas Drive

Moraceae Artocarpus

heterophyllus Lam. Nangka 10 NE Alien

Cebu South Road, Osmeña Blvd and N.

Bacalso

Ficus septica Burm.f. Lagnob 45 LC Native V. Rama, Cebu

South Road and Osmeña Blvd

Ficus benjamina L. Dakit 45 LC Alien

V. Rama, Cebu South Road, N.

Bacalso and Osmeña Blvd

Ficus religiosa L. Sacred fig

tree 45 NE Alien

V. Rama, Cebu South Road, N.

Bacalso and Osmeña Blvd Morus rubra L. Wild berry/

red berry 1 LC Alien N. Bacalso

Moringaceae Moringa oleifera

Lam. Malunggay 4 NE Alien Cebu south Road

and N. Bacalso

J.J.C. GARCES, J.P. PICARDAL 57

Muntingiaceae Muntingia calabura

L. Mansanitas 4 NE Alien N. Bacalso, Cebu

South Road and Osmeña Blvd.

Myrtaceae Psidium guajava L. Bayabas 4 LC Alien N. Bacalso and

Cebu South Road

Syzygium cumini

(L.) Skeels Lomboy 16 LC Alien

Cebu South Road, N. Bacalso, Osmeña Blvd and V. Rama Syzygium aqueum

(Burm.f.) Alston Tambis 16 NE Alien Cebu South

Road, N. Bacalso and V. Rama

Oxalidaceae Averrhoa bilimbi L. Iba 5 NE Alien Cebu South

Road, N. Bacalso and V. Rama Rhizophoraceae Carallia brachiata

(Lour.) Merr. False kelat 2 NE Alien Cebu south Road

and N. Bacalso

Rubiaceae Morinda citrifolia L. Noni tree 1 NE Native V. Rama

Sapotaceae Chrysophyllum

cainito L. Kaimito 5 NE Alien Osmeña Blvd.

Manilkara zapota

(L.) P. Royen Chicos 5 NE Alien V. Rama, Cebu

South Road and N. Bacalso

Strelitziaceae Ravenala madagascariensis Sonn.

Traveler’s

palm 1 NE Alien Osmeña Blvd

Legend: *NE- Not evaluated, DD-Data deficient, LC-Least concerned, NT- Near threatened, VU-Vulnerable, EN-Endangered, CR-Critically endangered, EW- Extinct in the wild, CD- conservation dependent (“The IUCN Red List,” 2021). The conservation dependent category

is part of the IUCN 1994 Categories & Criteria (version 2.3), which is no longer used in evaluation of taxa, but persists in the IUCN Red List for taxa evaluated prior to 2001, when

version 3.1 was first used. Using the 2001 (v3.1) system these taxa are classified as near threatened, but those that have not been re-evaluated remain with the “conservation

dependent” category (IUCN, 2016).

The current study also found that about 77.3% of the street trees belonged to the Leguminosae family (see Table 2). It is also evident in the distribution map that trees belonging to this family were widely distributed among the five selected national roads (see Figure 6). Trees from this family are hardier and more resilient to harsh roadside environment and possess the ability to fix nitrogen (N2) into usable forms (nitrate) (Tyrväinen, 2001;

Sreetheran et al., 2011). This species is followed by family Arecaceae, which had been planted widely in the city because of its exotic appearance and fast development, with a spectacular display of flowers after a dry spell. These trees are well known for their great heights, exclusive foliage, conspicuous inflorescences, and big seeds (Nowak et. al., 2015).

The frequencies of individual tree genus (see Table 3) showed an

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overwhelming dominance of four main genus Pterocarpus (77.35%), Adonidia (5.39%), Swietenia (4.09%), and Ficus (2.04%), which constituted

about 88.87% of the total tree population. Pterocarpus, a deciduous native tree in the Philippines, is the most abundant and is known for its hardiness, rapid growth, and pest resistance. This tree is commonly found all over the Philippines and is known to provide good quality of wood and shade. Its roots are fibrous that help keep the soil intact and prevent landslides caused by flood or even earthquakes (Sanders, 1981). Aside from its inherent abilities, Pterocarpus species such as P. indicus (narra), as it is locally known, are recognized for its aesthetic values as it blooms with yellow flowers that cover the tree’s entire crown foliage and produce a good smelling fragrance. For quite a long time, this tree has been a preferred choice as urban tree among foresters for its array of benefits. The Head of the Parks and Playground Commission in Cebu City noted that “narra has been mostly planted here in Cebu as early as Spanish colonization, and these trees were used as the main material for constructing boats during the time”

(L. Macaraya, personal communication, April 12, 2019). The dominance of narra as a heritage street tree was observed in Thailand, sharing 42% of the total street tree population in Bangkok (Thaiutsa et al., 2008) as well as in Yogyakarta, Indonesia, where it is commonly used as a shading tree in most

main roads of the city (Syahbudin et al., 2018).

Meanwhile, Adonidia species like Adonidia merrillii, locally known as Manila palm, are commonly planted along the streets for its aesthetic value due to its splendid structure and colorful fruits that are edible to some birds.

Since these trees are native to the Philippines, they enrich local biodiversity, thus benefitting other organisms in terms of food and habitat. Recent publications have claimed that Manila palm is native to Palawan (i.e., grows on karst limestone cliff) and neighboring islands in the Philippines, as well as to the coast of Sabah, Malaysia (Dransfield et al., 2008). The use of Manila palm as a popular ornamental plant along roadside, parks and gardens in the Philippines is due to its adaptability to tropical climate, favoring sunny areas under a well-drained, fertile soil. Recently, it has been used extensively for landscaping and interior design in shopping malls and atria (Lim, 2012).

J.J.C. GARCES, J.P. PICARDAL 59

Figure 2. Number of trees encountered in each selected national road

Genus Swietenia coexisted with the native trees along the national roads due to its unintentional introduction to our indigenous flora (see Table 1 and Table 3). The species that belongs to this genus include Swietenia macrophylla, locally known as mahogany which is easily distinguishable due to its wide range of seed dispersal. Wind easily spreads the seeds of these trees because the seeds of S. macrophylla is samara (has a wing like structure). Previous studies on Cebu’s urban trees reported that mahogany, being dominant in the city (Flores et al., 2020), had a potential use for carbon sequestration (Parilla et al., 2018; Pansit, 2019). Similar findings were reported by Nagendra and Gopal (2010) where mahogany was also one of the ten most commonly planted street trees in Bangalore, India. The same paper also highlighted that since mahogany was considered medium-sized tree with large canopies, it was more suitable to be planted among narrow roads with minimal sidewalk space. In Indonesia, mahogany trees were also favored in huge urban centers, considering that its cooling effect could effectively mitigate urban heat island (i.e. an urban area that is significantly warmer than its surroundings due to anthropogenic activities) (Ihsan &

Rosleine, 2020).

The fourth dominant genus among the selected national roads was Ficus. It is composed of relatively common species namely, F. septica (local name: lagnob, a native tree), F. benjamina (local name: dakit/balete, an alien

132

315

519

583

654

0 100 200 300 400 500 600 700

Salinas Drive V. Rama Cebu South

Road Osmeña

Boulevard N. Bacalso

Number of Trees

National Roads