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Some introduced alien species in the Philippines
and their effects on ecosystems

Monina Torres-Uriarte*


In the Philippines, the number and proportion of introduced alien species are rising. Most of these species, especially tree species, are introduced for economic reasons and for forest rehabilitation purposes. Almost all of the ecosystems are affected. Invasive insect pests are associated with introduced tree species.

Several activities have been undertaken, but much remains to be done. Research on the impact of these alien species on biodiversity, people and the economy is being undertaken. The most recent legislation passed in the country, Republic Act No. 9147 (The Wildlife Act) totally prohibits the introduction of alien species in protected and critical habitats.


One of the major threats to biodiversity, not only in the Philippines but also in ASEAN† countries, is the introduction of alien species. Over the last 40 years, the rate and risks associated with alien species have increased enormously.

Alien species, as defined during the Convention on Biological Diversity (CBD), include any species that are introduced into new habitats by human intervention; usually they are invasive or aggressive.

In most countries, the number and proportion of alien species are rising and their presence has a devastating effect on natural/endemic species. The threat to indigenous species posed by invasive alien species (IAS) is cited in Article 8h of the CBD: “Prevent the introduction of, control, or eradicate those invasive alien species which threatens the ecosystem, habitat and species”.

Introduced alien species and their effects on ecosystems

The Species Survival Commission of the IUCN reported that as competitors, predators, pathogens and parasites, alien species have invaded almost every type of native ecosystem and caused hundreds of extinctions. Accordingly, their impacts are immense and sometimes irreversible.

The introduction of alien species relates to human interests. Most people introduce an alien species into a new habitat for economic reasons – fish can generate excellent fish stocks; plants can provide food, fodder and raw materials for medicines; insects can enhance biological control.

It is common knowledge that introduced species can cause, inter alia, displacement or destruction of indigenous species, pollution of the gene pool, loss of species diversity, disruption of energy and nutrient cycling and increased production costs as they may require high inputs. There are even cases of IAS triggering indigenous species to become harmful and invasive.

Biological pollution reduces the diversity of plants and animals and increases their vulnerability to both native and exotic pests. This often leads to increased use of pesticides and insecticides that may impact on ecosystems negatively.

The specific effects of some alien species introduced in the Philippines on forest ecosystems are presented in Table 1.

Table 1. Effects on forest ecosystems of some alien species introduced in the Philippines

Alien species

Effects on the ecosystem

Tree species and insect pests

Gmelina arborea

Host of Ozola minor, Attacus and Xyleutis spp.

Acacia mangium

Host of Anoplophora luciphor

Eucalyptus camaldulensis

Host of unidentified termite species

Swietenia microphylla

Host of Zeuzera coffeae

Leucaena leucocephala

Host of Heteropsylla cubana

Toona ciliata

Host of unidentified weevil


Big headed ant (Pheidole megacephalus)

Displaced most invertebrate faunas; pest to agriculture as it harbours phytophagous insects that reduce crop productivity

Fire ant (Solenopsis geminate)

Invaded native communities and affected many or all of the animals and plants in the community; has fiery and painful stings; nests in the soil

Jumping plant lice (Heterophylla cubana)

Introduced by the typhoon in 1980. Has affected almost all standing L. leucocephala plantations

Alien species

Effects on the ecosystem


Leafminer (Liriomyza sp.)

Accidentally introduced with the importation of chrysanthemum: major pest of potato and ornamentals

Spiraling whitefly (Aleurodicus dispeures)

Affected vegetables and ornamentals. Accidentally introduced with the importation of ornamental kalanchoe in the 1970s

Mealy bug (Pseudococcus sp.)

Affects coconut in Northern Palawan. Accidentally introduced in 1990 with the importation of hybrid coconut planting materials

Riceblack bug (Scontiniphora coarctata)

Major problem for rice in Mindanao and Leyte. Introduced through vessels plying the route between the province of Palawan and countries south of the Philippines

Potato cyst nematode

Accidentally introduced in the importation of potato planting materials. Heavily infesting potato farms in Benguet in Northern Philippines

American cockroach (Periplaneta americana)

Ubiquitous house pest

Action taken on introduced alien species

The Conference of Parties to the CBD urged parties to strengthen guiding principles for the prevention, introduction and mitigation of the impacts of alien species.

The Philippines’ National Biodiversity Strategy Action Plan (NBSAP) formulated in 1995 recognized the threat posed by alien species. It did not actually include programmes to address the problem directly, but it discouraged the introduction of exotic tree species in critical habitats. The Republic Act No. 9147 provides for the conservation and protection of wildlife resources and their habitats. Chapter III, Article 1 Section 13 – Introduction of Exotic Wildlife – states that no exotic species shall be introduced into the country unless clearance from the Secretary of the Department of Environment and Natural Resources (DENR) or the authorized representative is first obtained. In no case shall exotic species be introduced into protected areas and identified critical habitats.

In cases where introduction is allowed, it shall be subject to an environmental impact study which shall focus on the bio-ecology, socio-economic and related aspects of the area where the species will be introduced. The proponent shall be required to secure prior informed consent from the local stakeholders.

Research on the effects of established alien tree species all over the country is being conducted. Biodiversity, economic and social impacts will be determined.

Some recommendations on the introduction and management of alien species

Surprisingly, in the face of the enormous economic losses and ecological damages that can result from biotic introductions of alien species, relatively meager efforts have been made to educate the public about these consequences. A great deal can be done at all educational levels.

The only way we can manage IAS is by understanding their characteristics and the processes involved in the invasion. Legislations and regulations to restrict the movement of unwanted organisms are very important. Prevention of introduction is clearly more cost efficient than eradication or control of IAS once they are established.

In 2002, the ASEAN Regional Centre for Biodiversity (ARCBC) conducted a workshop on Biodiversity and Management of Alien Invasive Species in the Philippines. Management approaches and possible policies to regulate alien invasive species are listed hereunder.

Pilot testing prior to introduction of alien species

On previous occasions, it was noted that the pressing need to increase food production made it easy to introduce alien species, which were later determined to be invasive. Similarly, some species were introduced easily on the premise of high commercial value or economic returns. There is also danger with regard to genetically modified organisms (GMOs). To determine beneficial and invasive attributes of introduced species, pilot testing has to be conducted.

Enforcement of rigid inspection and quarantine regulations

Rigid inspection and quarantine regulations are needed to safeguard against inadvertent transportation, especially of pests introduced through the importation of logs and reforestation species. It was emphasized that the evaluation of imports, especially of forest products, should be conducted jointly by the DENR and the Department of Agriculture (DoA). It was also agreed to advocate species–site matching as an approach to reforestation; it was recommended that indigenous species should be favoured over alien species.

Monitoring the effects of identified invasive alien species on indigenous and endemic species

This involves assessment of the extent of invasions by alien species and their economic implications.

Monitoring developments relevant to “altered species” or GMOs

This is in anticipation of eventual aggressive marketing by GMO-supported multinationals.

Mobilization of inter-agency efforts through task forces

This will involve the DENR, DoA, NGOs, other government agencies, communities, private entities and other related agencies.

One activity will be the development of a regional/national programme for taxonomists to build core competencies and expertise in identifying specific groups of alien species.

Enhancement of policies and other regulations related to invasive alien species

Review, update or amend existing policies and other regulations. New policies can likewise be formulated to manage alien species properly. These include sanitary and phytosanitary measures and other associated legislation.

Enhancement of public awareness and encouragement of advocacy campaigns

This will enable people to understand the effects of alien species on our ecosystems. Furthermore, their commitment and participation can be elicited. Improved education and dissemination of information should be undertaken.

Conduct more research on the effects and management of alien species

Research to determine the beneficial or invasive attributes of introduced alien species should commence or continue. This should include tracking through time, and tagging when applicable. Research results should be disseminated to the appropriate parties/end users so that action to control or eradicate IAS and limit further introductions can be justified and implemented.

Establishment or development of a database

A meta database that will enable agencies/interested parties to locate data or which agency to approach to obtain data shall be established on Web sites. Data holders will retain the information in their respective agencies and accessing will be governed by regulations and procedures. The database will include a list of recognized invasive species and case studies of levels of damage and of control measures employed.

Several of these recommendations are being conducted but more remains to be done. All countries should take these threats, especially due to invasive species, more seriously.

* Assistant Director, Ecosystems Research and Development Bureau, Department of Environment and Natural Resources College, Los Baños, Laguna, Philippines 4031. Telefax: 6349 536 7746; e-mail:
† Association of Southeast Asian Nations

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