DENR-XI airs concern over spread of invasive species

May. 31, 2010

DAVAO CITY—The Department of Environment and Natural Resources (DENR) is worried over an emerging alien invasion.

Emmanuel Isip, DENR Southern Mindanao technical director, says this is not the science-fiction kind of invasion but the proliferation of non-native species of flora and fauna, which is threatening endemic plants and animals, thus affecting biodiversity.

Isip said ‘invasive’, non-native species must have the following characteristics; the ability to reproduce quickly, to superbly adapt to a new environment and being a voracious eater.

Isip added invasive species are grouped into marine and terrestrial. Marine invasive species include the janitor fish, carps, big mouth bass, African catfish, among others. Terrestrial invaders include ipil-ipil (leucaena leucocephala), African tulip, hagonoy (Chromolaena odorata), lantana (Lantana camara), golden kuhol snails, etc.

According to Isip, these species compete and kill out native plants and animals. For example, the hagonoy or bitter bush, which is similar to an eggplant in appearance, is a pest in pasture lands. He says they are toxic to livestock when eaten. “If cows and goats eat hagonoy, they become sick. Some even die.

Invasive species like hagonoy and lantana have allelophatic effect on surrounding organisms, Isip said. He explained that allelophaty is a biological trait, wherein a certain species can control the growth of surrounding species. Isip further explained that hagonoy and lantana have the ability to choke off surrounding vegetation.

Isip said climate change is advantageous to the proliferation of these invaders because they easily adjust to a new environment, while native species are stressed with the warming climate.

These invaders were brought over either natural migration through bodies of water or vectors like migratory birds or they were brought by man as exotic pet or ornamental collections, Isip said. He added that some known invasive species have been brought over to develop agriculture such as carps, golden snails, catfish and tilapia. He cited that the golden kuhol snails, which were introduced for food, is a pest in many rice farms; that carps are threatening populations of native fishes in Cotabato; and that salt-water Tilapia poses a threat to other native saltwater fishes.

Jim Sampulna , DENR Southern Mindanao executive director, added that invasive fishes are threatening the freshwater fish tabong, endemic in Cotabato. Sampulna says tabong is in danger of being wiped out by carps and big-mouth bass.

Isip cautioned those introducing new species to bear in mind that there should be precautionary measures to protect other native species.

Isip also appealed to pet shop owners especially fish collectors to avoid disposing unwanted collections into bodies of water. He cited the case of janitor fish, which was once an aquarium fish. He saids when these were released into the wild, they grew and multiplied so quickly that they became pest. He said the Agusan marsh is threatened by the janitor fish, which are voracious eaters that devour eggs of native fishes and wipe out their food supply.

Among the remedies to control these invaders are strict quarantine and utilizing the beneficial usage of these species, Isip said. He cited that the skin of American frogs are being used as leather while golden kuhol are being used as feeds for ducks. (PIA XI)

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