Not out of this world: The danger posed by invasive species

A female snail lays 200 to 500 eggs at a time, and between 1,000 to 1,200 eggs during one month. (Henrylito Tacio)

By Henrylito D. Tacio

Cargo ships and other large vessels have a special hidden compartment called a ballast tank. These are empty when the ship is loaded with cargo. They are filled with seawater as cargo is discharged to keep the ship afloat on rough seas.

Usually, the ballast water is released at the ship’s destination, bringing with it invasive animals, plants, microorganisms and other alien species that can wreak havoc on local marine biodiversity and coastal ecosystems.  

A 2022 international study showed invasive alien species (IAS) have cost the world over US$1.1 trillion worth of damage since 1960 alone, with management costs amounting to US$95.3 billion per year. 

Treating ballast water

This global problem prompted scientists from the University of the Philippines – Diliman College of Science (UPD-CS) and the University of Cebu to invent a port water treatment system that costs about ₱12 million. That’s around $200,000, a small fraction of the cost of other commercially-available systems, which can run as high as US$5 million. 

“Our system utilizes UV sterilization and mechanical methods to treat ballast water, and has proven promising in initial tests in decreasing the number of invasive species translocated from port to port,” said Dr. Benjamin Vallejo Jr, the system’s co-inventor and professor at UPD-CS Institute of Environmental Science and Meteorology (IESM). 

The invention is very timely as the Philippines has joined other countries in the ratification of the 2004 Ballast Water Management Convention. The treaty, adopted by the International Maritime Organization, imposes regulations on the proper handling and treatment of ballast water.

“We hope this treatment system will be cheaper than other costly comparable systems. Now is the opportunity for Filipino investors to break into Southeast Asia’s ballast water treatment market,” Dr. Vallejo said.  

Golden kuhol

In agriculture and fisheries, IAS is even more of a bigger problem as it threatens food security. The International Union for Conservation of Nature (IUCN) defines IAS as “species of plants or animals that are introduced by man, accidentally or intentionally, outside of their geographic range into an area where they are not naturally present.”

The Philippines is replete with examples of IAS. Take the case of golden kuhol (Pomacea canaliculata). Like the common rice field snail, it was then recognized as a delicacy. Because it was good food and an equally good alternative source of income, enterprising farmers started raising golden kuhol in their backyards.

A female snail lays 200 to 500 eggs at a time, and between 1,000 to 1,200 eggs during one month. (Henrylito Tacio)

But barely three years after its introduction to the Philippines, the snail, which is said to have originated from the Amazon River in South America, was practically everywhere. The snail multiplies rapidly, a characteristic that transformed them from being a rare delicacy to a dreaded pest.

Golden kuhol are very prolific; a female snail lays 200 to 500 eggs at a time, and between 1,000 to 1,200 eggs in a month. They proliferate rapidly as their eggs and hatchlings are transported by rivers and streams. They are dispersed to the rice fields through irrigation water.

“The introduced snail has caused one of the worst biological disasters ever to have affected Philippine agriculture with its invasion of irrigated rice fields,” said Dr. Rafael D. Guerrero III, an academician at the National Academy of Science and Technology (NAST). “Because of its prolific breeding and voracious breeding habits, the snail is highly destructive to newly-planted rice seedlings.” 

“Not all that is good for other countries is good for us,” reminded Dr. Guerrero. “In fact, it can be a big problem.” 

Water hyacinth 

Another IAS is the water hyacinth (Pontederia crassipes), considered the most productive plant on earth as it yields more than 200 tons of dry matter per hectare per year under normal conditions. On water containing high concentrations of sewage, it yields up to 657 tons of dry matter per hectare.  

A free-floating perennial aquatic plant native to tropical South America. It was introduced in the Philippines sometime in 1912 as an ornamental garden pond plant due to its beauty. As they grow profusely, some of these were thrown out in the river. During the rainy season, they spread across the Pasig River. They were carried all the way from Laguna de Bay because of its rising water level.

Today, water hyacinths are considered a pest. They have been threatening inland bodies of water. “(They) thrive in water with poor quality,” said an official from the Ecosystems Research and Development Bureau (ERDB), a line agency of the Department of Environment and Natural Resources (DENR). 

Pasig River and Laguna de Bay are among the country’s water-hyacinth-infested waterways. It is also a major nuisance in the Liguasan Marsh in Central Mindanao. 

Touted as the most productive plant on earth as it yields more than 200 tons of dry matter per hectare per year. (Henrylito Tacio)

Janitor fish 

Janitor fish or sailfin catfish (Pterygoplichthys) was introduced in the country in the early 1990s as an aquarium fish to clean algae. Today, it is one of the most destructive invasive fish species. With no known natural predator to reduce its population, its population has increased throughout the years. 

Janitor fish threatens the livelihood of many fishermen in Laguna de Bay, which has an abnormal number of janitor fishes. As they are algae-eaters, they compete for food supply with other marketable fishes. They also prey on smaller fishes, feed on other fish species, and feed on eggs. 

It has also been reported that the breeding behavior of janitor fishes contributes to the filth of Pasig River, as they create deep burrows in lakes and riverbeds that can cloud the water. Not only that, their bone structure likewise damages gill nets used by fishermen. 

Threatening native species 

Invasive species can force out native species. It happened in Lake Lanao, according to Dr. Guerrero. History records showed there were 17 endemic cyprinids, a fish species that includes minnows and carp, in the lake. In a recent survey, only two species were found. 

“The loss was attributed to heavy predation of the cyprinids by the white goby and the eleotrid that were inadvertently stocked in the lake with Nile tilapia fingerlings coming from a government hatchery in Surigao del Norte,” Dr. Guerrero said. 

Since the 17th century, IAS have contributed to nearly 40% of all animal extinction for which the cause is known, according to the Convention on Biological Diversity.

 At the time when Ramon J.P. Paje was the environment secretary, he urged Filipinos to refrain from importing exotic species, which in the long run might turn out to be dangerous. 

“Exotic species can in fact become invasive by threatening the very existence of endemic and indigenous flora and fauna, and eventually affecting the livelihood in our rural communities,” Paje reminded. 

So far, the DENR’s Biodiversity Management Bureau has identified about 170 alien or non-endemic species of plants, animals and insects that have been recorded as causing damage to agriculture and local biodiversity. 

Among the IAS that are already widespread in the country, aside from those mentioned earlier, are the common carp fish, clown knife fish, Jaguar guapote fish, Asiatic painted frog, Asian house rat, Polynesian rat, and the makahiya and lantana plants.

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