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Canada geese and myna birds have made permanent aliyah to Israel and Europe, but the species are causing concern because of their tendencies to cause crop damage and threaten indigenous species.

They are only two of a wide variety of invasive plants and animals that are the subject of a European Union study in which two Israeli scientists also participated.

The researchers, Professor Bella Galil of the Israel Oceanographic and Limnological Research Institute in Haifa, and Dr. Salit Kark of the Hebrew University of Jerusalem, said some 75 foreign species of birds and over 500 species of animals have settled in the Mediterranean basin.

The project, known as DAISIE - Delivering Alien Invasive Species Inventories in Europe - collects information on the invasive species so as to map their distribution in the Mediterranean, including Israel.

Galil, who focused on marine invasive species, says many of the hundreds of such species, including jellyfish, shrimp, crabs and some fish species, entered the Mediterranean through the Suez Canal. Others came in water used as ballast in ships or came stuck on the hulls.

"We still don't know of a local species that has become extinct due to an invasive species, but we can see a decline in a number of species and there is concern over changes in the marine ecosystem," Galil says. Some are dangerous to humans, Galil explains, mentioning a species of catfish which has undergone a population explosion along Israel's coast. It has a stinger in its fins that releases a neurological toxin, and can injure fishermen pulling in their nets.

Galil says one way to better control marine invasive species is by replacing the water in the ships that might carry them.

Kark, who collected data on invasive bird species, says these are coming in mainly due to human intervention, and have nothing to do with climate changes, as is commonly believed. Some were brought as pets and escaped to the wild. Some, like the glossy ibis, eat local species or compete for their food sources. Others, including some kinds of pigeons and Canadian geese, cause major crop damage.

Over 20 invasive species now call Israel home.

"Conditions are comfortable here compared to northern Europe because the weather is more like the tropical zones from which many of these species come," Kark says.

Two of the most common species in Israel, which compete with local birds for nesting sites and food are the rose-ringed parakeet and the Indian myna bird, which come from East Asia.

Kark says the myna is a very aggressive species that steals the young of other birds from their nests. It is also pushing out the Syrian woodpecker, which Kark calls "the architect of building nests in holes in trees." If these holes are not made, she explains, the nests will not be there for other species either.

Following the discovery that most invasive species arrive in the country due to human intervention, Kark and other researchers recommend basing transport permits on scientific information regarding the damage they do elsewhere in the world.

Kark believes educating the public not to release foreign species to the wild is also key.