A carpet of green covering the Harod stream next to the kibbutz Merhavia in the Jezreel Valley would be considered a pleasant and refreshing sight by some, especially as the Harod stream all too often serves as a depository of local sewage. But for Avi Ozon, of the Israel Nature and Parks Authority, the first reaction was concern.
He didn't know the plant, and the shape of the leaves looked strange. He scooped up a sample, and sent it to be tested by his colleague, Dr. Reuven Avital of the authority's science department.
The authority's officials knew that this plant had never been seen before in Israel and sent it to Hebrew University in Jerusalem, where it was examined by Dr. Michael Avishai and Hagar Leshner. Identification was difficult, as the sample did not contain a flower. Finally, the plant was identified as the water spinach.
"This is a highly dangerous, invasive plant, which is considered a bad weed in many areas," Avishai told the authority.
The water spinach joins two other plants recently discovered invading Israeli waterways - the water cabbage and the water hyacinth. Together, the three are threatening to drastically change rivers and waterscapes, causing heavy ecological damage. The water cabbage is being spotted increasingly close to the Kinneret, having originally been discovered further north in the Hula Valley.
"We are afraid of losing control over the water spinach," said Yiftah Sinai, the ecologist for the valleys and lower Galilee area in the authority. "It quickly and densely covers wide territories, and prevents other plants from growing. It influences and changes the entire habitats. It also grows fast enough to block waterways, which can lead to floods and stagnant water, which in turn can become mosquito breeding grounds."
Sinai went to the Harod stream and cleared the plant from the area, but he says it could easily return there again.
"We'll keep monitoring this spot, hoping we won't be forced to use chemicals that would damage other plants as well," he said.
The current hypothesis is that the plant was imported by Thai workers, as water spinach is a popular dish in Thailand. The plant was found next to some of their homes on the banks of the Naaman stream.
Dr. Jean-Marc Dufour-Dror, an ecologist specializing in invasive species, said that "there's a serious risk we wake up too late. It's time to launch a national program to stop invasive water plants."
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