Tu Bishvat (Jewish Arbor Day ) will be marked next week with numerous tree-planting events. But in recent years, the Israel Nature and Parks Authority has been uprooting plants throughout the country in a bid to repair damage caused by planted flora that disrupted the natural environment.

At a conference last month, INPA staffers discussed several long-term uprooting projects intended to protect nature. Two major ones involve uprooting trees from the Dan nature reserve on the edge of the Golan Heights and the Bethsaida reserve near Lake Kinneret.

"Many years ago, eucalyptus trees were planted in the Dan reserve and proliferated rapidly," Dr. Didi Kaplan, the authority's ecologist for the northern region, explained yesterday. "They are hindering the development of the reserve's natural vegetation, among other things by preventing light from penetrating."

After much effort, the INPA persuaded the Jewish National Fund and Kibbutz Dan, which had planted the trees, to cut them down.

"The results are simply amazing," Kaplan said. "Immediately after the trees were cut down, indigenous plant species, like small-flowered willow-herb, appeared after decades of absence."

In the Bethsaida Valley reserve, parkinsonia bushes that were brought from Middle America for forestation had proliferated, pushing out indigenous species. Moreover, the drop in the Kinneret's water level had caused tamarisks to invade land that had dried up near the lake.

"The tamarisks developed densely on large areas, preventing the growth of indigenous vegetation, among other things by secreting salt in the ground," Kaplan said.

For the past four years, the INPA has been fighting parkinsonia and tamarisk proliferation in Bethsaida. It uprooted plants, used poison to prevent regrowth and brought in cattle herds to thin out the vegetation. As a result, the rare species Lepidium latifolium bloomed again in the area from which the tamarisks were removed.

In the Einot Tzukim nature reserve (Ein Feshkha spring ) near the Dead Sea, the INPA used a donkey herd to thin the reeds that proliferated after fires and had crowded other plants out. Around the Na'aman stream in the Western Galilee, it used heavy machinery to uproot the camphorweed, an invasive species from South America. And in Einot Givaton near Gedera, it chopped down blue-leafed wattle, another invasive species native to Australia.

The Nitzanim Dunes nature reserve, between Ashdod and Ashkelon, is the last large concentration of migrating dunes in the coastal plain. When sheep herds stopped grazing there, vegetation spread and covered the sands, turning them into stable dunes. That hurt the site's flora and psammophiles (animals that inhabits sandy areas ).

The INPA has been working together with a group of scientists to restore the migrating dunes by systematically uprooting the vegetation. Some flora and fauna indigenous to migrating dunes have reappeared, but success has so far been partial.

"In some of the dunes, the uprooted vegetation has begun to grow again," Kaplan said. "We will try to thin it out in the future with grazing."