A scheme devised by the Israel Nature and Parks Authority has successfully stopped the expansion of an invasive flora species that was threatening Israel's natural landscape.

The scheme was launched four years ago to battle the expansion of the blue-leafed wattle (acacia saligna ) in Nahal Sorek National Park. The native Australian plant is seen as one of the gravest threats to Israel's landscape due to its ability to oppress local species of shrubbery and the difficulty in suppressing its expansion.

Open gallery view Blue-leafed wattle (acacia saligna ). Credit: Geroge Jensen

The blue-leafed wattle invaded several areas, and INPA officials had despaired of suppressing it due to its extremely-high resilience.

A few years ago, numerous concentrations of blue-leafed wattles were found in eight spots along the main route of the Sorek park. Each spot consisted of hundreds of trees in various sizes, some of them especially large.

"This tree lives 12-15 years in Australia, but there it is killed by a fungus," says ecologist Jean-Marc Dufour-Dror, an environmental consultant to INPA. "But in countries it invades, it lives 30 to 40 years."

At Dufour-Dror's advice, INPA launched a project to get rid of the invasive species by drilling and injecting pesticide into the trunks.

"The method worked fine on isolated trees but is harder to carry out when it comes to hundreds of trunks," an INPA report says.

Fearing the blue-leafed wattle's continued expansion and its effect on local shrubbery in the Nahal Sorek region, INPA resorted to more aggressive measures. It hired a tree-cutting contractor, who agreed to cut down the blue-leafed wattle in exchange for cutting down 400 pine trees he sold for various uses.

The treatment began four years ago and has been applied repeatedly to this day. In addition to cutting down the blue-leafed wattles, INPA continued injecting isolated tree trunks with pesticide. It also set up plastic sheets above the ground, causing the earth to heat up. This resulted in the destruction of large quantities of blue-leafed wattle seeds. This measure succeeded only partially because the sheets were repeatedly damaged by visitors to the nature reserve.

After four years of relentless struggle, INPA conducted a survey in the region and found the blue-leafed wattle had all but disappeared. Isolated areas in which the invasive tree is spotted still need to be dealt with.

The best evidence of the scheme's success is the discovery of a great variety of natural shrubbery in the areas previously invaded by the blue-leafed wattle.

INPA officials say a few more rounds of treatment on the individual remaining trees should subdue the invasion completely.

"There is no doubt we've created a difference in the Sorek reserve landscape. We've rid it of an invasive species that had taken over parts of the area," INPA's report concludes.

A study conducted by Dufour-Dror says several dozen invasive plant species from other countries have established themselves in the Israeli landscape. Some of them arrived as ornamental plants or, in the wattle's case, to control and reduce soil erosion.