Cute and cuddly koalas, native to Australia, can’t survive without eating up to 800 grams of eucalyptus leaves every day during the three or four hours that they’re awake. There are no koalas in Israel except in zoos, but there are plenty of eucalyptus trees in the Western Negev, and they are causing trouble for the ecosystem.
A new study by Yuval Neumann and Dr. Niv DeMalach of the Hebrew University (HU) of Jerusalem’s Faculty of Agriculture, Food, and Environment has examined the impact on the region of three eucalyptus species: E. camaldulensis, E. loxophleba, and E. torquate.
Of the 800 eucalyptus species in Australia, only 60 are used for planting in Israel. They produce nectar in dry seasons, when there are few flowers, “but despite this advantage, the eucalyptus is a controversial tree, and not only in Israel.
“From igniting civil protests in Thailand in the 1990s to being called a ‘fascist tree’ in Portugal, eucalyptus plantings are objectionable,” the authors wrote. “Some of the objections are civil – for example, the Bedouin who are in conflict with the Israeli government regarding ownership of the land and lead to violent struggles and cutting down trees.”
On the other hand, some of the objections are related to nature conservation, and opponents claim damage to biological diversity following forestry operations on the loess soils – silty or loamy material that is usually yellowish-brown in color and mostly deposited by the wind – of the Western Negev.
The study was conducted in the spring of last year in the Be’eri forest and near Kibbutz Re’im to investigate the impact of eucalyptus trees on herbaceous plant communities.
Research took place before the Hamas massacre
Tragically, a few months after this research, Hamas launched a murderous attack on Israel, and the region was struck by devastating events that destroyed the kibbutzim and moshavim. “Our thoughts are with all those affected, both physically and mentally,” the authors wrote.
“We remain hopeful for the restoration of this region, known for its stunning natural beauty, and aspire that our findings will contribute to these restoration efforts.”
While conducting the research, said the team, “we could not imagine the tragedy that would occur in the area a few months after it ended. Our hearts go out to the victims and those injured in body and soul and to all the residents of the area. This article is dedicated to all of you. We are full of hope that this area, full of amazingly beautiful nature, will be restored. If the findings of our research can help with this, then that’s good.”
They found that many of these evergreen species have a significant allelopathic effect, reducing herbaceous plant biomass and the flowering density of red anemones, particularly in unshaded areas. Allelopathy is a negative or positive effect on one type of plant by a chemical produced by another type. Certain types of chemicals, including phenolics, hydroxamic acids, and short-chain fatty acids, have been found to have allelopathic properties.
The team’s findings, just published in Hebrew in the journal Ecology and Environment and titled “The effects of Eucalyptus on herbaceous plant communities in the Western Negev,” suggest that while eucalyptus trees provide certain benefits, such as shading for tourists and nectar for bees, their negative impact on local plant communities, the grazing of animals, and ecosystem services requires cautious planting, particularly in tourist areas and regions with rare species.
Since the eucalyptus species showed large differences in their effect, only those with a minimum of harmful effects should be included in future reforestation efforts, be led by data-driven decision making, and supported by further research to deepen our understanding, the researchers wrote.
The Western Negev, with its extensive eucalyptus plantations, has been the subject of ongoing debate because they are an alien, invasive species and infamous for allelopathy. They affect the ecosystem by reducing the flowering density of red anemones, which attract many tourists.
The study found major differences among the three eucalyptus species’ effects on herbaceous communities, with E. torquate having a negative effect on biodiversity (of up to 90% reduction); the other two species did not show such an effect.
Given the findings, the researchers advise caution in planting certain eucalyptus species in areas intended for tourism, such as the location of the Darom Adom (Red South) festival and in places home to rare or protected species. Significant differences among eucalyptus species were noted, with some exhibiting minor negative effects. Therefore, the researchers recommend prioritizing species with minimal impact on reforestation efforts.
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