A flood of rare intensity that took place three weeks ago in the southern Arava covered the Evrona Nature Preserve with sediment and sand — and the oil stains that remained from the spill in the area about a year ago disappeared from view. But anyone who digs a little and moves the top layer of soil will easily discover them all.
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Studies conducted in recent months reveal that this is a time bomb that threatens to cause serious damage to the acacia trees on which the entire ecological system in the region depends. On December 3 of last year, millions of liters gushed from the Eilat-Ashkelon Pipeline directly into the Evrona Nature Reserve, affecting its main source of life — the large concentration of acacia trees. Half the oil was pumped out in the days following the spill, the other half filtered down to a depth of dozens of centimeters.
Since then the Nature and Parks Authority has been trying to figure out how to handle the pollution. Total cleanup of the oil with heavy equipment is not an option because it would cause irreversible damage to the area. An essential condition for deciding on a policy to rehabilitate the reserve is an assessment of its affect on the pollution of the acacia trees that provide a significant percentage of the sources of nutrients and water of the flora and fauna in the preserve.
For that purpose the Eilat-Ashkelon Pipeline Company (EAPC) and the Nature and Parks Authority have commissioned research studies, with researchers from the Dead Sea & Arava Science Center belonging to the Science Ministry and the Arava Institute for Environmental Studies, in nearby Kibbutz Ketura.
The study was led by Dr. Eli Gruner and Nitzan Segev. According to the findings, about 10 acacia trees died from exposure to oil or clearance work, and a significant percentage of the hundreds of other trees were exposed to oil directly or indirectly and may also have been harmed. The researchers were interested not only in the immediate damage but also in the long-term effect of the pollution on the total population of acacias. During their research they discovered that in 1975 there was a large spill in a more southerly part of Evrona. Since it took place in the summer, the liquids and volatile materials in the oil dried quickly. What remained of the oil created a hard crust on the surface. It was decided not to treat the pollution and some remains in the soil to this day.
“We analyzed aerial photographs to see the changes in the area of the 1975 spill,” says Gruner. We also measured the tree population and compared it to a control area where there was no spill. It turned out that the adult trees did not suffer, but no middle-sized or small trees were found in the area. In other words there is no ‘recruitment’ of new trees to the population.”
The researchers believe that the oil left in the ground created a sealed layer that prevents the infiltration of rainwater and the sprouting of the seeds and their development into mature trees. Additional proof of that was recently gleaned from an experiment in the gene bank of the Vulcani Institute in Beit Dagan. They took samplings of soil from the area damaged in 1975 and the area damaged a year ago. They experimented with getting the samplings to sprout after watering the soil. In both types of soil they discovered a significant decline in the development of the seedlings. This means that if the oil remains in the ground there is a genuine threat to the ability of the acacias to survive in the future in Evrona.
“Some people thought that we could do nothing and let natural rehabilitation processes operate,” says Gruner. “Now it turns out that we have to take care of the oil that’s still in the reserve. The ecological system in Evrona has now returned to almost full functioning. Cameras have documented a rich variety of fauna in the reserve, including gazelles that continue to eat the seed pods of the acacias. Rabbits, foxes and other animals have also been recorded by the cameras. But in the long run they’re all largely dependent on the acacias and there is a fear that the unavoidable damage to the trees will affect the entire food chain in the reserve.
According to Dr. Yehoshua Shkedi, chief scientists of the Nature and Parks Authority, “Acacias are defined ecologically as a ‘key species,’ on which other species are dependent. The Nature and Parks Authority is now trying to decide how to handle the remaining oil. It has decided to begin with threshing the top part of the soil with a special machine. The purpose is to provide oxygen for the microbes in the soil and to encourage their activity that can break down the oil. It also enables water to penetrate. Later it may be necessary to use additional technologies to encourage the activity of the microbes that break down the oil.
“Shortly after the spill the Nature and Parks Authority invited several companies specializing in treating soil pollution to conduct an experiment with various technologies for breaking down the oil. The idea was to choose the company with the most suitable technology. But to this day they haven’t receive any answer.
“We delayed our answers for bureaucratic reasons, but also because we’re still trying to decide how to continue. We may make do with creating conditions for the activity of local microbes. We may carry out a broader experiment. We’re waiting because we’re afraid of causing irreversible damage. The spill that occurred in the past taught us that these are long-term processes and there’s time to check that you’re not making a mistake. The oil that remains in the soil is not the only threat to the acacias. North of the reserve Eilat’s new airport is under construction. The plans include building several ramparts to protect the airport from the occasional flooding in the area. But the nature preservationists are afraid that this will divert the floods from the channels where the acacias are located.”
“These are trees whose development is adapted to the channel where water flows,” explains Yuval Peled of the Nature and Parks Authority, who in the past conducted a study of these trees. We’re afraid of a situation in which some trees won’t receive any water while others will receive too much.” In recent weeks they have been examining the option of changing the ramparts system, in order to avoid a situation where the reserve was saved from oil pollution — but was left without a source of life.