Some 40,000 cranes visit the Hula Valley every winter, but scientists warn that their droppings could be playing havoc with Lake Agmon.
Zafrir Rinat Oct 02, 2016

The tens of thousands of cranes that arrive in the Hula Valley every winter have become a big hit with tourists, but scientists warn that the birds’ droppings could be wreaking environmental havoc on a local lake.

The cranes are not the easiest of visitors to host. They consume large amounts of food, and quite a lot of money is needed to ensure that they don’t find it in nearby cultivated fields.

But recent research has turned up another potential problem. When the droppings from these big birds make their way into the water system, it could lead to an overdevelopment of algae, harming the water quality and putting one of Israel’s most significant tourist attractions at risk.

A group of scientists, led by Prof. Iggy Litaor of Tel-Hai Academic College, Upper Galilee, has expressed concern that the algae could turn Lake Agmon could into a “green soup.”

The concern is a fairly new one. Only 20 years ago, less than 1,000 cranes came to the Hula, in northern Israel, every year. Their numbers increased after the Jewish National Fund (known in Israel as KKL-JNF) created Lake Agmon by intentionally flooding some 1,100 dunams (about 270 acres) of the Hula Valley, in an area where wetlands had been drained years before.

One of the project’s aims was to stabilize soil in the area and stop the flow of fertilizers through the groundwater into Lake Kinneret, to the south. But as a result, the area has become a popular stopover point for many of the birds that migrate through Israel’s skies. And in recent years, the number of cranes has grown to more than 40,000 — a tenth of the world’s population of common cranes.

Litaor became interested in the issue of crane droppings — and the large quantities of fertilizer they contain — and water quality after touring the Hula area.

“I saw that their feeding area was green, and vegetation had developed,” he said.

Indeed, a study at the site showed there was fertilizer in the birds’ droppings, which created good conditions for the development of vegetation. But farmers use a good deal of this vegetation to feed cattle, so the phosphorus in the fertilizer didn’t accumulate in the soil.

A crane’s toilet habits

The researchers then decided to study the impact of the birds’ presence on Lake Agmon itself.

“We know that most of the bird droppings accumulate at night, when they are in the Agmon area,” said Litaor, who is head of the master’s degree program in water sciences at Tel-Hai and head of Migal — Galilee Research Institute.

“We decided to estimate how much phosphorus was in the water of Lake Agmon, based on data from monitoring by the JNF and the Water Authority,” he explained.

The results, which were published recently in the journal Science of the Total Environment, showed that the quantity of phosphorus has risen significantly in Lake Agmon in recent years. Also on the rise is Chlorophyll A, a green pigment in plants and algae that is used to determine algae development following the increased presence of fertilizer.

The researchers found that the years of increased algae correspond to the dramatic rise in the number of cranes in the area.

If such a link can be proven conclusively, the scientists say, they warn that the algae and “green soup” will increase. This will lead to a reduction in aquatic plants, fewer fish, cloudier water and bad odors.

Such a future does not bode well for a site that is home to many animals and attracts thousands of visitors from across the country. The researchers say the current maintenance of the site needs to be reviewed.

Litaor passed his results on to the JNF, but its officials do not seem overly concerned.

“We monitor Lake Agmon, including a great many indexes connected to water quality, flora and fauna,” said Dr. Omri Boneh, JNF’s coordinator of scientific activity.

“We are aware of the concern, but we have not found a rise in phosphorous concentrations during the time the cranes are at Agmon. We will continue to follow it, and our job is to ensure that this situation does not happen,” Boneh said.

Litaor is convinced his findings are accurate. “We used the data we collected from the monitoring and analyzed them,” he said.

Aviram Tzuk, the director of the JNF’s Upper Galilee and Golan region, said, “The purpose of the studies, and particularly the monitoring, is to provide us with information about the system for its ongoing management.”

Whatever the final conclusion, scientists don’t currently have efficient means for dealing with the phosphorous threat.

One possibility — to remove the cranes from Lake Agmon — is hard to envisage, since they have become a big attraction.

Researchers are looking at various engineering solutions to remove the phosphorous from the area.

Another possibility is to use less chemical fertilizer containing phosphorus in areas near the lake, to reduce at least one source of the substance.
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