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Israeli researchers stem the tide of desertification
Posted By Tania Hershman On May 21, 2006 @ 8:47 pm In | No Comments
Jaap Van Rijn, pictured on the left, a senior lecturer in aquaculture, has developed a system for growing fresh or seawater fish in inland ponds, even in the desert. (Photo: Judy Siegel)As the planet heats up, the population grows and natural resources are exploited, drylands – over half of the world’s productive land – are becoming increasingly infertile and uninhabitable.
This process – called desertification – is a direct cause of famine in third world countries. But it is not just an African or Asian problem: desertification affects over two thirds of the drylands in the US.
Israeli scientists, using know-how gained from decades of ‘making the desert bloom’, are at the forefront of the global effort to find new technologies that take the pressure off of our valuable drylands.
“Israel is an arid and semi-arid country,” explains Eli Feinerman, dean of the faculty at the Hebrew University of Jerusalem’s Faculty of Agricultural, Food and Environmental Quality Sciences in Rehovot.
“Chronic scarcity of water is a fact of life in Israel.” This is why finding new methods for seawater desalination and waste water are critical for this region – but not just here.”
The HU researchers are among the world leaders working on novel solutions to desertification, an issue which is gaining worldwide attention. The United Nations declared 2006 the International Year of Deserts and Desertification, and the slogan of World Environment Day on June 5th is ‘Don’t Desert Drylands’.
Drylands, areas with low rainfall and high evaporation rates, cover 41 percent of the earth’s surface. But these are no empty stretches of sand dunes: one third of the world’s population lives and farms on these lands, ninety percent of whom are in developing countries. As well as its human inhabitants, drylands are home to various plant and animal life; each dryland area is unique in terms of how it evolved and who and what has made its home there. In 1981 the US had around 390 million hectares of drylands, but now it is estimated that around 74 percent are affected by desertification.
It is a fine line between dryland and desert, and drylands are crossing that line daily due to climate changes and human activities such as over-farming, deforestation and bad irrigation. This leads directly to a loss of the biological and economic productivity of these lands – and as our planet’s population increases, losing land that could be lived on and used for agriculture is a critical problem. From its establishment in 1948, Israel, with sixty percent of its land defined as arid, has developed many innovative tools and methods to prevent her lands from becoming desert.
Feinerman, former chairman of the Israel Committee for Agricultural Water Pricing, predicts that in the next few years agriculture in Israel will move from using from fresh water to treated waste water, and he hopes that by the end of the decade, Israeli farmers will get half their water supply from recycled waste water. “I don’t think that there is any other place in the world where 50 percent of the irrigation water is recycled waste water,” he says.
One of those working on ways to bring about this scenario is Avner Adin, professor of Water Treatment Technology from the HU Faculty’s Department of Soil And Water Sciences and president of the Israel Water Association. “Three thousand years ago, Moses struck a rock with a stick and water came out,” he told ISRAEL21c. “We don’t have that privilege so we have to use research, development and technology to provide solutions.”
Adin’s laboratory is working on how to clean water of particles of all sizes, ranging from several millimeters to a few nanometers (one billionth of a meter). These particles may be bacteria, algae, soil, earth, clay. The larger ones can be trapped by regular filters; it’s the tiny particles that pose the problem. However, one thing these minuscule contaminants have in common is that they have a negative electric charge which means that, like two similar poles of a magnet, these particles push each other away. “Our target is to neutralize the charge and get them to stick together into larger particles so they can be filtered out,” he explains.
To this end, Adin and his lab use a technique called electro-flocculation. Instead of using chemicals, which can pollute the environment, to neutralize the particles’ charge, their device uses electrodes made of iron or aluminum. When the waste water passes the electrodes, which have a small electric current flowing across them, positively-charged aluminum or iron ions attract the negatively charged particles and they join to form larger particles which can be filtered out. “We have constructed the first electro flocculation plant in the world,” says Adin. The plant, in the Israeli town of Gan Yavne, can clean 2400 cubic meters of water per day. “This is a major development in the field.”
Oded Shoseyov, a professor at the Faculty’s Institute of Plant Sciences and Agriculture, is concerned with the next step: the crops that this water is irrigating. “I am working on plant genetic modification for reforestation,” he says. “The importance of forests cannot be overestimated. Every year forest five times the size of the state of Israel is logged.” Less trees means more carbon dioxide, and this is a major factor in the greenhouse effect that leads to desertification.
Shoseyov and his team identified several genes connected with the cellulose in trees that is one of the crucial factors in tree growth. By modifying these genes, they have created transgenic plants that grow far faster than regular trees. The first tree they modified was the poplar, the paper industry’s most popular tree. Shoseyov conducted a field trial in the US, and “after two years most of [the transgenic poplars] outperformed the control group,” he told ISRAEL21c. “Some produced up to 370 percent more wood than the controls.” The transgenic poplars were logged and it was found that their wood was also of a higher quality. He is currently running a field trial of modified eucalyptus trees – also widely used to make paper – in Israel and planning a field trial in Thailand. “A normal tree takes about three times the amount of land to produce the same amount [of wood] as the transgenic technology,” he says.
Shoseyov has also modified potato plants to shorten their growth cycle and require less water. “This is important for Israel, and also for northern countries such as Sweden where the land freezes,” he says. Sweden is testing his transgenic potato plants. Shoseyov is the chief scientist for a Rehovot-based Israeli start-up, CBD Technologies, which licensed his research from the Hebrew University in order to commercialize the techniques.
Further up the food chain, fish are Jaap van Rijn’s research focus. The current method for growing cultured fish has them in earth-bottomed ponds, with only a few fish per pond. This takes a lot of water – around fifty cubic meters per kilogram of fish – and these ponds can only be used for around seven months of the year, when the weather is warm enough. If the fish need seawater, then the situation is even more limited: the fish are either grown in cages in the sea or in ponds very close to it.
Van Rijn, a senior lecturer in aquaculture, has developed a system for growing fresh or seawater fish in inland ponds, even in the desert – and with around a hundred times more fish in each pond. “We have done away with earth-bottomed ponds and moved to tanks, lined with plastic or concrete, where we treat and recirculate water,” he said. His temperature-controlled system can be used all year and is completely closed: only a small amount of water needs to be added to compensate for evaporation. The water is cleaned using various types of bacteria, which break down the most serious pollutants, carbon and nitrogen, turning them into carbon dioxide and nitrogen gas and removing them from the system.
After first testing the system with freshwater fish such as carp, Van Rijn then adapted it for marine fish like sea bass: “We fill up the pond and add salt to the optimum salinity the fish need,” he explains. The salt content stays level because the water is recycled.
In experiments, the prototype of the inland system demonstrated that only forty liters of water are needed per kilogram of fish, instead of around 5000 liters that a conventional system uses. And the fish seem to be happy: generally, a commercial fish is around 400 grams. “Two weeks ago we had a fish which was 1200 grams,” boasts van Rijn, peering down into the tank.
Recycling waste water, speeding up plant growth and raising fish in the desert are just some of the ways in which Israeli researchers are fighting desertification and preserving drylands and all those who live on them, not just in Israel but worldwide. If techniques such as these are adopted and commercialized, the future may not be as dry as the United Nations fears.
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