Invasion of the Bio-snatchers

From air, land and sea, alien animals, plants and insects are invading local habitats, disrupting the ecological balance and wiping out indigenous species. Israel, say worried experts, should take the problem much more seriously.

Coby Ben-Simhon
Coby Ben-Simhon
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Coby Ben-Simhon
Coby Ben-Simhon

"It arrived here in the summer of 2002," Shulamit Razhevsky, from Kibbutz Afikim, just south of Lake Kinneret, says in a disgruntled tone of voice. "At first we encountered it only on the lawns, but after two summers it began to enter the houses, the sofas, the showers. It's an ant so small you can barely see it and it can get into anything. It's a terrible pest, a real blow." The tiny fire ant, which has caused great agitation in the normally tranquil kibbutz, is one of the most violent invaders ever observed in Israel. And it's not alone.

Outside the window of an office overlooking the green zoological garden of Tel Aviv University struts a peacock that occasionally emits a long roaring sound. "I think we should all be worried," says Prof. Tamar Dayan of the Department of Zoology as she looks out the window. "Biological invasions are today considered second only to habitat destruction in terms of their potential to cause the extinction of local species and ecosystems. The invaders are capable of causing large-scale catastrophes, as we have already seen in some parts of the world." In recent decades, species have been disappearing at a rate a thousand times faster than would be the case without human activity. This development has been compounded by invasions of alien species - the new challenge in the struggle for nature preservation. The best-known example is the extinction of hundreds of species of Nile tilapia (St. Peter's fish) in Lake Victoria in East Africa, caused by the Nile perch, which was introduced into the lake with the purpose of enriching the local fish population. In the Caribbean islands, the Indian mongoose, which was introduced there to exterminate rats, destroyed land-nesting species of birds as well as local reptiles.

"An invasive species is defined as an organism that is transferred by man, whether deliberately or not, establishes itself outside its geographical sphere and impacts its new surroundings," explains Dr. Noam Leader, the chief ecologist of the Israel Nature and Parks Authority. "It is not a case of one individual that escapes from captivity and cannot multiply. These are whole populations that compete with local species for habitats." In addition to unintentional transfer by commercial routes, some invasive species are introduced into new environments deliberately and under supervision, perhaps in an attempt to biologically exterminate other species, or as pets. But then a few individuals escape and begin to multiply in nature. "Sometimes, wooden crates that arrive here from South America carry spiders, lizards and fire ants from the jungle," Leader says. "We have to fight back against the invaders and destroy them all ... otherwise, they will exterminate the Israeli species. Not dealing with the invaders means, in practice, to eliminate local species."

In 1992, the Convention on Biological Diversity (the Biodiversity Convention, for short) was drawn up by the UN Conference on Environment and Development, known informally as the Earth Summit, which was held in Rio de Janeiro. Article 8(h) of the convention - a document signed by Israel - stipulates that all the signatories "shall, as far as possible and as appropriate," work to "prevent the introduction of, control or eradicate those alien species which threaten ecosystems, habitats or species."

Part of the problem lies in legislation, or, more accurately, in its absence. "Current Israeli law does not recognize the phenomenon of biological invasions," says Ronit Justo, a doctoral student in the Department of Zoology at Tel Aviv University. "Laws to protect wild animals, flora and fish, which were enacted for traditional purposes of commerce and to protect endangered species or promote agricultural goals, do not refer explicitly to ecological threats posed by alien species or to biological invasions, which constitute a relatively new phenomenon."

A list of the 100 most aggressive and dangerous invaders has been drawn up by the International Union for Conservation of Nature (IUCN). Various countries, such as Britain, Australia and New Zealand, as well as the U.S. state of Hawaii, addressed the issue a decade ago, Justo says, by passing laws that address the problem. "We are lagging far behind," she says. "Commerce in and the dissemination of alien species are permitted under Israeli law. The responsible bodies in Israel lack explicit authority to prohibit the entry of species when this conflicts with other laws. The result is that when nature preservation and commercial interests clash, the latter will usually triumph. We have not even drawn up a formal list of dangerous invasive species."

Another problem in dealing with bio-invaders in Israel is that responsibility is divided among several bodies. "Some plant species are under the responsibility of the Jewish National Fund [JNF], others under the responsibility of the Ministry of Agriculture," Leader explains. "Invasive fish are dealt with by the Fisheries Department of the Ministry of Agriculture, and we, the Nature and Parks Authority, are responsible for mammals, avians, reptiles and amphibians. Even if understandings exist among all these groups, the division of authority is counterproductive. And even if we are constantly trying to uproot the Sydney golden wattle from all conservation areas, or eliminate Indian house crows in Eilat, such projects are not enough. Once an invader establishes itself, we face a long-term war of attrition. The ultimate solution is to prevent the entry of these species from the outset, but that is possible only if the state grasps the gravity of the problem and creates one mechanism to concentrate all activity against the invasive species."

Dr. Yael Gavrieli, director of the Nature Campus at Tel Aviv University, has long tried to fight the indifference of the Israeli authorities and society to these unwelcome new immigrants. "In most cases, the invasive species are introduced into Israel innocently, by people who did not intend to cause harm," she says. "Prominent invasive species in Israel, such as the rose-ringed parakeet, were released from cages and consolidated themselves in nature. There is a general lack of understanding about the subject. For example, I found a pond in an ecological garden in a school where they planted water hyacinth, a particularly dangerous invasive species. You can find invasive species for sale at every plant nursery in Israel."

The explanation for the indifference is cultural, Gavrieli believes. "The idea of bringing someone foreign and acclimatizing it here is integral to our culture," she explains. "There are countries that are very proud of their indigenous nature while some countries are waging a bitter war against invasive species that are harmful to nature. The English, for example, exterminated the nutria, a large rodent, which has also invaded Israel. They shot them one by one. But we, as a country of immigration, also cultivate the myth of making the wilderness bloom. We are not so crazy about the indigenous nature here - we want to change it a little, make it greener. The British started the trend by bringing in the Sydney golden wattle [a shrub native to Australia] and we are continuing it. People wanted a European landscape, so we got pine groves."

1. Rose-ringed parakeet

"I brought in the first three pairs of rose-ringed parakeets in 1962," Yossi Zahor, an army pensioner from Nahariya and pioneer breeder of the bird in Israel, says proudly. There were very few parakeets (called darara in Hebrew and Psittacula krameri in Latin) in Israel at the time, he says, "and the rose-ringed parakeet was bigger and more beautiful than the others. The reactions were wonderful. Serious bird breeders came to see the new birds. Nowadays they are a hobby for masses of people." Zahor gave a pair of the birds to a friend who lived in Tel Aviv, but they escaped and started to multiply in the area of the Mikveh Yisrael agricultural school near Holon. Nearly 20 years later, the birds began to be imported on a massive scale from Iran, and individual birds that escaped from cages in private homes established increasingly large colonies. Their main habitats were alongside water sources in the Jordan Valley, and today they can be found all over the country, from Ramat Gan to Western Galilee and in Hayarkon Park in Tel Aviv.

In addition to the congenial climate, one of the main reasons the parakeets feel at home in Israel is the alien tropical landscape: without the eucalyptus and Pride of India trees, the parakeets would probably not have settled here and become a major pest for farmers. "I really love that bird," Zahor says in defense of the parakeet. "I love its beauty and its pleasant sound. I am very upset by the huge number of crows that have multiplied here and become the enemy of the Israeli songbirds. As far as I am concerned, the rose-ringed parakeet has become an Israeli bird that does not have to apologize to anyone for its existence."

2. Little fire ant

It hides amid logs, fallen leaves, stones or cracks in walls. It is reddish in color, 2-3 millimeters long and its bite hurts. The little fire ant (Wasmannia auropunctata) settled in Kibbutz Afikim about seven years ago and shows no signs of leaving. "At one point I spotted a column of the ants in my house," says Shulamit Razhevsky. "I immediately collected them in a dish and sent them to the Volcani Institute [of Agriculture at Beit Dagan]. From there they were sent to the Department of Zoology at Tel Aviv University together with my whining letter."

Prof. Abraham Hefetz, an entomologist from Tel Aviv University, says, "When I heard about people being bitten by ants in the Jordan Valley I didn't take it seriously, because I knew there were no ants that bite in Israel. So I was quite surprised when the sample arrived from the kibbutz. I realized this was a whole new ball game."

The invaders were traced to a kibbutz sawmill that received lumber from all over the world. A genetic examination revealed that the ant came from Manaus, on the edge of the Amazon River in Brazil, one of the sources of the lumber. However, what at first appeared to be a localized problem soon assumed wider dimensions.

"Kibbutz Afikim supplied wood across the country, so the fire ant hitched a ride to all kinds of other places," Hefetz notes. "We now have confirmed sightings of the ant in Kibbutz Dafna in the north and Kibbutz Nir Am in the south. Besides the fact that this ant is harmful to human beings, it is also known to be aggressive toward other species in its surroundings. The result is that where the little fire ant is present, there is a drastic decline in the population of ground insects, such as spiders and beetles. This ant sterilizes the area of its habitation."

3. Water hyacinth

The tremendous spread of the water hyacinth (Eichhornia crassipes), a floating water plant with broad leaves and purple-pink flowers, can be seen clearly in Na?aman Creek in Western Galilee, in drainage canals in the village of Yesud Hama'ala in the Hula Valley, and in the Sharon District in the center of the country. Brought to Israel as a decorative plant and sold at nurseries across the country, the water hyacinth was probably introduced into water sources by passersby and immediately began to spread. According to Dr. Jean-Marc Dufour-Dror, an expert in bio-geography and an ecology consultant, the water hyacinth, if allowed to grow unchecked, can completely blanket lakes, creeks and ponds and cause tremendous damage. "This plant develops rapidly because it exists in an ecosystem where it has no enemies," Dufour-Dror says. "There are no fungi that attack it and no animals that eat it. The number of individual plants is capable of doubling every five years."

The water hyacinth, which is on the list of the 100 most dangerous invasive species in the world, changes the physical qualities of the water as well as the water temperature and the oxygen concentration, inflicting great harm on other marine species. According to Dufour-Dror, it is still possible to overcome the purple invader.

"Its habitation centers are still limited and our water sources are small, so it can be pulled out by hand," he points out. "The Nature and Parks Authority and the JNF have already done this in a few places, but the problem is that the water hyacinth returned, as is the case in Na'aman Creek. If we do not persist in our control efforts, the invasion might well spread to Lake Kinneret. That will cause a far more serious problem. Beyond the ecological damage, we will face formidable difficulties in pumping water from the lake, which is the source of our drinking water."

4. Nutria

The nutria ?(Myocastor coypus?), one of the most widespread mammals in Israel, is also one of the country?s major invasive species. It was imported from Argentina in the middle of the last century for the fur industry, a project that failed when it turned out that the fur it grew in the Middle Eastern climate was coarse and unsuitable for the industry. A number of individuals that escaped from the breeding farm in the north multiplied in nature. Today there are thousands of nutrias in Israel. This large rodent can be seen next to sweet-water sources in the coastal plain and in the Hula, Jezreel and Beit She?an valleys, where it feeds on aquatic plants. Because of its modest needs, the nutria can adapt with relative ease to a range of habitats.

The nutria's body is about 45 centimeters long and its tail measures 30 centimeters; its average weight is four kilograms. Pregnancy lasts about four and a half months and produces between four and eight offspring, which become independent two months after birth. "The nutria lives in burrows that it digs on the banks of water sources. It sometimes does damage to fishponds by creating water passages between them," says Asaf Meroz from the Society for the Protection of Nature in Israel. "But its greatest damage is ecological - the harm it does to the species of aquatic plants it feeds on. It has left the nuphar [water lily] on the brink of extinction. There?s a good reason why in Florida hunters get a $5reward for every nutria tail they bring in."

5. Red palm weevil

"It came to us as a gift full of unpleasant surprises," says Dr. Victoria Soroker, an entomologist at the Volcani Institute. The red palm weevil (Rhynchophorus ferrugineus), an invasive beetle, originates in East Asia (where its larvae are eaten by humans). The weevil is about three centimeters long and feeds on palm trees, particularly the canary palm. It was first discovered in Israel in 1999 around the Dead Sea. Vigorous action by the plant protection service of the Agriculture Ministry in cooperation with date growers brought about the weevil's extermination in the Jordan Rift Valley and in Eilat. It is thought to have entered the country in infected date shoots that were brought in as gifts to Israelis.

The red palm weevil does its deadly work insidiously. It lays its eggs in the trunk of the palm tree and the larvae excavate tunnels in the tree's "heart," soon killing the tree. "Our problem," Soroker says, "is that the damage done by this beetle is not apparent at first, and by the time it becomes visible the crown of the palm has dried out and it is too late to save the tree."

It is not only date farming and the export of palm seedlings - one of the most profitable crops in Israeli agriculture - that could suffer. The destruction of palm trees is liable to alter the entire Mediterranean landscape, a transformation already visible in the Canary Islands, Spain, Italy, Turkey and Greece, all of which have been invaded by the red palm weevil.

6. Sydney golden wattle

The yellow flowers of the Sydney golden wattle (Acacia saligna) can be seen in almost every corner of the country at this time of year. The shrub, which was brought to Palestine by the British during the Mandate period to stabilize shifting dunes and block soil erosion in hilly areas, has since become destructive to local ecosystems and landscapes.

"In the 1960s, the JNF, which adopted the British policy of afforestation, continued to plant the Sydney golden wattle in various places, such as the Judean hills and the Ashdod-Nitzanim dunes," says Prof. Pua Bar from the Department of Geography and Environmental Development at Ben-Gurion University in Be'er Sheva. "Those groves became a source for the spread of large numbers of seeds and for the plant itself. For example, the whole coastal region and the area of Sha?ar Hagai [on the Tel Aviv-Jerusalem road] are covered with dense groves of Sydney golden wattle, which spread spontaneously."

Originating in southwestern Australia, this plant is viewed as an invasive species that exercises a significant influence on the landscape and biodiversity of Israel.

"This shrub had a highly adverse effect on coastal plain ecosystems," Bar notes. "In the area of the Nitzanim and Palmahim dunes, which are nature reserves, one can see clearly how the variety of flora and fauna typical of the dunes disappeared as a result of its spread. Instead of jerboas and gerbils there are rats, and instead of the dunes snake, which is not venomous, we have the highly venomous local viper. The sand and landscape of the dunes have also disappeared.

"A similar phenomenon is occurring in the hilly areas and in areas where springs exist, such as Einot Givaton, east of Rehovot," she continues. "Unfortunately, it is difficult to deal with the problem today, because the trees have left their imprint in the seed bank that exists in the soil. Every tree produces millions of seeds a year, which remain vital for decades. This is a powder keg that in large measure has already exploded: the damage that has been done is almost irreparable."

7. House crow

"In 1976, we used to wait for the four Indian house crows on the northern shore of Eilat, by the border with Jordan," recalls Ohad Hatzofeh, an ecologist with the Nature and Parks Authority. "They used to fly in from Aqaba to the municipal refuse dump of Eilat, eat their fill and return to Jordan." That quartet of Indian house crows (Corvus splendens) has expanded to number hundreds in the Eilat area alone. ?The bird has become a genuine hazard in Eilat," Hatzofeh relates. "Besides ripping apart plastic bags in the search for food, these crows attack people and pets in the city. Dozens of such attacks have been recorded. The birds have invaded almost every country around the Indian Ocean. They came to us from Aqaba, which they probably reached as stowaways on ships that were anchored in Indian ports or in the Persian Gulf. The house crow is a gray and black bird and is truly uninteresting. It is clear to me that if we had not waged a persistent war against the birds, they would have multiplied by the thousands and perhaps even spread north to the Arava [desert] and finally to the Mediterranean."

The war currently takes the form of shooting them and destroying their nests. "But this is not just a local problem. The house crow has become a universal pest, like most of the invasive species," Hatzofeh says. "It preys on eggs and newly-hatched birds, but also on food in city produce markets and on crops. In Cape Town, South Africa, a special poison is used against house crows, in Yemen they are shot and in Australia there is a task force that shoots house crows that reach the coast."

8. Common myna

The common myna (Acridotheres tristis), considered one of the most dangerous and harmful invasive bird species, originates in the Indian subcontinent. It was imported into Australia as a natural predator of agricultural pests, but soon turned out to be a liquidator of local bird species. The myna was brought into Israel in the mid-1980s as a decorative bird for the Tsapari, a site in Hayarkon Park in Tel Aviv that houses birds in a tropical setting. At some point in the late 1990s it escaped or was released and spread across Metropolitan Tel Aviv, and from there to the north, south and east of the country. Mynas are now found throughout Israel, mainly in areas of human habitation. A dark-hued songbird with a yellow bill and legs to match, the myna has a classic starling look. It is a scavenger that subsists on a wide range of foods, including seeds, fruit, insects, earthworms and nectar. In Israel, as throughout the world, mynas compete with local species for food and nesting sites. They are also carriers of avian malaria. In Israel, they cause damage by seizing control of hollows used by local species of hollow-nesting birds, such as sparrows, titmice and Syrian woodpeckers, and preying on their young. Recently a case was reported in which mynas preyed on goldfinches, a species that has disappeared from many parts of Israel.

In addition to the ecological problems caused by the invasion of mynas, they are likely to pose a threat to agriculture as well, because of their fondness for pecking succulent fruits. At the moment, they are concentrated in built-up areas, but as they increase in number and spread to farm regions, considerable resources will have to be invested to eliminate them in order to avert large-scale economic damage.

9. Nomadic jellyfish

The sea, too, is being invaded. "Perhaps because we are land animals we take less interest in the sea, but our Mediterranean contains the largest number of invasive species on the planet," says Dr. Bella Galil, a marine biologist from the National Institute of Oceanography in Haifa. The nomadic jellyfish (Rhopilema nomadica) is one of the more familiar alien invaders. It appears almost every summer in vast swarms 100 kilometers long and two kilometers wide. "I believe that everyone who has ever bathed in the Mediterranean has encountered this jellyfish, which leaves a burning memory," Galil notes.

"The nomadic jellyfish has become one of the world?s prominent examples of an invasive species," Galil says. "We have a catastrophe on our hands, which is due to the Suez Canal and the distinctive conditions of the Mediterranean Sea, which is quite salty and warm. The majority of the 600 invasive species that entered the Mediterranean did so through the Suez Canal. They are not welcome guests: they have already erased several dozen local species. Accordingly, observers in Europe, North America and even in Asia view the developments here as an example of a significant disruption of the natural balance in the sea."

10. Gall wasp

Two types of gall wasps (Cynipidae) have established themselves in Israel in recent years. Both types - the Leptocybe invasa and the Ophelimus maskeli - penetrated from Australia in 2000, posing a mortal threat to all the eucalyptus groves in the country. "We were the first to discover the spread of these two types of wasps outside their original habitat in Australia," says Prof. Zvi Mendel from the Volcani Institute?s entomology department. "We found them in the Jordan Valley and in the area of the Gezer Regional Council [near Latrun junction west of Jerusalem]. It is not known exactly how the two species infiltrated Israel - they probably hitched a ride on international flights from Australia."

These wasps are violent pests that inflict heavy damage. "In 2003, at the height of the spread of gall wasps in Israel, schools were closed because of them in Petah Tikva and Yahud," Mendel says. The tiny wasps - they are about 1 millimeter long - "constituted a serious hazard by getting into children?s eyes and ears. But beyond that, their discovery outside Australia was extremely worrisome because of the severe damage they are liable to inflict on eucalyptus trees, which are mainstays of Israel?s planted forests, as well as to bee-keeping and in particular to the global lumber industry, in which the eucalyptus plays a key part."

The "galls" - abnormal swellings of plant tissues - created by the wasps are a kind of cancerous growth that develops on the plant in response to stimulus or activity by a foreign organism. The mass presence of galls dries out the leaves and causes them to fall off. "In the past few years, the two types of wasps spread very rapidly to all the areas where eucalyptus trees have been planted in Israel," Mendel says. After identifying the Australian invaders, Mendel's research set about finding a solution to the problem they represent. At the end of seven years of research, parasitic wasps which feed on the gall wasps were found in Australia. These have been acclimatized in Israel, thus averting a critical economic and ecological problem, the researchers say.