Um programa que usa aves de rapina no lugar de pesticidas
inspirou a colaboração internacional.
Em 1982, o Zoo da Universidade de Tel Aviv doou ao
ornitólogo Yossi Leshem um presente pouco usual: 15 corujas-das-torres. O zoo
estava com um excedente das corujas e Leshem disse que poderia fazer bom uso
delas. Ele então levou as aves até um kibbutz no Vale de Hula, onde fazendeiros
estavam sofrendo tanto com a invasão de roedores que em alguns anos campos
inteiros eram destruídos pelos ratos.
Leshem estava, então, trabalhando para a Sociedade de
Proteção da Natureza em Israel e preocupado com o uso pelos fazendeiros de um
pesticida tóxico, que já havia sido banido nos Estados Unidos por prejudicar
animais selvagens. Em Israel, o produto estava matando aves migratórias e
garças. Pensou, então, que as corujas – que gostam de caçar roedores em campos
de plantação e vivem bem próximas dos humanos – poderiam ser a solução. Elas
poderiam controlar os roedores naturalmente.
O resultado, mais de três décadas depois, é um sucesso para
além do que Leshem poderia imaginar e se espalha por boa parte do território
israelense, palestino e jordaniano. O projeto fez com que cientistas árabes e
israelenses trabalhassem em conjunto em uma época de tensões políticas crescentes.
“Os pássaros têm o poder de unir as pessoas porque não conhecem fronteiras”,
diz Leshem, que hoje trabalha também na Universidade de Tel Aviv.
Leia a íntegra da matéria sobre o projeto, em inglês, no artigo original da revista Nature ou na reprodução que fizemos dele logo abaixo.
Owls for peace: how conservation science is reaching
across borders in the Middle East
A programme that uses birds
of prey in place of pesticides has inspired international collaboration.
In early 1982, the Tel Aviv University
zoo in Israel presented ornithologist Yossi Leshem with an unusual gift: 15
barn owls. The zoo had an owl surplus, and Leshem said he could make use of
them. He packed the birds into a van and drove them north to a kibbutz in the
Hula Valley. There, farms were plagued so badly with voles that in some years
entire fields would echo with their high-pitched squeaking.
Leshem, who was working for the Society for the
Protection of Nature in Israel, was worried that to control the pests, farmers
were overusing a rodent-killing chemical called sodium fluoroacetate, or
compound 1080. It had been banned a decade earlier in the United States because
of its toxic effects on grizzly bears, hawks and eagles; in Israel, it was
killing migrating birds and native egrets. Leshem thought that barn owls (Tyto
alba), which like to prey on rodents in agricultural fields and are
comfortable living close to people, might be the solution. They could control
the rodents naturally.
That year, the farmer with whom Leshem planned to work
was called up to the Israeli army to fight a war in Lebanon — and was killed.
Leshem, who also served in the war, was undeterred. He relaunched his
experiment the next year with the help of another farmer, setting up owl nest
boxes at a kibbutz called Sde Eliyahu, farther south in Israel’s Beit Shean
Valley.
More than three decades and numerous conflicts later,
the barn-owl approach to controlling rodents has succeeded beyond Leshem’s
wildest expectations, spreading across much of Israel and into the neighbouring
Palestinian territories and Jordan. And the work has brought together Arab and
Israeli scientists at a time of increasing political tensions. “Birds have the
power to bring people together, because they know no boundaries,” says Leshem,
who now also works at Tel Aviv University.
In January, researchers from the Middle
East, Mediterranean and North Africa met at a Dead Sea resort in Jordan to see
barn-owl nest boxes in the field, discuss scientific findings and hatch plans
for similar efforts in Egypt, Cyprus, Greece, Tunisia and Morocco. The
programme benefits farmers, biodiversity and sociopolitical networks alike,
says conservation biologist Sara Kross at California State University in
Sacramento, who in March will host some of the researchers involved in a joint
US–Israeli workshop on the topic.
Proponents say that the project is more important than
ever following US President Donald Trump’s announcement in December that the
United States would recognize Jerusalem as Israel’s capital, which strained
relations between Israel and its neighbours. “It’s hard to ask people in
Jordan, or other Arab countries, to cooperate with Israelis in light of Trump’s
announcement,” says Mansour Abu Rashid, who works with Leshem and directs the
Amman Center for Peace and Development, a non-governmental organization
dedicated to promoting dialogue between peoples in the Middle East. “Scientists
should continue their cooperation for the benefit and peace of people in the
area,” he says.
Natural controls
The owl project did not start smoothly. The first nest
boxes, imported from Europe, were not designed for the hot climate, and they
baked some baby owls to death. But within about 15 years, the project expanded
to the entire Beit Shean Valley, covering about 16,000 hectares, says Shaul
Aviel, the Sde Eliyahu farmer who worked with Leshem to start the programme
there.
The first signs of victory, he says, were in date
plantations. Rats can climb and nest in the date palms, and rat-gnawed dates
contaminated with droppings cannot be sold. But the damage disappeared when the
barn-owl initiative was established. Aviel says that the programme “works 100%”
in wheat, dates, olives and pomegranates. But the owls aren’t sufficient to
protect all crops; rodents find the green shoots of alfalfa, for instance,
irresistible.
Israeli farmers caught on to using the owls, but
Leshem realized there was a problem with the programme. Young owls raised in
the nest boxes in Beit Shean Valley were spreading through the Jordan Valley,
which is shared by the Palestinian territories and Jordan. When they flew over
borders, the owls were sometimes poisoned by rodenticides.
But in 2002, Leshem met and began collaborating with
Abu Rashid, a retired Jordanian army general who was a key architect of the
1994 Israel–Jordan peace treaty. And by 2008, after some setbacks caused by
more political violence in the region, Leshem, Abu Rashid and Imad Atrash, the
director of the Palestine Wildlife Society in Beit Sahour, gained funds from
the European Union and the US Agency for International Development to launch
the project as a cross-border programme.
Researchers set up nest boxes in study sites across
three areas of the Jordan Valley, trained farmers and educated local
communities about the programme. Now, there are thousands of nesting boxes in
Israel and hundreds elsewhere in the region (see ‘Birds across borders’),
although curious children have vandalized some of the boxes in the Palestinian
territories, Atrash says. Although sceptical of the birds at first — the
ghostly white owls are considered a bad omen in many parts of the Middle East —
most farmers change their minds after seeing the project’s results, says Abu
Rashid. In the Middle East, a pair of barn owls can eat between 2,000 and 6,000
small mammals a year. “The farmers feel it in their yearly production,” he
says.
Fewer chemicals
Overall, results are impressive, advocates for the
project say. The use of rodenticide goes up and down with the natural rodent
cycles of boom and bust, but applications of compound 1080 in Israeli fields
have fallen by an average of around 40–60% since the programme began, says Yoav
Motro, an ecologist at the Israeli Ministry of Agriculture in Beit Dagan.
(Motro’s study has not been published, but he has presented the results at a conference.)
Other natural predators of rodents, including
kestrels, foxes, jackals and storks, also come in when rodenticide isn’t used,
he says. But the best evidence that the barn owls are effective, says Yoram
Yom-Tov, a zoologist at Tel Aviv University, is that farmers — who care about
their earnings per acre — choose to use them rather than spray chemicals.
Researchers have also learnt about owls’ hunting
habits through the programme. Wildlife ecologist Motti Charter of
the Shamir Research Institute at the University of Haifa in Israel has attached
radio transmitters to barn owls to show that they can fly 4–7 kilometres away
from their nest boxes each night in search of prey — farther than the 500
metres Israeli scientists had originally assumed. (Radio-transmitter research
on barn owls in other countries has produced similar findings.)
And at the Dead Sea conference this January,
ornithologist Alexandre Roulin of the University of Lausanne in Switzerland
reported yet-to-be published work showing that the barn owls’ white coloration
might enhance their hunting success. Mice are naturally averse to bright light,
so they tend to freeze in response to the owls’ ghostly white shine. Roulin,
who began collaborating with the project eight years ago after he met Leshem at
a scientific meeting, found that on moonlit nights, this effect is enhanced;
the Moon’s glow makes the owl’s plumage brighter, making the rodents freeze for
longer periods of time.
Spreading the word
Israel, Jordan and the Palestinian territories are not
the only places where barn owls have been used to control pests, although they
are home to the only cross-border programme. Farmers in Malaysia have used barn
owls since 1988 to control rodents in palm-oil plantations — although the
government also promotes rodenticide use, says Charter.
In California, some farmers have started using
barn-owl and kestrel boxes to protect citrus orchards, walnut trees, vineyards
and other crops, says Kross. The notion of birds as biological controls dates
back to the nineteenth century in the United States, she says, as part of a
field called economic ornithology — then defined, according to an 1899 review, as “the study of birds from the standpoint of dollars and cents”. But
once pesticides became widespread, the idea died out. Now, the practice is
slowly being revived, largely by word of mouth.
Kross and other scientists are watching the Jordan
Valley results with interest. “It’s a fantastic project,” says Javier Viñuela,
an ecologist at the Hunting Resources Research Institute in Ciudad Real, Spain.
In his own country, Viñuela has been collaborating with the non-governmental conservation
organization GREFA, which has set up some 2,000 nesting
boxes for barn owls and kestrels to control vole numbers.
Small-scale experiments inspired by the Israeli
experience have started in Argentina and Uruguay, says Charter. And in Cyprus,
27 barn-owl nesting boxes were installed in a pilot collaboration with Israel in 2015; the aim is to install around 60 more this
year, says Elena Markitani, a development officer at the non-governmental
organization BirdLife Cyprus, which works to conserve wild birds in the
country.
Martin Hellicar, director of the organization, says
that the Middle East programme is a “fantastic thing to try and copy–paste,
adapting it to local conditions”. Besides the Israeli project, however, there
is a dearth of robust data on the use of owls to control rodents, says Lourens
Swanepoel, a conservation ecologist at the University of Venda in Thohoyandou,
South Africa.
In general, scientists in the Jordan Valley project
avoid talking politics, says Roulin. But they are alert to their work’s
political resonance. Last year, Roulin, Charter, Abu Rashid, Leshem and others
published a paper entitled ‘‘Nature knows no boundaries’: the role of nature
conservation in peacebuilding’ (A. Roulin et al. Trends Ecol. Evol. 32, 305–310;
2017), in which they argue that measures
such as the owl project could help to reconcile communities in conflict,
building mutual trust without raising the sensitive issues at the root of the
strife. “In a conflict area, a project like this or any project in common can
help, because the bottom line is the politicians are failing,” says Leshem. “I
know I’m not going to solve the problems of the Middle East, but I can do my
small part.”
