The nine conservationists had embarked on one of the most ambitious wildlife projects in Iran in recent years, setting camera traps in seven provinces to monitor the critically endangered Asiatic cheetah, whose dwindling population stalks Iran’s central plateau.

They worked with the government, secured the right permits and received funding and equipment from abroad.

But the researchers, all Iranian, soon drew suspicion from the Revolutionary Guard, a powerful branch of Iran’s armed forces, and were arrested last year for alleged espionage.

Now, four members of the team charged with “spreading corruption on earth” could face the death penalty, and four others could be sentenced to up to 10 years in prison.

The team, from the non-profit Persian Wildlife Heritage Foundation, are awaiting a verdict in a trial that rights groups say has been marred by abuses and accusations of torture.

Revolution in Iran: In pictures Show all 11 1 /11 Revolution in Iran: In pictures Revolution in Iran: In pictures A demonstration against the Shah in 1979 Getty Revolution in Iran: In pictures Armed women on guard in one of the main squares in Tehran at the beginning of the Iranian Revolution Getty Revolution in Iran: In pictures Demonstrators hold a poster of Ayatollah Ruhollah Khomeini, in January 1979, in Tehran, during a demonstration against the Shah AFP/Getty Revolution in Iran: In pictures Iranian rebels pose with a U.S. flag they bayonetted upside down on trees at Sultanabad Garrison northeast of Tehran on February 12 2019 AP Revolution in Iran: In pictures A gun battle in Khorramshahr during the revolution, 1979 Getty Revolution in Iran: In pictures Ayatollah Khomeini's supporters demonstrate in the streets of Tehran against the Shah among tear gas. The "black friday" caused the death of 200 people according to the Iranian government, 2000 according to the opposition, September 8 1978 AFP/Getty Revolution in Iran: In pictures Women wearing the traditional Chador demonstrate in the streets of Tehran against the Shah on September 7 1978 AFP/Getty Revolution in Iran: In pictures Demonstrators in Tehran calling for the replacement of the Shah of Iran during the Iranian Revolution, 1979. They carry placards depicting Ayatollah Mahmoud Talaghani, one of the leading revolutionaries Getty Revolution in Iran: In pictures Ayatollah Khomeini's supporters demonstrate in the streets of Tehran against the Shah. The "black friday" caused the death of 200 people according to the Iranian government, 2000 according to the opposition, September 8 1978 AFP/Getty Revolution in Iran: In pictures Thousands of the Ayatollah Khomeini's supporters on the streets of Tehran calling for the religious leader's return in January 1979 Getty Revolution in Iran: In pictures The Iranian Islamic Republic Army demonstrates in solidarity with people in the street during the Iranian revolution. They are carrying posters of the Ayatollah Khomeini, the Iranian religious and political leader Getty

The ninth researcher who was detained, the foundation’s chairman, Kavous Seyed-Emami, died in custody shortly after his arrest last year.

Tehran’s prosecutor general said Mr Seyed-Emami, a professor who also held Canadian citizenship, had died by suicide, but family members and colleagues have rejected that account.

“He was hopeful and optimistic about the country’s future,” Mr Seyed-Emami’s son, Mehram, said in an interview. “He was never one to have hardline or polarised views.”

The plight of the conservationists, described by friends and family as passionate champions of the environment, has highlighted what analysts say is the growing criminalisation of scientific and scholarly research in Iran, spurred in part by the security forces’ profound suspicion of contacts with foreign institutions.

The Revolutionary Guard has increasingly targeted academics, researchers, business executives and dual nationals for arrest, and the repressive campaign is taking a particular toll on Iranian efforts to address a mounting environmental crisis.

In addition to concerns about vanishing species, the country is confronting dwindling water resources due to rapid urbanisation and excessive dam building.

The Persian Wildlife Heritage Foundation began using wildlife camera traps, deployed by researchers around the world, to track the intensely shy Asiatic cheetah amid concerns over its eroding natural habitat, which is threatened by Iran’s expanding mining sector and growing road network. The cheetahs now number fewer than 50, scientists say.

The rudimentary cameras are triggered by a mammal’s movement and body heat and snap images of animals within a few yards of a target spot, such as a game trail or watering hole.

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But conservationists – whose expertise includes wildlife biology, ecology and eco-tourism – were accused of using scientific and environmental projects, including the foreign-manufactured camera traps, to collect classified military information.

After the arrests, more than 350 scientists from around the world, including Jane Goodall, signed a letter to Iran’s supreme leader, Ayatollah Ali Khamenei, in support of the conservationists.

“We are horrified about the thought that the neutral field of conservation could ever be used to pursue political objectives,” the letter read. “We as a community strongly condemn that, and we are convinced our colleagues had no such part.”

Founded in 2008, the Persian Wildlife Heritage Foundation had long worked in cooperation with Iran’s Department of Environment, which operates under president Hassan Rouhani and had cordial relations with authorities, colleagues said.

“Their work as an NGO [non-governmental organisation] was very transparent,” Mehram said of his father and his colleagues. “They submitted annual reports highlighting all of their activities. There was nothing to hide.”

Earlier this year, two government agencies overseen by President Rouhani, including Iran’s Supreme National Security Council, cleared the researchers of wrongdoing in inquiries prompted by Mr Seyed-Emami’s death.

But the findings did not win their release. Human Rights Watch reported that at least two members of the group – Niloufar Bayani, a US-educated biologist, and Sepideh Kashani, a project coordinator – planned this month to begin a hunger strike to protest their detention.

“Members of the Persian Wildlife Heritage Foundation have languished behind bars for over 550 days while Iranian authorities have blatantly failed to provide a shred of evidence about their alleged crime,” Michael Page, deputy Middle East director at Human Rights Watch, said in a statement this month.

“The authorities should take the long overdue step of releasing these defenders of Iran’s endangered wildlife and end this injustice against them.”

French family run for their lives as they're chased by cheetahs at Beekse Bergen wildlife park

The fate of the conservationists has become tangled up in the tensions between President Rouhani’s moderate administration, which has sought dialogue with the West, and hard-liners in the Revolutionary Guard.

Within the past two months, Iranian authorities have detained two scholars with dual nationality – British Iranian anthropologist Kameel Ahmady and French Iranian researcher Fariba Adelkhah.

US scholar Xiyue Wang, who travelled to Iran to research his thesis on the Qajar dynasty for Princeton University, has been imprisoned since 2016.

Kaveh Madani, a former deputy director at the Department of Environment, said he was forced to leave Iran after he was arrested early last year and interrogated by the Revolutionary Guard.

He said authorities accused him, among other things, of trying to “shut down” the farming sector by criticising the government’s water and agricultural policies, which prioritise dam building. Many of the dams in Iran are constructed by the Revolutionary Guard.

“Iran can serve as a classic example of the effects of shortsighted management and plans for development on the environment,” said Mr Madani, an environmental scientist and water conservation expert.

“In Iran,” he said, “we have every environmental problem imaginable: desertification, deforestation, dust storms, sinkholes, water pollution, air pollution, diversity loss.”

Scientists warn that the conservationists’ detention has halted critical wildlife protection efforts in Iran.

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The country is home to several rare species, including Persian leopards, Baluchistan bears and other mammals. If the Asiatic cheetahs go extinct, they will join the Caspian tiger and Asiatic lion, which have also vanished.

The camera traps were considered a vital tool to keep that from happening.

In a study of Iran’s rare cheetah published in 2017, Houman Jowkar, one of the detained scientists, described using wildlife camera traps to confirm the cats’ presence in 18 locations. The 2017 study used mostly models made in the United States.

“A camera trap used to study wildlife would be a very poor tool to spy on anything from a distance,” said Rahel Sollmann, a biologist at the University of California at Davis and a camera trap expert.

Cole Burton, a conservationist at the University of British Columbia, added: “We’re not looking for magazine quality. We just want to be able to count spots on the side of the animal or what have you.”

Mr Burton, who signed the letter to Mr Khamenei, has used camera traps to study brown bears in Iran’s neighbour, Armenia.

Mr Burton said that two graduate students in his lab, both Canadian-Iranian, had planned to extend their bear research across the border into Iran. Those plans were cancelled after the arrests, he said.

“It has been very concerning for conservationists in general but definitely for those of us using this tool,” he said. “This has been a real setback” for conservation in the region, he said.