No one outside the Chinese government knows where Tashpolat Tiyip is. No one knows exactly what charges have been filed against him. The only thing that anyone really knows is that in April 2017, as the geographer and former president of Xinjiang University in Ürümqi prepared to fly from Beijing to Berlin for a scientific conference and the launch of a research center, he disappeared without even a phone call to colleagues or family.

Six months later, a Chinese propaganda video emerged saying Tiyip was one of 88 scholars who had “deeply poisoned the minds” of students by approving textbooks with too much content from Uyghur sources—the ethnic group that makes up about half of Xinjiang province’s 24 million people. The video calls Tiyip and three other Uyghurs “two-faced” separatists before announcing their sentence: death, with a 2-year reprieve.

“It just doesn’t make any sense to anybody,” says Gary Langham, executive director of the American Association of Geographers (AAG), which last week sent Chinese president Xi Jinping a letter asking him to halt the execution and release Tiyip unless there is evidence he committed actual crimes. It was signed by more than 1300 researchers from 50 countries. (AAG took action after Amnesty International warned that Tiyip’s execution could be imminent.)

China’s crackdown on mostly-Muslim minorities in the far western province of Xinjiang, which include the Turkic-speaking Uyghurs, Kazakhs, and Kyrgyz, has swept up as many as 1 million people. But Tiyip is one of its best-known victims. Scientific organizations outside of China are trying to help him and other internationally known researchers who have disappeared. But many are moving cautiously, worried about making things worse. And it’s unclear whether, in China’s current political climate, such support from abroad makes any difference.

Since late 2016, China has detained as many as one in 11 Uyghurs in Xinjiang, most in grim re-education camps with barbed wire fences and guard towers. There, they learn party slogans and songs, and study the Chinese language. Government officials say the camps are necessary to crack down on 20 years of “violent terrorism” in the region. But human rights groups say the operation is an attempt to erase Uyghur culture and traditions; some call it “cultural genocide.”

A spokesperson for the Chinese embassy in Washington, D.C., wrote in an email to Science that Tiyip was actually arrested in May 2018 on suspicions of “taking bribes and corruption involving a huge amount of money.” The spokesperson neither confirmed nor denied that Tiyip has been sentenced, but said: “At present, the case is going through the court proceedings.”

Tiyip’s detention came as a surprise to many colleagues because he was an official in the Chinese Communist Party and a “red person,” someone known for carefully following party rules, says a Uyghur social scientist who knows Tiyip and asked not to be identified. Tiyip studied in Japan after getting a bachelor’s degree at Xinjiang University, but in 1992, he returned to his alma mater to teach and study desertification and soil salinization using remote sensing technology. His work on arid ecosystems ecology led to an honorary degree from the École Pratique des Hautes Études, part of the Sorbonne in Paris, in 2008. By 2010, he was the university’s president as well as its deputy party secretary.

“They interviewed him on TV a thousand times,” the social scientist says, usually to showcase Tiyip’s rise from a humble farming background to his prominent position in Uyghur—and Chinese—society. “[They would say] he’s a president, a selfmade man with party support.” Yet that did not protect him, the scientist adds: “If they took [him] … there’s no hope for the rest of us.”

Tiyip was apparently replaced as university president in late March, just a few weeks before his arrest. He disappeared en route to Germany, where he was supposed to attend the launch of a joint center to study underground coal fires, a collaboration between Xinjiang University and the Leibniz Institute for Applied Geophysics in Hanover. Tiyip had championed the center as university president.

Other internationally known researchers have been arrested in the crackdown, including Rahile Dawut, an anthropologist at Xinjiang University who studied regional literature and Uyghur oral traditions; Halmurat Ghopur, an official at the Xinjiang Food and Drug Administration and past president of the Xinjiang Medical College Hospital, who has also been sentenced to death for separatism; and Ilham Tohti, an economist sentenced to life in prison in 2014 on charges of separatism who last month won the Václav Havel Human Rights Prize, an annual award from the Parliamentary Assembly of the Council of Europe.

The detentions have put international scientific societies in a difficult position, says Clare Robinson, director of advocacy for the New York City–based group Scholars at Risk, which has repeatedly called for Tiyip’s release. AAG is one of several societies that have publicly supported colleagues in Xinjiang. But Robinson says speaking out risks disrupting academic collaborations with China and could lead to visa bans for foreign academics—or put their Chinese colleagues at risk. “You need to pick your public voice carefully,” Robinson says. The private diplomacy of Nobel laureates and university presidents is often more effective, she says. Such behind-the-scenes work is ongoing in Tiyip’s case and others.

Robinson says the mass detentions in Xinjiang province are unconscionable, regardless of who’s affected. But by targeting academics and intellectuals, authorities are robbing Uyghur—and Chinese—society of an important part of its future, she says. “If you remove from your functioning society all of the future scholars, the current scholars, the scientists,” Robinson says, “you’re losing an entire generation of individuals who could contribute to the production of knowledge.”