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Lewis Ziska quit his job as one of the U.S. Department of Agriculture’s top scientists in July in protest of what he says are the Trump administration’s efforts to silence his research.

After researching how climate change affects plants for more than two decades at the department, Ziska and a team of other scientists looked at how rising carbon dioxide levels impact the nutritional value of rice since the grain is a staple food for people across the world, Politico reported in August.

“Plants, which are the basis of all life, are changing,” says Ziska, now an associate professor at the Mailman School of Public Health at Columbia University, “and how they're changing is going to have implications, not only for human health but also for the environment as a whole.”

Prior to submitting this research for peer review, he says his superiors gave him permission. When the paper was accepted, an editor asked the team to write a press release since the research would attract attention from the media.

But after writing the press release, Ziska says he was told that “the conclusions of the paper were not supported by the data.”

“If you had a problem with the paper, you would have done it initially. It’s not something you do after the paper's been accepted,” he says. “So it indicated to me that they were not going to support the scientific findings.”

Ziska and other researchers focused on countries like Bangladesh, where more than 50% of people’s calories come from rice alone, and used predictions for carbon levels that he is “almost certain will happen before the end of the current century.”

The study found protein levels in rice decrease as the amount of carbon dioxide in the atmosphere increases. Key nutrients that are important for human health ⁠— like iron, zinc and vitamin B ⁠— are also declining.

“What's happening right now is an unprecedented increase in carbon in the air that's not keeping pace with other elements such as nitrogen and phosphorus and potassium that come from the soil,” he says.

On top of questioning his work at an unusual point in the publication process, he says other groups involved with the research were discouraged from releasing statements on the findings.

Ziska perceived this act of suppression as “crossing an ethical line.”

The Trump administration does not have a good record of climate science and initiatives, from pulling out of the Paris Agreement in 2017 to appointing an Environmental Protection Agency head who has denied carbon emissions are a primary cause of climate change.

An article published in The Guardian mentions six ex-government scientists who say the Trump administration tried to silence them by making them bury climate science.

A statement from a USDA spokesperson says the department did not attempt to block the publication of this paper, but rather some leading scientists at the Agricultural Research Service had concerns about its conclusions.

“The concern was about nutritional claims. The nutrition program leaders disagreed with the implication in the paper that 600 million people are at risk of vitamin deficiency,” the spokesperson says. “They feel that the data do not support this.”

The statement lists three reasons for the agency’s decision, including that the numbers on the amount of rice consumed in some Asian countries are out of date and that various conclusions aren’t supported by the data.

“It was strictly a debate among scientists, and the draft press release was never offered for review to any political appointees,” the statement says.

Ziska stands by that if there was a scientific disagreement prior to submitting his paper to the journal, someone would have told him beforehand.

“This doesn't sound like they're disagreeing with the science,” he says. “It sounds to me that they're disagreeing with the outcome of the study and the fact that the study did not fall into what their political purview was.”

He also contests that the people who disagreed with him were qualified to do so because they don’t have backgrounds in climate change research.

“The people that disagreed with it, to the best of my knowledge, are not people that have any background looking at climate change or carbon dioxide effects on nutrition,” he says. “The person who contacted me and told me about it was actually a soil scientist, not someone who had published in this area at all.”

These carbon-induced protein, vitamin and mineral deficits suggest “potential consequences for a global population of approximately 600 million” people who rely on rice for nutrients, according to the study.

In addition to human food, the study also found a decline in protein levels in pollen-rich goldenrod plants, which has implications for pollinator-insects like bees.

When he tried to discuss why the paper was no longer acceptable, he says he received no explanation.

Scientists at the USDA need to study how climate change will impact agriculture to protect food security by ensuring the U.S. remains a sustainable producer of major crops for countries around the world — not tailor their findings to what any administration finds “politically inconvenient,” Ziska says.

“There are very good people that are still at USDA, good scientists, good technicians, who can make a difference,” he says. “But if you're not allowed to work on this, if you're steered away from doing this kind of research, then what impact are you going to have?”

Ciku Theuri produced and edited this interview for broadcast with Kathleen McKenna. Allison Hagan adapted it for the web.