Climate Change Scientist Joins the Columbia Mailman School

One of the world’s leading experts on the effects of climate change on plants and agriculture, Lewis Ziska, has joined the Columbia Mailman School of Public Health as associate professor of Environmental Health Sciences in the School’s Climate and Health Program. Previously, Ziska served for nearly 25 years as a scientist at the United States Department of Agriculture (USDA); he chose to leave after he saw politics get in the way of research on climate change.   

“I’m excited to continue my research in an environment supportive of the kind of work I do, where climate change is about science, not politics,” he says. “Here at the Columbia Mailman School and across the university, researchers are doing important work to understand and prepare for the drastic changes to our ecosystem already underway.” 

After earning a PhD in plant physiology from the University of California, Davis, Ziska began his career as a Smithsonian fellow, then took up residence as the project leader for global climate change at the International Rice Research Institute in the Philippines. There he contributed some of the first research into the effect of rising CO2 on agriculture, finding a marked reduction in rice protein. A follow-up study published last year identified additional harms, with evidence of declines in micronutrients and vitamins important to human health—deficiencies that threaten 600 million people who rely on rice for the majority of their calories.

“Carbon dioxide is often called ‘plant food,’” says Ziska. “That’s true, in the sense that carbon dioxide, the principal greenhouse gas, is also the principal source of carbon for photosynthesis. However, this does not mean that climate change is a positive for the plants we rely on. While yields of some crops could increase, the nutrient content in important staples is in decline. It’s also important to remember that extra growth we see from added CO2 doesn’t discriminate between desirable and undesirable plant species.”

Unwelcome plants expected to flourish in the changing climate include ragweed—warmer conditions produce more allergenic pollen—and poison ivy, which will grow more potent. The changing climate also promotes the growth of invasive species that make farming more difficult. His research found that herbicide use tracks with average temperature; on average, Louisiana soybean farmers spray their crops more than Minnesota farmers. Absent radical changes to agricultural practices and green energy sources, the warming climate will lead to more intensive use of herbicides that Columbia Mailman research shows come with its own health risks. At the same time, intensive spraying makes weeds more likely to evolve herbicide resistance. “Who’s going to win on the farmer’s field, the weeds or the crop?” he asks, rhetorically. “Turns out, it’s the weeds.”

In another study, Ziska, who has contributed to several United Nations Intergovernmental Panel on Climate Change (IPCC) reports, analyzed a collection of Canadian goldenrod samples from the Smithsonian dating back to 1842, finding levels of protein in the flower’s pollen had dropped by one-third since the start of the Industrial Revolution—potentially a factor in declines in the bee population which relies on pollen for food. Humans, of course, rely on bees to pollinate plants that produce our food. Currently, Ziska is repeating the experiment with several more flowering plants.

The full extent of the impact of the changing climate on plants and agriculture remains unknown. Could pollen become more allergenic? What other allergenic species will be affected? How many poisonous plants will be affected? How will CO2-induced changes in crop nutrition affect human nutrition? If plants proliferate, will disease-carrying insects and rodents follow suit? How will the quality of plant-derived medicines be affected? How is coffee affected? (Stay tuned: Ziska has research on coffee due out soon.) And not least of all, how can humans adapt beyond the obvious need to immediately transition away from fossil fuels?

In the battle between farmer and weed, Ziska suggests we move away from an industrial monoculture that relies on a small number of plant varieties in favor of a return to our agricultural roots. Since the first fields were planted millennia ago, humans bred crops to flourish under many different and difficult conditions, including flooding and drought—both which are becoming more common. In the same way, he says we should tap this rich library of crop varieties—cultivated rice alone has approximately 100,000 lines—to find those that are best suited to rising temperatures and CO2. In a paper published by the Royal Society, he details a method to identify these plant strains based on their physical characteristics and genetic makeup. Scientists in Australia, China, and Japan are currently testing different rice strains for these same characteristics.

Ziska’s interest in crop diversification dates back to a conversation he had with a Thai farmer in the 1990s. “I saw in his small rice paddy that he was growing many different rice varieties. I asked him why. He told me, ‘I do it so I can feed my family.’”