Climate change causes plants to flower earlier

As the climate warms, many plants are flowering 8.5 times sooner than experiments had predicted, raising questions for the world's future food and water supply, a new international study concludes. Higher carbon dioxide emissions from burning fossil fuels can affect how plants produce oxygen, and higher temperatures can alter their behavior. Shifts in natural events such as flowering or leafing, which biologists call "phenology," are obvious responses to climate change. They can impact human water supply, pollination of crops, the onset of spring (and allergy season), the chances of wildfires and the overall health of ecosystems. To better understand this, scientists from 22 institutions in Canada, Sweden, Switzerland, the United Kingdom and the United States studied 1,634 species of plants across four continents. They compared how plants responded based on historical monitoring data and on small-plot experiments in which warming was artificially induced. "Across all species, the experiments under-predicted the magnitude of the advance - for both leafing and flowering - that results from temperature increases," the study says. The findings appear this week in an advance online issue of the journal Nature. The study finds experiments had underestimated the speed of flowering by 8.5 times and growing leaves by four times. It says long-term historical records show leafing and flowering will advance an average of five to six days per degree Celsius. "Future plant and ecosystem responses to warming may be much higher than previously estimated from experimental data," study author Elsa Cleland, an assistant biology professor at the University of California - San Diego, said in announcing the results. Ecologists have often relied on warming experiments because historical records are not available in most locations and climate change may produce temperatures higher than previously recorded. The study was funded by the National Science Foundation, the state of California and the University of California, Santa Barbara. The U.S. Geological Survey and the USA-National Phenology Network also provided support.