Global Warming’s Impact On Plants Greater Than Predicted

Jason Farmer for

For over two decades, researchers have been conducting experiments that are designed to mimic the effects of rising temperatures on the rates at which plants first begin to leaf and flower each spring. However, a new study has found that that these models are inaccurate, and that the actual impact of global warming on plants may cause the flowering and leafing of plants to occur up to eight times faster than the models predicted.

For many years, researchers assumed that plants would respond in much the same way in experiments that simulate global warming as they would to changes in temperature occurring in the natural environment. To test this assumption, Dr Elizabeth Wolkovich, of the University of British Columbia in Vancouver, and her colleagues compared the data on the timing of the flowering and leafing of plants found in observational studies to data based on warming experiments.

Dr Wolkovich and her colleagues were surprised by the results.

“What we found is that the experiments don´t line up with the long term data, and in fact they greatly underestimate how much plants change their leafing and flowering with warming,” Wolkovich told BBC News.

Observational data is gathered by the long term systematic recording of flowering and leafing rates in the natural world. According to Dr Wolkovich, the recent research suggests that these observations carried out in many different parts of the world over the past three decades are in remarkable agreement.

“In terms of long term observations, the records are very coherent and very consistent and they suggest for every degree Celsius of warming we get we are going to get a five- to six-day change in how plants leaf and flower.”

The researchers have concluded that scientists have greatly underestimated the difficulty of mimicking the impacts of the natural world in an artificial setting where the warming experiments are conducted. Real world factors not only include changes in temperature, but also changes in precipitation, cloud patterns and other unpredictable variables.

“I guess we will never get to perfectly match nature, but I am hopeful as scientists we can do much, much better, given funding resources,” Wolkovich told BBC News.

The team found that the greater investment in the design and monitoring of experiments, the more accurate the result.

Several other researchers were also surprised by the results.

Dr This Rutishauser, at the Oeschger Centre for Climate Change Research at the University of Bern in Switzerland, says based on this new research, scientists will have to rethink the impacts of global warming.

“The bottom line is that the impacts might be bigger than we have believed until now. That’s going to provoke a lot of work to probably revise modeling results for estimations of what’s going to happen in the future for food production especially.”

Dr Wolkovich has also concluded that if the models so grossly underestimate the real world observations, there could be a much greater impact on the world´s water supply than had been predicted by the artificial warming experiments.

“If a whole plant community starts growing a week earlier than we expect according to these experiments, it’s going to take up a lot more water over the growing season and if you add to that many years of the model projections, you are going to see big changes in the water supply.”

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