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Climate Changes Timing of Leaf Growth

Extensive worldwide changes in the timing of leaf activity over the past few decades have been revealed by satellite data taken over the past three decades.

The findings, published in Nature Climate Change, provide the first global picture of changes in leaf phenology – the timing of leaf emergence, growth and death – due to environmental cues such as temperature, rainfall and atmospheric CO2 concentrations.

Research leader Prof Steven Higgins of The University of Otago says that changes in these environmental cues cause earlier leaf emergence in Europe and North America, but other parts of the world have not been well-studied, especially in the Southern Hemisphere.

“For the first time, we have shown that equally severe changes have occurred over large regions of Africa, South America and Australia,” Higgins said. “Overall we found that the phenological signature of 95% of the Earth’s land mass has altered, with 54% changing substantially.”

This could lead to higher extinction risks for species that depend on the leaf phenological cycle, with this process already being observed in the Northern Hemisphere. “For example, several bird species have already experienced population losses due to the effective seasons moving out of sync with their life-cycles, and similar changes have been reported for insect pollinators and even large mammals such as deer,” Higgins says.

These changes are also likely to have significant impacts on ecosystem stability and functioning, carbon and energy exchange between the land surface and the atmosphere, and agricultural practices.