We need urban trees more than ever – here's how to save them from extreme heat
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星期一, 九月 25, 2023
Human, Heat, Brachychiton, Overheating, City, Bureau, Garden, Tree, Survival, Meteorology, Research, Temperature, Carbon, Elm, Plant, Fraxinus excelsior, Time, Water, Bureau of Meteorology, Global Change Biology, Perspiration, Acer, Climate change, Death, Liriodendron, Silviculture, Agriculture, Forestry, Greater Western Sydney, Banksia
And we’ve just watched the Northern Hemisphere swelter through their summer, making July 2023 Earth’s hottest month on record.
Key Points:
- And we’ve just watched the Northern Hemisphere swelter through their summer, making July 2023 Earth’s hottest month on record.
- We studied the effects of extreme heat on urban trees in Western Sydney during Australia’s record-breaking summer of 2019–20.
- So we hold grave concerns for the survival of both native Australian and exotic species in our urban forest.
- Read more:
Climate change threatens up to 100% of trees in Australian cities, and most urban species worldwide
Trees during heatwaves in Sydney
- Those most vulnerable to heatwaves included both native Australian and exotic species.
- Some trees died, including red maple (Acer rubrum), tulip poplar (Liriodendron tulipifera), coast banksia (Banksia integrifolia) and water gum (Tristaniopsis laurina).
- Read more:
Without urgent action, these are the street trees unlikely to survive climate change
Why are some species more vulnerable?
- For example, species with large, thin leaves are particularly vulnerable.
- Thin leaves are less able to buffer against overheating on hot, sunny days when the wind lulls.
- Our research found most urban tree species –- even those under drought stress –- opened their pores to cool leaves on hot summer days.
- This results in rapid water loss but may help prevent tree leaves from scorching.
Why is water so important during heatwaves?
- We found water loss was higher than predicted during heatwaves for all plants.
- In urban trees, leaves reached lethal temperatures of 49–50℃ for species with the lowest rates of water loss.
- But when species with low rates of water loss had access to water, there was little heat damage or scorched leaves.
Preserving our natural air conditioners
- That means urban greening programs need to find ways to provide trees with enough water when rainfall is unreliable.
- Cities need trees now more than ever, as these natural air conditioners take the edge off the extremes.
- David S Ellsworth receives funding from the Australian Research Council, the New South Wales Government, Hort Innovation, and the Herman Slade Foundation.