Aug 25, 2025 20:00:00

The reason why street trees can withstand dry periods better than park trees is because of leaking water pipes

Record-breaking heatwaves and droughts across Europe are having a devastating

impact on people's lives and economies. A new study published in the journal New Scientist examines how these droughts affect trees in city centers and parks.

Trees on city streets cope with drought by drinking from leaky pipes | New Scientist
https://www.newscientist.com/article/2487804-trees-on-city-streets-cope-with-drought-by-drinking-from-leaky-pipes/

It has been shown that when there is no rain for a long period of time, the amount of water and sap flow in trees growing in parks tends to decrease more than in street trees, but the reason for this was unknown.

To investigate why this is the case, André Poirier and colleagues at the Université du Quebec à Montréal in Montreal, Canada, took trunk samples from silver and Norway maples planted in parks and streetscapes in two Montreal neighborhoods.

The team measured the concentration of lead isotopes in the trunk samples and correlated them with the tree's recent growth history by counting the tree rings. Lead isotopes are different isotopes of lead at the atomic level that can indicate the tree's origin.

The study found that the trees in the park contained lead isotopes typically associated with air pollution, while the street trees contained lead isotopes found in 'lead water pipes made from metal (geologically old lead) extracted from nearby mine deposits.'

Maple trees absorb about 50 liters of water per day, but street trees can barely absorb that much. However, rainwater falls onto concrete and flows into the sewer system, and in Montreal, 500 million liters of water leak from water pipes every day. Therefore, when asked why street trees are not reducing water as much as park trees, Poirier said, 'It's likely that street trees are absorbing the leaking water from the water pipes.'

Poirier will be presenting the results of his research at the Goldschmidt International Conference in Prague, Czech Republic, on July 8, 2025. 'The good news is that we can continue to plant street trees. They make people happier, and they survive better than trees planted in parks,' Poirier said.

'The water use of street trees is staggering, and contradicts the common belief that park trees are much healthier,' said Gabriel Filippelli of Indiana University.