Urban trees exhibit greater drought resilience than those in parks due to their access to leaking pipes, providing a unique water source.

During prolonged dry spells, trees in park settings experience greater decreases in water levels and sap flow compared to those on streets, although the underlying reasons were previously not well understood.

To delve deeper, Andre Poilier from the University of Quebec in Montreal, Canada, and his team studied trunk samples from both Norwegian and silver maple trees (Acer Platanoides and Acer Saccharinum) located in nearby parks and city streets. They analyzed various lead isotopes to establish a connection between isotopic levels and the trees’ recent history by examining the unique isotopic variations found in their trunk rings.

While park trees commonly showed lead isotopes linked to air pollution, those on the street displayed isotopic variations corresponding to lead from water pipes made of metals sourced from ancient local sediments.

Typically, a maple tree requires approximately 50 liters of water each day. Since street trees cannot rely on the rainwater that collects on concrete and drains into city sewer systems, Poilier suggests that the most plausible explanation lies in Montreal’s leaky pipes, which lose an estimated 500 million liters of water daily.

“The bright side is that planting trees along city streets can continue, as they thrive better than those in parks,” Poilier noted while presenting his findings at the Goldschmidt Geochemical Conference in Prague, Czech Republic, on July 8th.

“The sheer volume of water utilized by these urban trees is astonishing and contradicts conventional wisdom. I believe this will enhance the health of park trees as well,” commented Gabriel Filipeli from Indiana University.