They tower overhead and sway in the wind and often teem with squawking birds, yet trees are easy to ignore. Urbanites rush by them without noticing, and without appreciating all the work they do: Trees reduce temperatures, mitigate flooding, and provide habitat for animals.

City leaders are no exception to this oversight. As mayors around the world pledge to reduce municipal greenhouse gas emissions, they’re missing the literal low-hanging fruit of bolstering urban forests, dozens of scientists argue in a new essay. “We have to elevate it from something that is nice to have to something that we require — like, mandatory,” said Manuel Esperon-Rodriguez, an ecologist at Bangor University in the United Kingdom and lead author of the piece, which published today in the journal PLOS Climate. “In the same way that we treat education, security, transportation, it has to be elevated to that level.”