 Or are trees on site or on the lot next door equally important? There's also disagreement over the role urban trees play in a rapidly changing climate. Trees sequester carbon and filter polluted and smoky air. Their roots prevent erosion and stormwater runoff. The city recognizes these benefits on paper, along with the need for equitable tree canopy, but allows lots undergoing development to be clear-cut for housing, the majority of it for high-income earners.