The next time you take a walk downtown, take a moment to consider that life is hard for our city trees. They bake in concrete, get scalded in summer sun reflected from buildings, suffer regular abuse from dogs, bicycles and passersby, and generally don’t get the appreciation they deserve. It’s up to us as responsible Seattleites to change that; to recognize all the good that trees bring to our urban environment, and offer trees the gratitude, care and resources they need. For every 100 trees that get planted, only 50 will make it to the expected 13-20 year lifespan! While you think about that, here’s five other things to know about Seattle city tees:
The soil city trees get planted in has minimal organic matter and is compacted to reduce trip hazards. People walk across the roots and compact the soil even further; dogs use the tree pits for a toilet; generally speaking city trees regularly get beaten up by pedestrians, animals, bicycles and cars.
Most of the roots are under the surrounding concrete, which is porous and lets some rain get through to the roots below the sidewalk. Thus roots prefer to grow in the void space at the base of concrete, rather than fighting through the hardened soil that is deeper. This is why tree roots so frequently damage concrete, as roots can move up and down in response to the trees they support moving in winds.
Managing stormwater is likely the greatest ecosystem service a city tree provides. Trees capture as much as 30 percent of the rain that falls on them and hold it in their leaves, then transpire it back into the atmosphere before it even reaches the ground and needs to be diverted. Other rain travels down the trunk and leaves to be processed by the root system.
Sidewalk trees clean the air, calm people, smell good, lower surface temperatures, which overall support good mental health.
Streets with trees are shown to have lower traffic speeds; trees help separate cars from pedestrians; and they help create a visual wall to distinguish the street from the sidewalk.