Climate Conscious
True or false: Because a mature urban tree can absorb approximately 10–40 kg of CO₂ per year, carbon sequestration provides the greatest magnitude of climate benefit from urban trees.
What is false? Direct carbon sequestration is relatively modest compared with overall urban emissions. Urban trees can have a greater climate impact through indirect benefits, particularly by shading buildings and cooling the surrounding environment through evapotranspiration. This can reduce air-conditioning demand and associated emissions, with urban vegetation reducing building energy consumption by 5–20% during heatwaves. Trees also improve thermal comfort, air quality, and resilience to extreme heat.
I’m a large, long-lived deciduous tree native to our region, typically growing 40 – 70feet tall. My leaves have rounded, deeply lobed margins, and my gray-brown bark becomes thick and furrowed as I mature. I produce acorns and am well adapted to Oregon’s dry summers. Who am I?
What is Quercus garryana, the Oregon white oak?
A 40% urban tree canopy cover is an appropriate goal for all cities and should be the standard benchmark communities aim to achieve.
What is false? Research does not support a universal 40% target. Under ideal conditions, 40–60% may be attainable in cities in forested regions, while 20% is considered a realistic baseline for grassland cities and 15% for desert cities. Canopy goals should be tailored to local conditions and specific community objectives.
Through shade and evapotranspiration, urban trees can significantly improve thermal comfort for people walking through cities. By as much as how many degrees Celsius can trees lower pedestrian-level temperatures?
What is 12°C (21.6°F)? Urban trees can lower pedestrian-level temperatures by up to 12°C (21.6°F) by blocking solar radiation and releasing water vapor through evapotranspiration.
In Oregon, two sectors are responsible for more greenhouse gas emissions than any others. In 2023, one of them accounted for 35% of the state’s total emissions. What sector was responsible for this share?
What is transportation?
I’m a large, evergreen tree that can grow 60–80 feet tall. My leaves are large, glossy, dark green, and oval-shaped, with a distinctive rusty-brown fuzz on their undersides. In late spring and summer, I produce large, fragrant white flowers, followed by cone-like fruits with bright red seeds. Who am I?
What is Magnolia grandiflora, the southern magnolia?
True or false: Tree roots commonly break through intact sewer pipes because they seek out the water and nutrients inside.
What is false? Roots typically enter through existing cracks, leaks, or separated joints in defective sewer pipes.
Trees can help filter particulate matter and other airborne pollutants from the atmosphere, with especially noticeable effects when vegetation is planted along roads. When roadside vegetation is tall and dense, by approximately what percentage can it reduce pollutant levels downwind?
What is 30%? Tall, dense roadside vegetation can reduce downwind pollutant levels by approximately 30%. This occurs partly through deposition, when airborne particles such as particulate matter settle onto tree leaves and are removed from the air.
True or false: Adding more CO₂ to the atmosphere warms Earth because CO₂ absorbs incoming solar radiation that would otherwise pass through the atmosphere, trapping that energy near the surface.
What is false? CO₂ does not primarily absorb incoming sunlight. Instead, Earth’s surface absorbs solar energy and re-emits it as longer-wavelength infrared radiation. CO₂ molecules absorb some of this outgoing infrared radiation—particularly around 15 microns—causing their molecular bonds to vibrate and temporarily storing that energy. When the energy is re-emitted, some radiates back toward Earth rather than escaping to space, increasing the amount of heat retained in the climate system.
I’m a towering evergreen of the Pacific Northwest that can reach 150–200 feet tall. My foliage grows in distinctive flat, fan-shaped sprays, and my reddish-brown, fibrous bark can be torn into long strips. My small cones are less than an inch long, and despite my common name, I’m actually a member of the cypress family. Who am I?
What is Thuja plicata, the western redcedar?
This springtime phenomenon in maples and birches can look alarming after pruning, but despite appearances, it generally does not harm the tree or cause significant health problems. What is it?
What is sap “bleeding” from pruning cuts?
Trees and vegetation can improve water quality and reduce the impacts of stormwater in three key ways. Name all three.
What are: