How To Imagine The Best Climate Change Resilient Trees and Landscapes

by | Feb 25, 2021 | Pollinator

Axious about climate change? Wondering what climate change will do to trees, plants, and your landscaping? We’ll explore these questions and offer which local Portland trees we think will be worst and best for climate change resilience.

How Does Climate Change Affect Trees?

Wondering how your veggie garden or beloved landscaping plants will stand up to climate change? Unfortunately the short answer is we don’t really know.

Lots of smart people are thinking about this;

Ecologists, farmers, gardeners, water resource managers and other land stewards.

We are all visualizing how climate change will affect trees. Then thinking of anything we can think of to help slow down those effects.

Climate Change Resilience for Street Trees

Here in the Pacific Northwest we are lucky to have a concentration climate-aware  & progressive land managers. In 2014 there was a special conference called Cascadia Region Network Breakthrough Convening On Urban Forestry and Climate Change.

A gathering of regional & municipal city planners, forestry experts and environmental industry professionals convened in Portland Oregon. They held a series of “robust” conversations surrounding the health of street trees in the face of a changing climate.

Best Trees for Climate Change

They created a valuable jumping-off point for the discussion on what climate change will to do urban trees and plants. Cascadia Regional Network discussed climate change resilience in terms of diversity, latitudinal adaptability and plasticity. Here’s a few key points they discussed:

  • Determining if some trees would likely be better than others.
  • Addressing the role of soil health and increasing pest & pathogen pressure.
  • Noting the effects of extreme wind & weather events might create more opportunities for open canopy space.
  • Highlighting the concern of over-performance of any newly introduced species from southern areas. That is, their potential to become invasive species.
  • Centering the need for nurseries to begin selecting for climate-ready trees and landscape plant stock,
  • And bringing in a broader diversity of professional and academic inputs for best outcomes.

foliage or branchlets of the Western Red cedar

How Are Trees Affected by Climate Change?

While one of Portland’s most beloved tree species —the Western red cedar— is also one of our most vulnerable. 

Red cedar can help us imagine how trees might be affected by climate change. 

It appears to be showing the ugly effects already.

Why is My Western Red Cedar Dying?

The Willamette Valley of Oregon is towards the extreme southern end of Western red cedar’s native range. Western red cedars showing the following symptoms may be experiencing stress in association with climate change:

  • Defoliation or damage starting from the top.
  • Branchlets most exposed to the direct sunlight start drying, desiccating, browning, and thinning.
  • Heat, drought and reduced humidity create stress that lead to increased disease & pest pressure.
  • Increasingly this will likely result in tree mortality.

Traditional Food, Fiber and Medicine

Native American people utilized tall sheets of Western red cedar bark as fiber for items like baskets and hats. The finer fibers are used for clothing, towels and mats. Trunks are hollowed out for canoes and branches were used for rope and cordage. The aromatic essential oils in the branchlets are used for tea and topically. Cedar essential oils can have powerful anti-fungal and antibacterial medicinal properties. In fact Western red cedar has many more uses not listed.

Legacy of Harm

We must internalize that extractive industrial legacies affect indigenous people worse than people of settler colonist ancestry. Complete and repetitive removal of indigenous people from their ancestral lands causes irreversible damage to many different ways of life. We must make massive and substantial changes in the way we do things to protect native people and the living beings of earth.

Visit Native American Youth and Family Center (NAYA) learn more about helping local Portland policy & advocacy for enhancing the strengths of Native American youths and families.

Understanding Climate Change Ecology

Notably, western red cedar is a moisture & shade loving forest tree. In some places it’s basically a swamp tree. So prolonged periods of drought and temperature extremes can be rough on Western red cedar. Weakened trees are susceptible to attacks from soil pathogens, insects or mites.

This document by Oregon.gov suggests a combination factors:

Basically, longer stretches of higher temperatures, lowering of the water table and poor soil management are probable factors.

Top death of Western red cedar in Portland possibly foreshadows what climate change will do to our trees and plants.

Not the Best Portland Landscaping Tree

Western red cedar is arguably the most handsome ornamental landscaping tree that’s also native to the Pacific Northwest. Besides it’s very closely related to Arborvitae or Thuja occidentalis, the common hedge plant.

But Western red cedar is probably not the best landscaping tree for climate change resilience.

However, we just don’t know for sure. Looking out my window I can see my neighbors’ have some happy looking Western red cedars.

Selecting healthy looking cedar trees for seed collection and future plant propagation could be one climate change mitigation strategy.

Continue Reading Part 2:

So what is the best tree to plant for climate change resistance in Portland? Let’s take a look at one candidate in the next article: Pioneering Portland’s Best Trees to Plant for Climate Change.

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