Climate Change and the Future of Oregon Forests

August 16, 2016
Robert Scheller
Professor at Portland State University

Projected changes to the climate over the coming centuries will radically restructure many of our forests throughout the world. We read the worst case scenarios in the news: the total loss of forest systems due to drought, wildfire, and insect outbreaks.

But my research on forests and climate change over the past 20+ years has suggested that forests are not monolithically at risk due to climate change. There is a huge variation in potential responses to climate change, not all of it bad. When considering future investments in maintaining forest health, we may need to consider a broad ‘landscape triage,’ whereby we intentionally choose which landscapes to save, which to leave to natural processes, and in which to invest immediate care.

Climate change will not affect all forests equally

Robert Forest 3

Fire mortality, Strawberry Mountains, central Oregon.

For example, forests in the northeastern US appear to have high natural resilience to climate change. What makes these forests naturally resilient in part is their diversity.

Diversity encompasses the number of species, their genetic variation, and the broad range of their functional attributes. Landscape connectivity (the capacity for organisms to access the various components of a landscape) and evolutionary adaptations for change also contribute to their natural resilience.

This resilience was evident following agricultural abandonment across huge areas of the northeast, particularly in New England. The forests quickly rebounded and today astound visitors with their extent and apparent health. And my research on climate change in the midwest and northeast suggests that we should expect these forests to grow faster and sequester more carbon under climate change.

That’s not to say that other threats don’t exist: over-abundant deer populations have decimated natural regeneration in many areas. Non-native insects are wiping out many important tree species. And continued development threatens to severely fragment and degrade these forests. But relative to these other threats, climate change may not be a primary existential threat.

In contrast, other areas are severely threatened by climate change, to the point that forests may not persist without intensive management interventions. For example, scientists have projected that some forests in the southwest may never return following wildfire due to projected droughts and associated wildfire triggered by climate change. Should we invest the enormous resources, primarily in tree planting, necessary to maintain vulnerable forests? Will these actions ever be sufficient? Newly planted seedlings are particularly vulnerable to drought and wildfire.

Whitebark pine mortality, Mt. Hood.

Whitebark pine mortality, Mt. Hood.

Between these two extremes are forests that can be maintained in a healthy condition despite climate change. These are forests where, ‘managed resilience’ can make all the difference:  careful intervention can prevent the worst outcomes.

In these areas, management actions can help ‘bend the climate curve’ away from negative outcomes. These actions will vary widely by location but may include fuel treatments to prevent crown fires, thinning to reduce insect mortality, planting a broad species mix when planting is required, even potentially including facilitated migration in anticipation of an altered climate. These are areas where our scarce resource management dollars can make the greatest difference.

So what of Oregon?

Robert Forest 2

Fire mortality, Strawberry Mountains, central Oregon.

My research uses large-scale simulations to project potential forest futures throughout the world. Recent research suggests that the Coast Range of Oregon has high natural and managed resilience. Predictable and substantial precipitation grants the former and no climate projection suggests a sustained decline in rainfall (although drought frequency may increase).

An extensive road network and an institutionalized capacity for replanting vast acreage provides the managed resilience. Roads are often regarded as a net detriment to forest health; however, they also facilitate fire suppression by enabling people and equipment to quickly access a fire. Although our research is ongoing, I suspect that eastern and southern Oregon fall into the middle ‘bend-the-curve’ category: climate change has the potential to unleash unprecedented wildfire and insect outbreaks. At the same time, careful preparation and the capacity to quickly react and adapt can prevent large-scale forest loss.

Landscape triage is not an attractive future. It would be better not to have make difficult decisions. It would be better to have unlimited resources to save every forest. I fear though that this future will be a reality sooner than we expect. The good news is that science is delivering the forecasting tools to understand how risk is spatially distributed. And we continue learning how we can bend the curve to a better future.

We must next decide to do so. We can’t simply wait and hope the worst doesn’t happen or wish that every landscape will simply bounce back when the crisis is over.

This crisis will not end soon and action is needed now.

Immediate actions will include funding the US Forest Service to reduce fire risk, not just fight fires. We can advocate for more forest restoration funding to enhance natural resilience.  We can give land managers greater flexibility to achieve the long-term goals of ensuring forest health. Most of all, we need to stop digging a deeper hole: we all need to reduce our carbon consumption.

Climate change is happening now. At the same, there is much we can do to limit the consequences. Every degree matters.  

Robert Scheller is a professor at Portland State University where he teaches forest ecology and related courses. He received his PhD in Forest Ecology from the University of Wisconsin. His research focuses on forest landscape change: how forests have changed, how they will change, and why it matters. Specifically, his research examines how forest management and natural disturbances generate or reduce forest health, specifically in regards to climate change. His research is data-driven and deploys advanced technology to forecast landscape change.  These forecasts inform forest policy regionally and globally.  He has published more than 60 manuscripts and book chapters and otherwise enjoys the natural and cultural amenities of Portland.

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