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The future of red pine in Minnesota under a changing climate

September 30, 2020
A red pine cone.

Climate change presents many concerns for Minnesota’s forests. Environmental impacts like droughts and heatwaves, pests and diseases will all affect our forests. This situation creates uncertainty for the fate of forests, and the species that make up a forest. That includes red pine — Minnesota’s state tree.

Red pine (Pinus resinosa) grows throughout north and northeastern Minnesota. It is prevalent in our state parks and forests and private lands, frequently a prominent and iconic component of mixed pine forests in the region, and economically important.

Losing red pine would alter the forests that we know. And while it may not disappear, its role and prevalence in our forests may shift in the future.

Changing growing conditions

Species habitat ranges, like red pine’s habitat range, are bounded by suitable growing conditions. Those conditions are changing. Predictions for Minnesota include increasing average temperatures. We have already seen hotter highs, and more mild winters. We have also seen shifts in rainfall: wetter, more intense, and potentially more sporadic.

There may be risk of more intense droughts in between, and similar extremes. Each species has differing requirements, tolerances, vulnerabilities and abilities to adapt. As climate shifts, some regions may become more suitable, expanding habitat. However, some regions may change in ways that no longer support a species.

How much will red pine struggle? That is hard to know precisely, so we should be cautious about drastic statements that might imply, for example, local extinction.

Scientists often rely on models that simulate climate variables to understand habitat shifts. These models must incorporate uncertainties. For example, will we limit emissions in ways that keep warming below key thresholds? If so, we will continue to see impacts of climate change, including impacts on tree species like red pine, but these could be less severe.

On the other hand, where emissions continue at present rates or increase, we may see very dramatic impacts which will jeopardize the habitability of our planet.

Amidst this spectrum, research suggests there may be large-scale shifts in forest type, negatively impacting boreal species. That is, southern species may move  north and northern species may retreat.

How climate change affects tree species

The way that climate change impacts a tree species is complex, in part because there are many moving pieces. 

  • How will temperature and rainfall interact?
  • How will forest pests, like bark beetles, or diseases respond? 
  • How will factors combine or exacerbate conditions?

Although we have relatively strong models to predict largescale patterns, like rising global average temperatures, local and regional scales are more difficult. Rainfall changes, for example, are difficult to predict at a fine-scale. Spread of pests and diseases can be even more challenging, because these risks and their potential impacts depend on many underlying factors. Other uncertainties include our own limitations to respond or protect a species.

Using climate models, combined with observation and ecological knowledge of a species, we can make predictions for how species might fare in the future. Declining health, growth or shifting habitat does not necessarily mean a species will become locally extinct. However, it may become harder to support those species, or they may become a lesser component of a forest.

The future of red pine

When it comes to red pine, we expect impacts on health. For example, a study modeling climate impacts on height growth in red pine plantations predicted up to 30% decreases in the next 20 years, and up to 48% decreases for 2041-2070 under climate change scenarios, particularly in southern locations. Total precipitation and average temperature during the growing season were key variables affecting productivity.

According to the Climate Change Tree Atlas, which models shifting habitats, red pine will likely decline, especially under harsh climate change scenarios, but may not decrease everywhere throughout Minnesota. 

How red pine fares will also be affected by how it is grown. According to the Minnesota Forest Ecosystem Vulnerability Assessment, single-species systems may not be very resilient and will likely struggle. When red pine is managed densely, or as a single species, it may become more vulnerable to negative impacts like stress, growth declines, pests and diseases. 

This does not mean red pine will disappear, at least not in the immediate future. However, it does mean that we may need to consider alternative species to take its place, and adjust our management approaches to prepare for the future.

Jamie Mosel is a Ph.D. candidate in the University of Minnesota's Natural Resources Science and Management program.

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