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Freezing to death in a warming climate: yellow-cedars in trouble

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This map of Mount Edgecumbe shows the continually shrinking area that receives 250mm or more of snowfall. Areas of yellow-cedar decline are marked in red. From the report: “Shifting Climate, Altered Niche, and a Dynamic Conservation Strategy for Yellow-Cedar in the North Pacific Coastal Rainforest” in biosciencemag.org

Mount Edgecumbe, is a dormant volcano near Sitka, Alaska. Yellow-cedars grow abundantly from the pacific shore to near timberline. The researchers found that yellow-cedar decline occurs in areas that average around 250mm or less of snowfall each year. As the climate warms less and less of the mountain receives enough snow to protect yellow-cedar roots. The area of yellow-cedar decline expands. Without a strong effort to reduce global warming soon, climate models show the safe-snow-blanket zone for yellow-cedars will all but disappear from this mountain in this century.

Where will yellow-cedars live now?

As climate change banishes yellow-cedars from the areas they are dominant in, the question facing those who wish to preserve them is: Where will they live now? And what do we need to do to help them?

One hopeful fact is that today, in deep well-drained soils yellow-cedar can survive the lack of snow cover much better. Not only that, but in these deep soil areas they grow bigger.

Humans have noticed this fact. Most of the logging of yellow-cedars occurs in the deep soil areas spared by yellow-cedar decline. The researchers suggest perhaps switching yellow-cedar logging away from the deep soil areas and into salvaging the vast decline-killed areas instead.

But even stopping yellow-cedar logging in these deep, well-drained soils might not be enough. The study points out that trees like mountain hemlock and Sitka spruce are even better adapted to these soils and tend to out-compete yellow-cedars in the long term.

What to do?

Nobody is exactly sure.

For example the report highlights how “the dramatic and unexpected losses of yellow-cedar populations in protected landscapes has shown the “futility” of relying solely on protected areas. Forest managers are realizing that much of the prime old-growth habitat they set aside to preserve yellow-cedars are shifting with the climate to be deadly for them.

In the report’s dry academic-speak, yellow-cedars are becoming “maladapted” to their former prime habitat.

Because the climate is still shifting rapidly – and apparently will continue to accelerate for many decades at least because of increasing fossil fuel burning -- it isn’t clear what landscapes to protect. We aren’t sure where yellow-cedars will be able to survive on their own in long term, if anywhere. We don’t know whether we need to help move yellow-cedars, and if so where to move them to. Or even when to start moving them.

The researchers say that as long as the climate keeps shifting then humans are going to have to continually shift their efforts to protect yellow-cedars.

Forced to garden the wilderness

For now, the study suggests the best bet may be to curtail yellow-cedar logging in the deeper soils where they are currently resisting yellow-cedar decline. In addition we may need to selectively log other tree species in these areas to prevent them from pushing out yellow-cedars.

In other words, we may be forcing ourselves and future generations to become permanent gardeners of the “wildnerness”.

And not just for yellow-cedars.

Already serious discussions are underway for other iconic long-lived trees like the Giant Sequoias of California. They too are becoming “maladapted” to their ancient habitat as a result of fossil fuel pollution reducing snowfall and overall precipitation. Surveys show the number of giant trees dying each year has doubled. Concern is growing over the inability of seedlings to thrive in the drying climate. Scientists and forest managers talk about the need to water, raise and even possibly transplant these trees to new regions. For trees that can live thousands of years, the rapid climate shift underway now is going to be a struggle.

Here in BC and across the mountain west, global warming has caused many of our pine trees to become “maladapted” to their habitat. In this case the warming winter nights no longer get below -40 C long enough, or often enough, to hold down the populations of the native pine beetle. For millennia our pines have thrived by specializing in a freezing habitat that the attacking beetles couldn’t deal with as well. Surviving by specializing in extreme-cold tolerance has suddenly flipped into a losing strategy as fossil fuel pollution has removed that ancient cold protection in an evolutionary blink of an eye.

When pine beetle destruction is discussed in much of the media and by politicians it is usually as a single wave that is cresting and starting to retreat. But this is just the first wave. As new generations of pines try to grow back the beetles will be waiting. But the cold protection won’t be. We have fundamentally changed their habitat to the point that the pines have become “maladapted” to much of their own landscape.

Humans are discovering expensive ways to protect small numbers of pine trees that have high value to individuals from becoming beetle chow. Once again, we find ourselves faced with the need to garden yet another part of the wild if we wish to preserve it.

A similar story seems to be unfolding with the beautiful quaking Aspen groves of the west. These beloved and colourful trees are also suffering from a massive die off called Sudden Aspen Decline (SAD). Recent research by Stanford scientists is showing that many have been dying of thirst as the Rocky Mountain West dries out from global warming. Will we be forced to water quaking Aspen groves to keep them alive?

Just last week a report came out saying our western boreal forest is dying from climate change induced drought. This entire forest system spanning multiple provinces is now dying faster than it is growing back. It has become a carbon emitter, instead of a carbon absorber. What does “maladaption” mean on a scale that big?

Did I mention the latest research on the Amazon – the lungs of our planet – also drying and dying? Or that the Amazon rainforest has suffered two 500-year droughts in the last five years?

What to do? How long will humans choose to garden increasingly large swaths of the wild to try to prevent a collapse of species richness and bio-diversity? How much can we really do even if we decide we want to?

As far as stopping climate change, we already know everything we need to know. We have all the technology we need. Economists have described the policies and their costs. It won’t be easy, but many economists and climate scientists who have spent the most time looking at the problem say that we can do it.

What we don’t know is whether we will collectively choose to act in time.

The music of the rings

I’m going to end with a beautiful and inspirational piece of “tree ring music” from German artist Bartholomäus Traubeck. He invented a turn-table that “plays” tree slices by reading the lights and darks and transforming them into piano notes. Lovely.

 

(h/t to treehugger)

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