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Letter

A University of Montana research team has pinpointed new evidence that hotter, drier conditions make it hard for tree seedlings to survive after fire. This important new evidence confirms previous studies that arrived at the same conclusion, specifically that hotter, drier times leave western US conifer seedlings at risk of shriveling and dying before they can bring new forest into being after fire.

The Missoulian’s recent headline, Forest to Grasslands, summed it up pretty well. A longer summary is possible — the hotter and drier conditions so favorable to fire are unfavorable to survival of seedlings after fire has come and gone.

Many will have lingering questions even after the important new evidence provided by the UM team. One of these questions, likely of immediate interest, centers around seedling survival after logging — if hotter and drier conditions have killing effects on seedlings after fire, won’t those same conditions have the same effect on seedlings after logging?

Then there will be questions remaining about two variables already shaping the risk of forest conversion to grasslands — heat and elevation. The effect reported by the UM team has shown up when heat levels have risen by only 1 degree Celsius above levels existing before we started burning fossil fuels. And this effect has now shown up only at lower elevations on the mountain slopes.

Neither effect is likely to stop at this point.

Few if any believe that the heat will stop climbing at only 1 degree Celsius above the era before we started burning fossil fuels. Many understand that, instead, the heat will keep on climbing, that halting it at 1.5 degrees Celsius is extremely unlikely under prevailing sociopolitical conditions, and even doing what’s needed to stop its climb to 2 degrees Celsius faces muscular opposition. So, wouldn’t the conditions deadly to seedlings climb higher up the mountain slopes as heat increases it own climb?

There seems little if any doubt in the climate science community that heat will be climbing up the slopes. There is, for example, evidence that the rain-snow line will be climbing upslope in tandem with heat’s own upslope climb. This seems consistent with evidence reported in Science, in 2012, that “the distributions of species have recently shifted to higher elevations.”

It’s also consistent with findings that fire is capable of burning at high elevation when it’s hot and dry. And, in 2009, PNAS could already report that, “Observed heat wave intensities in the current decade are larger than worst-case projections."

Given the many lines of evidence including the recent UM analysis, what we are likely seeing now is just the start of forest conversion to grasslands that could shift farther and farther upslope as we continue with fossil fuel combustion and the heat its emissions add to an already hotter world.

Boiled down, that’s a scenario where continued combustion of coal, natural gas, diesel and gasoline leads to continued and even more intense combustion of the forest, followed by conversion of forest to grassland.

One thing seems certain. It would be increasingly difficult to offer logging jobs on increasingly grassy mountain slopes. Ditto for all the other employment now available thanks to forest cover, and we can’t ignore forest importance to wildlife or the health effects of more wildfire smoke.

The risk of an escalating forest crisis sheds new light on energy from solar and wind. This new industry can help reduce forest loss. Opposition to these promising new jobs needs to be put aside as soon as humanly possible.

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Lance Olsen manages a restricted listserv on climate and related concerns.

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