Ever since I met my friends Hig and Erin, who write Ground Truth Trekking, http://groundtruthtrekking.org/ , I've been inspired to pay more attention to the natural health and changes we see in our environment, on all our outings, and document them. They are the couple who trekked and pack-rafted from Seattle to the Aleutians in 2007, and made a movie of it. They invited me to spend some time with them, in their Life On Ice expedition, on the Malaspina Glacier in Alaska, in October, 2011. An extremely interesting and dynamic place.
Probably my most prominent memory of that area was the incredible pounding of the surf, it was deafening 200m inland and 5m higher; I had a hard time sleeping, having nightmares of being washed over. The Gulf of Alaska here has very strong low pressure systems in the fall, which generate huge and dangerous swells and waves.
With that in mind, I very much am noticing the changes in our environment here in the Central Rockies, between my departure in 1998, and recent re-arrival. I had been down here many times in the interim from Alaska, mainly working as an NWS Incident Meteorologist, providing forecast support to wildfire suppression teams. Along with a few personal visits. Nonetheless, the changes are very noticeable.
There is no doubt that Planetary Greenhouse Gas-Caused Warming has taken its toll on the forests/ecosystems here in the Central Rockies over the past 30 years. As the following article from 2009 attests.
"Persistent changes in tree mortality rates can alter forest structure, composition, and ecosystem services such as carbon sequestration. Our analyses of longitudinal data from unmanaged old forests in the western United States showed that background (noncatastrophic) mortality rates have increased rapidly in recent decades, with doubling periods ranging from 17 to 29 years among regions. Increases were also pervasive across elevations, tree sizes, dominant genera, and past fire histories. Forest density and basal area declined slightly, which suggests that increasing mortality was not caused by endogenous increases in competition. Because mortality increased in small trees, the overall increase in mortality rates cannot be attributed solely to aging of large trees. Regional warming and consequent increases in water deficits are likely contributors to the increases in tree mortality rates."
And in all our outings over the past 10 months here throughout the region, we have seen the effects, which we'll show you. But first, lets look at some actual data, in this case for Missoula, but it is representative for the larger area of the northern half of Idaho, and the western third of Montana. Which we have examined, places such as Lewiston and Lowell, ID, Kalispell, Butte, Bozeman, and Helena, MT.
This Applied Climate Information System (ACIS) is a climate data viewing program maintained by NOAA (National Oceanic and Atmospheric Admin.), which is publicly available, and very useful for analysing current and past climatic data for points anywhere in the USA.
Looking at just the annual average mean temperatures for Missoula, MT here since 1948 (chosen because that is when observations began at their current site of Johnson-Bell airfield), shows that it has increased about 3F (1.7C) since that time. Which is fairly representative of what has occurred across much of the mid-latitudes in the Northern Hemisphere, since atmospheric CO2 concentrations rose from around 305ppm in 1948, to their current level of 400ppm. Levels not seen for quite some time. The last time atmospheric CO2 levels were this high, 3 million years ago, global sea levels were 20m higher, the climate of Northern Siberia was more like northern ID is currently, and the Arctic Ocean was ice-free most of the year. http://www.sciencemag.org/content/337/6092/315.abstract
How is this manifesting, here in the Central Rockies? Well, for one thing, extreme winter cold has been diminishing. Fewer winter cold spells, with lower magnitudes, overall. But it has been the summers that are most dramatically warming, and producing the greatest effects. In fact as we see it, the main hazard in this region in the coming 50 years will be hotter, drier summers, leading to widespread tree mortality at all elevations and increasing wildfire acreages.
Which the two graphs, above, of Missoula/Central Rockies average fire season (mid June to the end of September generally) minimum temperatures, and the daily mean temperature (F) illustrate quite clearly. The minimum temperatures especially, as they are rising faster than the daily means and maximums. This is due to the increasing CO2 levels; CO2 absorbs long-wave infrared radiation emitted by the Earth's surface and atmosphere, which at night is very prominent. And since levels have increased from 305ppm in 1948 to 400ppm currently, mainly from fossil fuel combustion, this is showing up markedly throughout the globe. Warmer nights in general, wherever they are occurring add more stress to vegetation, in the absence of any significant precipitation increases. What is called the Vapor Pressure Deficit (basically the relative humidity) increases (or RH is lower) for longer periods during the evening and night-time hours, causing vegetation to lose more moisture to evapo-transpiration. Drought-stress, in other words.
As you can see from these graphs, the hotter, drier summers have the largest fire acreages, which have been occuring in a six year cycle, since at least 1988 (1994, 2000, 2006, 2012). Accurate fire acreages for the Northern Rockies (USA) Geographical Area (NRGA
-ID north of the Salmon R, all of MT, Yellowstone NP WY, North Dakota, and a small piece of South Dakota) only date back to 1998. There is also a three year occasional sub-cycle. Summer precipitation so far has shown no significant downward trend, staying nearly flat for the NRGA. So there you have the trends.
What have we been seeing?
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There are definitely more bug or other pest-killed trees, at the mid and higher elevations, mainly in the Subalpine Fir, as here in the Bitterroot Mtns. at the Bass Crk. falls, this past 21 November. This is around 1600m elevation.
Likewise, looking up from bottom, in any of the canyons of the Bitterroot Mtns., you'll see alot of dead, mainly Whitebark Pines. A formerly common sub-alpine tree here, found above 2100m generally. As here around the striking Horsehead Arch, on the south wall of Blodgett Canyon, elevation around 2200m.
An easily accessible area near Missoula where you can really see these effects is on the Carlton Ridge trail, which provides a quick route to get up 2795m Lolo Peak, the local high point.
From about 7km and elevation 2100m in on this trail, which starts at 1800m, to the top of Carlton Ridge at 2550m, you'll see very healthy Subalpine Larch, Subalpine Fir, and Whitebark Pine, on this very cool, moist, steep north-facing slope. I took a tumble snow-shoeing in here early last June, there was still 1-2m snow then!
As soon as you go up and over Carlton Ridge though, and start down the south-facing slope, the scenery changes dramatically. All of the Whitebark Pine are dead, Many of the Subalpine Fir are dying. So far the Subalpine Larch are hanging in. This is 2300-2500m, but the much warmer drier conditions on this south aspect have led to increased drought stress, and bug/pest-kill. All these trees were alive last time I was there in 1996.
Here in the higher-elevation Pintler mountains, there is some Whitebark Pine mortality, but they're not quite as prevalent there, and only a few signs are starting to show in the Subalpine Fir, as here on the Storm Lake Rd., last 21 Nov., at around 2200m.
2500m elevation Tamarack Lake, on the west flank of 3200m Warren Peak, showed healthy Subalpine Fir and Whitebark Pine stands. At these high elevations, in flat areas, night-time lows in winter can still occasionally get to -40C, which helps keep bug pest populations in check.
Further north, in the Mission Mountains, at 1970m elevation aptly-named Turquoise Lake, there has been much more Whitebark Pine mortality. Probably because of the lower elevations here, 200-400m lower than much of the Pintlers. Night-time winter temperatures are probably not cold enough often enough, to limit the bug-pests as much as say, 30 years ago.
You'll really see this on the beautiful purple and orange rock ridges above the amazing Turquoise Lake, looking back from 2100m toward the higher country on the other side of it.
On the approach in to Turquoise Lake, you wind a ridge above 1700m elevation Glacier Lake, which is fed from Turquoise lake, 270m above. Here, the mid-elevation forests of Western Larch, Douglas Fir, and Englemann Spruce, are still fairly healthy. Some die-offs have occurred in the Subalpine Fir however.
When you get to the 2100-2200m level on the Turquoise Lake trail, all the Whitebark Pine are dead, but so far most of the Subalpine Fir and Subalpine Larch look healthy. This makes for some striking sights, especially with these amazing purple, orange, and green, smooth rocks.
Other areas in the region are showing similar signs, for instance, the Sapphire Mountains, on the other east side of the Bitterroot Valley. We also noticed during the hottest, driest weather this past summer late July to mid-August, many of the lower elevation (1100-1500m) stands of Ponderosa Pine, Western Larch, and Douglas Fir in the Rattlesnake Wilderness, just north of Missoula, were browning in the newer growth tips. Especially on any southerly or westerly facing aspects. Not a good sign, as it had been a very moist winter previously. We'll take a look at what likely trends will bring here in future articles. Suffice it to say big changes are very likely coming. Cheers.
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