Colorado's changing forests

[Carl the Cuttlefish]

Colorado's forests are in an incredible state of flux this century and are bound to look different in the next 30-60 years. The most obvious change is the vast swaths of beetle kill that started around the 2000s and continue to roll through. The immediate results are pretty hideous, vast swaths of dead trees, and are quite a fire / hazard danger. But I've always wondered what comes after the beetle outbreak. According to this article, https://www.fs.usda.gov/rmrs/death-come ... e-beetle-1, on disturbed sites, lodgepole pine come back to cover along with aspen, but on undisturbed sites (which is going to be most of the state), the forest changed in structure to have more subapline fir and aspen and less lodgepole / spruce. I'd imagine at lower altitudes that'll be more douglas fir as well.

People blame the beetles and climate change, but fact of the matter is that any monoculture forest is just a really unheathy one. There was a fungus attack taking out white oaks in Georgia this year, but because there's dozens of species across Piedmont forests, there was no widescale dieoff, there's plenty of other tree genuses shooting up. And though the beetles cause damage in the short run, they are likely making the forests better in the long run by allowing a mixed conifer / aspen forest to rise up. And, for what it's worth, the foraging animals prefer beetle killed forests to full cover because there's more groundcover for them to eat. It occured to me when I went to Taos and hiked around the Sangres there that that type of forest is what CO will look like with warming. And I have to say that it's nicer down there forest wise than what we have in CO. You still have blue spruce and the alpine species up near the top, but the mid section had a lot more fir and less lodgepole / engelmann spruce.

And things are changing down on bottoms of the mountains too. According to this article https://www.wired.com/story/billion-dol ... e-problem/, grasslands and sagebrush land all across the western US and Plains are having trees pop up and convert the area to woodland. An area the state of Iowa has gone from no tree cover to some tree cover in the last 30 years, and an area the size of of Nebraska has the potential to become wooded as well. That's a HUGE change in a short period of time, and future CO will have more trees, not less trees. The author makes it sound like a bad thing because of less cow ranch profits, but that's just one angle to look at a change like this.

All in all, I think the state has a more beautiful forest future, as long as devastating intense wildfire outbreaks can be kept to a minimum.

[Scott P]

Has Colorado suffered from other episodes of Beetle kill in its past?

Yes. The 1940's had a bad one. The 1951 cold snap wiped the the beetles out, putting and end to it. Some of the mountain towns dropped to -60 and even some of the Front Range cities dropped into the -40s so the beetle epidemic ended abruptly. .

[Scott P]

Was it as extensive today? Suffered from wildfires? How did Colorado recover?

I don't think it was as extensive as today, but yes the previous ones had wildfires. Such epidemics have happened in the past, but cold snaps usually killed them off after a few years. Colorado hasn't had a severe cold snap in several years, especially in comparison to other historic time periods. In recent years the cold snaps haven't been severe enough to wipe out the beetles. The in February 2011 might have killed some of them off, but didn't last long enough to make a huge dent. To kill the beetles, we need a real cold snap with temperatures in the -40s and -50s in the mountain areas that last more than a day or two.

If we don't have a cold snap, the beetle kill epidemic will end eventually as the old trees all die and (hopefully) new ones take their place.

Some areas in Utah that I am familiar with where the wildfires wiped all the trees out haven't even started to recover after 20+ years. I assume this is because of the drought and there hasn't been enough moisture to grow new trees.

[Tony1]

It's easy to notice the drastic difference in plant diversity between your typical aspen forest vs. lodgepole forest here in Colorado. Hopefully the mass lodgepole deaths from the beetle infestation makes way for more species to pop up.

I've also noticed that many pine trees near roadways have started dying all of a sudden. It would seem that our forests are becoming more stressed and prone to shrinking in area, so I would be very happy if they were to actually expand as indicated by the article.

Lots of forest area here around Leadville, over to Breck, and down through the eastern flank of the Sawatch is so incredibly monoculture that not even grass grows in the understory. It's just all lodgepoles packed onto the hillside, and they're packed so tightly together that they don't even grow that tall. Can't imagine that's what a healthy forest looks like.

[the_hare]

Thanks for sharing this article and for the write-up, very informative and encouraging. Although it's sobering to see entire mountainsides turn skeletal, according to the research this current large wave of lodgepole beetlekill seems to be a good thing in the long run for overall forest health, wildlife habitat, and fire mitigation. Will be interesting to see how the more diverse plant and animal life in the future adds to recreation experiences in the forest. Good news too that the die-off of trees isn't really affecting water quality downstream.

[Carl the Cuttlefish]

-40F temps do kill beetles, but they also kill other plants that are trying to grow up along side. Parasites are promoters of biodiversity, preventing mass monoculutures like we see in our lodgepole forests from strangleholding. While CO has a fair amount of beetlekill, the main kill area was interior British Columbia. The beetles have hopped over the Rockies and are now on the eastern NW Territories side, where this same pattern will likely happen in the boreal north of Canada, given the winter warming going on there.

On the drought front, there's indications that the current megadrought isn't the future, and that the monsoons will likely strengthen as the water in the Pacific off California warms up https://www.wired.com/story/pliocene-li ... southwest/. Even if these monsoons don't quite make it up to CO, a wetter SW US means more transpiration and wetter air that will make it's way over to CO.

With all these trend indicators, there's positive tailwinds for a warmer wetter CO, but there's plenty of risk of going backwards ecologically as well from largescale fires and floods if those aren't accounted for and checked by intervention. I don't think we'd ever lose the snow completely, my reasoning for that is looking at Myanmar where they have snow at 12000 ft though they are at a much lower latitude.

[jibler]

i seem to recall reading something about a massive wind blowdown event in flattops - that in turn provided beetles with easy eatings


and that in turn lead to current outbreak?


does that track?


I still can't get over the buffalo creek and hayman burn scars. wtf. and then you look and see how many homes are packed in all around those scars. not a good long term prospect there.

[Dave B]

Of the forest problems across the western US, well over half of the cause is an almost century old Forest Service policy of fire suppression preventing even small fires from burning forests and reducing fuel loads. The result has been two fold: 1) stressed forests with too many weak and resource limited trees (making them more susceptible to insect infestations and drought related mortality) instead of fewer trees with adequate resources, and 2) a build up of fuels that has led to a massive increase in the number, size, and severity of wildfires. Climate change has exacerbated the issue for sure, but it's not the only signal driving the current shifts in forest health, structure, and species composition. One especially concerning trend in Colorado is high severity fires burning through overgrown and too-dense ponderosa forests. Ponderosa is not adapted to high-severity crown fires that kill all of their seed, hence most areas of ponderosa forest that have burned in the past decades have converted to grass/shrub lands rather than recovering to forest (e.g. Hayman burn area). Another example is Fourmile Canyon west of Boulder, take a drive through the overly dense ponderosa to the edge of the burn area which has not recovered at all in 12 years.

As far as monsoons go, the North American Monsoon is most definitely trending downward, and modeling suggests this trend will continue or worsen. I'm not sure the Pliocene fossil records reported in the paper summarized in the Wired article serve as a reliable analog to the Anthropocene, given the landscape and geology were quite different back then. And even if they were increasing, they'd have little impact on the current megadrought. In the SW "drought" is generally used to refer to hydrological drought, which is characterized by streamflow volumes and reservoir levels. All of which reached historic lows this past summer despite a record breaking monsoon season. Streamflow in the west is >70% snowmelt, with some studies showing monsoon rainfall making up as little as 4% of total streamflow. Increasing monsoon would be good for reducing fire risk, however.

Also, woody encroachment into shrublands/grasslands is a dire ecological problem and one where ranchers and ecologist tend to see eye-to-eye. Trees are not always good, especially in ecosystems not adapted to their presence or their more aggressive growth and water use patterns that can change hydrology and edge out keystone species. The sagebrush steppe is especially imperiled by woody encroachment which combined with shortening fire return intervals, invasive species, and climate change, is one of the most rapidly disappearing ecosystems in North America.

[two lunches]

I've also noticed that many pine trees near roadways have started dying all of a sudden. It would seem that our forests are becoming more stressed and prone to shrinking in area, so I would be very happy if they were to actually expand as indicated by the article.

you know, i've been noticing something similar in the lackluster color in the aspens adjacent to the road on kenosha pass. as the years pass it seems they are leafing less and later in the summer, then turning more gray than yellow in fall, whereas the trees further away from the asphalt still exhibit pretty awesome peak colors.

[HikerGuy]

you know, i've been noticing something similar in the lackluster color in the aspens adjacent to the road on kenosha pass. as the years pass it seems they are leafing less and later in the summer, then turning more gray than yellow in fall, whereas the trees further away from the asphalt still exhibit pretty awesome peak colors.

Some Colorado fall foliage viewing areas were impacted by spring frost, drought, insects this past year.
https://www.coloradoan.com/story/news/2 ... 464318007/

West said a late spring frost nipped some aspen, which forced the trees to drop their leaves and grow new ones. That, in addition to some pest damage, has impacted stands in the central part of the state, including the popular Kenosha Pass area.

[randalmartin]

One of the things I found interesting was when you go back and look at photos of Colorado from the 1800s and early 1900s and compare to a photo of the same location today, you will generally find that we have WAY more trees today than we did back then. I have always assumed it is due to the aggressive fire suppression strategy used today which doesn't allow the natural maintenance of forests.

[peter303]

Has Colorado suffered from other episodes of Beetle kill in its past?

One hypothesis I heard, I believe from a CSU forestry professor, is mild weather is 2-4 weeks longer now than a century ago. So there may now be TWO beetle generations in a summer.
This hypothesis can be tested with data.