In my previous aspen post I alluded to the fact that the aspen in Northern Arizona were facing a serious threat unrelated to global warming and tree fungus. In this post I'll outline what that threat is and explore some possible solutions. But before I start digging into Arizona history let's get to know the aspens' main adversary first:
Bull Rocky Mountain Elk in the meadow near Kachina Village. Source unknown.
Surprised that it's not loggers, drying forests, or tree fungus? Yeah, so was I. By far the biggest threat that aspen groves in Northern Arizona face is actually one of the most beautiful and magnificent animals in the forest: The Rocky Mountain Elk. People love watching and hunting elk. When I lived in Kachina Village I remember long lines of cars stopping along the frontage road to take pictures of elk grazing in the fields. I was guilty of this several times and I've got the pictures to prove it. There is just something awesome about elk.
But the problem with elk is that they really, really like to eat aspen. They'll strip all the leaves off a young aspen sapling in seconds and rub the bark off of older ones trying to get the velvet off their antlers. If given free access to a thicket of young aspen they can kill everything less than ten or fifteen feet tall. Unless physically prevented from doing so via an exclosure or steep incline this breaks the reproductive cycle of the grove, resulting in the situation we have now where large, mature aspen trees are reaching the end of their lives with no young aspen to replace them. If you take a walk among the aspen groves along the Kachina Trail you'll see what I mean:
Note how the aspen visible in the above picture are all large, mature trees. There are no saplings or young trees even though some of the older trees are beginning to come down, making plenty of sunlight available. The trees in this picture are not dead - just dormant for the winter.
When I first learned this my immediate question was why is this even a problem? I mean elk (and deer) have been in this forest for eons. Why are they suddenly such a threat to aspens now? The answer was surprising: elk HAVE always been in this forest, but not THESE elk and not in THESE numbers.
It turns out that before the white man came to the southwest there was another species of elk living here called the Merriam's Elk. It was physically larger than our elk today but had far fewer numbers and thus less impact on the forest. It's population was kept in check by two factors: lack of water and a healthy set of natural predators, with water being the primary control. But as settlers and ranchers moved into Arizona uncontrolled hunting forced the Merriam's Elk to extinction. By the early 1900's the Merriam's Elk was gone forever.
Of course not having any elk in the forest was a huge bummer so beginning around 1913 Yellowstone Elk (Rocky Mountain Elk) were imported and released into the woods 45 miles south of Winslow, AZ near Chevelon Creek. All the elk you see in northern arizona today are direct descendants of those original introduced animals. In a way, the big beautiful bucks with huge racks of antlers you sometimes see gathering in the meadows around Flagstaff are an invasive species!
Okay, so introducing one kind of elk to replace another extinct kind probably wouldn't have been a big deal except for the fact that their numbers soon ballooned out of control. There are now far more Rocky Mountain Elk here than there ever were Merriam's Elk so their impact on the forest ecosystems is much heavier. The Rocky Mountain Elk increased statewide from the original 157 introduced animals back in 1928 to some 35,000+ today (2002 numbers). This population boom is one of the largest increases of any large game animal recorded in north america and is the primary reason why young aspen have no chance to grow large enough to survive.
But why did the Rocky Mountain Elk population explode when the original Merriam's Elk population had always remained small? The population boom would not have occurred without a couple of other human-caused factors that happened around the same time. First, as cattle ranchers began using the forests to raise cows they knocked the natural predator populations down. Grizzly bear and wolves - the only predators really capable of tangling with large elk - were completely extirpated and black bear and mountain lion were severely curtailed to protect cattle interests.
Secondly, the lack of water, especially in dry summer months, was overcome by humans building thousands of stock tanks (i.e. dams) across the state. These low, earthen dams collect arizona's infrequent rainwater into small ponds and provide drinking water to thirsty cows and wildlife. They are everywhere in the forest - a simple search in my topographic map software shows more than 2,200 of them within a 50-mile radius of Flagstaff. Statewide there are something like 8,500 of these things! And these are just the tanks with names that made it to the maps. I'm sure there are many more out there that aren't documented.
Stock tank near Sedona, AZ. Note the large dissimilar tree growing in the center of it.
As usual in these types of situations it's not really fair to point the finger of blame at the most obvious agent of change (i.e. the elk). The elk, while undoubtedly the instrument of destruction, are just animals doing what animals do. They try to survive and reproduce as best they can in a tough environment. We mustn't be too hard on them. Instead, the elk are really just scapegoats for the real villain in this drama: human meddling in the forest ecosystem.
Ranchers and others trying to protect their cattle and maximize profits unwittingly removed the two limiting factors for the elk population, namely natural predators and scant water availability. With no natural predators and year-round water elk numbers boomed and now we find ourselves in the current predicament: aging aspen groves with no young trees to replace them. That old adage about the road to hell and good intentions surely applies here.
So what are we going to do about this? We have huge numbers of introduced elk eating away at the future of aspen groves. Wouldn't the easiest way to save aspens be to just reduce the elk population down to more "normal" numbers? And yes, that's the only long-term solution, but it's easier said than done. First, we don't really know what a "normal" population is. And secondly, today we have powerful economic forces in the state with vested interests in keeping elk numbers high. Hunting groups, guide services, sporting goods stores, and even the Arizona Game and Fish department itself make a lot of money from these animals. It's in their own best interest to vigorously oppose anything that would reduce elk numbers. They might be convinced to increase the yearly hunting quota but it's going to be a tough political fight and so far they're not going for it.
Another solution might be to reintroduce natural predators to keep the elk population in balance. That would work, but the people of Flagstaff and the surrounding communities might have something to say about packs of wolves and grizzly bear passing through their backyards. And cattle ranchers would certainly oppose such efforts as the experiment to reintroduce mexican gray wolves in eastern arizona has shown to be the case.
Breaching the thousands of stock tanks scattered throughout the woods might also work. Reducing water availability would surely bring populations down as lack of water was the original limiting factor in the Merriam's Elk population. But suddenly removing water would be a truly horrible and inhumane way to reduce elk numbers as everything in the forest is now dependent upon these water sources. I originally came into this environmentalism thing from an animal rights and anti-cruelty route and even knowing what I know about aspen trees I couldn't support such a thing. It would be just too horrible.
So that leaves us with physically preventing the elk from eating the aspen saplings. This works as the difference I saw between the inside of the aspen exclosures and the outside was quite pronounced. Inside were thick stands of young aspen well on their way to adulthood. Outside were nothing but large, older aspens that took root before the elk got out of control. Exclosures most definitely work but they're extremely labor intensive to build and maintain (as my aching hands and back could attest to last weekend). There are other techniques using deadfalls of downed pines and other unconventional stuff that the Forest Service will be trying besides building tall fences but they are not guaranteed to work as well and may actually do harm. But they have to try something and time is running short; putting up exclosures around every aspen grove in northern arizona is just not feasible.
As you can see, the challenges facing aspen groves are multifaceted and rooted in a couple different historical causality chains. You could almost say that we couldn't have done a better job of dimming the future of aspens here even if we'd purposely set out to do it. With so many interlocking problems and economic forces working together it doesn't look good. But it's also not completely hopeless. Maybe if more people learn about the plight of aspen in northern arizona we can do something about it. Maybe we can preserve a few groves so that in the future, when people eventually wake up to what's happened to the environment and decide to do something meaningful about it, there'll still be a few healthy groves to start fresh from.
