Rocky Mountains Change
Air Date: Week of August 7, 1998
Steve Curwood made a trip to Rocky Mountain National Park outside of Boulder, Colorado to talk with scientists and see first-hand what some researchers say is evidence of global climate change occurring there among the trees and snow fall.
CURWOOD: I'm Steve Curwood, with an encore edition of Living on Earth.
CURWOOD: Each year more than 3 million people bring themselves, their cars, trucks, and recreational vehicles to the gates of Rocky Mountain National Park.
(A window opens)
MAN: How you doing?
WOMAN: Good. Ten dollars. You get a yellow receipt, it's good for 7 days.
WOMAN: Thank you.
MAN: Thank you very much.
CURWOOD: This park is 4-wheel friendly. The popular and spectacular Trail Ridge Road is the highest paved 2-way traverse in the nation, and you can get right up to the tundra just by slipping your Winnebago into drive. The scenery is breathtaking and diverse. Going from the park's front gate to its highest peak is like traveling north from Colorado to beyond the Arctic Circle. And with 13 unique vegetation zones, Rocky Mountain National Park also attracts its share of scientists.
STOHLGREN: National parks provide us the greatest set of outdoor laboratories that we have to work with. It's a place where nature is still the predominant factor.
CURWOOD: Thomas Stohlgren leads a team of researchers based at Colorado State University working for the United States Geological Survey. They're here to study climate change.
STOHLGREN: If we learn what's going on in our natural systems, we'll develop a deeper understanding for how humans are tied to ecosystems and how humans can influence them, and perhaps how humans can protect them for future generations.
CURWOOD: So Tom, where are we?
(Music up and under)
STOHLGREN: We're in the Upper Beaver Meadows area of Rocky Mountain National Park.
CURWOOD: Upper Beaver Meadows, huh? What are we stepping on here?
STOHLGREN: We're stepping on actually some remnants. You can see some cactus if you're fairly careful here. Ah! Look at that.
CURWOOD: Cactus in the midst of tall, lush grasses is a reminder that climate is ever-changing. A few thousand years ago, Dr. Stohlgren says, this part of the Rockies was much cooler and drier than it is today.
STOHLGREN: The thing about climate change is, sometimes the vegetation can hang around a lot longer after the climate changes.
CURWOOD: So this tiny little cactus -- it's no bigger, really, than what -- an inch or so across. This dates from 3,000, 5,000 years ago?
STOHLGREN: Right, that vegetation type on this spot. And it just hasn't left.
CURWOOD: The ancient record is fascinating. It shows how climate change can effect an ecosystem over time, usually a long time. But what's driving Dr. Stohlgren's research now is much faster climate change. Today's cars, factories, power plants, and heating systems are releasing so much carbon dioxide and other greenhouse gases that scientists predict the average temperature of the Earth could change as much as 4 or 5 degrees in a matter of decades, instead of millennia. Dr. Stohlgren wants to know how life in the park would respond. To find out, his team has carefully mapped and catalogued 18 plots around the park.
STOHLGREN: We go out with our global positioning devices, you know, now that are hand-held units. You can tell exactly where you are, and we have trees measured and mapped to the nearest 10 centimeters.
CURWOOD: Ho! Ten centimeters.
STOHLGREN: Ten centimeters, 5 inches. They're a legacy for future ecologists, really. They can come back, measure the exact same trees we measured, and assess the growth rates of the different species and see who's gaining the competitive advantage. Who are going to be the winners in the next climate scenario.
CURWOOD: Dr. Stohlgren says they've already noticed changes that may be due to recent accelerated global climate change.
(A door shuts; a car engine starts up)
CURWOOD: He points up to a spot along Trail Ridge Road, 9,000 feet above sea level.
STOHLGREN: That's where we're going, that curve right up there.
CURWOOD: The drive only takes a few minutes, but the change in vegetation is dramatic. We leave the pine forest and grassy meadows below, and enter a sub-Alpine tundra. This climate zone covers a third of the park. It boasts winds of more than 170 miles an hour at times, and a very short growing season, about 40 frost-free days a year. Anything that survives in the stony pockets of soil has to hug the earth.
CURWOOD: Dr. Stohlgren hops down through a steep boulder field and stops in front of a bush.
STOHLGREN: Yeah, this is a Krumholtz-Ingleman spruce.
CURWOOD: It's about the shortest and fattest Christmas tree I've ever seen. It's as wide as -- it's like 8 feet wide and maybe 3 feet tall.
STOHLGREN: At these elevations, with really cold climates, the trees really take on more of a shrub-like form. But look at this leader right here; it shows that in fairly recent times, times have been very good for this tree. And it will take over more tree-like form from a shrub-like form, given some warming in the climate and then some additions of nitrogen.
CURWOOD: So this is evidence of climate change here?
STOHLGREN: It's evidence of a combination of probably increased CO2, which has a fertilizing effect; slightly warmer temperatures, which are great for tree growth; and then increased nitrogen from air pollution.
CURWOOD: So, how old is this tree? A hundred years?
STOHLGREN: Oh, this could be many more than 100 years old. This could be 200 or 300 years old. But this tree line that we see here was 100 meters, you know, the length of a football field, downslope in the Little Ice Age around 1500. So the trees have moved upslope, and then this is an indication that they're not only moving upslope but they're growing really well very recently. These are the rapid changes that we see throughout the treeline here, that you see here.
CURWOOD: A number of changes in the plant life of the park, Dr. Stohlgren says, are due to warmer winters, most likely linked to global warming, and to cooler summers linked to regional effects. Land use has shifted along the plains of the Rocky Mountain front, with farms and subdivisions that use a lot of water during the growing season. This serves to cool the park in the summer. But this localized cooling will not offset the effects of global warming in Rocky Mountain National Park, says Dr. Stohlgren. Indeed, it may make things worse.
STOHLGREN: What we're learning now about global climate change, it's not simply global warming; it's global change. And we're seeing changes in the variation, and that concerns us most, is that things are bouncing around from the average more. And that gives us a higher level of uncertainty and uneasiness about predicting what the future impacts will be for specific species or specific landscapes.
(A bell tower rings)
CURWOOD: Down the mountain to the east, in the laboratory of the University of Colorado in Boulder, another member of the team, Professor Thomas Veblen, is studying one of the most potent impacts of the climate bouncing around.
VEBLEN: One of the most important findings of our study is that increased climate variability is highly conducive to increased fire occurrence.
CURWOOD: By carefully sanding down tree samples and then studying the rings that date back more than 500 years, Professor Veblen can divine the history of the climate and its relationship to forest fires in and around Rocky Mountain National Park. One of his findings links the incidence of El Nino weather systems to forest fires.
VEBLEN: We expect that there's going to be increased variability in El Nino's southern oscillation events to the extent that we have global climate change. And when we look at the record of El Ninos that dates back to the 1520s, there is a strong statistical relationship of fire occurrence in Colorado with that El Nino record. We find that about 3 years following El Nino events, we get an increase in fire in Colorado.
CURWOOD: Dr. Veblen says El Nino typically brings greater precipitation to the region. The rain allows grasses and shrubs to flourish. When the dry weather returns, usually 2 or 3 years later, that new growth turns to tinder that fuels forest fires.
El Nino is a big deal this year.
VEBLEN: That's right....So if we trust the long-term record, you could make a prediction, then, that 3 years in the future we would expect to have a higher fire hazard as a result of the increased precipitation that should follow this El Nino event.
CURWOOD: And today the danger is multiplied, because over the past 100 years natural forest fires have been suppressed by people. As a result, a huge store of fuel has built up. Should a fire get out of control, the park could be devastated. Climate also affects another natural resource found at Rocky Mountain National Park.
CURWOOD: Water. Much of the water for the western and southwestern United States comes from the Rockies. Four major rivers start in Colorado. The research team's hydrologist, Jill Baron, says huge effects could be felt if the climate warms just a bit.
BARON: If you warm it up 4 degrees, you start the snow melt as much as a month earlier. So instead of it beginning in mid-April to mid-May, it'll begin some time early, late March.
CURWOOD: Dr. Baron says that change in timing may mean a drenching for the ecosystem in the spring, followed by a drought later in the summer.
BARON: The water supply community can probably adjust to that. These are the people that collect the water and then redistribute it for urban and agricultural needs. But to these uphill mountain ecosystems, they won't have any kind of storage like that to be able to compensate for changes in temperature.
CURWOOD: Moving tree lines, fires, floods, drought. If they all come to pass, it could be a scenario out of the Apocalypse. But on this day, as sunset approaches, Rocky Mountain National Park seems indestructible. We turn our greenhouse gas-emitting car around and head down Trail Ridge Road.
CURWOOD: Back near the entrance gate, we join tourists and rangers gathered to hear a sound that's been echoing in these mountains for perhaps thousands of years: the mating cry of elk.
CHILDERS: The deeper the bugle, the bigger the bull.
CURWOOD: Park ranger and naturalist Joan Childers.
CHILDERS: So he's out there trying to look as big as he can, have a very, very deep bugle, very rich bugle. And send out this message that I'm the biggest, I'm the best, come on, join me.
CURWOOD: So you mean this is like the guys on the beach and their cars rumbling up and down and the girls looking and saying Well, I like the one in the red convertible?
CHILDERS: That's a good analogy, I like that. Exactly, yeah. Yeah.
CURWOOD: Now, you've been doing this 6 years or so. Have you noticed any changes in the pattern of when this bugling, when the rutting season begins at all?
CHILDERS: This year it seems to be a little bit later than usual, and we're not seeing quite as much activity as I've seen in years past this early. But why, I don't know.
CURWOOD: We asked one of the team's elk experts what he makes of the bulls' late arrival. He says it could be because the snows that drive the animals down the mountains are behind schedule. But right now there's no research underway to see if this, too, is related to climate change. That's another study for another day.
CURWOOD: Our report on Rocky Mountain National Park was produced by Living on Earth's George Homsy, with assistance from Emma Hayes.
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