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How climate change could impact forests in Arizona and beyond

The warming climate has all kinds of implications for all kinds of aspects of our ecosystems.

New research from Northern Arizona University finds even a slight temperature increase in boreal forests can lead to less snow, which in turn leads to other changes.

Andrew Richardson, a professor of ecosystem science at NAU, says the research also applies to other forests, including those in Arizona.

He joined The Show to talk about it and whether it's a fair assessment to say that the data seem to suggest there's this kind of vicious cycle going on when the temperature is warm, even just a little bit on pretty much everything in the ecosystem.

Full interview

ANDREW RICHARDSON: Yeah, I mean, I think the take home message of the paper is really that it's, it's not like we're approaching a tipping point where warming is going to have major impacts on the amount and duration of snow cover. We're, we're at that point already and future warming is virtually guaranteed to have a major effect on winter snow cover. 

MARK BRODIE: So with less snow, there are obviously implications for plant life for runoff and, and water in certain parts of, of the country. But it seems as though they're also pretty significant implications for the forest themselves.

RICHARDSON: Yeah. You know, I think we'll, we'll see lots of changes in the future. With less snow, you don't have that insulating blanket that protects the, upper, upper layers of the soil from extreme cold. And so, that can lead to increasing freeze thaw cycles in the soil that can damage fine roots that can affect plant growth and nutrient cycling. Also low lying plants, low shrubs and things like that. If they don't have a blanket of snow cover on them in the winter, they can be more subject to temperature swings as well and that can damage foliage and have, you know, negative impacts on the health of those plants going into the next growing season. 

BRODIE: What does that mean potentially for the biodiversity of those forests? 

RICHARDSON: Well, I think some plants are, are just more sensitive to freezing temperatures than others. And we might see those declines in populations of those species and other hardier species better able to to survive through that freezing. And, and we may see increases in populations of those species.

BRODIE: If there are plants and other foliage that, that are damaged during the winter, does that potentially have implications for warmer times of year and potential wire wildfires going through those areas if there is sort of more unhealthy or dead trees, plants, et cetera.

RICHARDSON: Yeah. I mean, I don't think so, the freeze, freeze thaw cycles are not going to have such a major impact on the above ground parts of, of trees because they're already elevated above the snow, but damaging the fine root systems could impact the health of the trees could increase fuel loads. I think the real implication though for forest fires is just going into without that sort of big weather event in the spring when snow melts, we're going to go into summer with drier soils and that is going to give us a, elevated risk of, of forest fires. 

BRODIE: What are the implications of just in general having less snow? I mean, you, you talked about how, you know, that kind of leaves the leaves, the forest floor a little bit, maybe more vulnerable to the, the freeze thaw cycle. But I would imagine that less snow is, is not ideal here either. 

RICHARDSON: No, I mean, I think some people may be relieved. They won't have so much snow to shovel. There may be fewer accidents related to snow and ice on the roads. Fewer resources will have to be allocated towards plowing. Those may be seen as positives. But there's gonna be fewer opportunities for snow play and sledding. The ski season will be a bit shorter mud season, a bit longer. I think Flagstaff won't seem like an exotic winter destination for the residents of Phoenix and Tucson. So our tourism industry will suffer. We'll go into summer with those drier soils and elevated risk of forest fires. We'll probably see more forest closures and fire bans, and then reduced runoff in spring and summer is gonna also impact river flows and that could negatively impact whitewater recreation. So there's going to be these carryover effects that extend beyond the December to March period and affect not just sort of the health and productivity of the forest, but many of the services on which our society relies that forests provide. 

BRODIE: Yeah, it sounds like in addition to sort of the scientific impacts, there are economic and financial impacts here as well.

RICHARDSON: Yeah, I, I think that that's gonna be huge. Places like Flagstaff, you know, we're kind of right on the edge of some years, we have a good snowfall some years we don't on warm days that snow melts pretty quickly and if there's less snow to begin with, we're just gonna see a major reduction in snow cover in the future with any additional warming. 

BRODIE: So does what you learned in this research change the way you think about climate change and the impacts of climate change at all.

RICHARDSON: Yeah, I think it does. I mean, my expectation was that a little bit of warming wasn't going to change snow cover much at all and it was only when we got to the higher levels of warming in that experiment that we'd see major reductions. But the fact that any warming above where we're at right now causes reductions in snow cover. That's a big concern for me.

BRODIE: And did you find that it sort of goes up exponentially that, you know, you lose maybe a little bit of snow cover at minimal warming. But as it gets warmer and warmer, the amount of snow goes down in, in some correlating way.

RICHARDSON: Yeah. So what I think what I didn't anticipate was that the effects were, would, would generally be biggest with small amounts of warming and then they would be smaller as the warming increased. But that's largely because as the warming increases, there's so little snow left to begin with that it just, there's, there's not that much more to lose if you know what I mean?

BRODIE: Yeah. Well, I mean, yeah, as you, as you have less and less losing even a little bit doesn't seem like such a big deal because you didn't have that much to begin with, right.

RICHARDSON: When you're at, when you're at three days of snow cover per year, whether it's two or four doesn't really make a big difference. 

BRODIE: Right. Do you think that based on what you found that the forests themselves could stand to undergo some kind of significant change, like if there is an increase in the freeze thaw cycle and certain plants maybe don't do as well as others or trees, does that sort of change the nature of the forest themselves?

RICHARDSON: Yeah. I mean, I think probably the bigger effect there is going to be rapid, you know, trees are fairly resilient, but if we see more large fires because of these drier soils, those fires could really accelerate the shift from, say, Ponderosa forest to Pinyon and Juniper woodlands or something like that. I think that the, the fire is, is a key mechanism there that we didn't study in this research, but would make sense here in northern Arizona, in the Ponderosa forests.

BRODIE: All right. That is Andrew Richardson, a professor of ecosystem Science at Northern Arizona University. Andrew, thank you very much for the conversation. I appreciate it.

RICHARDSON: Thanks. It was great to chat and I hope you have a great day.

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Mark Brodie is a co-host of The Show, KJZZ’s locally produced news magazine. Since starting at KJZZ in 2002, Brodie has been a host, reporter and producer, including several years covering the Arizona Legislature, based at the Capitol.