A new study shows ponderosa pines in the Four Corners region rely heavily on the summer monsoon season to survive the current megadrought. But, it’s hard to predict if monsoon storms will strengthen or weaken with climate change. KNAU’s Melissa Sevigny spoke with lead author Brandon Strange, a researcher from the University of Arizona.
We’re in this two decade plus long megadrought. What has that done to our ponderosa pines?
It’s no surprise it’s really stressed them out. But there is a couple of different responses depending on how much monsoon precipitation the forests get. Some that are more southerly, they receive a lot of monsoon precipitation each year. They’re doing okay. Not great, but okay; they’re hanging on. Forests a little further north that less reliably receive precipitation from the monsoon, they’re doing quite poorly. What we’re seeing is they are losing a lot more water than would be good for them.
So the monsoon, the moisture we get during the monsoon season, is acting kind of like a buffer, it’s helping these trees get through the drought.
That’s a great way to put it. Obviously, trees need water for growth and photosynthesis, etc. But one of the biggest benefits that the monsoon is providing for these forests, is it reduces the atmospheric demand for water. The atmosphere is not as dry, the relative humidity goes up, and these plants, or ponderosa pines, aren’t losing as much water because the atmosphere is not trying to suck it out of their needles.
How well is that working? How happy are the trees that are actually getting that monsoon rain?
Like I said, they’re doing a little bit better, but not great. With a drought as extreme and as long as the current one we’re in, it’s really hard for the monsoon to buffer them. It’s done okay so far, but if the drought continues for a while or if it intensifies, our results suggest that the monsoon may not be able to continue buffering them.
That’s dismal news.
Yeah, it’s kind of a bummer.
And unfortunately unpredictable monsoon seasons is something else that climate change might be causing?
That’s a great point. We have a really hard time projecting what the monsoon is going to do in the future. Some people say it’s going to strengthen, it’ll be more intense with warmer temperatures. Some people say it going to be diminished or not as reliable. It’s hard to project what’s going to happen with these forests based off of that. If we see an intensification, maybe it’s okay to buffer them for a while. If it diminishes a little bit, then they’re really in trouble, right? Warmer temperatures, less monsoon, that would be a recipe for disaster.
Okay, wait and see what happens.
Unfortunately that’s really all we can unless we can find better ways to represent the monsoon in models, but it’s tricky because it’s a very stochastic system, it’s more or less random. If a wave comes through the Pacific and pushes moisture, we’re good. If it doesn’t than it’s not.
Which makes it I’m sure fascinating to study as a scientist.
It is. I love being able to try and project what the forest might do depending on these different outcomes. It’s fun and I think it’s important work because we’re at a crossroads where we need to know what’s going to happen in the future if we want to manage these forests with any success of all.
Brandon Strange, thank you so much for speaking with me.
Thanks for having me.
