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MICHAEL DUNNE: I'm Michael Dunne. Despite the fact that it exists only a few 100 yards from one of the region's largest malls and interstate five. Delta Ponds on the Willamette River in Eugene is a kind of natural oasis. At any given moment, one can see bald eagles, great blue herons, and so many birds and waterfowl that it feels miles away from town. But despite great measures to preserve and protect this restored wetland, climate change knows no boundaries. Today on the show a conversation with an ecologist from the city of Eugene to talk about this rare urban treasure. She'll discuss how the ponds have changed over time, some naturally, like the seasonal red bloom currently occurring, but others more connected to manmade intrusion. It's an in depth look at the continued shallowing of Delta ponds due to drought and climate change. Lauri Holts, who is an ecologist with the city of Eugene parks and open space department. Thanks so much for coming on and talking with us.
LAURI HOLTS: You're very welcome.
MICHAEL DUNNE: So, delta ponds is turning red. What's going on?
LAURI HOLTS: Well, we have an aquatic Fern that lives in the ponds, in particular on the east side of the pond, so east of Delta highway, okay, and it's, it looks like a big almost spill of paint. It's kind of a pinkish reddish color. And we actually get calls every year about it. If you were to go over to the ponds and walk down to the edge, you would see that it's actually 10s of 1000s of little individual floating ferns, and they don't look quite like a fern might like in your backyard or in your house. They're little flat plants that have little rootlets that come down. And so, they are in the genus azola. It’s the genus name, and they are found all over the world, actually.
MICHAEL DUNNE: Wow. Is it that this bloom happens because of temperature this time of year. Kind of, what sets it off?
LAURI HOLTS: Well, it can be a couple of things. It is definitely related to temperature, and also full sun. It can also be indicative of, you know, less than ideal conditions. Maybe they've depleted some of the phosphorus. I think they're limited by phosphorus, and so could be a combination of the heat we had, the dry weather, our pond levels are really low and full sunshine, and possibly some diminishing of nutrients. They're really interesting. It's almost always present in the ponds, but when it's healthy and in its full growing phase, it's green, and then it is able to change and produce a different type of pigmentation. And that's what comes, you know, appears to us as a red pigment, I see, apparently, that can help protect the plant from getting too sunburn. However, it is also an indication of maybe less than ideal conditions. And it could be that they're just senescing or, you know, like our trees are starting to go dormant for the fall, winter season.
MICHAEL DUNNE: Okay, do the birds and animals and amphibians and fish in the area? Is this beneficial to them? Is this a food source, you know, kind of, how does it, how does it impact, perhaps, the overall environment there in Delta ponds?
LAURI HOLTS: Well, it is native, and it is found all over the world. It can get quite thick. It's not actually as thick this year as it was last year in Delta ponds. And however, there's not really any negative impacts. It's a tiny little plant and ducks and most critters can swim through it. And in fact, it could improve water quality in the sense that it shades out the water column. And so, in some of our urban areas, urban ponds, we get these blue green algal blooms, and those need some of the same nutrients. They need a lot of sunshine, and so where you have something like azola covering the surface that could actually suppress the growth of some of those more harmful, quote, algal blooms. And I should mention that when I say harmful algal blooms are not actually an algae. It's a cyanobacteria bloom.
MICHAEL DUNNE: I see, in fact, we kind of hear that from time to time. I'm thinking of sometimes Odell Lake has something like that. Is that what you're talking about?
LAURI HOLTS: Yes, correct.
MICHAEL DUNNE: I see. About how long will this red pigmentation be visible? When will it? When will it sort of go back to what we're used to seeing?
LAURI HOLTS: Well, I think some of those will probably die off as we get into, you know, our below freezing temperatures, and so it'll probably start changing over the next month. I've never really, you know, watched it that closely. Yeah, we'll start diminishing here with the fall weather.
MICHAEL DUNNE: Let's talk just generally about delta ponds, you know, as I understand it, it, it was man made, gosh, decades ago. Talk about sort of, you know, Delta ponds, maybe either a little history lesson or why it was formed and why it's important, sure.
LAURI HOLTS: Well, I could spend an hour talking about delta ponds. It actually was originally the river actually originally flowed through that entire area. So historically, our rivers were allowed to meander, or I shouldn't say, allowed, but they did meander all over the valley, especially in the winter and the spring, when there was either a lot of rainfall or a lot of snow melt off. And of course, we've considerably constrained our rivers now with the building of dams and levees and so on. And so there's some records that show that as recently as 1850 the river flowed through the Delta, ponds area and, and then at some point, it shifted to the east, I'm sorry, West, and then became more constrained through some of the you know practices after the Euro Americans arrived. And so it. But after that period, it there was a period during the 1950s and 60s when there was gravel extraction, or gravel mining that took place for a couple decades, and that's what shaped the actual shape of the ponds and some of the islands and peninsulas out there, and so that had a big, significant impact on the area. And of course, in order to do those activities, they likely enhanced built and or enhanced levees along the river, between the river and the ponds to keep the high flows out. That may have happened prior to the gravel mining through, you know, agriculture, okay, and other practices, but, but yes, so the gravel mining significantly impacted the area and resulted in a series of ponds, rather than maybe a side channel of the Willamette River, which it was immediately prior to the gravel mining. And then, starting in 2004 we began a almost decade long habitat restoration at the site, and this was mostly funded, initially through the Army Corps of Engineers, and then multiple grants. I think at one time, I was either helping implement or overseeing nine different grants out there. This was from the period of 2004 to 2012 and so we had multiple goals, but one of the biggest ones was to reconnect the ponds to the Willamette during the winter. And one of the main reasons to do that is to allow our listed spring Chinook salmon, so they're listed under the Endangered Species Act. It allows that connection, allows the juveniles to come in in the winter when the river is raging and rest in a quieter, you know, place that doesn't have the high flows and maybe has some good areas for them to feed and grow and rest until they continue their journey downstream to the ocean.
MICHAEL DUNNE: I see is that, is that one of the reasons why it's such a great place to go see birds, because I would imagine it might be easier to catch some of those small salmon in shallower water.
LAURI HOLTS: Yes, I mean, that's one reason, but one of the other goals of the project that we did was to really enhance the riparian vegetation. And so, we planted over 100,000 native trees and shrubs as part of the restoration project. We did a lot of work to enhance the riparian vegetation at the ponds, and we planted over 100,000 native trees and shrubs as well as sedges and rushes and well. And prior to all that planting, we also removed acres and acres and acres of blackberry and scotch broom, you know, and then, and then we did the planting. And so, by converting it to from an, you know, highly invaded plant community to a native plant community, that, you know, was a significant improvement for bird and bird habitat. The other reason the ponds are a good place for birds is that there's kind of a variety of habitat. So, you can see birds that you know, like ducks and geese that like the water, but you also have mud flats and pond edges where you might see sandpipers. And then, of course, you have all the songbirds and new tropical migratory songbirds and raptors and things like that, using the taller vegetation.
MICHAEL DUNNE: I'm very familiar with, Delta ponds I run on the trail there, and it seems to be one of the best places if you want to see a non, a non-native species, nutria. Kind of, how does nutria play into this? Because I know it's, it's an invasive species and not, not supposed to be here. Kind of what do nutria do to Delta ponds? Are there benefits to them being there, or do they do damage?
LAURI HOLTS: Well, nutria were introduced into the US for the fur trade, and they're originally from South America, so they're definitely not supposed to be here, and they are mostly detrimental. They can burrow into banks and cause erosion and or, you know, even burrow into banks under things like bike paths. So, they can be quite problematic. They also they're just highly reproductive. So, I did a graph once for a presentation I did that showed their exponential growth. They can have babies at four months old, and they can have, I don't know, a litter of eight. And then each of those can then become reproductive. And so pretty quickly they can, you know, become too abundant. And if you've been in areas that are near waterways where there's nice green lawns, they come out on the lawns, not unlike Canada geese, you know, and they end up pooping everywhere. So, you have, you know, you can have some issues with water quality and nutrients. You know, excess nutrient from their excrement, sure, and then they do compete a bit with other some of the other rodents, in particular, our native muskrat, gets pushed out and out, competed by these more abundant nutria. Beaver and nutria seem to tolerate each other a little bit more. I don't exactly know what their dynamics are, but yeah, they're certainly not good. But because of their high reproductive abilities, it's really a little bit of a futile effort to try to trap them out, because they're so abundant in this part of Oregon that they just, you know, the young from a nearby population just moves in, and then it starts all over again.
MICHAEL DUNNE: You mentioned Canada geese. I apologize if this is sort of a dumb question, but I think a lot of us sort of see geese and think, Oh, that's a species that migrates that you know, flies south for the winter. But obviously, if you spend any time around Delta ponds, you'll see Canada geese year-round. Is our climate and in our environment, such that we have year-round populations of what are historically, perhaps even incorrectly known as migratory species.
LAURI HOLTS: There's definitely changes happening. I think we've always had some small population of overwintering or what we call resident Canada geese. However, there are changes, you know, and I'm not a bird expert. I love to bird ecologist, but I'm not following things so closely that I could, just off the top of my head, give you some examples. But we're definitely seeing changes in bird populations, and, you know, certainly around the country and probably around the world. You're seeing species shift, at least in this part of the world, shift north. And you know, we're seeing things that we may might not have seen in previous years because of the winters are warmer, sure.
MICHAEL DUNNE: And Lori, that's my last question for you. You studied this, this particular very, very important area in our community, Delta ponds. How has the changing climate impacted Delta ponds and the species that live there?
LAURI HOLTS: Well, if you've been out to Delta ponds lately, and actually for the last couple of months, you probably noticed that water levels are extremely low, and I have never, I've been working out there since 2004 and I've never seen the water levels so low and that's part in part, because the river levels were lower than usual all summer long. And our summers are getting so long and dry that it's definitely impacting the amount of water available, or in the groundwater. The ponds are filled, you know, largely through groundwater when they're not actively connected to the river I see. So that's a big change. Also, like with a lot of other natural areas, we're losing a lot of trees due to the same, you know, longer drier summers. They just aren't adapted to go that long without additional rain and so and also heat when we get these hot, hot days, especially for more than one day in a row, a lot of the deciduous trees can't handle the amount of transpiration that causes, and that stresses them out. So definitely seeing some changes, yeah, particularly in the later part of the summer and early fall.
MICHAEL DUNNE: Delta ponds is certainly a wonderful part of our community, and hope that it can continue to be that, that that wonderful environment. Lauri Holts, who is a an ecologist with the city of Eugene parks and open space department, thank you so much for coming on and talking with us.
LAURI HOLTS: You are welcome.
MICHAEL DUNNE: That's the show for today. All episodes of Oregon On the Record are available as a podcast at KLCC.org. Before we go, I wanted to read some of the recent comments we received on our social media pages about past episodes in our show about ICE protests and the possible deployment of troops to Portland. Alexander wrote, The Trump administration is using a lie to justify a military takeover of our city. People are being hurt in our city by agents of the federal government. Larry wrote, none of this is legal. When will the generals draw the line? But Rick wrote, thank you, ICE, take the criminals out. And Jesse wrote, This is so overblown, and MAGA is trying to push the Portland on fire narrative. And on our show about the digital license plate readers or flock cameras. Bonnie said, if you're not breaking a law, then you have nothing to worry about. But Larry said, this doesn't help clean up the streets. This helps make the police more money. Finally, in our interview with the new Eugene police auditor, Jay takes issue with how long it takes to lodge a complaint and asks for more transparency. Please keep sending in your comments to our Facebook Blusky or Instagram pages or to questions@klcc.org. Tomorrow, on the show, we'll talk with an Oregon State University professor about a new study which suggests that the famous and potentially destructive San Andreas fault could be linked with the Cascadia Subduction Zone, which could create an even larger seismic threat to the Pacific Northwest. I'm Michael Dunne, host of Oregon On The Record, thanks for listening.
