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Pacific Horticulture’s 2022 Gift Guide
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Book Review: A Field Guide to the Plants of Armenia
Port Gamble Forest Heritage Park
Quercus! The Genus and Genius of Oaks with Garden Futurist Dave Muffly
Ecological Regions of North America. Credit: United States Environmental Protection Agency[/caption]
Sarah Beck: I think a lot of us in the Pacific region have noticed that there's always some kind of disaster happening. Obviously, disasters happen a lot of places, but I think those of us in the Pacific region have started to take it personally. You know, there's a lot of extreme experiences here with wildfire and heat domes and droughts.
Ryan, I'm hoping you can share a little bit of the climate scientist view here, about these extreme changes that we are seeing, that we will see. I know Hawai`i often gets described as this sort of bleeding edge for extremes. Can you give us some orientation to thinking about drought for instance?
Ryan Longman: Well, yeah, it's a good question. One of the tricks in Hawai`i is that the interannual variability, right, these natural modes of variability are so pronounced that a lot of times people wanna say it's climate change, but that signal is hard to flush out because of that variability. So it takes time to collect data and really understand what's going on.
Some things like temperature increases, I mean, that's global. And we can document those in Hawai`i and they're in line with global. Other things, like extreme rainfall events, stuff like that, that's always been happening. So it’s tricky to really find that signal there.
In terms of drought, though, we just published something on looking at drought and we are finding, through this hundred-year record, that droughts are not necessarily becoming more frequent, but they're lasting a little bit longer and they're a little bit more intense. So that's a significant signal that we're finding.
So as new data emerges, people will actually put their heads down and try to take a closer look. You know, these things are starting to emerge.
The last 10 years are different than the last 20 years, and the last 30 years. And we see this dynamic. The normals are shifting. And I think that's always just going to open up more opportunities to take a closer look and do analysis and figure out what's happening. So 20 years from now, we might have a better idea that signals actually exist.
Dan McKenny: I think you're making a very important point with some variables that will affect, certainly, natural distributions of plants. In our part of the world, the prairies may be expanding or some mountainous areas—or more mountainous—turning more sort of mediterranean, which obviously will affect fire regimes, and fire regimes are really going to affect plant distributions, especially if plants can't get to their fecund part of their lives, right? They can't produce seeds naturally, so it's an important thing.
Ecological Regions of North America. Credit: Dr. Dan McKenney, Director of Integrated Ecology and Economics, Canadian Forest Service.[/caption]
Glenn Griffith: There are limits to our adaptations, though. But here’s my take on it. And I'm biased, I know. I think ecological regions influence our regional economies, our resource bases, our land use patterns, the flows of water. So strategies to ensure meeting just basic human needs, such as providing clean drinking water, ensuring healthy soil for food production, making location- and material-appropriate affordable shelter—these all have regional strategies that are needed. Tapping into more sustainable energy sources. These flows of energy go through our ecosystems in many different ways, in different forms and rates. These all have regional variations.
So I think our science can help us recognize the possibilities of these natural potentials and limitations. And art I think helps, as well. But yeah, there's a lot of opportunities to steward and regenerate and revive and be more resilient, but we have a lot of work to do.
Sarah Beck: Joining me again is Bart O’Brien.
To consider how this work that's being done on mapping, tracking climate and ecological data can inform a horticulturist, I'm wondering if it also includes like what those plants are that might be successful?
I’m wondering, in terms of what the climate scientists are describing as these bursts of, I don’t know, just chaos. We're have these big event weather events where it's like, “Oh, then when it rains, maybe it’s a flood, or the drought becomes super extreme.” Obviously, you can't just bring up a Baja California plant and be like, “Oh, you love it dry. Oh, it's going to be hot and dry,” and then suddenly there's like a monsoonal wet period.
Bart O'Brien: Well, I would say that sort of the global nature of vegetation will move toward more weedy plants.
Sarah Beck: That's interesting.
Bart O'Brien: That's sort of where it's going anyway, without a lot of climate change. It's just what's weedy survives. But as gardeners and restorationists and people really interested in plant diversity, there are things that you can do in your home garden that aren't really readily adaptable to restoration-type things.
When our garden reached 107°F on the day that San Francisco reached 109°F, and there had never been anything even close to that here, it burned a lot of the deciduous tree leaves, but the plants themselves were fine.
I happened to be down in LA during that extreme heat, it was over a Fourth of July weekend, probably about, what, eight years ago? Even coast live oaks (Quercus agrifolia), the sunny side of them were just completely bleached. But the plants overall, except for those that were compromised by disease or Phytophthora or just age, the regular plants seemed to survive okay.
Also, putting up temporary sunscreens during or just before you know one of these heat domes or heat wave things is going to happen. I mean, we had that one here earlier this year that was just a one-day event. Yeah, throw some burlaps or sheets over some plants for the day and wet it down a little bit.
Sarah Beck: Like what happened in Portland and Seattle recently, very similar. Maybe mulch is perhaps a piece of it. But like you're saying, maybe there are some more extreme practices we need to be ready for those moments.
Bart O'Brien: Yes, especially for those plants that you're in zone denial about. Almost all gardeners practice some level of zone denial.
In an era of climate change, that's not necessarily bad, particularly if you have like a more heat-loving and drought-tolerant and cacti and succulents and so on. The key thing to know, though, about some of those groups is that, as most gardeners know, there are cool-season succulents and warm-season succulents, and that most of the succulents people want that are from non-mediterranean climate areas need some water in the summer to look their best.
So if you really like the Mexican agaves, you need to water them on occasion in the summer, to have them really look nice. Otherwise yes, they'll shrivel, and they won't like the real wet winters. Yet they're very adaptable with minimal inputs.
That’s sort of what I look for and advise people that aren't terribly interested in gardening and plants, the plants that they can do a little bit for, and they'll really perform. Myself, yes, I grow everything at my house, and I experiment with all kinds of things just to see what happens.
Sarah Beck: I guess my question to you, Bart, is really: as the climate-appropriate gardener, how should you use that filter? What should be a potential rubric or a decision-making process for making good choices and not selecting something that really shouldn't be somewhere?
Bart O'Brien: Yeah. Well, number one, to me ,is avoiding plants that could be weedy.
My definition of a weed, there's the basic one: any plant out of place is a weed. However, I take that further. To be a weed, it's got to not only be out of place, but it also has to be able to aggressively cover ground, whether it's vegetatively or by seed, and that is oftentimes readily spread by wildlife or humans.
Sarah Beck: If we're thinking that some of these plants that are aggressive, and many of them are probably known to us already, do you feel like they're gaining an advantage in some of the changing climatic circumstance?
Bart O'Brien: Certainly. If you're thinking about California landscapes in general, both natural and artificial landscapes, weeds are a major, major issue. I mean, when you just even think of all the European grasses that come up everywhere. One of two weeds that gets up into the alpine zone is a non-native grass.
So these plants are very well-adapted to getting around and crowding out natives. And that if you think that the natives are going to be pressed because the climate isn't what they grew up with, it's going to make it easier for more aggressive, exotic plants, and maybe even some native plants, to become more weedy.
When I went to Chile, I saw California poppies all over the place in wild landscapes and Lupinus arborius all over the coast. So it's not that California plants are blameless worldwide as far as weediness.
Sarah Beck: Sure.
Bart O'Brien: One just is going to be seeing more of these kinds of plants out there. And I think a lot of them are probably going to be leguminous, simply because the seeds can survive almost anything, and are very, very, very long lived.
It doesn't mean that there won't be other plants and that you can't have interesting and diverse gardens. I expect people will always have interesting and diverse gardens. They may just get smaller and smaller because of space and more and more people now that there's over 8 billion of us. It just makes more pressure on the set-aside “wildlands” that we all enjoy, and that we all depend upon for housing so much of the biodiversity.
When I think about California in particular, it's that in geologic time, the coast was always the refugia for plants. And you see a lot more geologically older plants near the coast, or areas with coastal influence, or that are just more temperate, less extreme environments.
That's where so many of us live now. There's not going to be the major fog refugia all along the coast where things can just move up and down.
Sarah Beck: When we're seeing distribution of plants changing in these, I mean, maybe they're not completely wildlands, but there are wilder spaces. How should a gardener or how can a gardener think about watching these changes, and should we be reacting or following the lead of some of these areas we're seeing success of plant redistribution? Is there really a role for us as gardeners thinking about this and observing that?
Bart O'Brien: Yeah, I think that there is, and it gets very complicated in California simply because there are so many rare plants.
So if you think about manzanitas, our garden is ground central for manzanita diversity and collections. Here in the Bay Area, we have so many really localized endemic species, many of which are state or federally listed. And so should we be concerned about moving some of those San Louis Obispo coastal things, or San Diego coastal manzanitas up into our area, even though they might be happier here now? It's complicated.
Botanic gardens are already doing that on a couple of specimens basis. Yes, most of them are very happy here, but it would have to mean that you have to think about, okay, well, Arctostaphylos pallida, federally listed. Arctostaphylos imbricata, federally listed on San Bruno Mountain. They need help to go up to Crescent City, or wherever their ecological niche will be.
Whereas it's not going to be possible to do that whole-population-wise. It's why having these seed banks that are population-level based and long term are so important. They are the backstop for climate change, short- and long-term, as long as they themselves are protected.
There's a lot of support right now for seed collection of particularly rare and threatened plants, endangered species, and some that are less so, but California is very much in the forefront of that effort with wild species.
[caption id="attachment_32626" align="alignnone" width="919"]
Canada Extreme Minimum Zones. Credit: Natural Resources Canada, Canadian Forest Service[/caption]
Sarah Beck: This has been a great conversation and a lot to contemplate. I am joined now by my co-producer Adrienne St. Clair for a few final thoughts. Adrienne, I would love to hear your thoughts on this idea of regional shifts of plants.
Adrienne St. Clair: Yeah. And this ties into that idea of how the North American West Coast differs so much more dramatically than the rest of the continent.
So when people talk about climate change, a lot of people talk about this idea of south moving northward. And when you look at native plants, and specifically in the North American West Coast, that's not exactly the full story.
So if you look at the Midwest and the East Coast, the ability to predict climate shifts is more straightforward. If you pull a niche out and start to model how that niche will shift over time with climate, you see this general consistency to move northward and eastward, and in fairly long distances.
When you get to the Rockies, however, everything changes. And that's because of that topography and it's because of the influence of the Pacific Coast. And we've been hearing about these two things being such factors in climate science, especially on the West Coast. So if you take another climate niche on the West Coast, and you look at what components are there—the highest temperature, the lowest temperature, the rainfall, the sun aspect—and you look at that niche and see how it's going to change with climate, it's not necessarily going to move north.
In fact, when you look at many of them, you can see that there is no consistency with how they move. And it could be that that climate niche is actually moving from a south-facing slope around the north side of that mountain range. And now that niche is going to be found on the north side. And geographically, that distance is not very far.
But because of all of these factors of topography and the ocean, we can't as easily predict how niches are going to change.
Sarah Beck: That is super interesting.
Adrienne St. Clair: So what that means for sourcing native plants makes a really complicated story.
Sarah Beck: As we think about this as horticulturists and think about plants as gardeners, knowing that these changes are really unpredictable, how can we not get frozen in thinking about all of these data points and being like, “Oh my gosh, all these changes are happening.”
Adrienne St. Clair: I think that's an interesting strength that gardeners have that as a restoration ecologist, gives me pause. There's this idea that, as a gardener, you can push that edge a little bit. You can push that boundary.
I think the opposite has been the case for restoration. We've held climate envelopes as kind of sacred, these climate niches as this sacred thing that we can't change within, and maybe to our detriment.
So in the ‘40s, ecologists started recognizing that plants from the same species from two different locations might be different in important ways that help them survive better, right? So this is called local adaptation and it means that some plants from here, even though they’re the same species from plants over there, are going to survive here, where they wouldn't survive over there. Same species.
That research was out of Stanford. So I don't think that it’s ironic that this research is coming out of California, right? So we've got all of these very high variabilities, just like we're talking about. And through observation, people were able to see that these plants are a whole lot shorter and these plants are a whole lot taller, and what happens when we grow them in the same place? Do they hold that same stature? And that's what came of this, is this idea of local adaptation.
And so ecologists became hyper focused on this idea of local plants and using local plants within a system. As urbanization and land-use changes have happened, what we are also realizing is that genetic isolation is playing more a part on the health of populations, or rather is a stronger factor in the detriment of populations.
So maybe we need to actually be moving these propagules around, but to what extent through our range? And helping that genetic flow might actually be beneficial to the populations that we're working with.
So then the question becomes, well, how far do I move it? Do I move it from this park within my city to this other park within my city? Do I move it from this city to the neighboring city down the valley? Or do I move it into a whole other state? Right? And that's the question that people are trying to get to right now, is what does this genetic exchange look like when you're trying to build healthy populations?
So, for instance, snowberry is a plant that is found across two thirds of the northern hemisphere. But I don't think there's any ecologist in the West that would call a snowberry from Eastern Europe a native plant, right? But where's that line? So these Level III ecoregions help us draw that line. All of this mapping that we've been hearing from people, those are just layers of data that help us make these decisions.
And so this reality of plants having this differentiation, that can be kind of a boon for horticulturists, because you can bring this now unique and special plant into a new area, but it kind of became this limiting factor for ecologists.
If the goal is to have these populations that are locally adapted, what does that mean? And especially what does that mean for climate change and how do we prepare?
I mean, one of the main difficulties is that plants that we put in the ground right now need to be ready in 50 years, but they also have to survive right now. And so how do you find that balance?
There is a lot of work being done with those Level III ecoregions with some of the other tools that we see, and putting those on top of climate models to try and understand better about how things are changing and how to inform the decisions that we're making, specifically with native plants and native ecosystems.
Sarah Beck: Do you think the extremes of climate change are something that gardeners can start practicing adaptive response to in terms of their caring for plants?
Adrienne St. Clair: I wonder how gardeners and local restoration professionals might be able to team up to start thinking about some of these responses to climate change.
One of the big questions that is hard to pinpoint has to do with animal interactions, insect interactions. What pollinators are working with what plants, and will the pollinators be different if I have a native plant versus a non-native plant from the same genus? So if I have a geranium that's native and a geranium that's non-native, do they have different pollinators, and things like that?
Within the confines of urban areas, those are some answers that could be questioned by a simple observation every day at three o'clock in the afternoon, looking for what type of insects are out there.
So I wonder how gardeners might be able to pair up with research on species and species selection and climate change.
Sarah Beck: I think it was Dan, who was part of the panel, who brought in the community observations and citizen and community science element. I think that's really interesting, that people working on such a big scale have such an interest in that level of data collection, I think that could be part of this future story, right?
Adrienne St. Clair: Yep. We have a great program in Oregon called the Oregon Bee Atlas that takes volunteers and goes out and identifies bees and what type of plant they're interacting with. And the level of data and the quality of the data is amazing when you look at that data set that they've developed over the last 10 years.
