Talking Trees with Davey Tree

How Climate Change is Changing Your Landscape

April 28, 2022 The Davey Tree Expert Company Season 2 Episode 16
Talking Trees with Davey Tree
How Climate Change is Changing Your Landscape
Show Notes Transcript

Dan Herms, vice president of research and development at the Davey Institute, talks about how climate change is changing your landscape, such as what climate-facing trees you should be planting, what trees you should avoid planting and how pests are migrating. 

In this episode we cover:

  • Dan's research from the 1990's (0:37)
  • Dan's research for Davey Tree (2:51)
  • Hardiness Zone map (4:40)
  • Pests moving north (6:09)
  • Dan's perspective (8:13)
  • Trees - winners and losers (9:13)
  • How we can help (11:14)
  • Planting climate-facing trees (12:40)
  • How it feels to be researching climate change (18:24)

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To view the Future Plant Hardiness Zone map, click here

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Doug: Welcome to the Davey Tree Expert Company's podcast, Talking Trees. I'm your host, Doug Oster. Each week, our expert arborists share advice on seasonal tree care, how to make your trees thrive, arborists' favorite trees and much, much more. Tune in every Thursday to learn more, because here at the Talking Trees podcast, we know trees are the answer. I'm joined this week by Dan Herms. He is vice president of research and development for the Davey Tree Expert Company in Kent, Ohio, and we have a very important subject today. We're talking all about climate change. Dan, you've spent a lot of time researching this issue, right?

Dan: I have, Doug. I've been actively researching climate change since the mid-1990s, I guess.

Doug: That was way before a lot of us It was on our radar. Talk a little bit about what you discovered, especially early on, on the changes that you've seen.

Dan: I really got into this by studying the phonology, the seasonal development of plants and insects in the 1980s and the relationship of that to weather and climate. During my PhD program in the late 1980s, I was studying the effects of drought stress on trees. In 1988, it was a particularly hot year, very hot year, severe drought. That was the year that NASA scientist, Paul or Jim Hansen testified before Congress about climate change and saying that it was already here. That's when it really got on the radar screen of me and, I think many other people. That's when I started paying attention to it. I started actively researching various aspects of climate change in the mid-1990s.

When I became a professor at Ohio State University in 1997, I really started to focus on that from point of view of studying the literature and speaking about it. I joined the Ohio State University Climate Change Outreach Team and continued studies on the effects of climate on trees and insects and their interactions.

Doug: I'll never forget that summer of 1988. That was a scary time. At the time, I was just a home gardener, but running well water. That was a definite wake up call as an awful year with that drought. In your research for Davey, talk about how you're approaching that as a scientist and looking at the empirical data.

Dan: The Davey Tree Expert Company asked me to develop projections of how climate change would affect trees in the tree care industry and our operations over the next 30 to 50 years to increase awareness but also to help direct our strategic planning moving forward. I've spent a lot of time poring through thousands of studies that have been published on climate change to synthesize and integrate the literature that's been published as it relates to trees in the tree care industry. Everything from tree health, insect problems, storm damage, workers' safety during hot temperatures, the spread of disease-bearing insects, hurricanes, wildfire, all of these things bear directly on our operations.

Doug: It's important that this data is looked at from a scientific point of view. Right?

Dan: Right. We look at it impartially, non-biased, very objectively. We look at it maybe as a jury would in a trial. We're not trying to advocate for a particular position, for a particular policy. We're trying to understand what is happening, look at the science, understand what's happening and project what's going to happen because it will have impact on our bottom line.

Doug: I know part of it from looking online. The Davey website includes an interactive zone map predicting the future. It was scary to look at, to tell you the truth.

Dan: On our website, davey.com/climate, we have an interactive Hardiness Zone Map. This map can be used to show how the hardiness Zone is projected to change in any location in the United States, any zip code under different emission scenarios. Looking forward on how warm the climate is going to get, the biggest uncertainty in those projections is the future of greenhouse gas emissions. We look at different scenarios. A high emission scenario, which is kind of business as usual, and a low emission scenario which would be more consistent with, say, the Paris Climate Accord agreements. You can look at that and see how the climate is going to change in your location and it is eye-opening.

For example, Kent, Ohio, say, even under a low emission scenario, Kent, Ohio and northeast Ohio, where I'm located, will become more like southern Tennessee or northern Alabama by mid to late century.

Doug: That doesn't sound good to me at all. That sounds absolutely awful. Some people might think like, "Oh, well, we'll have this nice warm climate." But no, that's going to change everything. Just from looking at some of your research that we're already seeing a change in insects moving north, right?

Dan: That is correct. Insect species have moved north. That's been well documented. An example is a southern pine beetle, which is a native bark beetle in the south-eastern United States, which undergoes periodic outbreaks. That causes a lot of mortality in the pine. It's not very winter hardy and so it never spread much north of, say, Kentucky, Virginia. In the last decade or so it's been detected in New Jersey where it's killed pine trees and pine barren unique ecosystem. It's been detected in New York, Massachusetts.

It's made incursions into Ohio. The mountain pine beetle in western North America has spread up into areas of high altitude in the Rocky Mountains where it never existed. It's moved north into northern British Columbia, causing massive mortality of the lodge pole pine in areas where it never existed because it was too cold.

Doug: As the summers get warmer, insects could even have another generation, right?

Dan: Yes, we've seen that happen as well. As the summer gets warmer, the growing season gets longer. That can allow insects to have more generations, complete more life cycles during the year and build to bigger problems. That's been documented in everything from spider mites to-- There's an insect called oyster shell scale. In northern Ohio used to have just one generation per year. Now it has two fletcher scale. Another example, there's a number of examples of this kind of thing.

Doug: As a scientist, as you're over all these years watching this happen, it's so scary, I guess, from my point of view. What is it from a scientist's point of view?

Dan: It is scary. From day-to-day, year-to-year, you don't really notice much. Then all of a sudden, 30 years have passed and you realize, especially if you've been keeping records, that things are really different. We're seeing this in earlier springs, changes in precipitation patterns, changes in the species composition. Which trees are growing in which places? These are already being documented. It gets scary because things tend to be adapted to the climate that they've experienced historically.

When that changes, it's usually not for the better, because if it's cold, they're adapted to a cold climate. If it's a warm area, they're adapted to that. When it changes, it becomes drier, it becomes wetter, becomes warmer, becomes cooler, it usually means the organisms and the ecosystems are not adapted as well to the new situation.

Doug: When we think about our trees, when you're looking at this, are there winners and losers as the seasons change?

Dan: There certainly are winners and losers. That's a really good point. What we're seeing is northward migration of tree species. Even in, say, at the edge of the plain states in Illinois and areas like that, we're seeing westward migration of tree species as precipitation increases. These species that are migrating, they're migrating into places where they're doing better, but they're also migrating north, and so at the southern edge, they're doing worse. They're stressed, they're dying out. They're being replaced by species that are better adapted. This does mean there are winners and losers.

For example, if you look at Mane, the spruce trees, the fir trees that are adapted to that cool climate are going to be the losers, the oaks and hickories, in the maples that are adapted to the warmer climate will be the winners. This has important implications for deciding which trees to plant, for example, and tree planting is a really important response to climate change, but in 30 years from now, which is a pretty short period of time in the lifespan of a tree, the climate is going to be different. We have to select climate-facing trees, that will be adapted to the location 30 years from now, 50 years from now, rather than trees that are adapted to a particular location today.

Doug: That leads me to what can we do? What can we do as gardeners? What can we do as people who love trees? Can we help? Can we make a difference?

Dan: Well, certainly we can. Tree planting is a technologically very feasible thing that anybody can do. If you have some space, you can plant a tree. Trees are great for responding to climate change. Trees provide services, so to speak, that help mitigate the impacts of climate change.

Trees store carbon. They remove carbon from the atmosphere. Trees cast shade that reduces say urban heat, which reduces the heating air conditioning demands in energy use on a building. Trees inter set storm water and reduce runoff into storm sewers. With increased precipitation, especially in the eastern United States, that's an important impact. Trees filter air pollution. Trees do a lot of things that at the local level can help us adapt to climate change and increase resilience of our communities to climate change.

Doug: When I'm thinking about planting trees, in my case, in mid-Atlantic region, should I be thinking about climate change? Should I be thinking about what species I want to plant in regards to that? I know we always talk about right tree right place, but then throwing this also into the mix?

Dan: Yes. I think so. The climate has been and will continue, at least in the foreseeable future to be changing fast enough to impact trees that we plant today 30, 40 years from now. As we discussed with the Hardiness Zone Map that shows how the climate in a particular area is going to be different in mid-century to late-century. When we select trees to plant, we need to think about not only what does that site like today, but what does that site going to be like in 30 years from now.

We talk about planting climate-facing trees. Now I'm in Northeast Ohio. I like to think about and I will use a technical term here, what's called the climate envelope for trees. The climate envelope is the climatic variables that determine what trees grow where. Precipitation and temperature are the two main drivers there. Rainfall and temperature controls the distribution of tree species. You think about how are those going to change.

A relatively I think heuristic or simple way to think about it is look at the current distribution of trees and look at where we are. Look at trees that currently grow here. Now they're adapted, but they also extend farther south. They're adapted to warmer climates. For example, red oak. Ohio is right in the heart of the climate envelope for red oak. As red oak migrates north, it will still be in Ohio for a long time to come. Hickory, Bur oak, honey locust, these are all trees for which red maple, Ohio's very much in the center of their climate envelope. Those will be good choices now, and they're good choices for many years to come. Other species, like sugar maple, for example, not going to be a very good choice in Ohio 30, 50 years out.

Doug: That's such a shame because that's a tree, that whenever I talk to an arborist, and I ask them what tree would you recommend and they always come up with sugar maple. They love sugar maples, but to think of that not being a mainstay in a place like Northeast Ohio again is scary. Now, if we all got on board, can we change this do you think or is it too late?

Dan: Well, no, I don't think it's too late. I think we can change it. I think we need to get busy. It's going to require a number of things. Just planting trees is by itself is not going to do it. An aggressive reforestation program, eliminating deforestation in the tropics, the Amazon, for example, this could solve 10% to 15% of the problem. It's going to require reducing emissions of greenhouse gases, changing land use, making buildings more efficient, reducing greenhouse gas emissions from transportation sectors from electricity generation. It is going to require a multifaceted effort. Then it's probably going to require removing carbon dioxide from the atmosphere in the future. That technology doesn't really exist in terms of mechanical methods. Trees right now are the way to do it.

Doug: In 20, 30 years, do you think we'll be like, "Oh, I'm so glad we listened," or is it going to be, "I wish we listened to Dan and his research because he had it all laid out for us."

Dan: Well, and of course, other people have it all laid out for me. I'm understanding the science as it exists. I think the answer to that question will become apparent in the next 5 to 10 years if we're going to reduce emissions. The goal of the Paris Climate Accord, for example, is to limit warming to about three degrees Fahrenheit. We've already experienced two degrees of that. There's already more warming baked into the system. If we're going to meet that goal, we have to respond very quickly, reduce greenhouse gas emissions by about 40% by the end of this decade, and reach net zero in terms of carbon emissions by 2050 mid-century. That's going to require some aggressive action, but anything helps. If we can't limit it to three, four is better than five, five is better than six, six is better than seven, but when you're getting up to five, six, seven, that's getting pretty extreme.

Doug: I want to finish off by asking you what it feels like to be able to spread this message because this is an important message to tell people. I have to assume it feels good in a way but also it's sad in a way too.

Dan: I do a lot of speaking about climate change. I focus on the causes, the consequences that we're already experiencing, and the solutions. I think the solutions can provide some hope. Public awareness is increasing as more people experience the impacts of severe weather, for example, they see it firsthand. Hurricanes, wildfire, flooding, and so forth. I try not to relay a message of gloom and doom, but my message is realistic. I talk about things that have already happened. I'm not laying out very pessimistic projections. I'm talking about what has happened and the very likely scenarios as we move forward.

I do find it rewarding to help inform people, motivate them to take action, to support policies, to contact their politicians, their representatives to

help all of us work together to solve this big problem.

Doug: Dan, I know you've motivated our listeners and you certainly, every time that you and I talk, motivate me and I appreciate the great work you're doing and also appreciate your time today. Thank you so much for spreading the word.

Dan: You're welcome, Doug, a pleasure to speak with you today.

Doug: That's very important information for sure. Next week, we get a much-needed pruning lesson about spring flowering trees and shrubs. We'll find out the exact time that job is done and how to do it the right way. Tune in every Thursday to the Talking Trees podcast from the Davey Tree Expert Company. I'm your host, Doug Oster. I'd love it if you'd subscribe to the podcast. Where else will you have this fun, right? As always, we like to remind you on the Talking Trees Podcast, trees are the answer. [00:21:16] [END OF AUDIO]