Sustainability: Cool Urban Spaces Report

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Scientists from Arizona State University, in partnership with the City of Phoenix, released a report evaluating the city’s Cool Roofs and Tree and Shade Master Plan projects. City officials plan to use the report to take further steps in mitigating the extreme summertime heat. Richard Adkins, Forestry Supervisor for the City of Phoenix Parks and Recreation Department, will discuss the report and the city’s plans for it.

Ted Simons: Tonight's edition of Arizona Sustainability looks at a report that's designed to help Phoenix officials ease the impact of summer time heat through the city's cool roofs and tree shade master plan projects. Joining us now is Richard Adkins, forest industry supervisor for the city of Phoenix parks and recreation department. Good to have you here.

Richard Adkins: Thank you. My pleasure.

The Phoenix -- First, what is this cool urban spaces project?

Richard Adkins: This was a study that we worked with in collaboration with ASU to look at our heat island mitigation strategy that the city has in place. And where we should put our effort.

Ted Simons: What are some of the strategies?

Richard Adkins: One was a cool roof project for all new city buildings with an initiative started in 2006 to paint 70,000 square foot of city building roofs with a high reflective material. The other is the tree and shade master plan which is to increase the tree canopy throughout the city.

Ted Simons: The study looked at both plans, what did the study find?

Richard Adkins: Basically that if you have a combination of a cool roof and trees that of course you're going lower the heat around your building. But it found that for most of the effort that planting trees would be a longer sustaining methodology.

Ted Simons: Interesting. And when we're talking about trees, are they desert oriented trees? Because there's so many factors that come into play there. Are water concerns, landscape concerns, cost concerns.

Richard Adkins: Right. And it's also just the urban form. Because you have different building sizes, and they create shade, different shade and wind areas.

Ted Simons: And these trees, what are we looking at here?

Richard Adkins: Those are Chinese Pistachio trees. Very large deciduous tree. Excellent shade.

Ted Simons: Those provide excellent shade. Do they survive?

Richard Adkins: Absolutely. Fairly drought tolerant, and use very -- They need water to get established but they grow and provide excellent shade.

Ted Simons: I've seen some of Chinese pistachio these trees planted in Tempe and they don't look that hot. Are you sure they can handle it?

Richard Adkins: There's another variety called the red Push Pistachio that does even better.

Ted Simons: All right. The urban heat island effect, trees like we're seeing here, the park with the sculpture, how much of a difference does that stuff make?

Richard Adkins: From the study we found through the modeling they did, it could be from where we are now, which is about 10 or 11% shade canopy in the city, that it could actually decrease temperature by 4.7 degrees Fahrenheit if we get up to our 25% goal.

Ted Simons: Now, as far -- Are there differences, let's say this looks like -- this is Cano. This Cano area, very green, a lot -- An oasis kind of area. What about canopies in desert parts of town?

Richard Adkins: Well, they still provide -- The Sonoran Desert is one of the richest desserts in the world with a lot of tree species and canopy. That's where native peoples were always made their homes, and used all the products of the trees.

Ted Simons: And again, as far as the heat island effect, when we talk about that, it's what, concrete, taking the sun's rays and getting rid of the sun heat at night?

Richard Adkins: Absorbing the heat during the day and holding it, and releasing it at night, increases the temperature, our night time temperatures. And that's been doing for decades, we've been increasing our temperature probably with a half a degree a decades probably for the last 67 years.

Ted Simons: There are people watching right now that see this house and see these huge trees, these are Eldaricas or Olapos?

Richard Adkins: These are Arizona ash trees?

Ted Simons: Those are Ash trees? My goodness! How old are those things?

Richard Adkins: Those are probably in the 45 to 50 year range.

Ted Simons: They've been around the block. But people will see those and say, that's a waste of water, we're in the desert, we can't afford that kind of landscape and lifestyle.

Richard Adkins: Most of those trees right there at that age, they're getting water from the turf, the grass surrounding them, and just our annual rainfall of over seven inches. They're not really receiving supplemental water.

Ted Simons: When you do want to add trees, I'm assuming the plan calls for additional trees, how do you do it and keep those water needs down?

Richard Adkins: You just have to manage the water. The biggest thing here in the Phoenix area is we use water we don't manage it appropriately. You can still grow trees and manage the amount of water needed. We tend to overwater.

Ted Simons: Yes.

Richard Adkins: Here in the valley. And so by managing it appropriately, I don't see we're going to increase our water use that much, but we can increase our shade, which will actually decrease our water use for the energy save -- As well as air conditioning costs.

There are some in low-income neighborhoods that would love a bunch of trees lining their neighborhood, their property, the block. They can't afford it, A, and they can't afford the water to keep them up, B. How do you address it?

Richard Adkins: That's just some projects that we need to work through on how we can get trees out to some of these neighborhoods. And it's more of an education process as well. To show them the water needs are really not that high, but still just working together, because it has to be a city community partnership.

Ted Simons: And when you look at -- When the city looks at planting more trees, how do you decide where are the best areas to go with these things?

Richard Adkins: Well, I've done an inventory of all the city properties and where we have trees. We have about 94,000 trees that the city maintains on its properties. And so I know where trees are missing, I know where the species are required, I know where the age component differs and where we could put different trees.

Ted Simons: And where you don't put a Pistachio?

Richard Adkins: Exactly. Or if you need to depending on the rooting space, there are different trees for street landscapes versus park landscape.

Ted Simons: As far as people that do want to get trees in their neighborhood on their property, where do they learn about this stuff?

Richard Adkins: We have classes. I do for the city of Phoenix, we go out into the neighborhoods and do homeowners workshops. You also have the Arizona community tree council, they do workshops throughout the state. You can easily just contact me at my office, and we'll be more than happy to come, I speak to communities all the time.

Ted Simons: As far as the study is concerned, anything surprise you there? Was there anything that you thought, or needed to be emphasized other folks maybe weren't emphasizing enough?

Richard Adkins: It just gave more credibility to the need for trees. Everybody likes trees. But they really don't appreciate the benefit. The multiple benefits that trees do provide us. So it just adds more science behind that fact that trees should be considered a part of our infrastructure when we're developing the city.

Ted Simons: All right. Very good. Very interesting stuff. We'll keep our eye on the canopy. Good to have you here.

Richard Adkins: Thank you, my pleasure.

Richard Adkins:Forestry Supervisor, City of Phoenix Parks and Recreation Department;

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