May 16, 2008

Planting for evaporative-cooling and water conservation

Yes, this book, whose cover features a squirrel on a patch of green lawn, holds insights about energy and water.

I highly recommend Suburban Safari by Hannah Holmes, pictured above. Here are a two excerpts related to landscape and energy. It's unusually hot in the East Bay and we are on the cusp of summer water rationing, so Hannah Holmes's observations and well-researched findings are salient!
...the flood-irrigated neighborhood where we began our tour was cool and shady, wasn't it? That shade keeps the entire city a little cooler. And those water-hog trees, grasses, and shrubs cycle water much faster than desert plants do, and that evaporation cools the city even more. So which would you have? More water use and less air-conditioner use? Or less water use and more AC? A water shortage, or fossil-fuel smoke in the air? Chris chuckles. Heh heh. He has no easy answer. However, the university owns a plot of Phoenix houses and plans to landscape them three different ways to compare the effects. Not that Chris expects science to change anyone's mind about his or her lawn (p. 127).
Nothing 's clear with energy and ecology....Grass, like most plants, cools itself, and the air around it, by releasing moisture. Measuring the effectiveness of this trick is as easy as stepping barefoot from the lawn to the street on a hot day. A thirty-degree difference isn't uncommon. The contrast is strongest after sunset, when the grass cools quickly but the street throbs late into the night. All this cooling around the house reduces the amount of air-conditioning we need indoors. Grass is even better than trees than trees at the evaporative-cooling business. (Trees win overall because their shade prevents sunlight from soaking the city in the first place.) (p. 116).
Surprised by the previous statement? According to Dr. Cynthia E. Rosenzweig at NASA, "all else being equal," there is a small difference in the urban heat island effect in going from impervious cover to grass versus going from impervious cover to trees. On the other hand, in a city like Manhattan with more area to plant sidewalk trees, street tree planting is a more effective strategy than planting trees in open space, i.e. parks composed of lawn and widely-spaced trees. If you are considering planting vegetation to capture the "evaporative-cooling" effect, consider water-conserving plants in light of the water shortage in the Bay Area. EBMUD (East Bay Municipal Utility District) has over 100 pages of water-conserving plants from trees to ferns in its publication, Water-Conserving Plants and Landscapes for the Bay Area (1990). I purchased my copy used at Black Oak Books in North Berkeley. Remember though, plants, even natives, require regular watering in their first year to establish well. If you are unmoved by the "evaporative-cooling" effect of the lawn, alternative grasses, recommended by EMBUD, include California fescue, blue oat grass, zebra grass, deer grass, fountain grass, and needle grass (view a purple needle grass). Chamomile and moss verbena, of the ground covers, seemed most suitable for recreation, "the lawn's least debatable benefit" according to Holmes. Planting dwarf sedge in an "urban forest" garden is recommended by the U.S. Forest Service. Suburban Safari is available in our bookshop. Proceeds from the bookshop will support our efforts to document citizen nature makers.

Ecological design titles in the bookshop include

Redesigning the American Lawn Rain Gardens Imported Comments In response to: Planting for evaporative-cooling and water conservation Comment from : nalini [Visitor] that is so interesting! i love your blog! In response to: Planting for evaporative-cooling and water conservation Comment from : jordan [Visitor] Hey! Thanks for the great info, I am always looking to find good books about being eco-frinedly. I was browsing through a bunch of green websites and blogs and I came across yours and found it very interesting. There are a bunch of others I like too, like the daily green, ecorazzi and earthlab.com. I especially like EarthLab.com’s carbon calculator (http://www.earthlab.com/signupprofile/). I find it really easy to use (it doesn’t make me feel guilty after I take it). Are there any others you would recommend? Can you drop me a link to your favorites (let me know if they are the same as mine). In response to: Planting for evaporative-cooling and water conservation Comment from : Georgia [Member] Jordan, for environmental issues/news, I read Gristmill and Treehugger.

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