The case for landscape water use, Natives top ASLA trends, Is Denver next for mandatory green roofs?

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News and commentary for emerging green infrastructure markets GrowerTalks MagazineGreen Profit Magazine

Wednesday, March 15, 2017

Debbie Hamrick Subscribe
New Terrain

The case for landscape water
Natives top ASLA trends
Denver next for green roofs?
Insects that love urban heat
Farther to forest than ever
Colombia’s Deregulation Tracker
Your state’s climate change
Track Western milkweed
The deep soil/CO2 connection
Worth reading 


Investing Colorado’s water in landscapes = $ in returns

Landscapes are a great investment of Colorado's water. Photo by the Army Corps of Engineers of Cherry Creek dam and reservoir.

The driving message of The Hidden Value of Landscapes: Implications for Drought Planning by Colorado State University is simply this: Investing water in Colorado’s landscapes delivers high returns. While Colorado landscapes use about 3% of all of Colorado’s waters, they deliver significant economic and ecosystems services. Such as:

  • ROI Residential landscapes: For every $1 invested in the landscape, the yield is $1.35
  • Rent: Commercial properties with attractive landscapes get 7% higher rents
  • Crime: 25% fewer domestic crimes occur in public housing with landscapes
  • Learning: Children who spend time outdoors are better learners
  • CO2: Each tree absorbs 48 lbs. of CO2 annually; urban trees offset about 5% of all human CO2 emissions
  • O2: Every 55 sq. ft. of lawn generates enough oxygen for one person for a day; lawns also sequester CO2
  • Temps: Cars parked under shade trees are 45F cooler; well-placed trees in the residential landscape can save $100-$250 a year in energy costs

The document is written to enable policy makers to understand why investing a portion of Colorado’s limited water supply in landscapes is a wise choice.

It’s easy to look at the landscape and simply dismiss its importance as “non-essential” compared to other water-use stakeholders such as agriculture, household use and recreation. Indeed, restricting outdoor water use is generally the first regulatory action undertaken in times of drought. The authors argue that cutting off all landscape irrigation has significant unintended consequences.

“Eliminating landscape water is a short-term fix that creates complex, long-term problems,” they write.

Policy recommendations include:

  • Base drought policy on research-based horticultural BMPs
  • Prioritize watering trees and large shrubs that cannot be quickly replaced
  • Prioritize sports/recreational fields for the physical and psychological benefits to people
  • Provide incentives to consumers to save water before drought strikes through smart controllers, rain sensors, etc.
  • Maintain irrigation systems so they are efficient
  • Eliminate over irrigation/conduct irrigation system inspections
  • Educate about water saving technology and appropriate plant material

The Hidden Value of Landscapes: Implications for Drought Planning by Zachary Johnson, Tony Koski, and Alison Stoven O’Connor, Colorado State University.

Native plants, low maintenance top ASLA trends

Natives are hot for residential landscapes. Photo of Aesculus pavia.

Sustainable, tech-friendly residential landscapes are in high demand, according to the American Society of Landscape Architects’ annual survey “Residential Landscape Architecture Trends” conducted in February.

For the first time, wireless/internet connectivity entered the top 10, suggesting that people want a backyard that allows them to enjoy both nature and connectivity. The survey asked landscape architects to rate the expected popularity of a variety of residential outdoor design elements in 2017. 

“Well-designed residential landscapes provide social interaction, enjoyment of nature, and physical activity, while also reducing water use and stormwater runoff,” said Nancy C. Somerville, Hon. ASLA, executive vice president and CEO of ASLA.

ASLA’s Top 10 Residential Landscape Architecture Trends

  • Native/adapted drought tolerant plants – 82%
  • Native plants – 81%
  • Low-maintenance landscapes – 79%
  • Food/vegetable gardens (including orchards, vineyards, etc.) – 76%
  • Permeable paving – 76%
  • Reduced lawn area – 72%
  • Fire pits/fireplaces – 71%
  • Drip/water-efficient irrigation – 71%
  • Wireless/internet connectivity – 70%
  • Rainwater/graywater harvesting – 70%

From an ASLA press release.

Denver mulls mandatory green roofs for heat island mitigation

Denver is one of the hottest cities in the United States—literally. Temperatures in the city are about 4.9 degrees higher than in the surrounding countryside, making it one of the Top 10 hottest cities in the United States.

The public health impacts of hot cities are increasingly well documented. Increased mortality, especially among vulnerable low income populations, is one outcome. Others include exacerbation of existing disease conditions for anyone having to live there, such as diabetes, asthma and other respiratory illnesses.

A group of Denver residents wants to do something about it. Current efforts to garner 10,000 petition signatures for a November ballot initiative are underway. The initiative would require green roofs or a combination green roof/solar array on new construction and major renovation of more than 25,000 sq. ft. in “gross floor area" after January 1, 2018.

Buildings with 25,000-49,000 sq. ft. would be required to cover 20% of available roof space with green roof. Requirements scale up to 60% required for buildings with more than 200,000 sq. ft. The proposed ordinance also has a “cash in lieu” provision of $25 per sq. ft., funds that would be directed to the Denver Office of Sustainability.

Mandated green roofs are required in just a few locales—San Francisco and Toronto, for instance. Other cities, including Philadelphia, Seattle and Washington, D.C., encourage use of green roofs through incentives. The practice is part of green stormwater infrastructure and helps cities meet mandatory stormwater rules. The climate cooling benefit that green roofs provide is secondary.

To mandate the use of green roofs for urban heat island mitigation is new. The University of Colorado-Denver student behind the effort says she’s driven by recent election results to act in positive ways to effect climate change. “I’m very passionate about climate change, and with our recent election, it’s time for our citizens to take the initiative and battle some of the climate changes we are experiencing,” Madison Backer told the Denver Post in the story “Should Denver require rooftop gardens to reduce heat island effect?” by reporter Jon Murray.

The Colorado Apartment Association’s incoming president Rocky Sundling released the following statement to the Denver Channel. CAA represents 2,820 members with 252,068 apartment units. The CAA says that while green roofs “are a great solution to the urban heat island effect, are an effective roof insulator, and are aesthetically pleasing,” they are costly to install and maintain.  “Allow the market to work and let buildings that choose to install green roofs experience the competitive advantage that these roofs will likely provide.  Other buildings will follow to maintain competitive equality.  We have seen this voluntary building standard work very effectively with the LEED energy certifications. We believe the green roofs program will have similar success by allowing the market to demand their installation."

The Denver Green Roof Initiative has a GoFundMe site

Proposed initiative for large buildings could go on November ballot, but it likely faces fight from developers by Jon Murray for The Denver Post.

Climate Activists Pitch Mandatory Green Roofs for Denver by Rachel Dovey on Next City.

Urban heat-loving scale harms red maple

Gloomy scale turns out to really like hot, dry urban spaces, areas likely to be increasing with climate change. That's going to be an issue for one of America's best native trees, Acer rubrum.

They are known as gloomy scales (Melanaspis tenebricosa), and these insects can make a red maple’s life dreary. This is because the arthropods feed and thrive on them, especially in warm and dry urban landscapes, a University of Florida Institute of Food and Agricultural Sciences researcher says.

Gloomy scale insects reproduce more when the trees they live on are under the stress of heat and drought, according to new study led by University of Florida/IFAS entomology assistant professor Adam Dale.

Adam’s new research is important as residents and urban landscapers decide when and where to plant red maples. The shade tree native, widely distributed in North America from Florida to Canada, helps cool urban areas.

Adam conducted the study in Raleigh, North Carolina, when he was a doctoral student at North Carolina State University. He wanted to know how the gloomy scale, an insect widely distributed in the eastern and southeastern U.S., would respond to hot, dry weather—conditions typical for urban trees. Researchers studied urban red maples at various temperatures around the city. Then they irrigated half the trees twice a week during the summers of 2014 and 2015.

Acer rubrum trees plotted with hot (red) and cooler areas (blue) in Raleigh, North Carolina.

At the end of 2015, they collected gloomy scales from each tree, measured their body size, dissected them and counted the number of eggs the insects produced. They then looked at the relationship between the temperature in the tree’s canopy and whether the tree was irrigated. Scientists wanted to see if either factor had an effect on the insects’ body size or egg production.

The hotter and drier the trees were, the more eggs the gloomy scales produced.

“This insect is drastically more abundant on urban than rural trees throughout the southeastern U.S.,” Adam said. “It reduces the health of these trees along with the services they provide to people and the environment.”

In many ways, this native pest acts like an invasive insect when it is in urban landscapes, he said.

The scale’s favorite host tree is red maple, also “the most common urban landscape tree in the eastern U.S.,” Adam said. “Since the gloomy scale benefits from warming and drought—two features common to urban landscapes—and urban landscapes are rapidly expanding, there is a potential for this pest to proliferate and cause even more problems in the future.”

Urban foresters and landscape architects can use the study’s findings by selecting more appropriate trees to be planted where heat and drought stress may likely be. 

“Sites that are surrounded by more impervious surfaces—roads, parking lots, buildings and more—and thus warmer and drier, are not the most suitable sites for these trees,” Adam said. “If they are in such sites, irrigating during the warmest months to reduce drought stress can help manage these pests.”

University of Florida Press release
Warming and drought combine to increase pest insect fitness on urban trees
by Adam Dale and Steven Frank in PLoS One.

Distance to a forest increased by 14% in a decade

If you’ve ever doubted the importance of what you do in the economy and greater world, paste this on your computer: You connect the American populous to nature. Never underestimate how important your role and the managed landscape has in that job.

From 1992 to 2001 the distance to the nearest forest from any point in the United States increased by 1/3 mi. (about 1,780 feet). The loss of forests and forest fragments is changing the urban and rural landscape in ways that are not yet fully understood. What we do know, however, is that the role of the managed landscape is surging.

Properly designed, installed and managed, landscapes provide biodiversity, secure soils, infiltrate water to recharge aquifers, cool the climate and provide vital connection to nature—and that's just a few of the benefits.

The authors of “Forest dynamics in the U.S. indicate disproportionate attrition in western forests, rural areas and public lands,” published in PLoS One, are calling their measurement the “forest attrition distance” to directly reflect the loss of forest fragments. In analyzing satellite data over a 10-year period, they found that an area of forest the size of Maine disappeared from the U.S. The metric they are specifically quantifying in their PLoS One paper is to give attention to forest patches and their importance to wildlife.

While some biologists question the need for yet another urbanization/loss of habitat benchmark, no one disagrees that as we continue to march toward greater and greater urbanization, natural landscapes are disappearing at an ever-faster rate.

How Far to the Next Forest? A New Way to Measure Deforestation by Steph Yin in the New York Times and Forest dynamics in the U.S. indicate disproportionate attrition in western forests, rural areas and public lands by Sheng Yang and Giorgos Mountrakis in PLoS One.

Climate monitoring

Climate Deregulation Tracker

Do you want to keep up with how the Trump Administration is changing the federal climate landscape? The Columbia Law School’s Climate Deregulation Tracker identifies steps taken by the administration and Congress to scale back or eliminate federal climate mitigation and adaptation measures. The tracker is linked to Columbia’s database of climate change regulations. 

How is your state’s climate changing?

Ever wondered how your climate is changing? NOAA’s State Summaries were produced to provide state-level information that originates primarily from the Third National Climate Assessment (NCA). The summaries include observed and projected climate change information and focus on aspects that are part of NOAA’s mission (characteristics of the physical climate and coastal issues). The NCA activities derive from the U.S. Global Change Research Act (GCRA) of 1990. These state summaries contain information both on historical trends and scientific knowledge about potential future trends.

Help track milkweeds and monarchs across the West

Join the effort to conserve western monarch butterfly populations by mapping milkweed. The collaborative effort, Western Monarch Milkweed Mapper, will improve understanding of the distribution and phenology of monarchs and milkweeds, identify important breeding areas and help scientists better understand monarch conservation needs, writes Candace Fallon in her Xerces Society blog post

Key research questions that these data will help answer include:

  •     Where are different milkweed species growing in the West?
  •     Where are monarchs occurring in the West?
  •     Where are monarchs breeding in the West?
  •     When is milkweed emerging and senescing in the West?
  •     How does milkweed phenology differ by species?
  •     When is monarch breeding occurring in specific areas of the West?
  •     What types of habitats are different milkweed species associated with?

Partners in the Western Monarch Milkweed Mapper include the Idaho Department of Fish and Game, the Washington Department of Fish and Wildlife, The Xerces Society for Invertebrate Conservation, National Fish and Wildlife Foundation and U.S. Fish and Wildlife Service.

Soils could release more carbon than expected

Caitlin Hicks Pries downloads soil temperature data while fellow Berkeley Lab scientists Cristina Castanha (left) and Neslihan Tas (middle) work on an experimental plot in the background. (Photo credit: Berkeley Lab)

Soils could release much more CO2 than expected into the atmosphere as the climate warms, according to new research by scientists from the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab). Their findings are based on a field experiment that, for the first time, explored what happens to organic carbon trapped in soil when all soil layers are warmed, which in this case extend to a depth of 39 in. 

Soil organic carbon harbors three times as much carbon as Earth’s atmosphere. In addition, warming is expected to increase the rate at which microbes break down soil organic carbon, releasing more CO2 into the atmosphere and contributing to climate change.

Until now, the majority of field-based soil warming experiments only focused on the top 2 to 8 in. of soil, which leaves a lot of carbon unaccounted for. Experts estimate soils below 8 in. in depth contain more than 50% of the planet’s stock of soil organic carbon.

The need to better understand the response of all soil depths to warming is underscored by projections that, over the next century, deeper soils will warm at roughly the same rate as surface soils and the air. In addition, simulations of global average soil temperature by the Intergovernmental Panel on Climate Change, using a “business-as-usual” scenario in which carbon emissions rise in the decades ahead, predict that soil will warm 7 or 8 degrees F by 2100.

Researchers heated soil plots at California’s Blodgett Forest Research Station. They discovered that, of the 34 to 37% increase in CO2 released at the three warmed plots, 40% of this increase was due to CO2 that came from below 6 in. They also found the sensitivity of soil to warming was similar across the five tested depths.

The scientists say these findings suggest the degree to which soil organic carbon influences climate change may be currently underestimated.

“There’s an assumption that carbon in the subsoil is more stable, and not as responsive to warming as in the topsoil, but we’ve learned that’s not the case,” says co-author Margaret Torn. “Deeper soil layers contain a lot of carbon, and our work indicates it’s a key missing component in our understanding of the potential feedback of soils to the planet’s climate.”

The research was supported by the Department of Energy’s Office of Science.

Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) press release.


March 16 - Webinar: Working With Commercial Landscapes to Manage Irrigation

Adjusting watering schedules is critical to efficient irrigation. The webinar Working with Commercial Landscapes to Manage Irrigation will be put on by the EPA’s WaterSense program and the Alliance for Water Efficiency (AWE). Attendees will learn how the University of Texas at Austin tracks landscape water use through live dashboard monitoring. WaterSense will also highlight best practices for irrigation in the commercial and institutional sector, and AWE will discuss its Outdoor Water Savings Research Initiative. 

March 18 - Designing for Nature, Chattanooga

The 6th Annual Native Plant Symposium by the Tennessee Chapter of Wild Ones was created with both casual and experienced landscapers in mind. Presentations include "Planting in a Post-Wild World" by Claudia West, author of the book by the same name. Other presentations include "Challenges to Using Native Plants in Commercial and Residential Design: A Landscape Architect's Perspective" by Steve Sanchez; "Practical Considerations in Native Plant Landscapes" by Mike Berkley; and "Native Plants and Sustainable Landscapes" by Rick Huffman.

March 22 - Webinar: Monitoring for Reptiles and Amphibians

In the Wildlife Habitat Council webinar Monitoring for Reptiles and Amphibians you’ll learn about how to monitor habitat that benefits the aforementioned fauna. Sampling for reptiles and amphibians is an important aspect of the monitoring. Dr. JJ Apodaca, Partners in Amphibian Conservation, will discuss active and passive sampling techniques, including using surveys and artificial cover objects, how to collect scientifically rigorous data, and different monitoring techniques for specific taxa. 

March 24 - Reading the Land through Climate Change, Philadelphia

Reading the Land through Climate Change: Local Plant Adaptation Past, Present, and Future with Mark Demitroff, Stockton University, will be held at Morris Arboretum, Philadelphia. Ancient climate change profoundly influenced the character of the flora that we cherish today, he says. Local ecosystems and the native plants that depend upon them owe much of their inheritance to cold, non-glacial processes that characterized much of the last 2.5 million years. Mark will reconstruct local past environments through geology, climatology and plants to help develop a long-term view of ever-changing plant adaptation. The audience will then be better able to preserve and manage habitat in the future.

April 4-5 - One Health, One Planet, Pittsburgh

Scientists, medical and public health professionals, animal health professionals, ecologists, architecture and green building professionals, community officials and organizers, educators,and students are invited to join One Health, One Planet, an exciting new symposium designed to explore the interconnectedness of environmental, human and animal health and examine the relationship between health and the built and natural environments in which we live, work, learn and play. Through this novel connection between the One Health Initiative and Phipps’ Research Institute for Biophilia and Science Engagement, experts from disparate fields will gather around the shared goals of tackling environmental issues, addressing disease prevention and improving health and well-being. The opening keynote is by Dr. Richard Joseph Jackson, UCLA Fielding School of Public Health. He is the co-author of the books Urban Sprawl and Public Health, Making Healthy Places and Designing Healthy Communities.

October 9-11 - Pollinator Conservation, Traverse City

The second national conference related to pollinator conservation in ornamental plant production and urban landscapes, organized by Michigan State University and North Carolina State University, will be held at Park City Hotel, Traverse City, Michigan. The conference, geared to research, extension, industry, government and NGOs, fosters discussion about issues such as insecticide safety and habitat conservation.

Worth reading

When it rains, Los Angeles sends billions of gallons of "free liquid gold" down the drain by Bettina Boxall in the LA Times

Connecting plant phenology and local climate change by Tatyana Lobova in the Virginian-Pilot.

Invasive bushes in Decatur killing cedar waxwings by Mary Margaret Stewart on and Feeding Behavior-Related Toxicity due to Nandina domestica in Cedar Waxwings (Bombycilla cedrorum) by Moges Woldemeskel and Eloise L. Styer in Veterinary Medicine International.

Why artificial turf may truly be bad for kids by Stuart Shalat on The Conversation.

Study shows US grasslands affected more by atmospheric dryness than precipitation on

Improving the biodiversity of green roofs from a press release by the University of Portsmouth and Microbial inoculants as a soil remediation tool for extensive green roofs by Heather Rumble and Alan C. Gange in Ecological Engineering,  DOI: 10.1016/j.ecoleng.2017.01.025

The Transformative Power of Spending Time Outside by Amelia Urry on CityLab.

Maine’s native bees a ‘very optimistic story” by Abigail Curtis in the Bangor Daily News.

How the United States Looked Before the EPA on Fortune.

How to Fight Plants with Plants by Nancy Lawson on the Humane Gardener.

Happy New Era? by Jim Lenhart in Storm Water Solutions.

Black cohosh native plant of the year by Mary Reid Barrow for the Virginian-Pilot.

Brighten Up Your Balcony or Patio with a DIY Native-Plants Garden by Meghan Bartels for Audubon

Admiring the desert’s native shrubs by Maureen Gilmer for The Desert Sun

Communicating the Value of Urban Biodiversity to Foster City Resilience by Rowan Schmidt, Matt Chadsey and Jessica Hanson for 100 Resilient Cities

Santa Rosa set to showcase rainwater capture at new City Hall garden by Kevin MacCullum for The Press Democrat.

Seeds of Commerce: Saving Native Plants in the Heart of Appalachia by Nancy Averett on Yale Environment 360.

Water Conservation by Joann Gonchar in Architectural Record.

Pussy Willow -- A Valuable Native Plant by Penn State Extension.

700+ native bee species spiraling toward extinction by Melissa Breyer on Treehugger.

Let it pour: How to rainscape your yard by Kris Wetherbee for The Oregonian/OregonLive.

The Value of the 1st Year's Maintenance for Green Infrastructure by Anthony Kendrick for Convergent Water Technologies.


Debbie Hamrick


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