Episode 60: Sustainable Landscaping with Dr. Sharon Hall (Arizona State University)

Learn more about the natural environment here!

Episode Intro Notes

What We Will Cover

• What do we mean by sustainable landscaping?

• What is the impact of landscaping on our environment?

• How can we bring about more sustainable landscapes at scale?

• Who are the leaders in sustainable landscaping?

• How can listeners landscape in a way that minimizes the impact on the environment?

• Dr. Sharon Hall, Professor, Arizona State University

what do we mean by sustainable landscaping?

• In the textbook Sustainable Landscaping: Practices and Principles, it refers to sustainable landscaping as the problems of environmental harm caused by human practices in the process of constructing, implementing, and managing our residential and commercial landscapes.

  • Sustainable practices in landscaping are those practices which attempt to minimize or eliminate harm to our environment. Examples include water conservation, preventing erosion and soil degradation, minimizing air, soil, and water pollution, and reducing greenhouse gas emissions. We’re going to get into a lot of these techniques in just a bit.

  • The textbook notes that the earliest papers in academic horticulture literature exploring how sustainability applies to horticulture and landscaping was in the early 1990s.

• Another definition we saw is that, in contrast to traditional landscape practices that highlight ornamental value, sustainable landscaping is driven by mindful choices of design, plant selection, and gardening practices to maximize the value to the environment.

• In terms of the where, we’re going broad, including areas such as the grass in front of your house, the manicured gardens outside a corporate office, city parks, nature preserves and the managed (or not so managed) land in the median of streets.

  • No doubt these landscaped areas can provide us with a place to relax and to recreate, mental health benefits with their aesthetic beauty, and also habitat for various organisms. But there are times where the practices we use to maintain these manicured landscapes have deleterious impacts on the environment.

what are the impacts of landscaping on our environment?

• First, let’s talk scale. Grass is the largest irrigated crop in the United States. Just talking your typical lawn grass, about two percent of land in the United States is covered with it. That’s compared to 1.3% of land that is paved. 

  • There are more than 10,000 grasses in the world. The most popular grasses used on lawns fall into two categories--warm-season grasses that grow well in warmer climates (e.g., bermudagrass) and cold-season grasses that grow well where there are cold winters and varied temperatures (e.g., Kentucky bluegrass).

• There are an estimated 40 to 50 million acres of lawn in the United States: 40% is residential lawns, 20% lines roadsides, and about 3% is on golf courses. The remaining turf accounts for public parks, fields, and other green areas. That toal lawn area is about three times the size of New Jersey. And Americans spend about $60 billion a year on the turfgrass industry, which is lawn supplies and services on sports fields, commercial properties, private lawns, etc.

  • This is especially crazy to wrap your head around considering the “lawnscape” didn’t really grow until suburbanization after world war 2.

  • Note that we’re not just talking grass outside your house. One estimate is that there’s 17 million acres of roadside vegetation (think medians, grass along roads but not on private property, etc.).

  • So the impacts of making our landscape look perfectly manicured and green add up. Let’s look at a couple different areas

  • Carbon dioxide

    • First, let’s talk fertilizer. Fertilizer helps increase agricultural output, but that fertilizer comes at the cost of greenhouse gas emissions.

      • First, let’s talk about the carbon that comes from the manufacture of synthetic fertilizers. Synthetic fertilizers are those that come from man-made, inorganic compounds, typically from petroleum by-products. Most fertilizers contain nitrogen, but to varying amounts, and this nitrogen provides essential nutrients for the plants we desire. For every ton of nitrogen made, four to six tons of carbon typically end up in the atmosphere.

      • Now let’s talk nitrogen. Most fertilizers provide more nitrogen than plants can take up, and soil microbes convert excess nitrogen to nitrous oxide gas, which has 300 times more heat-trapping ability than CO2.

      • To give even more context into this issue, it is estimated that Americans use ten times more fertilizer on lawns per acre than they do on food crops.

      • Given all of this, we weren’t surprised to learn that just fertilizer applications are estimated to represent about 1.5 % of global GHG emissions. 

    • Looking specifically at residential lawns and looking more generally than just fertilizer applications, the total CO2 emissions from lawns in the U.S. is about 25 million tons annually. That’s the equivalent of about five million passenger vehicles driven for one year. Not as much as commercial aviation globally at 860 million tons annually but still a significant source of emissions.

      • There is some uptake of CO2 taking place with your standard grass lawn. A 2018 research paper estimated that lawn grasses in a U.S. metropolitan area account for 50% of the carbon captured in the entire city. But this carbon storage in lawns is typically outweighed by the emissions from maintaining such a lawn.

  • Air quality

    • One estimate is that garden equipment produces about 5 percent of urban air pollution.

    • A University of Florida researcher estimated that one gas mower produces more air pollution than 43 cars driving 12,000 miles each. In other words, hour-for-hour, gas-powered lawn mowers produce 11 times as much pollution as a new car. This is a pretty big deal considering 54 million Americans mow their lawn weekly. Here’s some more crazy stats: gas-powered lawn equipment produces as much as one-tenth of the smog-forming pollutants as all mobile sources (think cars, planes, etc), and Americans use 800 billion gallons of gasoline every year on lawn maintenance activities. 

      • And that’s just what’s used. There are 17 million gallons each year spilled when refilling lawn mowers, which is more than the oil spilled in the Exxon Valdez spill in 1989. 

      • Leaf blowers are particularly bad. The amount of carbon monoxide emitted from a typical backpack leaf blower for just 1 hour is equal to the carbon monoxide coming from the tailpipe of a current automobile operating for over 8 hours. It’s even worse for other pollutants.

      • And that gas powered equipment doesn’t just emit pollutants, it also makes a heck of a lot of noise. Some places have actually banned leaf-blowers or restricted their hours.

  • Water use and management

    • Every square foot of turf grass requires 28 gallons of water per year in coastal areas and 37 gallons in more arid areas

    • Looking at the aggregate now, in dry areas of the U.S., three quarters of annual household water use is for lawns. More generally, on the east coast lawn irrigation is about 30% of water use and it’s about 60% on the west coast.

      • It adds up to a lot of water use. An article from Natural Resources Defense Council says 9 billion gallons of water a day, or nearly three trillion gallons of water a year, go straight into our lawns.

        • A Freakonomics podcast titled “How Stupid Is Our Obsession with Lawns?” cites an even larger number, 20 trillion gallons of water used on lawns. Pretty crazy considering we use 30 trillion gallons a year to irrigate crops.

    • And it’s not just water use, as landscaping also impacts how well the land manages water. If someone chooses shallow-rooted turf grass, it will result in much more run-off compared to something like native prairie grasses. Native prairie grasses have deep root systems, some over ten feet long, that open up spaces in the soil for the water to go so more of it can go into the ground rather than becoming run-off.

  • Pesticide use

    • Homeowners use up to 10 times more chemical pesticides per acre on their lawns than farmers use on crops.

    • We apply about 70 million pounds of pesticides each year to our lawns.

  • Fertilizers

    • Pesticides help kill the things we don’t want in our landscapes, while fertilizers help us grow the things we do want. We talked a bit about the connection of fertilizers to carbon and nitrogen. Now let’s talk about fertilizers in the context of the excess nutrients they can create.

    • According to the U.S. Environment Protection Agency, 40-60% of fertilizer applied to lawns ends up in surface and groundwater, contaminating them with excess nutrients. These excess nutrients lead to algal blooms, low dissolved oxygen, and impaired ecological health in our rivers, lakes, ponds, and coastal waters.

      • This is something called “eutrophication.” The nutrients create algal blooms that choke off sunlight and reduce the dissolved oxygen in the water. This can create massive dead zones. One estimate is that eutrophication costs the United States $2.2 billion in damage a year.

  • Waste

    • According to the U.S. EPA, most yard trimmings (defined as grass, leaves, tree, and brush trimmings from residential, institutional, and commercial sources) were composted in 2018 but still about 10.5 million pounds of it was sent to landfill, which is 7.2% of all municipal solid waste that went to landfill. 

      • These yard clippings going to the landfill is quite wasteful considering they’ll now break down in an anaerobic environment (i.e., without oxygen) and turn into methane, a potent greenhouse gas, when they could have been composted or simply left alone on a lawn. In fact, if these yard clippings were left to decompose on lawns, 16.7 million tons of carbon would go back into the soil rather than contributing to our CO2 emissions. We’ll talk more about grasscycling in just a bit.

  • Biodiversity

    • Monoculture lawns support very few species. Some even call them biological deserts, which isn’t very helpful for the pollinators we depend on.

      • For more on pollinators, check out episode 53.

      • Note that most people don’t perfectly maintain lawns to be monocultures even if they are trying to grow one kind of grass. So, there can be more species in lawns than one might think.

    • Some have called this urban homogenization, which can be defined as the increasing similarity of species composition due to the local disappearance of native species, and the increase of common, widespread alien species due to urban development.

      • The result is that one study found a Phoenix suburban lawn is more ecologically similar to a Baltimore yard than to its neighboring Sonoran Desert ecosystems.

      • We’ll hear more about homogenization in our expert interview.

how can we bring about more sustainable landscapes at scale?

• There is such a thing as a grass-free lawn. You can use only low-growing plants that create the same effect as a lawn, and you can walk on it.

• There’s also the “no-mow movement” where people have yards that fall into one of four categories:

• naturalized or unmowed turf grass that is left to grow wild

• low-growing turf grasses that require little grooming (most are a blend of fescues, a cool-season grass)

• native or naturalized landscapes where turf is replaced with native plants as well as noninvasive, climate-friendly ones that can thrive in local conditions; and 

• yards where edible plants—vegetables and fruit-bearing trees and shrubs—replace a portion of turf.

• Cool stat with growing your own food: the National Gardening Association says that one in three families grows some portion of the food they consume.

  • Policy can help in the transition to more sustainable landscaping

    • Create incentives

      • California launched a turf replacement initiative that offers rebates of up to $500 per yard for homeowners who convert turf lawns to native, drought-resistant xeriscaping. 

        • Xeriscaping is a style of landscape design requiring little or no irrigation or other maintenance, used in arid regions.

      • In Los Angeles, they paid residents to install rain barrels to capture water for their lawns, and it paid them to replace their lawns with drought-tolerant plants. In 2016, LA’s mayor was reporting that in just a couple years, the city had reduced its water usage by 19 percent “without having to fine anybody, without having to crack down with the water police, but by inspiring people through public education and rebates, giving them free cisterns, changing out their toilets, all those sorts of things.”

    • Don’t fine people for letting their yard grow wild.

      • There was a 99% Invisible podcast titled “Lawn Order” (get it?) that told stories of people being apprehended and put in jail for brown lawns (although most just pay a fine).

      • Ohio law allows local governments to control any vegetation that they deem a nuisance on private property, after a seven-day warning to the property owners. But, the law does not define what “a nuisance” is, effectively giving local leaders the power to remove whatever grass or plants offend them. 

      • It may take some pushing from local residents to get a change. Montgomery County, Maryland, for example, amended its nuisance laws to allow for naturalized lawns after locals made the case that their wild gardens improved air and soil quality and reduced stormwater runoff.

    • Let people grow food in their laws to create an “edible landscape.”

      • Yes, dear listeners, in most places you can’t just grow food in your front yard. The City of Orlando was one of the first cities to allow for front yard farming. It now allows 60% of a front yard and 100% of the back yard to be edible.

    • The government controls a lot of lawn, including the around 17 million acres of roadside vegetation mentioned earlier. One argument is that we can’t go “no-mow” on that land because then the invasive species will move in. But one researcher examined what happened when Rhode Island went from regular mowing of its roadside vegetation to low-mow and no-mow. The researchers found no significant difference in the level of invasive species between the low-mow and no-mow areas, as well as nearby young forest.

who are the leaders in sustainable landscaping?

• Ecological Landscape Alliance. Started in 1992, the Ecological Landscape Alliance is a membership organization that advocates for ecological landscape practices through education, collaboration, and outreach. They host events including webinars and conferences. They also have an eco-directory on their website with lots of great resources.

• Fleet Farming, the non-profit urban agriculture program of Ideas For Us, pioneered the idea of turning your front yard into productive farmland. It operates in Orlando given the legal flexibility mentioned a bit ago.

  • It started in 2014 and to date, it’s impact is 114,500 square feet of lawns converted, 7,710 pounds of produce harvested, and 5,140 locals fed.

• Resource Central in Boulder, Colorado sells a “Garden in a Box” xeriscape and native plant boxes designed for Colorado yards.

  • These gardens in a box use a plant-by-number plan, just like the paint-by-number coloring books you may have encountered as a child in the 90s, to make it very accessible to the average person who isn’t an expert in landscape design but wants to replace some of their turf grass with pollinator and/or water friendly plants. The result is less watering and mowing while getting a beautiful yard that is pollinator-friendly.

• There are also sustainable landscaping design firms out there. Some that we found include April Philips Design Works, HGA, and Owen Dell and Associates.

• And we also want to note that indigenous peoples are leaders in sustainable landscaping. Prior to Europeans arriving in America, Indigenous People lived in harmony with nature, managing it largely for hunting and fishing but in a way that did not degrade it. 

  • Globally, Indigenous Peoples actually still manage many landscapes. A recent study in Nature Sustainability found that Indigenous Peoples manage or have tenure rights on at least ~38 million square kilometers in 87 countries or politically distinct areas on all inhabited continents. This represents over a quarter of the world’s land surface, and intersects about 40% of all terrestrial protected areas and ecologically intact landscapes (for example, boreal and tropical primary forests, savannas and marshes).

how can listeners landscape in a way that minimizes impact on the environment?

Let’s first talk about your personal garden

• One step is to take stock of what’s already there. Perhaps there are some plants that require too many inputs (water, fertilizer). It may be best to transition away from those. You also should observe if you have water issues, perhaps standing water after a rain or erosion.

  • After that analysis you can then take small steps to make your garden more sustainable like building a rain garden to deal with water run-off issues or choosing plants that are less prone to major insect or disease problems. 

  • You can also then consider if perhaps you are overtreating your lawn.

• Plant native species and avoid problem plants.

  • Consult your state native plant society and Audubon’s native plant database for planting recommendations.

  • One cool local program is DC’s RiverSmart program called Bayscaping. It encourages residents to replace grass with plants native to the Chesapeake Bay watershed.

• Reduce grass area. Maybe the grass on your lawn serves an important purpose and that’s fine but if you want to keep your green grass lawn, perhaps consider if you could have a smaller one and still meet your needs.

  • Remember that through the early 20th century, most Americans did not have front yards. There is peer pressure to keep a green grass lawn and some places require it, but we encourage you to try to get past that if you can.

• Grasscycle. Leave your grass clippings in your lawn to return the nutrients back to the soil. Not having to bag and dispose of the clipping means less work for you and reduces what ends up in landfills.

  • Back to that peer pressure. It works the other way too, encouraging sustainable landscaping. The City of Alberta started a grasscycling campaign and results weren’t what they wanted. So then they started using social influence to turbocharge the initiative. Messages were left on residents’ doors: “Your neighbors are grasscycling. You can too.” Within two weeks this simple intervention resulted in almost twice as much residential grasscycling as did the control condition.

• Consider using electric or manual tools rather than gas-powered ones.

• We link in our intro notes to a video from a Florida local news station profiling electric ride-on mowers and other landscaping equipment that Suntek Zero Emission Lawn Care uses and powers with solar panels on its van. They save on maintenance costs and no noise!

• And if you are going to mow, mow right. Cut your grass to 3 to 4 inches. Taller grass is healthier, and its shade is inhospitable to weeds (but with weeds, it’s ok to embrace diversity, some flowering weeds are helpful to pollinators). Use the mower’s mulching mode, which will cut the grass into fine clippings and deposit them back into the soil.

• Then there’s the influence you can have over the management of other landscapes

  • We already talked about how the government manages a lot of land. Tell your representatives you want them to take sustainable landscaping seriously.

  • Also talk to the businesses you patron.

    • For example, you may be one of the 24 million Americans that plays golf. There are two million acres of golf courses just in the United States. These golf courses can degrade natural areas, withdraw large amounts of water for irrigation, and pollute groundwater or surface water with the use of pesticides and fertilizers. However, they can also provide needed wildlife sanctuaries, filter stormwater runoff, and support plants and wildlife native to the area. Tell your golf course that you want them to follow the golf course environmental best management practices that the Golf Course Superintendents Association of America just completed for all 50 states and tell them you want them to consider joining the Audubon Cooperative Sanctuary Program for Golf.

about our expert guest

• Dr. Sharon J. Hall is an ecosystem ecologist and associate professor at the School of Life Sciences at Arizona State University. She is also special advisor to the director for justice, equity, diversity and inclusion. Her research focuses on ecosystem ecology and the ways that human activity interacts with the environment. Many of her papers explore the residential landscape.