The Suburban Ecologist, Part I: Albedo

An ecologist in the suburbs is constantly faced with the failure of the well-informed to impart their knowledge to the population at large.  The rift between better environmental practices and actual environmental practices is so wide, it seems impossible to breach.  There are too many fronts to attack: homeowners who want their yards to look like golf courses, parks that are devoid of wildlife and preserve only non-native species, riparian zones that are too narrow to support a community of amphibians, roads that are too wide and too busy for animals to cross, and the ever expanding parking lots.

Yet, solutions exist for all these problems.  Human development is not necessarily the issue, it is the haphazard and greedy way that we do it.  Landowners and builders have such narrow considerations, that they fail to realize the impact that they have on the surrounding community of humans and the ousted wildlife.

Many people are sufficiently worried about the increase of average global temperature, but few realize the warming they cause on a micro-scale.  Urban and suburban areas increase localized temperatures through the effect of reduced albedo.  Since the early 1800s, many have noticed that urban areas are 5-10 degrees Fahrenheit warmer than the surrounding countryside.  This effect has come to be known as the urban heat island.  While these islands are a very small percent of the earth’s surface, they add to human discomfort and air conditioner use, which is expensive.  Even a slight increase in temperature makes the environment intolerable to many species of wildlife, such as certain frogs, toads, and salamanders.

Light energy from the sun behaves differently depending on the surface it hits.  The amount of light reflected is the albedo.  High albedo means low temperatures on the ground, and low albedo means sunlight is being absorbed and transferred into heat.  The heat energy combines with all the other heat producing activities of humans in cities and suburbs to create the urban heat island.  However, certain types of surfaces are more reflective.  A roof surface reflects only about 20% of light energy, transferring the rest into heat. White paint reflects 80%.  Just painting a roof white increases its albedo 300%.  Many types of vegetation also counter the effects of low albedo.  Plants such as vines, trees, and bushes cool the air through transpiration, which is the enhanced evaporation of surface water.  Furthermore, vegetation absorbs energy for photosynthesis instead of transforming it into heat.  Trees, bushes, and vines have the added benefit of providing shade.  Areas in shade are much cooler than those in direct sun, and shade has been proven to reduce the cost of air conditioning, extend the life of roads and parking lots, and block surfaces with low albedo.  Even a vine on a wall can reduce the surface temperature by as much as 36 degrees Fahrenheit. *

The most common type of vegetation in suburban areas is neither trees, bushes, nor vines, but grass (Figure 1).  Grass does far less photosynthesis than trees, so more energy is transferred to heat. It provides no shade on roofs or roads.  The grasses we plant, Saint Augustine and Bermuda grass, are non-native invasive species that require costly maintenance and heavy inputs of selective herbicides and fertilizers, which run off and poison the creeks.  The lawn mowers in constant operation contribute to the urban heat island.  Every time it rains I can smell the Roundup, which is used to keep Bermuda grass from spreading into the streets, parking lots, and gutters. Grass requires more water than other ground cover, so much that it robs water from tree roots.  Even with full coverage from sprinklers, I often see parched trees on the edge of wilt due to the grasses catching the majority of the water.

Our parks, which are supposed to be the final refuges of vegetation, are mostly mowed grass.  Land which has been set aside for the express purpose of preserving a natural environment is being wasted.  These areas could be cooling oases from the surrounding heat, filled with trees and bushes of every shape, size, and color.  Instead, most of our parks look like flat surfaces painted green, almost as hot as the surrounding roads and parking lots.

I’m not saying we should get rid of golf courses or soccer fields, but a front yard does not have to be a golf course or a soccer field.  Allen is an affluent suburb of Dallas, Texas.  There is a beautiful front yard in Allen without a single blade of grass.  Flower beds are artfully spaced between shrubs and trees.  This yard is just as manicured and pristine as the neighbors’, but requires no mowing and no chemical input other than compost.  This yard not only reduces the temperature around it, it is more beautiful than any of the traditional manicured lawns everywhere else.  Add a backyard to match, and this property is doing something to fight the urban heat island.

Turning a lawn into a flower garden is no more difficult than laying sod, and weeding doesn’t take longer than mowing.  A layer of mulch will block most weeds, and mulch naturally adds fertilizer to the soil as it decomposes.  The human input is the same, but the environmental impact is vastly different.  This type of yard provides all the benefits of vegetative ground cover without any of the nasty side effects of grass.  Flowering plants, like our native Liriope, look like grass but require no mowing and have a higher rate of photosynthesis.  I must insert a word of caveat when it comes to native bunch grasses.  Areas like Allen were historically prairies, which contained grasses that do not grow in a mat like Saint Augustine or Bermuda.  With their increased vegetative mass and thereby increased rates of photosynthesis, transpiration, and shade, uncut bunch grasses used as ornamentals contribute variety and health to a landscaped yard.  If yards filled with flowers, bunch grasses, and ornamental bushes and trees became common, they would significantly reduce local surface temperatures and combat urban heat islands.  Moreover, they would break the monotony and add beauty to suburban areas.

Converting parks follows the same lines as residential yards for small areas with pedestrian traffic.  The most intensive effort that could be necessary is plowing furrows and installing native tree saplings.  For large areas with fertile soil, it can be as simple as installing a “No Mow Wildflower Area” sign.  Every 1-2 years, a qualified arborist or biologist should cull unwanted volunteers, and within a decade the area will fill in with native trees, bushes and vines.

When I pass through Allen, I try not to look at all the grass.  I try to pay attention to the trees, but then I am often disappointed for other reasons.  However, tree selection and care are topics for future articles.  In this post, it is enough to say that I hope the information about albedo and the urban heat island has enriched you and encouraged you.  The solutions are easier than imagined and easy to grasp.  For those in Allen with disposable income for a team of landscapers, $100 Japanese maples, and a daily deluge from expensive sprinkler systems, the conversion to a healthy yard takes no more than a plan submitted to an existing landscaping company.  For anyone with a small yard who doesn’t mind rolling up their sleeves, the conversion only takes a few months of weekends.  Then we can be proud of the positive impact we have on the environment around us, even if it is on a micro-scale.

This is the first installment of a series of articles on better environmental practices in the suburbs of America.  Feel free to click the Follow icon in the lower right corner of your screen and enter your email to receive a notification when I post a new article.  For more information on reducing the urban heat island, refer to the free pdf of the “Trees and Vegetation” chapter of the EPA’s Reducing Urban Heat Islands: Compendium of Strategies.  At the end of the above document are 32 links to other websites that discuss smart urban and suburban development.  The EPA’s website and NASA also have much more information on urban heat domes and albedo.  Each person must take responsibility for the impact that they have on the world around them.  This begins with educating ourselves, and continues with taking action.  Please take the next action and spread the information in this article to others, whether through social media, word of mouth, or your own suburban or urban garden.

Please check out the other articles in this series, The Suburban Ecologist, Part II: Tree Selection and The Suburban Ecologist, Part III: Tree Care.