Chipping Away At Blacktop

Photograph of amur honeysuckle, an invasive species in Michigan, with berries

Mark 8:36 Contemporary English Version Bible

"What will you gain, if you own the whole world but destroy yourself?"

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Ecological historian Donald Worster writes that, despite all our technological advances, "we have not learned how to live on a planet that is dead(1)." Rewilding our own landscapes is about bringing the planet back to life, one yard at a time, and with it our own relationship to the earth.

We can start this healthy relationship at our own doorstep, by changing the way we tend our gardens and lawns. Our current practices have imported invasive species, worsened climate change, and destroyed habitat. Our lawns and gardens are a microcosm of how we treat the Earth, and can be crucial places where we start to repair the ecosystems we need to survive.

Sustainable landscaping encourages us to shift our perspective and see our backyards as a place that can produce resources, not consume them. There are landscapes that work collectively for many life forms. If we renegotiate the boundaries we have drawn to wall ourselves off from the world, we can coexist with the Earth. In order to make these positive changes, however, we must understand the big problems we're faced with, and how they connect to our little lawns and gardens.

As flood waters inundate our gardens, wildfires threaten our backyards, and hurricanes tear up our landscapes, climate change has arrived on our doorstep. According to the Fourth National Climate Assessment;

"Observations from around the world show the widespread effects of increasing greenhouse gas concentrations on Earth’s climate. High temperature extremes and heavy precipitation events are increasing. Glaciers and snow cover are shrinking, and sea ice is retreating. Seas are warming, rising, and becoming more acidic, and marine species are moving to new locations toward cooler waters. Flooding is becoming more frequent along the U.S. coastline. Growing seasons are lengthening, and wildfires are increasing. These and many other changes are clear signs of a warming world(2)."

These changes not only affect our homes and our gardens, but originate from them. Lawn maintenance is a highly energy-intensive activity, from the gas-powered equipment to the petroleum-derived chemical sprays.

There are more than one hundred million pieces of gasoline powered lawn and garden equipment in use in the United States, including equipment with especially dirty 2-stroke engines. Together these leaf blowers, lawn mowers, and weed trimmers account for between 24-45% of all non-road gasoline emissions. These emissions include not only the carbon dioxide that contributes to climate change, but also carcinogenic volatile organic compounds and fine particulate matter that are linked to cardiovascular disease, asthma, and stroke(3). Even setting aside lawn and garden equipment pollution, the minimal plant cover on lawns is insufficient to capture the carbon dioxide produced by the respiration of the lawn's soil bacteria. This means that lawns continue to produce greenhouse gasses even when the mower is turned off(4). Allowing lawns to revert to forest, or other native ecosystems(5), can prevent these emissions, store carbon, and purify harmful particulates from the air(6).

Increased plant cover, like forests or wetlands, can absorb more water than lawns and pavement, and can also trap the eroded soil or pollutants that stormwater picks up(7). This kind of landscaping can protect homes from flooding and waterways from pollution. Some cities, like Portland, Oregon, are harnessing this potential with rain gardens that help take the burden off aging storm sewer infrastructure(8). Plantings like these can also capture the flow of noise through neighborhoods, improving quality of life at the same time as water quality(9). Rain gardens don't have to be complicated to plan or difficult to install. Wet areas, over time, will spontaneously grow with appropriate plants as intolerant species are drowned out(10).

Traditional landscaping is an important contributor to water pollution through what is called non-point source pollution. Point source pollution is simple to address - pollution comes from one point, such as a factory dumping waste into a river. Non-point source pollution is more like death from a thousand cuts. Many lawns and gardens each contribute small amounts of runoff, which flow through watersheds into rivers, lakes, and oceans(11). This pollution includes a range of harmful substances like heavy metals, pesticides, PCBs, eroded soil, plastic trash, and even human pathogens(12). Water pollution can also include plant nutrients, the excess from agricultural and landscaping fertilizers. When these nutrients wash into waterways, they cause an explosion in the growth of algae. According to the EPA, these algae blooms decrease the oxygen in the water surrounding them, posing a suffocation risk to fish.

Just as important to life as the water we drink is the air we breathe. Landscaping can also have important impacts on air quality, especially in urban environments. Urban forests can improve air quality by filtering air particulate matter and greenhouse gasses(13). They can also reduce emissions by shading buildings, reducing the need for energy-intensive air conditioning. Trees themselves create a form of air conditioning via transpiration(14). Transpiration is the process by which liquid water from the soil is pulled up and through the body of a plant and released into as water vapor, cooling the air(15). Although these effects might be small relative to the problems we are facing, the are significant and impactful(16). Every acre of forest (or any native ecosystem) lost to lawn represents a real reduction in this amazing ability plants have to shield us from polluted air and a warming climate.

We lose so much when we mow our lawns or cut down native landscapes to plant exotic species. We lose the capacity of those native landscapes to protect us from climate change by storing carbon. We lose the clean air and water they generate. We lose the interconnected beauty and the sense of belonging to something greater than ourselves. Life is lost, through direct destruction by mowing and tilling and by the subsequent starvation and exposure of animals whose habitat is destroyed by lawns and gardens.

Habitat fragmentation describes the way human activity breaks apart the landscape into smaller, separated chunks of habitat. The majority of the remaining forests in the world are within a kilometer of the forest's edge(17). Blockages like highways, subdivisions, and crop fields make it difficult for animals, plants, and fungi to find shelter, food, and pollination or mates. As a result, many can't survive and are much more likely to become extinct(18).

The hard data on extinction and population loss is difficult to comprehend in its enormity. Ceballos writes, "wildlife abundance on the planet decreased by as much as 58% between 1970 and 2012(19)." Much of this destruction is the result of human encroachment into formerly wild landscapes. Our resource extraction, our development, and our lawns all play a part. Of mammal species surveyed, Ceballos found that "almost half have lost more than 80% of their ranges in the period 1900–2015(19)." These animal habitats are not just faraway national parks or iconic wildlife refuges, they are our own back yards.

Genetic diversity can be destroyed with exotic, sterile, clonally propagated ornamental oligocultures. An oligoculture is a system where only a few species dominate, pushing out the normal diversity that we might expect to see in the ecosystem(20). Take a parking lot median, for example. Across the United States one can expect to see a few common ornamental species here - daylily, juniper, yuccas. The horticultural industry has moved these plants around the globe, taking them out of their local ecosystems, for centuries. It is largely due to the sale of these exotic plants (plants that evolved in different ecosystems than they are planted) and breeding for vigorous traits that most invasive plant species gained their foothold(21).

If native plants were allowed to grow in these spaces, thousands of different species could be found across the country - a huge variety of trees, grasses, flowers, and shrubs. All of these species would have specific interactions with the insects, which in turn have specific interactions with birds, and so on. Exotic species, not having evolved where they are planted, do not support these relationships(22). Only plants that have evolved for millions of years together with surrounding insects, animals, and fungi can efficiently pass the energy of sunlight on to the rest of the food web. Invasive species have been shown to have hugely damaging effects on the diversity of native species, causing significant destruction wherever they appear(22).

Landscaping practices of the past century years have focused on a high level of destruction, aesthetic control, and importation of exotic plant species resulting in millions of acres of ecologically barren lawns(23). Lawn mowers are excessively inefficient users of fossil fuels that contribute to climate change not only in their production but in their use and effect. Green carpets are the ornament to dirtier air and water. Each and every lawn represents a loss of life and home for native plants, animals, bacteria, and fungi. Doug Tallamy summarizes it succinctly, "We can no longer hope to coexist with other animals if we continue to wage war on their homes and food supplies(24)."

It is overwhelming for any individual to contemplate an entire planet, with its innumerable beings and relationships. What we can understand and participate with is our personal landscape - whether that is a backyard, community park, or apartment balcony. With this small area, we can cultivate a new ecological relationship. In these small places, we can grow communities of people who believe in rewilding. With these small landscapes, we can begin to change our relationship to the Earth.

Instead of fearing change, we can let it excite us. Entomologist and noted environmentalist Doug Tallamy writes; "Evidence suggests... most species could live quite nicely with humans if their most basic ecological needs are met(25)." Low maintenance lawns and gardens, full of spontaneous animal and plant surprises, are rewarding and beautiful. Best of all, they are good for our health, and the health of our planet.

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1. Donald Worster, Nature's Economy: A History of Ecological Ideas, 2nd Edition (Cambridge: Cambridge University Press, 1994) 430.

2. Jay, A., D.R. Reidmiller, C.W. Avery, D. Barrie, B.J. DeAngelo, A. Dave, M. Dzaugis, M. Kolian, K.L.M. Lewis, K. Reeves, and D. Winner, 2018: Overview. In Impacts, Risks, and Adaptation in the United States: Fourth National Climate Assessment, Volume II [Reidmiller, D.R., C.W. Avery, D.R. Easterling, K.E. Kunkel, K.L.M. Lewis, T.K. Maycock, and B.C. Stewart (eds.)]. U.S. Global Change Research Program, Washington, DC, USA, pp. 33–71. doi:

3. Environmental Protection Agency, National Emissions from Lawn and Garden Equipment, Jamie L. Banks, Robert McConnell, accessed December 23, 2019. https://www.epa.gov/sites/production/files/2015-09/documents/banks.pdf

4. Susannah B. Lerman, and Alexandra R. Contosta, "Lawn mowing frequency and its effects on biogenic and anthropogenic carbon dioxide emissions," Landscape and Urban Planning 182 (2019): 114-123, accessed December 23, 2020, doi.org/10.1016/j.landurbplan.2018.10.016.

5. William J. Mitsch, et al. "Creating Wetlands: Primary Succession, Water Quality Changes, and Self-Design over 15 Years." BioScience, 62, no. 3 (2012): 237-250, accessed January 3, 2020, www.jstor.org/stable/10.1525/bio.2012.62.3.5.

6. see 3

7. Sarah Taylor Lovell, and Douglas M. Johnston, "Designing Landscapes for Performance Based on Emerging Principles in Landscape Ecology," Ecology and Society 14, no. 1 (2009): 44, accessed January 6, 2020, www.jstor.org/stable/26268059.

8. The City of Portland Oregon, Environmental Services, "What We Do/Stormwater Management/City Stormwater Projects/Green Infrastructure," accessed January 6, 2020, https://www.portlandoregon.gov/bes/34598.

9. ibid

10. Monica M Palta, Nancy B Grimm, Peter M Groffman, " 'Accidental' urban wetlands: ecosystem functions in unexpected places." Frontiers in Ecology and the Environment 15, no. 5 (2017): 248-256. Accessed January 14, 2020. https://www.jstor.org/stable/26164334

11. Thomas C. Brown, and Pamela Froemke, "Nationwide Assessment of Nonpoint Source Threats to Water Quality." BioScience 62, no. 2 (2012) 136-146, accessed January 2, 2020, www.jstor.org/stable/10.1525/bio.2012.62.2.7.

12. Welty, Claire et. al. Committee on Reducing Stormwater Discharge Contributions to Water Pollution, Water Science and Technology Board, Division on Earth and Life Studies. "Urban Stormwater Management in the United States" report of the National Research Council of the National Academies (2008) accessed January 6, 2020, www.nap.edu

13. Francesc Baro', et al. "Contribution of Ecosystem Services to Air Quality and Climate Change Mitigation Policies: The Case of Urban Forests in Barcelona, Spain." Ambio 43, no. 4 (2014): 466-479, accessed January 2, 2020, www.jstor.org/stable/24709042.

14. The United States Environmental Protection Agency, "Green Infrastructure: Reduce Urban Heat Island Effect," accessed January 7, 2020, https://www.epa.gov/green-infrastructure/reduce-urban-heat-island-effect.

15. United States Department of Agriculture, Cooperative Extension, "How Do Trees Cool the Air?" (2019) accessed January 14, 2020, https://trees-energy-conservation.extension.org/how-do-trees-cool-the-air.

16. David J Nowak, Daniel E Crane, Jack C Stevens, "Air pollution removal by urban trees and shrubs in the United States," Urban Forestry & Urban Greening 4 (2006): 115-123.

17. Haddad et Al. "Habitat fragmentation and its lasting impact on Earth’s ecosystems" Science Advances 1 no. 2 (2015): E1500052, accessed December 23, 2019, DOI: 10.1126/sciadv.1500052

18. Fahrig, Lenore. "Effects of Habitat Fragmentation on Biodiversity." Annual Review of Ecology, Evolution, and Systematics 34 (2003) 487-515, accessed January 2, 2020, www.jstor.org/stable/30033784.

19. Ceballos, Gerardo, Ehrlich, Paul R., and Dirzo, Rodolfo, "Biological annihilation via the ongoing sixth mass extinction signaled by vertebrate population losses and declines." Proceedings of the National Academy of Sciences of the United States of America. July 25, 2017 114 (30) E6089-E6096; first published July 10, 2017

20. Trentanovi, Giovanni, et al. "Biotic Homogenization at the Community Scale: Disentangling the Roles of Urbanization and Plant Invasion." Diversity and Distributions 19, no. 7/8 (2013): 738-748, accessed January 2, 2020, www.jstor.org/stable/23479795.

21. Mark van Kleunen et al, "The changing role of ornamental horticulture in alien plant invasions," Biological Reviews of Cambridge Philosophical Society 93 (2018): 1421-1437, accessed January 14, 2020, doi: 10.1111/brv.12402

22. Patrick C. Tobin, "Managing invasive species,” F1000Research vol. 7 F1000 Faculty Rev-1686 (2018) accessed January 14, 2020, doi:10.12688/f1000research.15414.1.

23. Sarah Hayden Reichard, and Peter White, "Horticulture as a Pathway of Invasive Plant Introductions in the United States: Most invasive plants have been introduced for horticultural use by nurseries, botanical gardens, and individuals," BioScience 51, no. 2 (2001): 103-113, accessed December 13, 2020, https://doi.org/10.1641/0006-3568(2001)051[0103:HAAPOI]2.0.CO;2

24. Doug Tallamy, Bringing Nature Home: How You Can Sustain Wildlife with Native Plants, Portland: Timber Press, 2009.

25. Doug Tallamy, Bringing Nature Home: How You Can Sustain Wildlife with Native Plants, Portland: Timber Press, 2009, 37.