By Anna Miteniece
Quaint two-story house, white picket fence and a sprawling, freshly mown lawn… all familiar symbols of chaste success and The American Dream that have been dominating our cultural landscape almost as pervasively as various turfgrass species have been dominating the modern urban landscape. The contemporary obsession with cultivating monocultural gardens began in 18th century France and England when ability to maintain a verdant courtyard was only accessible to the ultra-wealthy, establishing lawns as a symbol of prosperity later adopted by the burgeoning American nation.
With time and various technological advances (most notably the land mower and the sprinkler), lawn cultivation became accessible for the middle-class Western consumer. Today it is estimated that over 165 000 km2 of land in the USA is used for the sole purpose of growing turfgrass. This is thrice the size of area utilized for growing all agricultural crops combined. Considering the impressive and intentional prevalence of lawns, it is important to investigate the ecological ramifications of this phenomenon, especially in the context of ongoing climate change.
Turfgrass, as all plants, is a relatively good carbon sink, taking up carbon dioxide from the atmosphere in the process of photosynthesis. Various turfgrass species (Poa pratensis, Agrostis capillaris, Agrostis stolonifera etc.) sequester carbon most efficiently when left undisturbed. Therein lies our first problem: lawn culture is predicated on meticulous, almost ritualistic trimming by its owners. Every week the turfgrass has to pour all of its energy into re-growing the plant bodies lost to the insatiable hunger of appearing well put together to our neighbors, and carbon dioxide is being emitted, due to the increased metabolic activities, almost as fast as it is taken up. Leaving the grass clippings on the lawn instead of throwing them out is also correlated with higher rates of carbon sequestration but this is not a practice associated with the image of a tidy garden. (British Ecological Society, 2020) Still, any sort of vegetation is better than the concrete and tar landscapes of some cities, with lawns increasing the overall albedo of our planet and decreasing the urban heat island effect. Unfortunately, this is where the lawn benefit well runs dry and we are left with the harsh problems posed by the continued upkeep of our green backyards.
Turfgrass species have been introduced to areas far from their native living conditions and many of them are not adapted to growing all summer long in hot, dry environments (for example, Texas or Spain), so considerable amounts of water are needed to support their continued survival and level of pleasant greenness. Approximately 150 000 liters of water are needed every year for this purpose, subject to increase if the year has experienced more hot temperature extremes. (Robbins, Polderman and Birkenholtz, 2001) This puts undue stress on various water resources, decreasing water available for growing food and supporting wildlife. (t is only going to get worse in the wake of climate change.
Unfortunately, it is often not enough to dump copious amounts of water onto our lawns to sustain its verdant splendor: we must also dump copious amounts of nitrogenous fertilizers and toxic pesticides on it as well. Carbaryl, Glyphosate, Chlorpyrifos, Diazinon are only a couple of scary-sounding and highly toxic compounds utilized for this purpose and all of them are significant contributors to degradation of the integrity of water resources, impacting the biological health of streams, fish, and macroinvertebrates. (Robbins, Polderman and Birkenholtz, 2001) 37% of the species listed in the Endangered Species Database are at direct risk from pesticides. 30% of the pesticide run-off in USA is contributed by lawn cultivation, and there is relatively little regulation of this imposed on individual households.
This amount of time, money and resources are used to establish a monoculture of a particular turfgrass species that outcompetes all other plant life that would naturally grow in its place. Monocultures are ecologically detrimental in many ways. Most notably, as the name implies, they decrease overall biodiversity of the surrounding area. (Miles and Knops, 2009) Weeds such as dandelions attract many species of insects, including honeybees and bumblebees, but the structurally fairly boring turfgrass is not a very good substitute and as such decimates the local pollinator diversity. (Tommasi, Miro, Higo and Winston, 2004) The usage of large amounts of pesticides also lead to soil degradation as various types of beneficial saprotrophic bacteria and fungi are killed in the process. Studies done on long term shifts from native C4 plants to C3 turfgrasses indicate a staggering 27% loss of biodiversity from the area over the span of 20 years, displaying steady degradation with no signs of stopping. (Miles and Knops, 2009) Santa Barbara Botanic Garden Director Steve Windhager said it best: “I’ve heard lawns compared to a biological desert. That’s really unfair, because deserts can be very diverse places.”
Finally, the operation of everyone’s worst enemy on a Sunday morning – the lawn mower – constitutes 5% of all carbon dioxide emissions annually. Lawn mowers emit as much pollution in one hour as 40 cars driving. Taking into account the rapidly declining climatic conditions, the need for an alternative to monocultural lawns becomes acute and immediate. Many options have been proposed with cultivation of polycultural lawns composed of native species chief among them. However, substantial change in this regard can only be expected by changing the cultural significance of lawn ownership and overhauling deep-rooted capitalistic notions of individual success and private property rights.
References:
British Ecological Society. 2020. Mowing Urban Lawns Less Intensely Increases Biodiversity, Saves Money And Reduces Pests – British Ecological Society. [online] Available at: <https://www.britishecologicalsociety.org/mowing-urban-lawns-less-intensely-increases-biodiversity-saves-money-reduces-pests/> [Accessed 30 August 2020].
Miles, E. and Knops, J., 2009. Shifting dominance from native C4to non-native C3grasses: relationships to community diversity. Oikos, 118(12), pp.1844-1853.
Robbins, P., Polderman, A. and Birkenholtz, T., 2001. Lawns and Toxins. Cities, 18(6), pp.369-380.
Tommasi, D., Miro, A., Higo, H. and Winston, M., 2004. Bee diversity and abundance in an urban setting. The Canadian Entomologist, 136(6), pp.851-869.s
Imperial Bioscience Review 