October 7, 2020

 

Much has been written on the environmental costs of lawns (see e.g. books by NPCC Advisor Doug Tallamy, or his video presentations). Now, case studies show that in addition to improving air and water quality, reducing erosion and flooding, and supporting pollinators, songbirds and other wildlife, replacing lawns with locally appropriate native plants also saves money!

 

From 2004 to 2013, Santa Monica College  in California  compared two gardens on campus in collaboration with the City of Santa Monica and the Metropolitan Water District of Southern California. The project was designed to test a “native” vs. a “traditional” garden.

 

The Native Garden was designed to be climate-appropriate and sustainable, based around local native plants replicate local chaparral ecosystems. The project included a dry creek bed and infiltration pit to keep rainwater on site.

 

The Traditional Garden featured popular garden plants, primarily from Europe and the Eastern U.S., and used standard sprinkler irrigation. Ninety-five percent of the “Traditional” garden was lawn. Following Santa Monica city policy, no chemical pesticides or herbicides were used in either garden.

 

After establishment, the Native Garden received a yearly pruning and once per-month maintenance. Irrigation was provided by a weather-based controller with low-volume drip irrigation.  In the Traditional Garden, the sprinkler system was wasteful and the exotic plants required more water, fertilizers, and pest management. Lawns were mowed weekly and annual plants were replaced two to three times a year as needed. Occasional treatments were required for disease and insect attacks.

 

The study found that “the sustainable landscaping principles demonstrated in the Native Garden, are cost-effective, environmentally beneficial, and easy to replicate.” On average the Native Garden used 83% less water; required 68% less maintenance than the Traditional Garden, and generated 56% less green waste (such as lawn clippings.) A recent article reported that yard waste constitutes 20 to 50% of US landfill.

 

This year the Xerces Society for Invertebrate Conservation produced a Guide For Creating And  Maintaining Mid-Atlantic Native Meadows. The goal of the Guidebook was to encourage land managers to convert turf and other ecologically damaged lands to native meadows in order to create habitat for pollinators and other wildlife. Guidebook authors Stephanie Frischie and Alice Sturm estimated the relative costs for installing and maintaining traditional turf lawn vs. seeded native meadow. They estimated that over a 20 year period, conventional lawn cost up to $5815.00/acre/year whereas seeded native meadow cost $1012.00/acre/year.

 

The authors note that much of the cost savings is due to the fact that healthy diverse native plant communities need almost no expensive and  polluting chemical inputs whereas lawns require large quantities fertilizers and pesticides as well as frequent labor to mow and to apply chemicals (see below).

 

Data such as these on the costs of lawns vs. native gardens are still sparse. However, we do know some things:

Native plantings deliver numerous ecosystem services in addition to supplying pollinator, songbird and other wildlife habitat. According to the Environmental  Protection Agency, native plantings are superior to non natives in erosion and flood control, climate resilience, and in sequestering greenhouse gasses. Soils under established prairie grasslands , for example, can contain more than 10 tons roots per acre, and some prairie plant roots extend to a depth of 10 feet or more, storing up to  1.7 metric tons per acre per year. Most lawn grasses have much shallower and less dense root systems and so store less carbon.