What do you see when you think of a forest? Do you see oaks or redwoods? Look below the canopy, between and below the trees. There are mosses and lichens hanging and climbing amongst branches, trunks, and rocks. The creeks and rivers are full of fish and aquatic insects. Below the soil, fungi connect the forest in a mycelial network that orchestrates communication and nutrient exchanges. Just like wild* forests, urban forests are composed of much more than just trees. Urban forests are ecosystems that integrate humans and our built environments with cultivated and wild plants, wild and domesticated animals, fungi, microorganisms, bodies of water, soil, minerals, and organic matter. Our City Forest is dedicated to planting not just trees, but also understory plants that create habitat and save water.
*For lack of a better term, I use the word “wild”. The reason this word can be problematic is that the word wild implies a place where nature lives outside of human society. It brings up images of pristine places untouched by humans. However, the myth of the pristine wilderness is highly inaccurate, especially in North America where we know that forests and other ecosystems were tended to for thousands of years by Indigenous peoples and continue to be tended to this day.
The Urban Environment
Integrating the built environment with urban forests often requires innovation to solve problems. Ideally, the built environment (which consists of buildings, infrastructure, agricultural lands, etc.) would mesh with the rest of the environment with no conflict. However, many of the systems in urban and suburban environments make the built environment difficult to survive in and even uninhabitable in some situations. For example, the Urban Heat Island Effect describes how surfaces common in urban settings, such as glass, concrete, and asphalt, absorb and retain heat, causing higher temperatures. These higher temperatures put more physical stress on trees, animals, and other organisms in the urban forest while also evaporating more water.
Worldwide urban development has also caused habitat loss and habitat fragmentation, which are both tied to one another. Habitat loss is the reduction in total land while habitat fragmentation is the isolation of habitat islands from others. Generally, habitat loss leads to fragmentation, making it difficult and dangerous for animals to migrate, establish new ranges, escape wildlifes, and adapt to climate changes. However, it doesn’t need to be this way. Creating and maintaining habitat corridors, safe road crossing (under or over), green roofs, lawn conversions, and more can help solve the conflict between the environment and urban development and lead to integration. Our City Forest has a role in this integration not by just planting trees but also by converting lawns into drought-tolerant landscapes.
Lawns
One of the biggest issues regarding the urban environment across the United States is the lawn. In the United States, there are over 40 million acres of lawn, roughly the same size as the state of Florida! Lawns, including artificial grass, pose many negative consequences. Grass lawns consume up to 31 gallons per square foot, per week. The average residential lawn in the U.S. is 10,871 square feet (in California the average is 5,575 square feet). That’s up to 337,001 gallons of water per week to water the average U.S. lawn and up to 172,825 gallons per week in California! To put these numbers into context, the average shower is 17 gallons of water. The upper limit of water used to water the average U.S. lawn is equal to 639 showers! Alternatively, many drought-tolerant native plants usually do not need any watering once they have become established.
Besides the issue of water use and waste, lawns and artificial grass have no ecological value. They are desolate places for most plants and wildlife. They do not provide food, shade, or shelter for animals. Many grasses used for lawns are invasive, spread easily, and can be difficult to remove or kill, such as Bermuda Grass which is common in warmer climates and is used in San Jose. Grass like this pushes out native plants that animals and other organisms have evolved to depend on.
Non-native grass lawns are also not able to capture as much water as native grasses and other native plants. The image below demonstrates the difference in root systems between lawns and prairie plants. To the far left, you can see that the root system of typical lawn grass is only 3-4 inches, whereas the native plants to the right have root systems up to 12 feet long! Longer root systems help to stabilize the soil and prevent erosion, capture more stormwater, filter pollutants in the water before it ends up in the ocean, and help to restore groundwater.
Lawn Busters
The Lawn Busters Team at Our City Forest is dedicated to converting lawns into drought-tolerant landscapes that save water and create habitat in a county that has suffered much habitat loss and fragmentation. We plant a wide variety of native and drought-tolerant plants from California Lilacs, Penstemon, succulents, native grasses like Creeping Red Fescue and California Fescue, tree-like shrubs such as Toyon and Elderberry, various Mediterranean species, and more! In some cases we also include trees in a landscape design, but overall we focus on grasses and shrubs. While trees are important to the urban forest, shrubs are just as important and provide food, shade, and habitat for non-arboreal species.
Recently, the Lawn Busters Team sent out a wildlife reporting survey to homeowners who had their lawns converted by Our City Forest. The majority of respondents reported an increased presence of wildlife in their new landscape, especially pollinators such as bees, butterflies, and hummingbirds as well as lizards, hawks and other bird species, and even opossums!
In addition to transforming lawns, we also teach the community how they can transform their lawns by themselves through workshops held at our Urban Forestry Education Center. Many of the plants we use in lawn conversions can be seen in our various gardens at our Education Center and more gardens are being added, such as a bioswale, a native wildflower meadow, and a Lawn Buster’s demonstration garden.
If you would like to continue learning about the urban forests and the projects Our City Forest works on to increase San Jose’s canopy and understory, consider volunteering with us! As a volunteer, you can learn how to plant trees and shrubs, learn gardening skills, learn about native and drought-tolerant plants, climate change, community science, and more!
