The City of Davis spans 6,426 acres with 1,964 acres of publicly owned land and 4,462 acres of privately owned lands. A total of 73.7% of land in Davis is privately owned (4,738 acres), highlighting the importance of trees on private property to the overall urban forest. 

Canopy Cover Distribution Between Public and Private Land

Publicly-owned lands have an average canopy cover of 25.4% and a potential to reach 43.8% canopy. The average canopy cover on privately-owned lands is 26.5% with a potential to reach 49.2% canopy. Public land contains 50.3% impervious surfaces whereas private land contains 41.1% impervious surfaces. Public land is needed for key infrastructure and private land can help augment tree canopy in public areas with limited space for tree planting. Additionally, in some areas, space may be so limited in the public rights-of-way that the only opportunity for tree planting  will be on private land. 

Land Cover and Potential Planting Acres by Public and Private Land

Parcels show a more detailed distribution of tree canopy.

City Parcels with Above Average Tree Canopy Cover

City Parcels with Below Average Tree Canopy Cover

Davis includes 6,200 acres with designated zoning and tree canopy cover varies widely across these designations. Considering the different zoning classifications, Mixed Use has the highest average canopy cover at 40.6% (641 acres), followed by Residential (33.6%), and Retail (30.9%). A total of 641 acres of tree canopy are in residential zoning and are a key resource for the community. Public/Semi-public Districts have the lowest average canopy cover at 6.5%. Types of the land within the Public/Semi-public Districts are maintained as a public service by private or non-profit organizations and in Davis some examples are church property, Frances Ellen Watkins Harper Junior High School, and the Davis’ Amtrak Train Station. Planned Development zoning covers the largest area, a total of 3,845 acres. It includes 921 acres of tree canopy and an average canopy cover of 24%. 

Tree Canopy by Zoning Class

Percent Contribution of Zoning Class to Overall Tree Canopy

 

 

Zoning Map³

 

Although Davis is a relatively small town, it has distinct neighborhoods. Some neighborhood groups and Neighborhood Associations are involved in urban forest initiatives and may have specific approaches to tree planting. The City of Davis is divided into 10 Neighborhoods and 74 Neighborhood Associations. Neighborhood Associations are spread across 6.9 square miles (4,427 acres) with 2 square miles of tree canopy (1,308 acres). The average canopy cover is 31.4%, and developed neighborhoods range from 1.3% canopy to 96.8% canopy showing large variation across the community. Generally, Neighborhood Associations closer to Davis’ downtown core have greater tree canopy cover than Neighborhoods Associations in areas of Davis zoned as Planned Development.

Newer developments tend to have younger, less established tree populations. Over time, these young trees will mature and provide more canopy cover as they age and increasingly add to the benefits to the community. While more established areas like downtown Davis provide more canopy cover, these neighborhoods also have a large portion of aging trees. The City’s Urban Forestry Manager should explore tree planting scenarios in TreeKeeper Canopy to identify neighborhoods with residents that have less access to trees and tree canopy and would benefit the most from tree preservation and additional tree planting. 

Neighborhood Associations with Below Average Tree Canopy Cover 

Neighborhood Associations with Above Average Tree Canopy Cover

 

Davis has 41 areas designated as parks that total 258 combined acres. The parks vary in size, form, and use, where some parks provide residents with ball fields and others have open green spaces. The availability of space to plant trees is limited by the different land uses in parks. For example, ball fields are unsuitable sites for tree planting. However, parks that do have ball fields likely can still support some tree planting. In fact, Playfields Park, the fifth largest park, currently has nearly 19.8% canopy cover. Even if the current spors fields remain in Playfileds Park, it could support additional trees and has potential for 32.9% canopy cover.

Northstar Park and Community Park are the two largest parks and they are tied for the most canopy acres (7.7 acres). Northstar Park is the largest park and has nearly 26.3% canopy cover with a potential canopy cover of 55.9% and Community Park follows a similar trend. 

The land cover classification for nearly 84 of the park acres is tree canopy for an average canopy cover of 32%. Of Davis’ top 10 largest parks, Slide Hill Park has the highest level of canopy cover at 46.6%. John Barovetto park has the lowest level of canopy cover at less than 6% but nearly 51 acres of plantable space for a canopy potential of 57.2%. In recent years, there has been a focus on tree plantings along trails in this park. All of Davis’ parks have space to accommodate additional tree planting.

Canopy Cover by Parks

 

Davis Parks

To better understand the canopy distribution provided by trees that are actually maintained by the City, canopy cover was reviewed for the public rights-of-way (ROW). Davis’ public ROW encompass 1,671 acres, with 275.2 acres of canopy and an average canopy cover of 15.4%. Several street segments have no canopy cover in the ROW but the highest level of canopy cover in the ROW is 80.4% on College Park. Among the largest City Streets, 2nd Street (28.9 acres) has the lowest percent canopy cover, 6.2%. This ROW runs along a railway and the lack of canopy cover can be explained by the zoning restrictions near key infrastructure such as railways. Whereas the largest street, 5th Street (31 acres), runs through Downtown Davis is not limited by zoning and has 25.6% canopy cover.

Some areas of Davis, such as the railroad and California Department of Transportation (Caltrans) ROW, are under the jurisdiction of other governing organizations. The major Interstate 80 and main highway 113 run through Davis and are the responsibility of Caltrans. Both have lower than average ROW canopy cover. Interstate 80, including on and off ramps, comprise 121.2 acres and 9.7% canopy cover. Highway 113, including on and off ramps, comprises 60.1 acres with an average canopy cover of 7.0%, including ramps Highway 113 has 12.2% canopy cover.

As of 2022, there are 20 double-decker bus routes that serve the downtown Davis area. The City trees along the double decker bus routes do not currently receive increased maintenance for clearance pruning to ensure driver and public safety. Strategic plantings in ROW that accommodate transit routes and associated bus stops can have a positive impact on urban heat island effects and pollution removal.

Canopy Cover by Rights-of Way

Canopy Cover by Rights-of Way

 

Parking lots in Davis are a component of the City’s infrastructure and allow the community to pursue commercial and corporate endeavors. Parking lots and other impervious surfaces absorb and retain heat. This absorption and reemission of the sun’s heat contributes to urban heat islands. Urban heat islands occur when urbanized areas experience higher temperatures than outlying areas. Because parking lots are largely impervious surfaces, they also contribute to increased stormwater runoff.  Davis was one of the first communities to attempt to reduce the environmental impacts of parking lots through a parking lot shade ordinance in 1979. Section 40.25.100 (f) of the City of Davis Municipal Code states: “Fifty percent of the paved parking lot shall be with tree canopies within fifteen years of securing building permit; development of such canopy shall be in accordance with master parking lot tree list guidelines.”

Recently, similar parking lot shade guidelines in Sacramento were evaluated  and researchers found that the shade standards are not being met for a number of reasons such as:

• Design plans and/or species lists overestimating the projected amount of shade
• Species selection deviated from the approved list
• Tree planting did not occur
• Tree removals occurred shortly after planting and spaces were not replanted
• Approved plans did not meet the guidelines (McPherson 2001).

In addition, trees in parking lots may be damaged from vehicles, compaction from foot traffic, and other stressors that make it a challenge for them to thrive. Modifications to planter designs may help to improve tree health and result in greater tree canopy cover in parking lots. However, even with changes in design, compliance with standards requires resources and staffing to monitor, which historically Davis has not had. 

In 2021, the City of Davis created a temporary committee, called the “Parking Lot Shade 2x2”, to review the parking lot shade guidelines and make recommendations. The land cover information included in this summary is meant to provide a benchmark of canopy cover in parking lots that can be used to evaluate whether or not the parking lot shade ordinance has been met. It can also be used to aid in discussions around future parking lot shade guidelines while maintaining compliance with State law surrounding parking lots, solar installations, and tree canopy. 

There are 665 parking lots that fall wholly or partially within Davis’s city limits. These parking lots encompass 410 acres on both public and private property. Of these parking lots, 299.4 acres are impervious surfaces, like asphalt and concrete. In contrast, 82.2 acres are tree canopy. Trees in parking lots provide an average of 20% canopy cover. 

Tree Canopy by Public and Private Parking Lot within Davis City Boundaries 

A total of 629 parking lots are privately owned. Private parking lots encompass a total of 388.3 acres or 95% of the land dedicated to parking lots in Davis. Private parking lots have an average of 19.8% canopy. Of these parking lots, only 87 meet the 50% canopy requirement. In contrast, there are a total of 36 parking lots that are publicly owned. Public parking lots encompass 21.7 acres and have an average of 25% canopy. Of these 36 parking lots, only 7 are currently meeting the 50% canopy requirement. 

Land surface temperatures in Davis parking lots range from 88.7°F to 101.4°F. Average land surface temperatures are nearly 2°F cooler in public parking lots when compared to private lots (93.9°F and 95.7°F, respectively). The associated shade from parking lot trees reduces ozone formation, which results in improvements to air quality.

Overall tree canopy cover in Davis parking lots ranges from 0% to 100% canopy cover. The largest parking lot is a private parking lot encompassing 14.6 acres with 1.2 acres of tree canopy and an average canopy cover of 8.2%. 

 Number of Davis Parking Lots by a Range of Tree Canopy Cover

Areas with more than 100 parking lots within the City boundaries include apartments (227), commercial areas (188), and condos (136). UC Davis has two parking lots within City boundaries, but most of the campus falls outside of City boundaries. The two county parking lots within City boundaries have an average of 46.1% canopy cover, the highest of all the area types. 

 

Understanding the spatial distribution of canopy and the condition of the tree canopy across the community can allow the Urban Forestry Division and stakeholders to explore equity, inform planting plans, and identify canopy goals. 

Twenty census tracts fall wholly or partially within Davis city boundaries. Canopy cover in the census tracts ranges from 15% to 41%. The largest census tract encompasses nearly 800 acres and has the lowest canopy cover at 14.6%, followed by 17.7%. Despite the low canopy coverage there is space available for additional tree planting. The highest preferable plantable acres of all census tracts is 210.7 acres followed by 126.7 acres. These acres can be used to increase canopy cover within the census tracts. 

Tree Canopy by Census Tract

Census tracts including Downtown Davis and UC Davis have relatively high canopy cover, both close to 36%. Newly developed areas of Davis and areas planned for development are likely to increase in canopy cover as trees are planted through the development process and given time to mature. Design standards that ensure adequate planter space and policies that require planting and maintenance of trees in new developments as well as the protection of existing trees are needed to encourage tree canopy in newly developed parts of Davis.

 

Canopy by Census Tract

City of Davis Census Information

Tree Canopy and Socioeconomic Indicators

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The Sacramento Valley region has a history of social systemic precursors like mortgage loan redlining and restrictive covenants that have impacted the demographics (Hernandez, 2014). These injustices are known to impact resource allocations and accessibility to green space and tree canopy within a community (Nardone et al. 2021). The area is also known to have high particulate matter concentrations.

Trees help clean the air and reduce the effects of urban heat islands, and therefore may be a way to reduce inequities and improve public health. To determine where the benefits of trees are needed most in the community, the relationship between where tree canopy is located and other community characteristics such as community demographics and environmental and socioeconomic indicators were studied. Davis’ land cover and community forest canopy distribution were analyzed along with data from the U.S. Census and CalEnviroScreen. Trends between canopy cover, canopy condition, and other variables were explored using scatterplots and the associated r-square (R²) values⁴. Although several trends are reported here, additional analysis should be done when making decisions on planting prioritization.

• There was a trend at the census tract level that indicates canopy cover is lower in more affluent areas (R²=0.31), but this trend is not clear at the census block group level (R²=0.07).

City trees are managed in the same way across the community. Private trees can be managed differently, along with trees on County, State, or other jurisdictional property. Despite this, the condition of tree canopy was relatively similar across public and private land ownership within the community. Nor were tree canopy trends observed between renter and owner occupancy. 

While the majority of tree canopy (92.4%) is in fair or better health, several differences in the canopy health were found across census categories, including:

• Census tracts with a higher level of diesel particulate matter had trees in better health. Areas with higher levels of diesel particulate matter are located on the south side of the community along the freeway. 

• Census block groups with a higher level of age groups that are 65 years and older  had a lower percentage of trees in very good health (R²=0.25). 

There are a few concentrated areas that have a greater proportion of trees in poor health. To have a better understanding of why tree health trends are appearing in Davis, field visits and further research are needed. Further exploration of the species, site conditions, and differences in management may provide the Urban Forestry Manager with clues as to what is happening.

-CAAP

Canopy Condition

Capturing land surface temperature is essential to monitoring heat islands, air quality, and overall well-being for residents in Davis. To establish an understanding of how urban forest canopy affects heat islands, a land surface temperature analysis was conducted using Landsat 8 imagery taken during the late afternoon during summer conditions. Two images taken two years apart were used for this analysis and averaged together to make the land surface temperature more accurate (imagery was taken on July 24, 2020 and July 11, 2022). 

Unshaded sidewalks, streets, and parking lots are among the greatest contributors to the creation of urban heat islands. The largest section of land with a high surface temperature is in an area zoned for future development (located in the northwest corner of Davis and indicated in red on the map below). This area consists mainly of bare soil and no canopy cover. Other warm areas, indicated in yellow, have key infrastructure elements with low canopy cover like the railway along 2nd Street (6.2%). 

The coolest land surface temperatures, indicated in blue, correspond to areas with more canopy cover like Davis’ Downtown Core Area (33.8%). Trees and their canopy distribution can greatly affect the surface temperatures of an area. Trees, especially large mature trees, can provide relief to these areas and should be considered if possible.  

Land Surface Temperature

The overall health of Davis’ urban ecosystem depends greatly on the ability of trees, plants, wildlife, insects, and humans to interact as a whole. The urban ecosystem is extremely complex and diverse; existing in a multitude of layers formed by small, functional ecosystems that together form a larger system. Ecosystem health declines when there is urban build-up and land clearing that results in habitat fragmentation. The ideal urban forest provides canopy cover and connectivity that supports wildlife.

This analysis focused on how tree canopy was spatially distributed throughout the City and provided an index displaying the degree of fragmentation. Davis has approximately 1,681.2 acres of tree canopy in four classifications, establishing the following baseline measures for the City:

• Core Canopy and Perforated Canopy: This is high quality, high-functioning forestland and represents 1.2% of Davis’ forests. Because of small openings within them, perforated areas of the canopy are just beginning to lose connectivity with large forest tracts.

• Edge Canopy: This type of forest is defined as the boundary between core forests and large tracts of developed and non-forested land. This category accounts for 6.7% of Davis’ canopy.

• Patch Canopy: This classification is for tree canopy that comprises a small forested area that is surrounded by non-forested land cover. This category of forests is the least productive and beneficial and comprises 1,548.5 acres (92.1%) of Davis’ urban tree canopy.

Most of the canopy in Davis is patch canopy. This canopy is generally not productive for wildlife habitat. Strategic planting will be required to help bridge gaps in connectivity to larger forested stands of trees. Knowing the locations of the forest types can guide land acquisition decisions and tree planting priorities so that these kinds of efforts are targeted in areas that can connect isolated areas of trees to create more contiguous and larger urban forest tracts.

Canopy Fragmentation

Forest Fragmentation is Identified by Canopy Structure

Urban forests provide a range of benefits, some of which are quantifiable and others are not (see the Story Map for more information). The quantifiable benefits, known as ecosystem services, can be given values with the help of iTree tools⁵. To date, Davis’ urban forest has stored 57,370 tons of carbon in woody and foliar biomass, valued at $9.8 million. Additional annual environmental services include pollution reduction, carbon sequestration, and stormwater management and are valued at $1 million. Each year:

• 2,900 tons of carbon is sequestered, valued at $494,595 

• 56.9 tons of abated air pollutants, including carbon monoxide (CO), nitrogen dioxide (NO₂), ozone (O₃), sulfur dioxide (SO₂), and particulate matter (PM₁₀) valued at $373,370 

• 16.9 million gallons of intercepted stormwater, valued at $151,543

Environmental Benefits from the Urban Forest 

 

 

Annual Air Quality Benefits from the Urban Forest

 

 ¹ 2020 NAIP imagery, for the full methodology see the Classification Methodology and Accuracy Assessment

² In this assessment, impervious surfaces were designated as roads, sidewalks, buildings, and other built surfaces. Pervious pavements have been implemented in parts of Davis, but were designated as impervious surfaces.

 ³ Zoning boundaries provided by the City of Davis (2020)

⁴ Relationships were reported if the R² value is greater than or equal to 0.15, the threshold commonly accepted in social studies.

⁵ iTree tools: iTree Canopy (v7.1) was to quantify the ecosystem benefits (e.g., lb. and tons). The dollar value of those benefits was calculated based on the cost-modeling dollar valuations from i-Tree Eco (v6.0.25)