Southern Nevada at risk of losing tree shade to extreme heat
(Nevada Current) Southern Nevada is at risk of losing the few trees it has due to extreme heat, a loss that would only exacerbate how unevenly protective tree shade is distributed across communities in one of the fastest-warming metros in the nation.
As climate change disruption continues at a faster pace than predicted by climate scientists, the region’s little canopy coverage is at risk, said Southern Nevada Water Authority Director of Resources Zane Marshal.
You only need to look outside to see wilted trees that once tolerated the Southern Nevada summers.
Several years ago the water authority examined global climate models to project what climate conditions would be like for Southern Nevada in the next century. The agency found that 16% of the 100 most common tree species in the Las Vegas Valley would exceed their heat tolerance by 2025, meaning those trees would not survive climate change.
Italian Cypress, purple-leaf plum, and elm trees will likely be the first to go, said Marshal.
“In the next couple of years, those trees are expected to exceed their heat tolerance and they’ll be stressed by heat throughout the year,” he continued.
Another 38% of the most common tree species in Southern Nevada is expected to exceed their heat tolerance by 2055, including ash trees, olive trees, pine trees, African sumac, and roses.
The Las Vegas metro area experienced the hottest July ever recorded this summer, with the last two weeks of July being the hottest 14-day stretch on record, with an average high of 112 degrees. Those temperatures proved too much for some of the most resilient trees.
“We’re also seeing that a lot of the pine trees — the big Afghan and Mondo and Aleppo pines — are already stressed in many cases,” Marshall said. “There is real concern, and I think our research suggests that yes, in fact, there are certain varieties of trees that are currently stressed by extreme weather conditions like what we had this July.”
The loss of some of Southern Nevada’s most common trees would likely only exacerbate the lack of cooling tree shade for marginalized and disadvantaged communities.
A recent study by American Forests found that Black, brown and low-income neighborhoods in Southern Nevada’s cities have significantly fewer trees and shade than wealthier, whiter communities.
Dubbed the Tree Equity Score, the metric measures neighborhoods using several factors: population density, neighborhood income, average surface temperatures, existing tree canopy, racial demographic makeup, employment and various health statistics.
More than 400,000 trees will need to be planted in Nevada to reach “tree equity,” or the number of trees needed so that all residents can benefit from shade, cooler temperatures and reductions in carbon, according to the study.
Data for Las Vegas — a metro area where more than half the population consists of people of color — revealed a stark disparity between the wealthy and affluent majority-white neighborhood of Summerlin and the neighborhoods surrounding North Las Vegas, where a majority percentage of Black and Hispanic families live.
Neighborhoods in Las Vegas with less than 36% people of color had 2.1% more tree canopy compared to the average tree canopy in city neighborhoods. In contrast, neighborhoods with at least 66% people of color had on average 1.3% less tree canopy than other Las Vegas neighborhoods.
Las Vegas would need to plant more than 18,000 trees to reach tree equity.
In North Las Vegas, where 75% of the residents are people of color, nearly 55,000 trees would need to be planted to benefit from the same tree coverage as the average Nevada neighborhood.
“In the West Las Vegas neighborhood in downtown Vegas—a community of 100% residents of color, 88% of whom are living with poverty—only 2% of the surface area is protected by tree cover,” said Julia Twichell, a cartographer and director of data design at American Forests. “Compare that to the historic and affluent Rancho Circle neighborhood, just a 5 minute drive away… This community is over 75% white with only 14% below the poverty line. With 27% canopy cover, street temperatures are nearly 8 degrees cooler than West Las Vegas during a heat wave.”
That trend of inequity continues in the City of Henderson, where nearly all of the 32,000 trees needed to reach tree equity will need to be planted in neighborhoods along Boulder Highway, a low-income census tract. Green Valley, an affluent majority-white community in Henderson, however, is flush with canopy cover.
In the City of Las Vegas, many tree species commonly planted in Southern Nevada including Ash, Catalpas, and Purple-Leaf Plum trees are struggling under higher summer heat and watering restrictions, according to City of Las Vegas urban forester Bradley Daseler.
‘Inappropriate species selection’
The city already lost some trees this summer, officials said. While the city can’t be sure heat was the main factor, July broke the record for most days with a day-time high temperature of at least 105 degrees in Las Vegas, beating a record of 25 days, which happened in 2017, 1989, and 1972.
Daytime high temperatures in July reached at least 100 degrees every day of the month. Only four other Julys on record reached at least 100 degrees every day of the month: 2010, 1988, 1971, and 1963.
Daseler said “inappropriate species selection” was also a factor in the loss of tree coverage, meaning some juvenile trees the city hoped could adapt to the heat did not survive after being planted in the fall.
Some alternative trees planted by the city have proved to be compatible with the Las Vegas climate, including some species of acacia, havardia, and Palo Verde, several species of eucalyptus, and oaks originating from dry climates.
Since the beginning of the city’s tree planting program in 2020 close to 3,000 trees have been planted. Those trees have been planted throughout the City of Las Vegas. The city is working to diversify the species and age distribution of the trees in order to make its tree canopy more resilient.
The Southern Nevada Water Authority is now working to increase tree canopy across the region. The agency’s Tree Enhancement Program pays participants a bonus of $100 for every new tree planted, up to 100% canopy coverage. However, planted trees must be from the agency’s approved list of heat-resilient trees.
Water users must be part of the Water Smart Landscapes rebate program to benefit, which pays $3 per square foot of turf removal.
“While our customers are participating in the water smart landscaping program and in helping our community become more resilient by removing turf, we thought we could also help to address the urban heat island effect by working to enhance urban tree canopy,” Marshall said.
The program, which started in July, is still in its early stages. The water authority hopes to spur the planting of 100,000 trees through its rebate program, using $10 million funds authorized by its board.
“I think there’s broad recognition that our urban tree canopy is important to the health and viability of our community,” Marshall said.