As extreme heat increasingly threatens lives in Southern Nevada, the region is intensifying its efforts to plant trees. Despite these efforts, a new study indicates that trees may not significantly mitigate daytime temperatures.
The research highlights how trees can cool the air at night by nearly 35 degrees, providing much-needed relief. However, the cooling effect during the day is minimal, primarily due to the extreme heat preventing moisture release through transpiration.
Juan Henao Castaneda, a postdoctoral researcher at the Desert Research Institute (DRI) and lead author of the study, explains, “When you measure air temperature, the cooling effect of trees is usually very, very low. Reducing air temperature below one degree or two degrees is hard for any of the most common adaptation measures.”
Given the rising temperatures exacerbated by climate change, the issue of extreme heat remains a significant concern for Southern Nevada. In the past year alone, over 500 individuals succumbed to heat-related causes, with hospital visits for heat-related incidents soaring by 40 percent from 2023 to 2024. Remarkably, this summer has been comparatively mild.
John Mejia, a climatologist at DRI and co-author of the study, cautions against relying solely on trees as a solution to extreme heat. While trees are beneficial, they require extensive care and maintenance, which can be costly. For many urban areas, keeping trees alive poses challenges, even in environments that may seem more conducive to tree growth.
In response to rising temperatures, Las Vegas is working towards planting a substantial number of trees by 2050, including plans for 60,000 trees through various initiatives. The Las Vegas Urban Forest Center, in collaboration with UNLV, aims to plant an additional 3,000 trees by 2028, and the nonprofit Impact NV has committed to planting 100,000 trees by 2032. Recognized as the second-fastest warming city in the United States by Climate Central, Las Vegas is actively pursuing these tree-planting goals.
Research by Peter Ibsen, a U.S. Geological Survey ecologist, states that no other hot city could experience the same cooling benefits from trees as Las Vegas. He acknowledges that while the DRI study presents valuable findings, its approach and outcome differ.
Ibsen emphasizes the need to be strategic about tree placement and design, considering their role in enhancing biodiversity and aesthetics along with heat mitigation. “Trees are one part of the heat mitigation toolkit,” he remarks, underscoring that while shade structures can provide shelter from heat, they do not offer other ecological benefits that trees might.
To counteract extreme heat in the short term, Clark County has opened community cooling centers, such as libraries and community centers, whenever the National Weather Service issues extreme heat warnings.
Ariel Choinard, coordinator of the Nevada Heat Lab, stresses that previous assumptions about tree effectiveness should be reassessed. According to the study, while trees may not significantly lower daytime air temperatures, they do have a marked impact on nighttime temperatures, which are rising in Las Vegas rapidly. The cumulative heat effects can severely impact human health if nighttime conditions do not provide adequate relief.
“There’s an emotional reaction to hearing that trees weren’t the one weird trick to solve Las Vegas being one of the fastest warming cities in the nation,” Choinard notes. “Trees are a solution. They are not the solution, but they still will provide people with incredible relief.”
Future adaptation efforts must consider the realities of climate change, as many commonly planted trees may struggle to survive increasingly hot summers. A 2019 study by the Southern Nevada Water Authority concluded that nearly 38 percent of the most common landscaping plants may not persist beyond 2055 under current climate conditions.
Concerns have emerged regarding the water authority’s conservation strategies, which include removing nonfunctional turf by 2027 as mandated by the Nevada Legislature. Some community groups, such as the Water Fairness Coalition, fear this could lead to less greenery in urban heat islands, potentially exacerbating heat issues.
The water authority asserts that many trees are failing due to private property mismanagement rather than conservation policies. They provide incentives for residents to plant trees in place of traditional landscaping.
Cayenne Engel, a new urban forestry expert at the Nevada Heat Lab, believes localized studies like this one offer critical insights into how trees can effectively combat heat in Las Vegas. With many community members expressing surprise at the findings, there is a growing awareness of the complexities involved in tree physiology when it comes to managing extreme heat.
The study does not suggest that trees lack value in protecting individuals from extreme temperatures. Henao Castaneda and Mejia are committed to conducting further research on various adaptation strategies, ultimately aiming to provide tailored data for city planners and decision-makers.
Under Assembly Bill 96, municipalities with populations over 100,000 are now required to revise their master plans to include climate change mitigation strategies.
“The beauty of what we are doing is we are creating basic information to help guide policy in the future,” Mejia affirms.
As Las Vegas seeks to navigate the challenges of extreme heat, the ongoing conversation about tree planting will undoubtedly continue, emphasizing that while trees are an essential part of the urban environment, they must be supported with other strategies for effective heat mitigation.
image source from：reviewjournal
