Desert Botanical Garden is committed to maintain one of the most complete collections of agaves and cactus in the world. These plants are represented in various forms, as herbarium specimens, seeds, greenhouse collections and, most visibly, as living displays throughout the Garden’s trails.
But hotter and drier summers in the Phoenix metro area pose a threat to the collection. Many of the Garden’s plants are struggling to adapt to the extreme conditions. High nighttime temperatures interfere with the plants’ gas exchange during their specialized photosynthesis process. A lack of monsoon rainfall adds stress, sometimes leading to plant death. In addition, sun scorch can weaken the plant and leave it more susceptible to pests and diseases.
These environmental stressors have become increasingly apparent to Garden researchers and horticulturists, especially with record-breaking heat in recent years. The Garden is worried about the potential loss of key species within its living collections. As the local climate grows more extreme, the risk of losing these critical plants increases. Such losses wouldn’t just affect the Garden; they would diminish vital genetic resources relied upon by botanists, conservationists and institutions worldwide.
In response, the Garden’s Horticulture and Research, Collections and Conservation teams have joined forces to develop innovative solutions. One such effort involves using the Garden’s internal geographic information system (GIS) to map and expand tree canopy coverage—a natural way to cool the landscape and protect plants.
The project began by taking inventory of the Garden’s current tree population—more than 2,200 trees across 50 cultivated acres. During this process, staff also collected the width values of these canopies to capture how much coverage they provided throughout the Garden.
They discovered that tree canopies currently provide 28% coverage across the cultivated areas.
Garden staff then recorded temperature readings from both canopy-shaded and full-sun areas to analyze the difference in ground temperatures. What they found was those shaded surfaces, from palo verde, mesquite, ironwood and desert willow trees, were between 27 to 44 degrees cooler than those in direct sunlight.
With these findings, Garden staff is now developing a strategic plan to increase canopy coverage in key areas. This includes identifying plants in the collection that will thrive in the new microclimates created by expanded shade.
By doing so, the Garden not only protects its current specimens but also builds long-term resiliency into its living landscape.
