Help save cactuses in Phoenix with the 2023 saguaro census


The Desert Botanical Garden (DBG) is trying to find and assess all of the saguaro cactuses in metro Phoenix. But with thousands of plants across hundreds of square miles, they need your help to pull it off.

What’s happening: The garden launched its second annual saguaro census last week, and it will last throughout the year.

  • Anyone with a smartphone can download the iNaturalist app and join the saguaro project.
  • Then, when you see a saguaro in metro Phoenix, upload a photo and answer a few questions about its size and location.

What they found: Last year’s inaugural count revealed some insights about the saguaro population.

  • Volunteers documented about 8,000 cactuses last year, and roughly 1,000 showed signs of damage or illness.
  • They also found that most metro Phoenix saguaros are middle age and there are very few babies, which could spell trouble for the future, DBG cactus specialist Tania Hernández tells us.

Why it matters: The annual data will help the garden monitor the health of urban saguaros and determine how to keep the towering plants thriving in our challenging ecosystem, she says.

The intrigue: While cactuses thrive in desert climates, the intensity of heat in urban areas like Phoenix might actually be too much for saguaros.

  • Because cities are covered with sun-absorbing pavement and rooftops, they’re on average 2°F to 6°F warmer than their surroundings.
  • High levels of air pollution may also harm urban cactuses, Hernández says.

Flashback: In 2021, the Desert Botanical Garden got dozens of calls from concerned residents who saw saguaros dying in the Valley.

  • Hernández hypothesized that the record-breaking temperatures during summer 2020 were likely the culprit.

Yes, but: There was no inventory of saguaros in metro Phoenix and therefore no way to prove that their death rate was higher than usual — much less determine their causes of death.

What they’re saying: “The community really demanded [the census] … Saguaros are really an icon for us in our culture,” Hernández says.

Zoom in: DBG scientists plan to take samples from some of the documented saguaros that appear to be under stress.

  • They will then use a plant version of 23 and Me to find the cactuses’ closest genetic relative growing in a natural environment outside the city and compare the biology to try to determine the toll of urban living.

What’s next: Researchers also plan to investigate which genetic makeups survive best in extreme heat and drought-stricken areas and plant those types of saguaros in the Valley.