Why a Census? Every ten years, Saguaro National Park leads a citizen science Saguaro Census to study the long-term health and vitality of the park’s namesake cactus. Although we have studied saguaros at the park for many decades, beginning in 1990 scientists developed a new study to assess the overall conditions of saguaros across the entire park, including both the east and west districts. The saguaro census is meant to be repeated every ten years and coincides with the US Census. Beginning in late 2019 and continuing through late 2020, park scientists, staff, and citizen scientists collected data on tens of thousands of saguaros throughout the park.
The 2020 Saguaro Census is Complete. Due to the COVID-19 pandemic, in March 2020 the Saguaro Census was suspended in the interest of safety. The Census was already drawing to a close, but we were very sorry to have to cancel the final scheduled events. Fortunately, we were able to finish the last few Census plots, safely, with our small intern crew.
The great news is that between October 2019 and March 2020, Citizen Scientist volunteers had accomplished amazing work. Over 500 individual volunteers worked an astonishing 750 person-days and over 3,500 hours. We finished all of the 45 plots (plus a number of "historic plots" that date to the 1940s). Together with park interns and youth crews volunteers mapped, measured, and collected other data on more than 23,000 saguaros!
What Have We Learned So Far? Preliminary analysis of the data indicate that the number of saguaros has increased slightly in Saguaro National Park since the estimated 1.9 million in 2010. We do know that about half of the 45 plots saw declines in saguaro numbers, while about half saw increases since 2010 (see the "Results" section below). The most saguaros found on a single study plot (each plot is about 10 acres) was 1,746.
We are working on writing up the final results of the 2020 Census, and hope to make them available during early 2021. We hope that someday soon, when the pandemic is over and we feel safe, to celebrate with our volunteers and friends. We are very grateful for our volunteers and our sponsors: the Friends of Saguaro National Park, Western National Parks Association, and National Park Foundation. Thank you!