Young “citizen scientists” are trekking into the deserts of Saguaro National Park this winter to count, measure and study the park’s namesake cacti in a project called the Centennial Saguaro Survey.

Working with park rangers and scientists, the students from Tucson-area high schools and organizations are gathering data that will help determine how factors such as weather, climate change and invasive species may impact saguaros. The survey, which began in October, will continue into the 2016 centennial of the National Park Service.

“The purpose of the survey is to see how our cactus forest is doing,” said Carolyn Harper, a next-generation ranger at the park who is helping coordinate the students’ work. “We’re gathering data and comparing data from the 1970s, and in some cases, back to 1941.”

Harper said 40 to 50 students have taken part so far — working about six hours during a typical day.

They’re carrying out surveys in about 40 study plots, each measuring about 200 by 200 meters, in units of the park east and west of Tucson.

“We’re counting all the saguaros that are in the plot and measuring their height,” Harper said. “We’re counting bird holes and counting cactus arms, and observing characteristics to see if there’s any damage.

“Most of the plots take some hiking to get to, and some involve off-trail hiking.”

Among other things, scientists and students are seeking to determine if there is an increase in germination in higher elevations of the park’s desert areas.

“That could be an indication that they (saguaros) are moving up in elevation — and that can indicate a change in climate,” Harper said. “We’re looking at that question now, and we will keep looking at those higher elevation plots for the next 10 or 20 years.”


Findings are being posted on Saguaro Park’s website as the work continues until April 2016.

For a look at the results, go to the park’s home page — — and click on “get involved.” Then click on “Centennial Saguaro Survey” and scroll down to “results.”

“There will probably be a report at the end of the survey as well,” Harper said.

She said saguaro surveys usually are conducted every 10 years, but this one is being done ahead of schedule to coincide with the National Park Service centennial.

citizen science

Part of the value of citizen science projects, Harper said, is “to understand the area where you live and how you can protect it.”

She said that “whenever I experienced something that was hands-on, or I was on a field trip, I learned so much more. With this project, what we’re doing with students can help increase their awareness and grow their fondness for this area they live in.”

Contact reporter Doug Kreutz at or at 573-4192. On Twitter: @DouglasKreutz