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Counting Cacti At Saguaro National Park


Saguaro National Park officials are looking for volunteers to help them count cacti in a part of the park to better understand what makes a healthy saguaro forest. These two photos show how saguaros have declined in one section of the park. NPS photos.

In an ongoing effort to better understand the life cycle of saguaros and what environmental threats are fatal to them, Saguaro National Park officials are conducting a saguaro census in the park and are looking for help.

The census is being conducted on "Section 17," an area at the eastern end of Broadway Boulevard in Tuscon.

Back in 941, Paul Lightle, Lake Gill and James Mielke counted all 13,304 cacti in the section. They were motivated to do so by a decline in saguaros that was thought to have been caused by a contagious bacterial disease.

"To experimentally test this hypothesis, dead and dying saguaros were removed and buried and smaller lesions caused by bacterial rot were treated with antibiotics in the southern half of the section, while saguaros in the northern half of the section were simply monitored," park officials say.

But after nine years of monitoring, "Gill determined that there was no evidence to support a contagious bacterial disease and that the continued lack of saguaro reproduction in the cactus forest was a major problem," they add. "Sub plots within Section 17 have been monitored continuously since 1941, making Section 17 one of the longest vegetation monitoring programs in the National Park Service."

Earlier this year park officials decided to resurvey the entire Section 17 for the first time since the early 1940s. The counting is continuing through the winter, and there are plenty of opportunities for volunteers to help. Check out the calendar on this page to see when help is needed. To volunteer, go to this page.


Has anybody been able to determine exactly why there is such a decline??

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