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  • Writer's pictureMark L. Johnson

Saguaro Facts & Status




It has not been a good year for our treasured saguaros. Strong-Arm passed after a wonderful 160-year life in the Tortolita Preserve. We saw the destruction of mature saguaros as the result of housing development and to make way for a 3-day professional golf tournament. Disease appears to be on the rise.


Seems like a good juncture to present some facts and assess the status of the saguaro in our region.





 

Name & Culture

Saguaro scientific name is Carnegiea gigantea---named after Andrew Carnegie (industrialist/philanthropist,1835-1919) who established the Desert Botanical Laboratory in Tucson in 1903. It is now called the Desert Lab on Tumamoc Hill and part of the University of Arizona.


Saguaro common name came from Mexican Spanish, likely from Ópata, the Uto-Aztecan language of Sonora, Mexico.


Ha:sañ is the O'Odham word for saguaro. Tohono O'Odham stories say the saguaro was once a human being that turned into a saguaro. They believe that fruit from the saguaro should go to the birds and animals first and humans second. A total respect for nature.


Range

The Sonoran Desert covers 100,000 square miles in southern AZ, southern CA and the Mexican states of Sonora and Baja California. See tan areas on the map (right).


The saguaro only grows in a portion of the Sonoran Desert. See green saguaro hatch on the map. Let's assume its range is 50% of the Sonoran Desert or 50,000 square miles. That is only 0.087% of the earth's land surface.


The limited range reinforces the need to do everything feasible to protect the saguaro.


Note: There is an Argentinian Saguaro (Echinopsis terscheckii) that grows in northwest Argentina and the western slopes of the Andes in Peru, Bolivia and Ecuador. Range coverage information is not readily available.


Age


Saguaros do not have growth rings so age is primarily determined by height. The following charts are from a recent visit to the Saguaro National Park showing the approximate age based on height. Saguaros grow very slow and only get flowers after 35-65 years and branches (arms) after 50 to 100 years! This places the age of mature saguaros recently destroyed (referenced above) in the 50-100 year range.





Note: There is another method to determine saguaro age. Acanthochronology is the study cactus spines or thorns to determine the age of saguaros. The spines at the base of the saguaro are the oldest and can be dated using carbon dating techniques.


Disease & Other Environmental Impacts


Beyond human impacts, saguaros have to endure other environmental extremes in the Sonoran Desert including cold weather (freezing), drought, wind, wildfire (invasive grasses), epidermal browning, sunburn, insects, pests, fungi, virus and bacteria.


Bacterial infection (bacterial necrosis) by the bacterium Erwinia cacticida is a major cause of saguaro death. Bacterial necrosis is evidenced by a brown/black odorous liquid oozing from lesions in the outer tissue of the saguaro. The following photos were taken this week of a saguaro in the Tortolita Preserve with advanced bacterial necrosis.




Erwinia cacticida is ubiquitous in the Sonoran Desert and bacterial necrosis is not new. However, some scientists believe that climate change is accelerating saguaro deaths from bacterial necrosis. This appears to be true, as I have observed about 10 saguaros in the Tortolitas (Preserve and Mountains) that have succumbed to the disease in the past year, including Strong-Arm. We've had some weather extremes to support this theory with a very dry summer in 2020, the third wettest monsoon season in 2021 and a cold winter in 2023 with some snow. More study and research is essential to determine if death by bacterial necrosis is primarily related to old age and/or climate change,


Regulations


Arizona

AZ native plants (including saguaros) are subject to Arizona Revised Statues (ARS) 3-901-3-934 and AZ Administrative Code (AC) Title 3 Chapter 3 Article 11-Native Plant Regulations. In summary, native plants cannot be removed or destroyed from any private or public land without a permit from the AZ Department of Agriculture. Removing or destroying a saguaro without a permit is a felony if the value of the native plant is greater than $500.


Pima County

Pima County regulates native plants within unincorporated county areas via its Chapter 18.72 Native Plants Preservation. Table 18.72.090-1 provides for at least 80% of saguaros to be preserved-in-place (PIP) or transplanted-on-site (TOS). All saguaros 18 feet or higher or with arms 6 feet or greater must remain in place.


Marana

Marana regulates native plants via its Title 17-Environmental Resource Preservation, Native Plant Protection and Landscape Requirements. A native plant plan is required for all new development projects with an exception that it is voluntary if the project provides 30% Natural Undisturbed Open Space (NUOS). It further requires that only 50% of viable saguaros be PIP or TOS.


TA has provided comment to Marana on several occasions that Title 17 needs to be amended to increase NUOS to at least 80% to match that protection included in the proposed Marana Habitat Conservation Plan that was never adopted. This would also protect at least 80% of the saguaros on site rather than the current 50% and match Pima County's requirements.


Final Thoughts


The saguaro facts are clear:

  • unique species with a very limited range covering a portion of our Sonoran Desert

  • grows very slowly and can live well beyond the human life-span

  • adversely impacted by human activities and other environmental factors

  • protective regulations (AZ and Marana) are weak

What needs to be done:


Research-expand the scientific research that was started in the early 1900's to other areas in the Sonoran Desert including the Tortolita Preserve and Tortolita Mountains. This would include research to better understand the cause(s) of the apparent accelerated death of saguaros from bacterial necrosis.


AZ Regulation-enhance AZ native plant regulation laws and include more impactful punishment for violating the regulations.


Marana Regulation-change Title 17 to require 80% NUOS for all new development and/or adopt the Pima County standard of 80% for PIP/TOS and the requirement to leave mature saguaros in place.


Invasive Grass Eradication-provide more funding and resources to eradicate buffelgrass and other invasive grass species that present a wildfire risk to the saguaro population.


Saguaro Relocation & Rescue-expand saguaro relocation programs and rescue programs offered by organizations like the Tucson Cactus & Succulent Society.



There are many saguaros out there of all ages and hopefully more to come. Let's treat the saguaro like the Tohono O'Odham and work together to ensure they all live well beyond our lifetimes. Rest assured, TA will be working toward this goal in the years ahead.


 

Additional Reading & Sources


Native Plant Rules - AZ Dept of Ag
.pdf
Download PDF • 640KB

UACES-1962-Saguaro Horticulture-Dec 2021
.pdf
Download PDF • 7.02MB

Ecology of the Saguaro_ II (Table of Contents)
.pdf
Download PDF • 142KB

UACES-1506-AZ Native Plant Law-Jan 2010
.pdf
Download PDF • 4.23MB

Town of Marana DHCP
.pdf
Download PDF • 4.28MB

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