My first experience viewing saguaro cacti in Arizona was as a young adult. I was fascinated by this desert plant, the largest native cactus in the United States, that can grow up to 40-60 feet tall. The largest saguaros are estimated to be about 200 years old and can weigh 6 tons or more with their impressive capacity to store hundreds of gallons of water.  A 2018 report by the National Park Service from a long-term study at Saguaro National Park details the ongoing decline in saguaros.

According to the document “A History of Saguaro Cactus Monitoring in Saguaro National Park, 1941–2007,” the study of saguaros began in the early 1900s. Researchers began suspecting that the population of saguaros was falling as early as the 1930s.  They linked this to an increase in cattle grazing, deforestation for home development and then later to the occurrence of unseasonal temperatures. Over the decades, researchers attributed much of the decline in saguaros to disease, and programs were put in place to reduce the spread of the disease.

The current decline in saguaros is more complex, given the multiple human-induced stresses on wildlife. While saguaros populations continue to be affected by disease, wildfires and other severe weather from a changing climate add to the problem. Researchers note that young seedlings are more sensitive to weather and other adverse conditions than adult cacti; much of the current loss is with these younger ones. Invasive grasses and plants compete with saguaros for water. Woody plants, such as ironwood trees, which are part of the ecosystem that facilitates the growth of seedlings, are also on the decline. 

“Lord God, Who made the earth and every living creature, help us to treat with compassion the wildlife entrusted to our care, that they may not suffer from our neglect nor become victims of any cruelty.” www.franciscans.ie

Julie Peller, Ph.D., is an environmental chemist (Professor of Chemistry at Valparaiso University ). Julie has been writing a weekly column for the past ~6 years called the Green Junction and is helping to move the call of Laudato Si to action forward. Her Research Interests are advanced oxidation for aqueous solutions, water quality analyses, emerging contaminants, air quality analyses, Lake Michigan shoreline challenges (Cladophora, water, and sediment contaminants), and student and citizen participation in environmental work.