Roy and the Last Saguaro (A story lesson about evolution and ecology for kids.)
“Roy and the Last Saguaro” is different from other Roy stories. It is really all about evolution, written so a child can understand it. It is the second story of a series about a little boy, his sister Millie, and two loving parents that come to realize that their son has a special ability to communicate with animals. Roy’s father, Ambrose Dimwitty, tells this story about the family trip to Arizona. Roy and Millie are introduced to evolution by the family trip. Adults are recommended to read the story to children and explain how evolution works.
Maggie and I played the Last Saguaro Game with Roy and Millie, as we drove from Phoenix to Sedona on vacation. It was our first trip to Arizona and we were fascinated with its topography and wild life. Compared to our home in New York City, Arizona was like another world with a variety of new and fascinating animals and plants. Several car games kept the kids occupied for much of the trip, but their favorite was called the Last Saguaro Game.
Who would see the Saguaro cactus with the most arms? Roy held the record when he counted 18 arms on an old giant. (I had to slow down the car so Roy could get an accurate count.) Who would see the tallest Saguaro with the fewest arms? Millie held that record when she saw a twenty-footer with no arms. Who would see the most “crestate” Saguaros (cactus with strange lobes)? Maggie held that record when she counted three one day, (they were in a roadside cactus farm but the count was allowed anyway). By far, the most hotly contested competition was for the sighting of the last Saguaro. Driving back from Sedona to Phoenix we renamed the game and called it the First Saguaro Game. In case you don’t know, a Saguaro is the world’s largest cactus that grows up to 50 Feet tall with a girth of 10 feet. Its life span can be over 150 years and it is only found in portions of Arizona, Southern California and Northern Mexico.
As we drove from the flat lowlands of the Sonnoran Desert into the mid- elevation of the Chaparral and Shrublands northwest of Scottsdale, the abundant Giant Saguaros gradually thinned out until only a few remained, scattered on sunny slopes. Soon they too were gone except for that one last sentinel that stood alone, high on a slope basking in the last rays of the setting sun. It was the prize we had all been looking for, and whoever saw the last one first would be the winner of the game. For the next several miles, we kept searching for just one more of the lonely giants in hope of being the new winner of the game. Just when the kids were about to give up, there it was, one last Saguaro on a distant slope. A few miles later, someone might spot another one, until finally, they were all gone.
I explained to my family that Saguaros are the largest cacti in the USA and one of the most interesting of the earth’s giant plants. Although they grow to fifty feet in height, they are small compared to other plant giants. The Giant Sequoia grows to a height of over 270 feet, the Giant Redwood to over 360 feet. The biggest of giant plants is a species of the Eucalyptus tree of Australia, which, in the recent past, was reported to have grown to a height of over 425 feet! Other plants on my “most interesting giant plant list” are: the Banyan tree which grows from the top down. From branches of the parent tree it puts down a maze of hundreds root trunks. If you walk under a single mature tree, you have the impression of walking in a whole forest of trees: the Giant Kelp off the California coast, that grows eighteen inches a day and reach a length of 200 feet: and finally, the Giant Bamboo, which is really a grass, grows three feet a day, and reaches a height of 200 feet.
The Giant Saguaro, while not the largest plant, has a unique characteristic of not being supported by a strong wooden trunk like trees, or supported by floatation sacks like kelp. The Saguaro has a strong internal skeleton that supports up to ten tons of fluid filled tissue, similar to the skeletal support system common in many animals.
Roy and Millie looked at the Saguaros from their own imaginative perspective and a little bit of their imagination rubbed off on Maggie and me. To the kids the Saguaros represented a silent army of giants standing in battle array against the Sun God and the Frost Queen. So far the giants were winning the battle and had adjusted well to their inhospitable environment, including long periods of drought, 120-degree temperatures during the day and overnight freezes. The kids considered the “last Saguaro” a lone sentinel guarding its domain. They saw the old, decaying Saguaros as the infirmed great grandparents of the population, and the Saguaros with arms bent to the ground as those wounded in battle. Scattered among the population were their children of all ages and sizes patiently waiting for a chance to take their place in the ranks of the army.
Millie and Roy felt that a slow motion real battle for survival was going on, so slowly that it could not be seen any more than they could see the movement of the hour hand on a clock. I smiled when I heard the kids express themselves about their theory. They were right of course. I explained to them that Saguaro were in a battle for existence with the environment but they had no defense against their biggest enemy, expanding human population.
I told the kids, the Saguaros we passed are the lucky few among uncounted billions that never won the battle to survive. Each cactus has to wait until it is sixty years old before it is mature enough to have flowers and reproduce. By late June and July, the flowers are gone, replaced by red-orange fruits that soon split open and offer all takers a feast of about 2,000 black seeds each. It is estimated that each Saguaro produces over forty million seeds in its lifetime. Insects and birds take all the seeds but a precious few which would find safety in the shade of sparse desert grass and shrubs. In the first year these tiny survivors would grow no more that 1/10 of an inch.”
“Wow!” Millie exclaimed, “Only 1/10 of an inch? If I grew that slow I’d be less than an inch tall.”
Yes, and it takes another twenty-five years for the survivors to reach the three-foot mark.
I took that opportunity to compare the similarity of the Saguaro’s survival to human survival. When we take into account all the millions of germ cells that never develop into animals and plants throughout numerous generations, it is testimony to the success of natural selection and explains why we are here to see the Saguaros and why they are here to be seen. Natural genetic variability and natural selection are the reasons why life has been able to survive on a planet that has undergone so many drastic changes in climate.
Animals and plants have to change with their environment, move to new locals, or perish. The Saguaro and humans, and all surviving life on the face of the earth, have truly won the Grand Lottery of Life!”
“We are the lucky ones aren’t we dad?” Roy chimed in.
I told him it was much more than just blind luck. A more accurate explanation of why the Giant Saguaros stand there and we are here to drive by in wonderment is best explained by evolution. That last sentinel Saguaro might possibly have been a bold explorer testing its new genetic makeup against the extremes of nature. As climate changes over the centuries, plants and animals must also change in order to survive. Perhaps that last Saguaro had a new, tiny genetic mutation that enabled it to survive the occasional frosts on that lonely slope where others could not survive. Perhaps, on the other hand, global climate change was warming the temperature of the higher altitudes, as it appears to be melting mountain glaciers, and the last Saguaro was a scout sent out by the army to test the temperature of the high, northern slopes. For the kids and their mom it was food for thought.
That evening at dinner, Roy and Millie were still fascinated with the topic so I explained more. The Saguaros, the Sequoias, the Redwoods and the Kelp could not stand alone and survive, as they have, without help. Each of these giant organisms is one link in the giant ‘web of life’. They all depend upon other plants and animals for their survival. The Giant Saguaro depends upon ground cover plants to protect its seed from the sun and predators. It depends upon birds, insects, and bats to pollinate its flowers and make new generations possible. In return, it provides food and shelter for a multitude of desert creatures. We humans, like the Saguaro, cannot survive on our own.”
“We need help, just like them.” Roy told his sister. “We must give back to nature what it needs to survive. The Giant Saguaro, and all of us, are part of the great web of Life.”
I felt that the Last Saguaro Game was more than entertainment for the kids. It was a fun way forme to educate them about nature and stimulate their fast growing brains. Their growing intellect was like a Giant Saguaro sucking in the precious run-off from a spring downpour. Their knowledge swelled as the Saguaro’s body and arms swell with life giving moisture. That knowledge, hopefully, would help them survive whatever hardships they might encounter in life and excel where others would not.
Roy and Millie spent a lot of time thinking about the interdependency of plants, animals, and their habitats during the rest of their vacation. They learned, that the concept is called ecology. Roy thought, when he grew up, he would like to be an ecologist. It would be a fantastic way to help animals and plants survive on our crowded planet. Maggie and I felt our car ride through the Arizona desert turned into an evolution and ecology lesson for our kids.