As an Arizona native, covering our beautiful and unique Sonoran desert makes the most sense! When people think of the desert, they think of a lifeless, barren, ugly sand-filled place. But in reality, deserts often have plenty of biodiversity, and, according to the National Park Service, "The Sonoran Desert is thought to have the greatest species diversity of any desert in North America" (nps.gov) The Desert is also home to "at least 60 species of mammals, more than 350 bird species, 20 amphibians, some 100 reptiles, and about 30 species of native fish. More than 2,000 species of plants have been identified in the Sonoran Desert, and each of the three physiological groupings of vascular plants (C3, C4, and CAM photosynthetic pathways) dominate one or more major biotic communities." (nps.gov) The Sonoran Desert is full of interesting and unique animals and plants alike. Let's explore!!

Stretching across Southern Arizona and southeastern California, and covering most of the Sonora and Baja California Mexican states, the Sonoran Desert is one of the largest in North America. According to the National Park Service, the desert covers "approximately 260,000 square km (100,387 square mi)" (nps.gov).   

Deserts are the most arid, dry regions in the world, and they are known for their extremely high temperatures. The Sonoran Desert goes over 104 degrees Fahrenheit in the summer and at its peak, easily goes over 118 degrees Fahrenheit. One of the most notable characteristics of the Sonoran Desert is the extreme temperature swings. During the monsoon season, as the heat on the surface interacts with the cool air in the atmosphere, monsoons are created and they bring strong winds, lighting, and sometimes rain. This brings extreme changes to the temperature, dropping the weather by 18 degrees Fahrenheit or more in as little as ten minutes. The lighting also brings about very violent thunder, as well as the danger of wildfires.

 Another key feature would be the variety of fauna and flora found in the Sonoran Desert. The Sonoran Desert is home to flora such as the saguaro cactus, velvet mesquite, paloverde trees, and acacias. This is not a comprehensive list, and there are many more types of flora. Some examples of fauna would be coyotes, javelinas, chuckwallas, Gila monsters, and diamondback rattlesnakes. 

A keystone species of the Sonoran Desert is the Saguaro Cactus. These cacti are not only an icon of the Sonoran Desert, they are one of the most important parts of it. 

The Saguaro Cactus is a plant unique to certain parts of the Sonoran Desert. They do not grow anywhere else in the world, and this is mainly due to the very specific climate needed for them to grow. For starters, they need rocky soil for their roots to hold firm and they also need more moisture than is typically found in lower-elevation deserts. They also cannot withstand any type of freezing temperatures, as that is detrimental to them. The amount of time needed for them to develop reflects their delicate nature. According to the U.S. Forest Service, "Plants are at least 50 years old before they flower for the first time and usually about 75 years old when the first side branches develop. Plants can live for 200 years." (fs.usda.gov). They also "can reach almost 50 feet in height and 10 feet in circumference. They are by far the tallest plants in their desert scrub environment. A large plant full of water can weigh up to 6 tons." (fs.usda.gov).  

So, how are they a keystone species? 

The Saguaro Cactus is vital to the Sonoran Desert ecosystem for various reasons. For one, the cacti provide shelter for animals found throughout the Desert. An example is the Gila woodpecker, which pokes a hole in the cactus and uses it as a nest. When it abandons the nest, other animals like the screech owl, the elf owl, and house finches will take over the nest and this gives the animals shelter from both the elements, and predators. But it is not only the prey that use the cacti. The predators also use the cacti! Harris's hawks will also use the cacti to make their nest on the arms of the cacti and use them as hunting perches as well. When the hawks leave their nests, ravens and owls will take over their nests. All of these animals will mate and have their offspring in these areas, and they all rely on the Saguaro Cactus to be strong and sturdy. 

Another benefit of the Saguaro Cactus is that it provides food and water to the animals. Birds, bees, insects, and even bats visit the flowers throughout the night and day, pollinating them and also getting their food source from the flowers. Then, in the middle of the summer, the flowers bloom into the ripe, red fruit, which splits open and is just about the only food source for the animals in that time of year. The fruits give water and nutrition to all wildlife, and support the fauna through the summer. We can even see an example of adaptation from the Saguaro Cactus. The flowers open at night, and close the following afternoon, a perfect schedule for the bats who need their food, and the cacti that need the pollination and the spreading of seed. Fun fact, bats are the main pollinators of the Saguaro Cactus! 

The Saguaro Cactus is the keystone species of this biome and without it, many of these creatures would die off, or be forced to leave. That is why the government protects them so much, and that is also why the fear of climate change is so real. Unfortunately, these beautiful cacti are threatened by increasing temperatures, more intense and unpredictable storms, and longer droughts. 

Humans have impacted the Sonoran Desert for over 3000 years. According to the National Park Service, "Early practitioners employed runoff irrigation, called Ak-Chin by the Tohono O'odham, wherein seeds of crop plants were sown near washes to capture runoff during the rainy seasons. The Hohokam constructed massive systems of irrigation canals along major river valleys, such as the Gila, before abandoning them by around the 15th century." (nps.gov). The Native American tribes would disperse specific types of seed throughout the desert. The biggest impacts, however, came from the European colonization of the Americas. The Europeans brought with them European plants, animals, and cotton farming. They also brought with them the practice of mining. According to the National Park Service, "Livestock grazing was the most extensive Euro-American modification of the Sonoran Desert, while mining was the most intensive land-use practice introduced to the region. Both practices caused substantial degradation in the southern and central Sonoran Desert by the mid-19th century, with numerous descriptions of overgrazing and subsequent abandonment during the colonial period. These practices were not prevalent in southern Arizona, as the Apache and other hostile indigenous groups greatly limited Spanish and American settlement until the late 19th century." (nps.gov) As we saw, the Saguaro Cacti and Southern Arizona in general were not affected. Unfortunately, that is not the case today. 

300 years ago, the Europeans were far more effective at altering the land than Native Americans were. Today, we are masters at it. Pollution, farming, and mining decimate the land today. Animals and Saguaros are constantly having to be moved, as more people move into Arizona. The loss of natural habitat creates a hardship for animals, and even the noise can overwhelm animals like bats, who rely on echolocation. Large mines are still present today, and new-build homes are continuing to rise. Natural Sonoran Desert land continues to be turned into hay fields, cotton fields, or cattle grazing territory and while there are protections put into place by the government, we need to do more to protect this beautiful desert. Climate Change is a serious issue as well because as the Desert suffers more droughts and more intense thunderstorms, it also increases the risk of wildfires. 

The Sonoran Desert is a unique and beautiful biome and shows the complexity and fortitude that evolution and adaptation bring. The plants and animals that live here have adapted perfectly to the weather here, and work hand in hand to protect it and survive in it. Now we must do the same, and make sure to protect this wonderful biome and make sure future generations can marvel at its complexity and beauty. 

Arizona State University (aka ASU) has a fun, interactive VR overview of the Sonoran Desert. I will provide the link here. It is very interesting!! 

https://askabiologist.asu.edu/explore/Virtual-360-Biomes

National Park Service: https://www.nps.gov/im/sodn/ecosystems.htm#:~:text=In%20the%20Sonoran%20Desert%2C%20the,to%20name%20but%20a%20few.

https://www.nps.gov/sagu/learn/nature/saguaro.htm

U.S. Forest Service: https://www.fs.usda.gov/wildflowers/plant-of-the-week/carnegiea_gigantea.shtml

Center for Biological Diversity: https://www.biologicaldiversity.org/programs/public_lands/deserts/sonoran_desert/index.html