• Michael O'Keeffe

Mountain Series: Madrean Sky Islands, AZ/NM

A hiker admires the rhyolite hoodoos in the canyons of the Chiricahua Mountains in Arizona.
The stunning rhyolite hoodoos of the Chiricahua Mountains in Arizona.

In southeast Arizona and far southwest New Mexico lies a fascinating chain of mountain ranges known as the Madrean Sky Islands. These "sky islands" are a series of widely spaced mountain ranges that rise abruptly from the vast flat desert valleys below. Thus creates the analogy that the mountains are the "islands" and the desert is the "sea". In fact, the Madrean Sky Islands are sometimes referred to as the Madrean Archipelago (term for a chain of islands). The geographical and environmental factors that make up this special chain of mountains is staggering and quite interesting so prepare to nerd out!


There are at least 27 mountain ranges spread across southeast Arizona, far southwest New Mexico, and northern Mexico that are apart of the Madrean Sky Islands chain. Climatically, the Archipelago sits in a unique position squeezed between the cold temperate Rocky Mountains to the north and the warmer subtropical Sierra Madres to the south. To make things more interesting, the sky islands also sit at the transition zone of two very different ecoregions, the Sonoran Desert to the west and the Chihuahuan Desert to the east. Not to mention the summer monsoon season which brings frequent heavy thunderstorms to the region between July and September.

Above all else, the factor that makes the Madrean Archipelago so ecologically dramatic is the elevation. Some of the ranges reach upwards of 10,000 feet above sea level making for prominences of over 6,000 feet in places. What occurs in turn due to temperature and precipitation differences with altitude is a dramatic collection of life zones found over a very short distance, sometimes only a few miles. A change of just 1,000 feet can transport you into a completely different ecozone. Tack on the isolated nature of each range along with the climatic influences listed above and you have the makings of a biodiversity hotspot rarely seen anywhere else on Earth.

Sunset in the Santa Catalina Mountains near Tucson, Arizona.
The Santa Catalina Mountains are a sky island rising above the Sonoran Desert near Tucson, Arizona.

Flora & Fauna

Lets take a look at one range in particular, the Chiricahua Mountains in far southeast Arizona. This is one of the largest ranges in the Madrean Sky Island chain and one of the tallest at 9,759 feet. The range features a prominence of over 5,000 feet allowing for a number of different biomes to occur as you work your way up the slopes. We will break down each biome and discuss a few of the more interesting flora and fauna found in each.


Hiker standing next agave bloom stock in the Chiricahua Mountains in Arizona.
Standing next to an agave bloom stock in the desert grasslands at the foot of the Chiricahua Mountains.

The entirety of the Chiricahua Mountains sit within the Chihuahuan Desert. The Chihuahuan is the largest desert in North America, spanning from southeast Arizona through southern New Mexico across much of West Texas and northern Mexico. It sits at a higher elevation than the bordering Sonoran Desert to the west meaning winters here can get cold. One unique aspect of the Chihuahuan are the vast desert grasslands that dot the region. These dry desert grasslands can be found along the lower reaches of the Chiricahuas (below 5,000 feet) and are peppered with cactus, agave, and yucca, many of which are endemic to the region. Precipitation in these lower elevations may reach only 10-15 inches per year most of which falls during the summer monsoon thunderstorms.


A hiker stands in an oak pine forest in the Chiricahua Mountains in Arizona.
Enjoying the cool shade of an oak-pine forest in the Chiricahua Mountains.

Climbing higher into the range (between 5,000-7,000 feet) one enters the oak-pine forests where you will find the highest concentration of unique flora and fauna. Though receiving slightly higher annual precipitation (15-25 inches) than the grasslands below, sheltered canyons and north facing slopes tend to harbor the most successful oak-pine forest in the Archipelago. In the case of the Chiricahuas, deep canyons dissect the range where a majority of these forest are found. Ephemeral streams (streams that only flow periodically) found within the canyons create rich riparian zones filled with cottonwoods and sycamores among other common species. Many of the plant species in the oak-pine forest zone come from subtropical origins meeting the northern extent of their range in the Sky Islands. A few examples include the Apache Pine (Pinus engelmannii) and the Silverleaf Oak (Quercus hypoleucoides), both with a majority of their native range in Mexico.

The oak-pine zone is also where you will find a majority of the wildlife that call the range home. Common species you will find here include skunks, deer, black bears, mountain lions, and javelina. Another common yet unique creature that calls the Chiricahua Mountains home is the coati. PSA: If you haven't heard of a coati stop everything and Google them right now because they are adorable. Coatis are in the same family as racoons and have an extensive range that begins in the Sky Islands of southeast Arizona and stretches down through most of Central America into the majority of northern South America. Their appearance is similar to that of a racoon, but with orangish colored fur and a long bushy tail that is almost primate like. Unfortunately, during our time in the Chiricahuas we didn't see any coatis, but I vow to return and see one for myself someday.

There are a few other animals whose native ranges span across the Sky Islands as well. One of which is the jaguar, once found all throughout this region has since been exterminated. However, scientists have been able to capture trail cam images of jaguars roaming around in southern Arizona in recent years signaling the big cats may be returning. Jaguars elusive nature have made it hard for scientist to determine if these are just isolated occurrences or a true return to their historic range. Interestingly, jaguars aren't the only wild cat who used to roam these mountains though, the ocelot is also native to the Sky Islands region. Also exterminated from the United States, a few sightings in recent years have increased curiosity that these beautiful cats may be returning as well.


An Apache pine in the Chiricahua Mountains.

The highest reaches of the Chiricahua Mountains sit between 7,000 - 9,759 feet, featuring a plant community more in line with the Rocky Mountains than the Desert Southwest. It is here the forest is dominated by ponderosa pine (Pinus ponderosa) and Apache pine (Pinus engelmannii) with Douglas-fir (Pseudotsuga menziesii var. glauca) and white fir (Abies concolor) clinging to north facing slopes. More unusual species such as Chihuahua pine (Pinus leiophylla) and Arizona cypress (Cupressus arizonica) also can be found in this zone. The Chiricahuas also feature the southern most extent of Engelmann Spruce (Picea engelmannii), a common subalpine tree in the Rockies, which can be found in small stands on a few north facing slopes. Precipitation here can reach up to 30 inches a year with snow falling in winter and heavy thunderstorms occurring in summer.

Above all one of the most interesting native animals of the Sky Islands in my opinion has to be the Thick-billed Parrot. These colorful birds look like something straight out of the Amazon rainforest and were once a common sight across the Sky Islands. To make things more unusual these tropical looking birds lived high up between 6,000 and 9,000 feet foraging on pinecone seeds and were adapted to survive the cold snowy winters at these altitudes. One of only two species of parrot native to North America (the Carolina Parrot was the other), these birds (along with the other) were hunted to extinction in the United States by the 1940s. Their loud calls and large flocks made them easy to spot and take out by hunters. A small population of these parrots still live wild in northern Mexico and reintroduction methods have been attempted on several occasions to bring these parrots back to the Sky Islands, but unfortunately they weren't successful. It must've been a magnificent sight to be high on a snowy ridge in mid winter among the Douglas fir and ponderosa pines witnessing flocks of brightly colored green and red parrots fly overhead. Times have certainly changed.

This brief glimpse into the flora and fauna of the Chiricahua Mountains offers a small sample of the great biodiversity the Madrean Sky Islands possess. I like using this example because it can apply to many of the other ranges in the Sky Islands as well. Having said that, each range differs in its character making the area a wonderful place to explore. No two ranges are the same. You could spend a lifetime hiking, climbing, and backpacking this fascinating archipelago set among a vast desert sea.

Hiking through a Saguaro cactus forest in the Santa Catalina Mountains near Tucson, Arizona.
Hiking through a Saguaro forest in the Santa Catalina Mountains near Tucson.

Thanks for reading! If you enjoyed this let me know in the comments below and be sure to subscribe to the blog to stay up to date on more nerdy geography posts such as this one!

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