The Atascosa Highlands are a series of five small mountain ranges located in Southern Arizona, which straddle the international boundary between the United States and Mexico. The 203,799 acres that make up the Atascosas are officially referred to as the Tumacacori Ecosystem Management Area, and are managed as a part of the Coronado National Forest.
Precipitous cliffs rise hundreds of feet from rolling valleys, creating a mosaic of varied microclimates that allow for species with wildly different habitat preferences to grow within a few yards of each other. This topographical variation defies traditional elevational life zone delineations, bringing habitat types together to form diverse ecotones where the lines between ecosystems blur.
Indigenous use of the Atascosa Highlands is a chain stretching back across time. The links of which are formed by the numerous cultures which have found food and shelter in the rugged hills and verdant valleys of this region. While there has been little archeological work conducted on the Highlands compared to nearby areas like the Santa Cruz and San Pedro valleys; oral histories, mission records, artifacts, and archeological evidence offer glimpses into the lives of the people who have called these mountains home for millennia.
You don't see a border, you see the opposite of a border. You see an endless, interconnected landscape. You see this incredibly rugged place where Mexico, U.S., those terms become irrelevant.
It’s where everything’s converging, it’s the place where the jaguar and the black bear share the same trail, and you go further north and that ends, and you go further south, and that kinda ends but right where we’re at, right here, is where you see something happening.
All of our crops in the United States, have a narrow genetic base upon which the major varieties are constituted...the only way to get around that, is looking deeply at the history of the wild ancestors of those plants.
If you care to wander down to the southern border of Arizona, following the unsurfaced road indicated on the sketch map here, you will find, in a neglected nook called Sycamore Canyon, a remarkable botanical garden in which the agencies of nature have been the only planters. In this narrow, precipitous ravine, extending scarcely five miles from north to south, plants from the tropics and species from the north combine with other rarities, as in a man-made garden, to present a pattern of vegetation that is unique.
The Atascosa Highlands are part of a larger chain of “sky islands,” isolated mountain ranges which connect the peaks of the Sierra Madre Occidental of Mexico with the Rocky Mountains of the United States and Canada. This is an area of incredible biological diversity located in one of the most ecologically rich regions on the planet. These mountains bridge political boundaries, and act as essential migratory routes for wildlife; providing a home for plant and animal species which would not survive in the harsh deserts below.
It’s the region, or a region, where species are forming, and are going to be forming. Where disjunct populations become isolated from parent populations, genetic mutations accumulate, populations diverge in some of their characteristics, and traits, and become new species. It’s just a fantastic natural laboratory in which evolution is unfolding before our eyes.
The Atascosa Highlands has species that aren’t even found anywhere else in the United States, or in Arizona, or in any other Sky Islands. So that begs a lot of biogeographic questions, how plants and animals arrived to where they're at, through what geological, and evolutionary theaters.
Three days were occupied in traveling this short distance. The trail for the first two was over almost impassable mountains; massive rocks, and steep precipices constantly impeded…progress…and turned the party out of its course, making the route circuitous as well as hazardous, rough ascents were surmounted, steep ravines followed down, and deep gullies passed, the mules had actually to be dragged along. The soil is very rich, the vegetation is profuse and there is a fine abundance of grama grass, live oak, and occasionally cedar (juniper) are seen on the hills. Some strange specimens of natural history were found at this place.
Despite the interest of many prolific biologists there has never been a comprehensive flora of the Atascosa Highlands until now. A flora is a snapshot of a region at a given time; carried out by recording observations, collecting botanical specimens, and depositing these at an herbarium so that they can be referenced by future researchers. Floras are an essential element of understanding the ecology of a region.
When we collect these (botanical specimens), we won't know, how they'll be used in 20 years from now, 15 years from now, 100 years from now, who knows, they'll be around, they should be around for centuries.
You learn so much about the particulars, of a particular species, or a particular area, and then from that build a larger view of the earth and nature as a whole, life as a whole...you learn answers to big picture questions by studying the individual parts.
Riparian canyons, grasslands, and oak woodlands are the most recognizable habitats of the Atascosa Highlands. However, there is another habitat type which is sometimes overlooked in botanical studies, the anthropogenic biome. These are places where the dominant factor driving the ecosystem is human disturbance. From tiny stock ponds to large lakes created by damming up canyons, and from old mine sites to strips of land blasted and cleared for border wall construction. These “anthromes” are ground zero for the spread of disturbance loving and invasive species. The greatest change wrought by intensive human disturbance is often not the complete eradication of life but rather the introduction of different species demographics into the delicate balance that supports diverse native habitats.
The habitats that these animals occupy now are largely human-constructed habitats like stock tanks, whereas historically they would have been in springs and streams, and through climate change or human activities some of those springs are gone.
The Atascosas have been inhabited for thousands of years, but over the last few centuries human activity has begun to have a profound effect on this landscape. In a day, a bulldozer can undo the progress of centuries of natural selection, precipitating radical shifts in the flora which ripple out to all the plants and animals of the Atascosa Highlands.
If we have the ability to preserve something, and save something from our excesses, or our excessive footprint, and consumption, then we should. Because the rate of change is happening at a rate that we've never recorded before, by orders of magnitude.
You look out over the Pajarito Wilderness and you see the folds of the landscape and you can't even count them all. It looks endless, and it kind of looks indestructible. It looks so vast, and intimidating in a way that makes you feel really small.