Ancient Forest Management in the Chaco Canyon

From 600 AD to 1300 AD

There are some places on this Earth where it is easy for civilization to put down roots and sprout into an amazing and complex society.  Places like the Fertile Crescent, which seemed to practically call out for humans to endeavor into agriculture. Then there are places like the Colorado Plateau.

The Ancient Pueblo people, errantly referred to as the Anasazi by many outsiders, settled this plateau in spite of it’s many challenges, and they built an amazing society there, composed of the biggest buildings in the ancient United States.

The barriers faced by the Ancient Puebloans were plentiful; regions with enough rainfall didn’t have enough habitable space, or cropland. Fickle rain and flood patterns would make one area of the plateau ideal for agriculture, while others were stricken with drought or overrun with floodwaters. The following season all the rules would change, and new regions would be ripe for harvesting. The earliest societies in the region, forming around A.D. 600, coped with this unpredictable habitat by diversification. Small groups would spread out across great regions, and when a good season came to one area, the residents there would share their bounty with places suffering from drought or flooding. This way all the people within the group had an opportunity to flourish, and all of them had a social safety net when times got thin. This system also set up a deep historical precedence of trade and inter-dependency in the region. In this way society took root on the Columbia Plateau, in amazing but seemingly uninhabitable places like Chaco Canyon.

The early residents of Chaco Canyon took advantage of a reliable floodplain with fertile soils and local forests. These simple necessities gave them the opportunity to thrive. Yet even in Chaco, a place originally plentiful in all the resources necessary for humanity to put down foundations, the challenges were great. The increase in members in this society quickly meant that the amount of harvestable land had to be expanded. This need spring-boarded experiments in irrigation. Irrigation all over the Colorado Plateau is difficult because of arroyos. Arroyos are essentially irrigation canals that have eroded too deeply into farmland soils. The canal originally dug for irrigation during a dry year is widened and deepened during a severe flood year. Then the water running through the canals is below crop level, and without some method of moving the water uphill, it cannot be applied to the thirsty crops. The Chaco canyon region had difficulty with arroyos after attempts to irrigate crops interrupted the natural floodplain agriculture that had originally brought the people there. The irrigation challenge didn’t cause the people of Chaco to give up on living there, instead they built dams on local streams and across the canyon itself, they gathered and stored the rainwater that came down the canyon walls, and they used many other irrigation techniques which compensated for the challenges they faced.

Water wasn’t the only limited resource in Chaco canyon; timber was also a valued and finite resource. “Deforestation, as revealed by packrat midden analysis” (Diamond, 145) quickly became a problem within the confines of Chaco canyon. Packrats only travel a short distance, so by dating ancient middens (deposits of pooh and partially digested foods etc.) and cataloguing their contents, we can get an idea of what surrounding landscapes looked like. Packrat middens at Chaco canyon show that pinyon/juniper woodlands in the canyon disappeared around A.D. 1000. Those forests have never returned.

The discussion of forestry brings me to the crux of this essay. Chaco canyon residents handled their forests in very different ways. Trees within the canyon were harvested without discrepancy, in a manner that left the land essentially the victim of clear-cutting. Meanwhile, forests outside of the canyon were only harvested for wood of a certain species and diameter, in a manner that is more like selective thinning. The difference in harvesting came not out of an informed choice based on the health of Chaco canyon resources, but instead emerged from a series of social and environmental demands.

Early settlers in Chaco primarily used local resources. Trees nearby were harvested for tools, fuel, architecture, and a plethora of daily activities. The confines of the canyon helped to determine the local resource areas, and anything useful within the canyon was consumed.

Wood within the canyon may have been used indiscriminately as a whole, but when it came down to the building of Chaco canyon architecture only some wood was acceptable. Architecture throughout the cultural region was uniform, and it is because of the symmetrical doors and similar construction of walls etc. that we know this group of people was spread out across a large geographical region, but still connected socially and culturally. One of the key aspects of this uniform architecture is the use of relatively small (in diameter) pinyon/juniper tree trunks for construction beams. You can see the architectural style and the beams in these photos:

It was the demand for uniform trees in Ancient Puebloan architecture, which created the unique forestry practices in Chaco canyon. Within the confines of the canyon walls every bit of wood was useful and worth the effort necessary to harvest and consume it, but beyond the canyon walls, at tree-stands sometimes 50 miles away, only the treasured architectural beams were utilized. This is probably due to the simple fact that transporting the wood across great distances was really only worth the time invested when it came to the specialized beams needed for building.

There were two major sources for timber once the architectural supply within the canyon began to dwindle, and they became the primary source of architectural wood once the canyon was completely deforested. The mountains were the Chuska Mountains and San Mateo, and the Chaco canyon residents seemed to prefer neither canyon to the other, using them equally in their building projects. These timber stands were located at outlier communities which already had trade ties to the Chacoans, and whom were part of the aforementioned social safety-net system used by many Ancient Pueblo groups. The early alliances, which allowed Chaco canyon to exist in the first place, were now allowing the residents there to thrive.

As the residents of Chaco canyon proceed with their clear-cut style consumption of local resources, outlier communities ‘picked up the slack’ and Chacoans were undeterred by dry years and other ominous signs of environmental danger. Yet, as I said before, the Colorado plateau isn’t a kind and easy place for humans to live. No, the plateau is a harsh and unforgiving mistress, and the situation within Chaco canyon began to spiral out of control.

Once the canyon was deforested the people of Chaco had very few options to fuel their homes. Pottery making stopped because there simply wasn’t enough wood to spare and the kilns were too resource-expensive for the Chacoans to use. “Chaco Canyon became a black hole into which goods were imported but from which nothing tangible was exported (Diamond).” This system was only sustained because of social ties, “Chaco society turned into a mini-empire, divided between a well-fed elite living in luxury and a less well-fed peasantry doing the work and raising the food (Diamond).” The thriving society was now dangling on the edge of an environmental precipice… and although experience had given them some hints, they had no idea how desperately they were clinging to existence there.

The problem with the arroyos was exacerbated by deforestation. Soil runoff became more aggressive, and crops harder to sustain. Still, every time there was a great climate season, Chaco canyon populations would swell, and when the internal resources became scarce once again, outlier communities were more heavily burdened to sustain the urban elites of Chaco canyon. The outlier communities at Chuska Mountains and San Mateo mountains became a crutch upon which the Chacoans were extremely dependent. The strength of the cultural bonds in the Ancient Puebloan culture was strong enough to sustain the residents of Chaco canyon through a great deal of turmoil, but social alliances alone would not be enough to sustain the canyon dwellers.

Chuska Mountains run north to northwest along the Colorado plateau for about 50 miles that span the border between Arizona and New Mexico. The Chuska mountain range forests were never fully depleted by Chaco canyon’s export demand, and the industry remained strong in that region through colonial times until 1994. In 2008 logging started again in the Chuska Mountains. Will this new logging venture be managed in a sustainable way, utilizing the lessons of thinning and moderation learned by sustainable thinning, or will they resume with the clear-cut mentality which eventually decimated forests and devastated humans within Chaco canyon?

As for the ancient inhabitants of Chaco Canyon, a climate change eventually sealed their fates. Around A.D. 1300, a drought hit the region, causing collapse of many nearby groups, and the Chacoans were also victims of the harsh environmental trap created by an already stressed ecosystem. The canyon was abandoned, and residents there probably moved into outlying communities, not romantically disappearing as many accounts would overzealously exclaim, but instead absorbing into nearby groups and becoming a part of a newly woven cultural fabric.

The lessons of Choco Canyon are plentiful, the most obvious displayed to the viewer as they gaze upon the treeless landscape of the canyon. The choice for our modern society, as always, is: will we heed these lessons? Will we practice sustainable forestry and irrigation? Will we live within the ability of our environment to sustain, or will we overrun that ability and import the material goods that we desire at the expense of ecosystems all over the planet? It’s time to ask these questions of ourselves, and to think deeply before we decide, because we cannot pick up the remains of our environmental disaster and move on anymore. We are reaching the end of our available resources, and have forced the entire planet to perform in an environmental balancing act upon which all of our collective fates are now hanging. We have the opportunity now to make an informed decision, and protect the future of our entire species.

What is this?

Let's not repeat history - that's boring, and probably disastrous. To avoid that, though, it's important to know where we've been... so here's a quick little rundown of what we've done wrong - and right - over the 10,000 years since we started on this whole "civilization" experiment.