This week’s picture comes from Mesa Verde National Park in the southwestern corner of Colorado, USA.
The ancestral puebloan (nee “Anasazi“) people that once lived in this area developed a number of ways to support an agricultural lifestyle in an arid environment. The ancestral puebloan version of terrace farming was one of the more interesting ones.
Farming on terraces was hardly unique to this ancient society — a number of other cultures have used some version of them over the centuries. What is different about many of the terrace fields in Mesa Verde is that they are built in dry washes, essentially the beds of seasonally flowing creeks.
As a result, these terraces had a number of functions in addition to their usage as farmland. For starters, they helped slow runoff from snow melt and thunderstorms, reducing or avoiding damage that would otherwise be caused by erosion. In the process, they also trapped sediment that could have been washed away with the water. By slowing water flow and capturing sediment, the terraces helped what little water they saw to soak into the soil — allowing it to be used rather than lost.
If they were built in the same fashion as their more modern counterparts in the same part of the country, many were constructed not as dams, but as simple lines of rocks. One layer of rock is set down at a time, not to stop and block water from flowing through, but to slow it. As silt slowly builds up behind the stones, another layer is added, then another — with possibly just a few layers being added in a generation.
After careful tending of the land over centuries, the local population apparently reached some sort of breaking point around 1300 AD. A number of things have been suggested for the relatively rapid depopulation of the area. Maybe a change in the local climate made agriculture unworkable, or religious and political changes damaged the formerly cohesive social network of the inhabitants. In any event, the mesa’s villages were completely abandoned within a generation as their former inhabitants moved down-river to settle the pueblos now home to their descendant tribes.