Mega-Drought and Dryland Gardening
By Carolyn Dunmire:
Recent national headlines have trumpeted that the Southwestern US is in a mega-drought., one that has not been experienced since the 1200’s. Jerry Fetterman of Yellow Jacket Dryland Vineyards and long-time dryland gardener confirms that “we have been in a drought for a long time.” Precipitation records for Montezuma County show a consistent pattern of wet years followed by dry years. What makes the current pattern mega-different, is the depth and duration of the dry years. Archaeological records for southwest Colorado document past mega-droughts in the region and how residents responded to them. The last mega-drought of this scale spurred the depopulation of the Mesa Verde region. Will we fare any better?
A mega-drought is distinguished “as a dry period 1) that is found in most of the chronologies such as tree ring data, 2) that occurs over an extended period of time; and 3) when dry years are drier than the threshold for a typical drought year” according to Mark Varien, PhD and executive vice president of the Research Institute at Crow Canyon Archaeological Center in Cortez.
Varien explained, “In the Southwest, we are able to model precipitation patterns for the past 1000 years or more because we have long chronologies derived from some of the oldest living trees in North America, as well as standing dead trees and wood from archaeological specimens.” Crow Canyon conducted research using tree ring data to estimate precipitation, temperature, and annual crop yields during a mega-drought in the Central Mesa Verde region in 800 AD. This research found that, “Ancestral Puebloan farmers, just like farmers today, had to deal with an ever-changing environment, including many droughts. One of the most important strategies to survive these droughts was growing and storing enough produce to last for several years and to buffer against bad years. When Europeans first encountered Puebloan farmers in places like Hopi, their fields were large enough that in a good year they would produce three years worth of crops, with corn being the most important. The other important strategy was sharing among community members within local communities and with communities across the region.”
Modern gardeners and farmers faced with the current mega-drought are being forced to consider similar strategies as their once reliable irrigation supply is not available. At Yellow Jacket Dryland Vineyards, Fetterman continues the practices of growing grapes and vegetables using dryland cultivation techniques, using only soil moisture delivered by precipitation. There is no supplemental watering to help the plants through dry summer months. Fetterman notes that “summer moisture is not as important as winter moisture for successful dryland cultivation.” But he recalls that, “Winter precipitation, such as the two to four feet of snow that previously covered the region throughout the winter, allowed slow accumulation of soil moisture over the winter. Even more importantly, the October rains, which have not materialized lately, recharge soil moisture at a critical time.” While the timing is similar, these autumn rains are not the foundation of a monsoon-based growing season as in southern Arizona and New Mexico. Freezing temperatures at the relatively high elevations of Southwest Colorado (6000 - 7000 feet) make it impossible to grow a crop at that time of year. Rather, the autumnal rains promote moisture to penetrate deep into the soils for the next year’s crop.
Dryland farming, particularly of pinto beans and winter wheat, has been a common practice in the deep red soils of SW Colorado for centuries, long before the development of irrigation infrastructure centered around the Dolores River. The principles behind dryland gardening, in this part of the Southwest, are based on promoting and preserving deep soil moisture. Some of these techniques such as “clean cultivation” and “dust mulching” seem counter-intuitive to conventional gardening practices. Fetterman sums it up as, “It’s the weeds!” According to Fetterman, “Clean cultivation requires that anything that could compete for soil moisture must be eliminated, such as weeds and mulch material.” While this seems obvious when you are trying to preserve each precious drop, dust mulching is not. Dust mulching, using dirt as mulch, is preferred because it allows surface moisture to percolate into the soil. “Using a vegetable-based mulch keeps the moisture too close to the surface” says Fetterman. “You want the moisture deep in the soil where it can be accessed by the plant’s roots and is protected from surface evaporation.” The advantage of the red dirt in southwestern Colorado, exploited by past and current dryland growers, is its great depth. It is not uncommon to have a depth of 10 feet of red dirt in a field.
“You can grow anything; watermelon, asparagus, tomatoes, and chilis using these dryland techniques.” Fetterman is known for pioneering grape-growing in the high and dry. While it is well-documented that Spanish explorers successfully introduced grapes into the Southwest, Fetterman has undertaken the challenge of growing grapes at an elevation of 6850 feet exclusively using dryland techniques. The Yellow Jacket Dryland Vineyard produced a bumper crop of 6.5 tons of grapes on one acre in 2020, a year with unremarkable precipitation.
Is the current mega-drought the end of agriculture in the Southwest? Crow Canyon’s research concludes with a dire warning, “Thus, it is not merely climate change, but the way in which climate change interacted with a historically constituted social landscape and a pattern of great reliance on maize agriculture that best accounts for the collapse of Mesa Verde society. This is an important and cautionary note for those attempting to forecast the effects of climate change and population growth on our world today.” It’s not just the change in climate but how gardeners and farmers respond to the this change that will determine our fate during the mega-drought.
Carolyn Dunmire has been a Colorado gardener for more than 30 years, most of that time in the Weatherhill at 7000 feet. She and her husband have 60 acres where they grow a wide variety of fruits and vegetables year-round in a large outdoor garden, a greenhouse, a hoop house, and an orchard with 200 fruit trees.