Playa lake in bloom. Photo by T. Mc Alavy. Texas Cooperative Extension
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The biotic community supported by playa lakes is impressive. Almost three hundred and fifty plant species have been described around the playas in the PLR. Some of these plants are wetland species and others are native, high plains plants that have found refuge in the playa zone from the surrounding, human-induced destruction of habitat. Over 200 species of birds
Photo by A. Safranek. USFS
(including song birds, migrating waterfowl, shorebirds and raptors) have been observed around the playa. Also, 37 species of mammals, 13 species of amphibians, and 124 species of aquatic insects have been described in and around playa lakes. These plants and animals employ an incredible array of ecological strategies to survive in these ephemeral and unpredictably occurring aquatic ecosystems. Migration, torpor, aestivation and prolonged survival of seeds or underground rhizomes and roots all match up with incredibly fast metabolic and behavioral responses to the appearance of water and also to extremely rapid rates of reproduction and offspring development.
The playa is a miraculous ecosystem!
Playa lake in Anston, Texas. USDA, Public Domain
Greeley, Colorado is just outside the PLR, but I am sure that there are playa lakes within a short drive east of here. All we need is some rain to wake them up! When I last lived in this arid, southwestern climate I was in college at Texas Tech University in Lubbock, Texas. Lubbock gets, on average a few more inches of rain a year than Greeley (18” of rain/year in Lubbock vs. 15 “ of rain/year here in Greeley), but they are both very dry places.
During my four years at Texas Tech, I only remember it raining (and I mean REALLY raining not just a little drizzle or spit!) twice. The first rain was at the start of the fall semester of my sophomore year. It rained for days and days. The university had to lay down wooden walkways (which they must have had stored somewhere for just this purpose) so that we could walk from our dorms to the academic buildings for classes. I remember looking out my dorm window at the shallow, muddy lake that had taken over the entire south campus!
The second time was during the summer of 1973. It rained so hard we couldn’t work outside at the museum (I was working on a crew that was re-constructing some early, West Texas farmstead buildings for the museum’s adjacent historical village). I remember taking at least two (maybe three!) “rain afternoons” off from the very hot, hard work at the museum. I spent the unexpected free time sitting in a big, soft chair in the living room of my rental house reading some books just for fun (one was “Martin Eden” by Jack London, I don’t remember the other titles). I also remember listening to the pouring rain coming down outside.
I wanted to check these memories against some unbiased record, so I pulled up The National Weather Service’s data sheet on Lubbock’s monthly rainfall from 1911 to present and sure enough, there were the August and September rains in 1972 (a total of almost nine and half inches!) and there was the rain in July 1973 (over four inches). Almost all of the other the months that I lived in Lubbock were relatively dry and, with regard to precipitation anyway, uneventful!
Buffalo Lake windmill. Photo by Leaflet. Wikimedia Commons
These two rains were sufficient to fill the playas around Lubbock and trigger explosions of plant and animal life. It seemed like it happened overnight: dry, barren plains on the edge of town were transformed into lush patches of green. Dragonflies and squadrons of other flying insects swarmed over the standing water of the lakes. Toads sang and trilled incessantly. They were probably the plains spadefoot toad. I occasionally turned up a mucous encrusted, “sleeping” spadefoot toad sometimes six feet or more feet underground when I was digging various holes and foundations out at the museum. Other amphibians (frogs and salamanders) and reptiles (turtles) splashed about in the water. Flocks of birds descended on the lakes and gorged themselves on anything small enough for them to swallow. Flowers bloomed, and the air smelled so sweet.
And then, in a couple of weeks, it was gone! Ah, the magic of water!!
White Sands dune field. Photo by NPS, Public Domain
White Sands National Park is located in southeastern New Mexico. Within the boundaries of the park are many biological and geological curiosities along with some extremely compelling relics and signs of ancient human beings. White Sands is in a true desert climate zone (10 inches of rain per year) and is close to the present day, western edge of the PLR. Playa lakes can form within the boundaries of the park, and in the past, under more moderate climatic conditions, playa lakes were undoubtedly quite common within the area of the park.
Old playas, in fact, are still detectable across White Sands. One of these ancient dry lake beds dates back to the end of the last ice age (about 12,000 years!), and it contains hundreds of thousands of tracks made by humans and animals. Many of the animals that left these tracks are now extinct possibly due to the combination of the impact of human hunters on the large megafauna of North America and ongoing climate change.
One extremely important sequence of human tracks in this playa is a 1.5 km, round-trip sequence that has very recently been extensively analyzed by researchers from Bournemouth University in England. Precise imaging of the individual footprints and their patterned sequence has generated an incredibly human story about the people that lived in this site at the end of the last ice age. The analysis of these footprints was published in the December 1, 2020 issue of Quarterly Science Reviews and had been previewed in October and November articles in The New York Times, The Scientist, and Conversation.com.
White Sands human footprints. Photo by NPS. Public Domain
The tracks, as interpreted by the researchers, were made by a young, possibly adolescent female. She was carrying a child, possibly a two year old toddler. The woman was walking quickly across the slippery clay-mud of the playa lake bed perhaps because she knew there were predators lurking about (both saber-toothed cat and dire wolf tracks have been found in this playa). Occasionally, she had to put the child down (there are scattered sets of tiny, toddler footprints along the long track), and she shifted the child from one hip to the other (as seen in the depth and quality of her left and right footprints). She only carried the child in one direction, though, and then returned along the same path without him.
Two ancient, ice age mammals made tracks that crossed the young woman’s path: a giant ground sloth actually paused at the human tracks and reared up (probably to look around for the presence of any humans (and their spears!)), and a large, bull mammoth seems to have crossed the woman’s path without any pause or recognition.
Was the woman taking the child to be cared for by someone else in her clan or had she been caring for someone else’s child and was hastily returning him? What kind of human social organization does this vignette reflect? Were there predators near the area of the playa or had they fled the presence of the stone-bladed spears and knives of the humans? Was the toddler crying and fussy or was he quiet and content?
The observations of the footprints generate inferences that lead to more and more questions! This ancient playa lake bed gives us a glimpse of these ancient people and paints such a familiar, human picture!