[A preview of a piece I wrote for the upcoming El Paisano.]

What landscape could be more sterile than a playa? Dry lake beds in desert valleys seem as devoid of life as any place on Earth. Playas are the desert boiled down to its essentials: the horizon, the sky, the occasional dust-devil dancing across the seemingly lifeless plain. But that plain isn’t really lifeless. Complex communities of organisms have evolved strategies for survival in these incomprehensibly hostile places.

Playas form in valleys that collect enough runoff to fill lakes, but not enough to keep those lakes from drying up. When a desert lake dries it leaves behind a dry lakebed, usually referred to in North American deserts by the Spanish word for beach: playa. In valleys where the ephemeral lake has some outflow – either in a surface channel, or through the soil into an aquifer – the lake will leave behind a brownish mudflat. Where water cannot flow out of the lake it leaves behind dissolved minerals when it evaporates, and the playa that forms will thus be full of those salts.

When the playa is dry its residents go into hiding. After a rain, when a bit of standing water stays on the playa’s surface for a few days, they emerge and multiply. Green algae such as Dunaliella and Dangeardinella begin to tint the water – green if the salinity is mild, reddish as the water evaporates. Other contributors to the red tint often found in saline lakes are Haloarchaea, also called “halobacteria.” Haloarchaea are not true bacteria but are rather a family within the domain Archaea, and are the main reason for the pink tinge in the salt crusts in places like Owens Lake.

After water has stood in ephemeral desert lakes for about a day and a half, the eggs of fairy shrimp begin to hatch. Fairy shrimp are crustaceans in the order Anostraca, which includes about 500 species in two dozen genera. They include brine shrimp, the “sea monkeys” sold to generations of curious children.

There are dozens of species of fairy shrimp native to ephemeral lakes in the southwest deserts. Most of them are filter feeders about a half-inch long, gathering up the halobacteria, algae, and organic detritus that may have been blown or washed onto the playa. One species, however – Branchinecta gigas, the giant fairy shrimp – has found a niche a step higher on the food chain. Growing to as long as six inches, the giant fairy shrimp preys on its smaller cousins.

Branchinecta gigas, the giant fairy shrimp.

Other crustaceans that emerge from wet playa soil include tadpole shrimp and clam shrimp, both named for their general appearance. Tadpole shrimp prey on fairy shrimp and anything else smaller than they are. Their dormant larvae can withstand several years of drought before a wet year allows them to become adults and breed. Clam shrimp can ride out long droughts too: seven years or more of desiccation isn’t enough to kill these survivors from Devonian times.

About a week after a good rain, spadefoot toads will emerge from their burrows. If the playa is of the mudflat variety rather than salty, the spadefoots head for the ephemeral lake, where the males fill the air with their odd, sheep-like calls to attract potential mates. The females lay eggs in the water, which hatch in a day or so, and the resulting tadpoles race to eat as much as they can – including algae, smaller invertebrates, organic detritus, and occasional smaller tadpoles. The tadpoles grow and develop quickly. If the standing water persists for a week, young adult frogs emerge and head uphill to dig burrows in which they can wait out the next drought. If the lake dries up in three days rather than eight, a generation of toads will perish.

With the sudden flush of new life when a playa fills with water, it’s no surprise that other creatures show up to take advantage of that bounty. Ephemeral lakes in the desert often play host to an astonishing range of birds, from the local ravens and wrens to ducks and shorebirds, to dramatic visitors such as white pelicans, sandhill cranes, and even great blue herons.

When the playa dries up, the birds leave and the spadefoots dig their holes, and the smaller organisms’ eggs and spores settle into the mud, where passing dust devils pick them up and carry them to other basins. Wherever they land, they need only a good monsoon to come to life once more. Not bad for a “lifeless” environment.