Watching Desert Springs and Ice Age Fossils in the Mojave

Based on the spring 2022 issue of The Oasis, the twice-yearly newsletter of the National Park Service's Mojave Desert Network Inventory and Monitoring Program.

Desert springs

Springs form where groundwater reaches the surface. Compared with the desert around them, springs and wetlands in the Mojave and Great Basin support far more plant and animal life, in greater variety. They also face threats from climate change, drought and land use.

The Mojave Desert Network (MOJN) monitors the health of nearly 240 desert springs in five parks: Death Valley, Joshua Tree, Lake Mead, Mojave and Parashant. To help managers make decisions, the monitoring asks two questions:

1. Is water availability at the springs changing over time?
2. Is water quality at the springs changing over time?

That winter the network published a project overview brief on the work, and its Desert Springs Monitoring web page links to two videos about it.

Hydrology assistants check that a spring's flume, a channel that lets water height be converted to flow, and its gaging station stay level over time. Image from the National Park Service's page.

Field work at the springs includes leveling the flumes, and sampling aquatic invertebrates by sliding a long net along the bottom of a spring's source pool, then sifting and sorting what it catches.

Ice Age fossils at Tule Springs

By Lauren Parry, Park Guide, Tule Springs Fossil Beds National Monument.

Desert wetlands and springs have long been part of the Mojave, and they signal climatic and ecological change. The Pleistocene (Ice Age) sediments of Tule Springs Fossil Beds National Monument record desert wetlands expanding and shrinking over roughly the last 570,000 years.

Those wetlands supported a varied ecosystem, including Columbian mammoths, horses, bison, camels, giant ground sloths and saber-toothed cats, all now extinct. The cause of that extinction is still being studied, but many animals survived, among them coyotes, jackrabbits, hawks, badgers and kangaroo rats.

A fossil ram's horn snail (Planorbella sp.), in place for thousands of years. NPS/Lauren Parry.

Fossil snails are evidence of a wetter past, and monitors record them to help reconstruct past environments. Ram's horn snails still live in Mojave wetlands today, grazing on algae. Scientists study modern springs, including the sediments that collect in them, the animals that live in them, and how fossil pollen compares with living water-loving plants, to understand the Ice Age wetlands here. Years of analysis of Tule Springs' rock and fossil records have found a strong link between global climate change and spring activity. But these records are highly vulnerable to natural and human threats.

Left: paleontological monitor Lauren Parry applies a specialized glue to a fossil vertebra. Right: the same vertebra in 2020 (top) and 2021 (bottom), showing a year's erosion of the sediment around it. NPS/Lauren Parry.

Monitoring instead of collecting. The monument's paleontological site monitoring program revisits known fossil sites to check fossil condition, natural erosion and human disturbance. Wind, water and hot sun wear away fragile fossils and crumble the soft sediment. With more than 670 known fossil sites, Tule Springs is the largest open-air Ice Age fossil site in North America, so leaving fossils where they lie is the practical choice. Each site is given a low, medium or high priority, which sets how often a monitor visits.

Excavation is rare there today, but the program also protects intact historic excavation sites from the 1930s and '60s. Especially vulnerable to vandalism and erosion, they are checked every quarter by volunteer paleontology site stewards.

Also in the issue

• Training. The Inventory and Monitoring Division held a virtual Scientists' Training from January 24 to February 17, 2022, now recorded for NPS staff. MOJN data scientist Sarah Wright helped lead a two-week course in the R programming language, and physical scientist Jennifer Bailard spoke on publishing datasets with the new data release report template in R Markdown. Other sessions covered using monitoring science in park decisions, decision-making tools, climate-smart conservation and water balance, and GIS.
• Seasonal work. Four new interns joined for bat and vegetation monitoring, including acoustic bat monitoring, white-nose syndrome surveillance, and upland, spring, white pine and aspen vegetation monitoring. Two hydrology assistants on the springs projects, Emma Kaufman and Evan Kolb, moved on.

Sources

• National Park Service, Mojave Desert Network Inventory and Monitoring Program, "The Oasis Newsletter: Spring 2022," prepared by Linda Mutch and Lise Grace: https://www.nps.gov/articles/000/the-oasis-newsletter_spring2022.htm
• Desert Springs Monitoring: https://www.nps.gov/im/mojn/desert-springs.htm · project brief: https://irma.nps.gov/DataStore/DownloadFile/668353
• The newsletter's logos, report cover, meeting screenshots and staff portraits, and its 2022 field schedule, are not reproduced.