Reading Desert Springs From DNA: What the Sonoran Desert Network Did in Summer 2022

Water leaves a genetic trace of whatever has been in it. The National Park Service's Sonoran Desert Network (SODN) is using that trace to find out which species use the desert springs in its parks, without capturing any part of an animal. The network's summer 2022 newsletter, The Heliograph, also reported new wildlife-camera results, a faster way to survey stream channels, and a research center coming back to life. What follows describes the network's work as of that issue.

DNA from springs

At nine SODN parks, the springs crew added environmental DNA (eDNA) sampling to its regular monitoring, using methods developed partly by an international volunteer. A hand pump pushes water through a filter, and the DNA caught on it shows which species were present, without even a photograph of an animal.

Image from the National Park Service: a manual pump moves water through a filter for eDNA testing.

The results could change which springs get monitored: a spring where something important turns up may move up the list. They may help park managers rank springs for conservation by what lives there, and they add to general knowledge about which species are common where. The Chihuahuan Desert Network plans to collect eDNA at springs too, looking for the same threats (bullfrogs, chytrid fungus and ranavirus) but targeting somewhat different species.

Routine springs monitoring continued. In June the crew finished its fifth year of perennial-springs monitoring in the nine SODN parks that have springs, and fall sampling was planned for higher and then lower springs. Early data suggested that most sites had recovered from the historically dry conditions of 2020, largely thanks to a very productive 2021 monsoon, though a few springs described as perennial were still dry before the 2022 monsoon.

Cameras and the first wildlife reports

The first reports from the network's terrestrial wildlife protocol were released, for Chiricahua National Monument, Organ Pipe Cactus National Monument and the west unit of Saguaro National Park. The protocol uses images from remote cameras triggered by passing animals to track which medium and large mammals occupy an area, aiming to detect meaningful changes in communities and populations over time.

Image from the National Park Service: a collared peccary at Saguaro National Park.

In 2022 the field crew placed cameras at three park units:

Placing that many in remote backcountry takes a lot of fieldwork, with help from citizen scientists, international volunteers, university students, Tucson Audubon technicians and park interns. Several years of data will feed occupancy models that show managers how mammal populations are doing.

Image from the National Park Service: a bobcat at Chiricahua National Monument.

Drought, then super monsoon

The climate and water report for Organ Pipe Cactus National Monument for water year 2021 shows the effect of the 2020 "nonsoon," regionally one of the driest in the past century, in its perennial-springs data. The climate data show the nearly record-breaking "super monsoon" of 2021.

Surveying streams from satellites

For three weeks in May, staff from the Park Service, Rio Bravo Restoration and Mexico's National Commission of Protected Areas collected channel-shape and riparian-vegetation data along the Rio Grande at Big Bend National Park, following a big-rivers protocol from the Northern Colorado Plateau Network. SODN staff took away techniques for its own streams protocol, which had a channel-shape component but lacked tools for reliable results.

Real-Time Kinematic (RTK) surveying equipment changes that. The old total stations need a clear line of sight, which dense streamside vegetation blocks. RTK relies on satellite signals, so cover bothers it less, it is several times faster, and it gives real-world coordinates instead of positions relative to a known fixed point. It is expensive, but the Southern Arizona Office bought new RTK gear with servicewide GNSS equipment funding, trained SODN staff on it, and the network has already used it to measure channel shape and riparian vegetation at Gila Cliff Dwellings National Monument. Earlier total-station data can be used alongside the new readings.

Riparian vegetation monitoring was planned for a fourth round at Gila Cliff Dwellings in August, the third since the 2011 Miller Fire killed a high share of the park's tall cottonwood and willow trees, to follow how those communities recover.

A learning center reopens

After a quiet couple of years, the Desert Research Learning Center was hosting international volunteers and student interns again, and working with Saguaro National Park's education team on Junior Ranger programs, a hiking club, a poetry workshop and elementary school visits.

Image from the National Park Service: the Desert Research Learning Center.

Activities mostly took place outdoors. With Arizona Game and Fish, a school group helped survey the center's tinaja (rock pool) and stream to estimate its desert pupfish, speckled dace and desert sucker populations. Fifth- and sixth-grade students working with the PBS series SciGirls built small adobe test walls to compare plaster mixes, feeding the center's larger adobe-wall research, and a phenology trail around the center now feeds plant-timing records into the USA National Phenology Network.

Sources

• National Park Service, Sonoran Desert Network, The Heliograph: Summer 2022; rewritten in hubnx's own words. The newsletter's portraits of interns and staff, photographs of children, and expired event notices are left out.