Desert Tortoises Affected by Slow Response to Climate Change

Every time thick, dark rain clouds move over the deserts that surround Las Vegas, there’s an anticipatory buzz. Flora and fauna alike begin preparing for the rare event, lying in wait for the first few drops.

Todd Esque is usually waiting for them too from his office in Henderson, Nevada. He knows how much desert life depends on their arrival. So when they do come, he’s smiling.

“People will be like, ‘Well, how are things going for you today,” Esque said. “And I’ll say, ‘I’m happy because it rained. Everybody got a drink today.'”

By everybody, Esque means the species of plants and animals he studies as a U.S. Geological Survey research ecologist.

The Ivanpah solar thermal project’s glowing towers are visible from the desert tortoise study plot. (Luke Runyon / KUNC)

On a cool December day, Esque and his research colleague Felicia Chen ventured out into a study plot south of Las Vegas on the Nevada-California border to check on one of those animals, the desert tortoise.

Few species are equipped to handle a hot and dry climate better than the desert tortoise. The ancient creature inhabits some of the harshest areas of the American Southwest. But with climate change making their home hotter and drier, and energy projects meant to limit carbon emissions springing up in the desert, the tortoises are being hit with a one-two punch.

They’re feeling the effects of climate change itself and bearing the brunt of our efforts to halt it.

The threats to tortoises are many, Esque said, while walking through the sprawling Ivanpah Valley. This stretch of prime tortoise habitat is home to solar farms, a railroad, the interstate highway between Las Vegas and Los Angeles and a few casino resorts. The futuristic-looking Ivanpah solar thermal project – with its rings of mirrors and glowing towers – is within eyeshot of the tortoise study area. A proposed cargo and freight airport is slated to be built in the valley as well.

Tortoises are listed under the Endangered Species Act, and a research plot like this is meant to give researchers insight into the best ways to help their populations rebound and provide scientific findings to decision-makers at the federal, state and local levels.

All of the known individual tortoises – 25 in this square kilometer – are tagged with radio transmitters. Chen walked through the desert scrub holding a metal antenna in the air to pick up their signal. As she approached burrows with a tagged tortoise inside, the device beeped with increasing frequency.

U.S. Geological Survey biologist Felicia Chen uses a receiver to pick up the frequency of radio-tagged desert tortoises in the Ivanpah Valley. (Luke Runyon / KUNC)

This is how tortoises spend most of their lives, a couple feet under the desert floor. They come out when it rains to drink and in the spring and fall to eat and mate. When cacti are blooming, the tortoises munch on their fuchsia-colored flowers, Chen said.

“It looks like they have lipstick on,” she said. “Their mouths will just be stained pink.”

In the study area, researchers have taken the time to mark each burrow. The holes are distinguished from burrows made by other desert wildlife, by their characteristic tortoise shell-shape, like a half moon. In the study area each is marked using a rock with a number etched into it.

“Because these are permanent study plots they all have an address,” Esque said.

“This is like 5679 Tortoise Lane? Something like that?” I asked.

“Yeah,” he said.

Because of where the Ivanpah Valley sits in the Mojave Desert, the area likely acts as a nexus for desert tortoises, Esque said. It’s a place with many entrances and exits, which allows a free flow of genes among the animals that live in other valleys.

“It’s very useful for humans as well as it is for the wildlife, and it has created some conflict in the conservation and development world where there’s people who have had to come together and make agreements on what are we going to allow in these areas.” Esque said.

That’s a short-term challenge for tortoises – figuring out how to keep them from being displaced and their habitat fractured. One strategy is to simply relocate tortoises, temporarily or permanently, to make room for massive solar arrays and other development.

A tortoise shell rests in the Mojave desert on the Nevada-California border. (Luke Runyon / KUNC)

But climate change presents an existential threat for the long term, Esque said.

“If we have hotter temperatures and less rainfall — first of all, they’re not going to get a drink as often. If we just have long droughts, we’re going to start seeing populations blink out in one valley or another,” he said.

Which tortoises have withstood before. They’ve lived on the planet for millions of years, and are incredibly resilient to climate swings. But with human infrastructure blocking their way, it could be close to impossible for tortoises to repopulate parts of the desert devastated by drought now and into the future.

Tortoises have evolved to persevere through water scarcity, Esque says. A third of their body cavity houses an auxiliary bladder, which stores water and waste. Using the bladder as storage, the tortoises can go more than a year without drinking water.

But even they have a breaking point. Short-term droughts in the Southwest over the past 20 years have caused tortoise mortality, Esque said. In the last decade, nearby Las Vegas set new records for hot and dry weather. And studies have shown the likelihood of so-called megadroughts to increase in the coming decades.

The latest review of tortoise population, published in 2018, showed that despite a concerted effort to boost their numbers, declines continue. In four out of five designated recovery areas in southern Nevada, California, Utah and northern Arizona, desert tortoise population densities dropped from 2004 to 2014.

Desert tortoises are listed as a threatened species under the Endangered Species Act, and their survival has been at the heart of a multi-million dollar effort by several federal, state and local agencies. (Luke Runyon / KUNC)

Another climate change-related problem comes from how tortoises reproduce, Esque said. Their sex is assigned based on the incubation temperature of the eggs. Too hot or too cold and you can have a whole set of baby tortoises come out as all male or all female. A warming desert could tip the biological scales.

After more than a mile of wandering, Chen located a burrow with a visible tortoise inside. Esque pulled out a small mirror to direct sunlight into the hole. Under the intense desert sun, it’s more effective than a headlamp or flashlight.

“It works like dynamite,” Esque said. “So I can see back there easily a meter.”

Chen and Esque moved aside some brush so we could get a better look.

“You can see the entire tortoise,” Chen said. “Pretty much the entire side of it.”

The adult tortoise’s shell was lodged into the burrow’s clay walls. Even with all the hubbub on the desert floor, with researchers chatting, shining lights, a journalist peering, and the constant hum of interstate traffic, the tortoise stayed still.

This one likely came out after the last rainfall 10 days before. It was the first rain this stretch of the Mojave had seen in more than 100 days.

“Once you start to learn about them and you see how harsh it is out here in the desert,” Esque said, “your appreciation just keeps growing.”

Because, he said, you get to see what they’re up against.

This story is part of a project covering the Colorado River, produced by KUNC and supported through a Walton Family Foundation grant. KUNC is solely responsible for its editorial content.

Climate Change Is Decimating Bird Populations in the Mojave Desert

LOS ANGELES – We found out last year that hotter, drier weather due to climate change is likely causing bird populations in the Mojave Desert to collapse at an alarming rate. A new study suggests one big reason why: Birds are having a hard time staying hydrated, which means they’re having a hard time staying cool.

Over the past century, temperatures in the Mojave Desert have risen about 3.5 degrees Fahrenheit, while precipitation has declined in some parts. That’s coincided with a roughly 40% decrease in the number of bird species documented there.

Adapting has been harder for some birds than others.

“Birds that required more water over the last century to cool off experienced more decline in the desert,” said Eric Riddell, postdoc in museum of vertebrate zoology at the University of California, Berkeley and co-author of the paper. “If birds had an unlimited amount of water they could probably deal with a lot more heat.”

The water requirements for desert birds are increasing as heat increases. (Courtesy of Eric Riddell at UC Berkeley )

Different species of birds get water in different ways.

Birds with primarily plant-based diets hydrate by eating seeds, some insects and by drinking from pools of water.

Primarily carnivorous birds, on the other hand, hydrate mostly by eating other animals, and don’t tend to drink from oases. The problem is that they have to hunt in order to eat, which means expending lots of energy in increasingly hot environments.

“Compared to 100 years ago, some birds needed to collect up to 60 more bugs per day just to replenish their water reserves,” Riddell said. “So that extra cost per day of having to go out and find a little more bugs and a little more bugs, we suggest has contributed to the collapse of the desert bird community.”

Larger birds with high energy demands have an even harder time. The daily grind can lead to a decline in reproductivity and premature death.

Birds like the American kestrel, prairie falcon and turkey vulture have all suffered.

The authors estimate that there’s been a roughly 10% to 30% increase in water requirements for desert birds over the past century. That need could increase by up to 80% by 2100.

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To estimate how bad things could get, the researchers created computer models of 50 different types of desert birds, all of which they subjected to increased heat due to climate change. Thirty-nine of the species declined significantly.

“For people that want to go out and see these birds, not only will they see fewer of them, but they will have much smaller windows of time when they can see them,” Riddell said. “Not only that but the conditions that make the desert hard to live and be active in for birds will also be true for humans, as well.”

A separate, larger study published earlier this month estimated that 3 billion birds have disappeared from North America in the last 50 years.

Will Arizona’s saguaros survive climate change and drought?

TUCSON – The click of container lids and swoosh of zippers filled the air on a still morning in Saguaro National Park East.

Tom Orum and his wife, Nancy Ferguson, pulled measuring equipment from the trunk of their dusty white truck, parked in a flat landscape of majestic saguaros towering over teddy bear cholla, prickly pear, woody shrubs and spiny plants.

Orum, 71, and Ferguson, 74, have visited this spot for four decades. Their job is always the same: to monitor the health of more than 600 saguaros on 60 acres of the park. They’re the third generation to measure and monitor these iconic symbols of the West since 1941, and the work has become a treasured ritual for them.

“It’s sort of like having roots yourself to get back to the same place and repeat a process year after year,” said Ferguson, a retired biologist dressed in jeans, a baseball cap, and a gray T-shirt decorated with green saguaros.

Ferguson walked past tall, ribbed cactuses, their fat arms pointing in different directions.

“The thing about saguaros is they’re noticeable individuals,” she said. “For most of us, plants are like, ‘Oh they’re all like other plants.’ But saguaros are very much individuals, and that’s something that our culture really relates to.”

But since the 1990s, she and her husband have seen what could be troubling changes in their beloved saguaro flatlands.

Saguaros in the park, scientists say, are responding to climate change and prolonged drought by reproducing less frequently. This worrisome downtick could signal the state’s saguaros are in decline.

Orum, a retired plant pathologist, remains cautiously optimistic. He believes another decade or so of scientific study is needed before scientists can be certain Arizona’s iconic saguaros are declining.

He and Ferguson are a spry couple, fast hikers, efficient at inspecting the saguaros they love. Orum measured the smaller saguaros with a carpenter’s ruler he carried in his khakis, and recorded data on taller saguaros with a 6-foot white plastic pipe he calls Charlotte. Ferguson, armed with a map on a clipboard, wrote down the new measurements on a notebook.

When they visit the park, they always hope to find young, new saguaros. If they do find one, they record its size and log its whereabouts with a compass, which they find more accurate than GPS.

They would drink a milkshake to celebrate finding the young saguaro. It’s a 65-year tradition started by Stanley Alcron, who once monitored these same plots of saguaros.

But for Orum and Ferguson, there haven’t been a lot of milkshakes recently.

Tom Orum measures a saguaro and his wife Nancy Ferguson records the measurement in Saguaro National Park. The couple has been recording measurements of saguaros in the park for nearly forty years. Their research shows not as many new saguaros are taking root, and that rising temperatures and ongoing drought may be the reason why. (Photo credit by Nicole Neri)

An uncertain future

From 1993 through 2016, Orum and Ferguson found only three new saguaros in the 60 acres they monitor in Saguaro National Park East. (There are two parts to Saguaro National Park. The eastern part was designated a national monument in 1933. An additional 25 square miles in the Tucson Mountains west of the city were added to the monument in 1961, and it was elevated to national park status in 1994.)

But a 2018 study found the problem of fewer young saguaros on both sides of the park.

Saguaro National Park biologist Don Swann and colleagues found only 70 saguaros younger than age 15 among the 10,000 saguaros surveyed in the park. The study names climate change, prolonged drought and human activity, such as cattle ranching, for the decline in young saguaros.

The results of the study are “broadly applicable to other desert areas for predicting how the saguaro and other long-lived desert species may respond to anticipated climate change,” the authors wrote.

“Some of our biggest concern does have to do with the survival of the younger saguaros with higher temperature and longer dry periods being a potential for the future,” Swann said.

Adult saguaros are well-adapted to dry conditions. Their shallow roots quickly absorb moisture from the soil and their flesh expands to store water.

But saguaros start out just a few inches tall and aren’t able to store much water. Higher temperatures cause water to evaporate more quickly from the soil, which, coupled with drought, has made it hard for new saguaros to survive, scientists say.

Saguaros seem tough, but they’re fragile. Their delicate white blossoms are pollinated by bats, insects and birds, producing fruits rich with tiny seeds. Coyotes and other animals eat the fruit, depositing the seeds in their scat. Most seeds are destroyed by drought, freezing conditions and animals. The few survivor seeds germinate beneath protective “nurse” trees and grow slowly – it can take 10 years for a saguaro to reach 1 inch. But once established, a saguaro can live 175 to 200 years, reach a height of 45 or more feet and weigh more than 2 tons.

Saguaros evolved only in the Sonoran Desert because it offers the two rainy seasons key to their survival. But the challenges posed by climate change and drought show that even a resilient desert species is vulnerable.

Arizona has experienced significant drought since 2000. A recent national study published in the Environmental Research Letters found Saguaro National Park has warmed about 1.2 degrees Celsius from 1950 to 2010.

“That’s the equivalent of moving the park over 150 kilometers (nearly 100 miles) south from Tucson to hotter areas in Mexico,” said Patrick Gonzalez, a climate scientist at the University of California, Berkeley. “Small increments of heating can translate into big changes on the ground.”

This means changes in the saguaro population, which could harm many animals that rely on the cactus for food and shelter. The saguaro is a keystone species, essential to maintaining the delicate balance of the Sonoran Desert ecosystem.

“Species in a community evolve over long periods of time, and not all the species respond equally to those changes in climate,” said Osvaldo Sala, founding director of the Global Drylands Center at Arizona State University. “They’re all very tightly connected one to the other, so that can cause unexpected consequences.”

Tom Orum shows how much a saguaro, which used to be the height of a pen, has grown in Saguaro National Park. He and his wife Nancy Ferguson update Ferguson’s mother on the cactus’s status whenever they see it, since it is her favorite. (Photo by Nicole Neri/Cronkite News)

Not alone

Saguaro National Park isn’t the only national park facing these challenges. Gonzalez and fellow climate researchers conducted the national study and found climate change is causing national parks across the country to warm twice as fast compared with the rest of the United States.

The scientists said location was the main factor causing the disproportionate temperature increases. Most national parks are in areas especially sensitive to human-caused warming, including the arctic, mountainous areas and the Southwest.

Out of Arizona’s 22 national parks, Gonzalez said, 16 have experienced significant warming.

“Our national parks have been exposed to conditions hotter and drier than the U.S. as a whole,” he said. “Climate change is certainly a major driving factor of vulnerability in the future.

Hope in the rocky slopes

Scientists are cautiously hoping saguaros will outsmart a changing climate by reproducing on rocky foothills where precious rainwater better resists evaporation.

Swann and his colleagues found a smaller decline in the number of young saguaros in these slopes compared with the flatlands. In these areas, water can get trapped in cracks or crevices and doesn’t evaporate as quickly, providing slightly better conditions for young saguaros.

“In general what we see over time is that in those rocky areas, the saguaro populations tend to be more stable,” Swann said.

Identifying and protecting these resilient areas is one way national parks can ensure species and ecosystems survive future changes. Gonzalez said Joshua Tree National Park in California already has found some success using this method to protect their namesake species.

Scientists have yet to figure out how, exactly, to protect saguaros in the park from climate change and drought. They say they need to understand more. They need to further monitor the cactuses in the rocky foothills, and they need to determine how much of the current decline is caused by climate change versus natural cycles.


— Video by Jordan Dafnis/Cronkite News

Lifelong learning

Tom Orum and Nancy Ferguson have kept watch over the saguaros on the same 60 acres of the park for nearly 40 years.

Each year, they measure the height, note scars or damages and count the number of arms on each cactus. They also identify new or dead saguaros. Their painstaking, regular monitoring of saguaros has long informed scientific knowledge of the lifespan and population trends of the species.

And they have four favorites. They found these four in 1986, when the saguaros were about 4 years old and just a half-inch tall.

“We found them when they were so small,” Orum said. “When you’ve followed them every year, you get attached to them.”

Now the tallest is 11 feet tall. It grew 8 inches in the past year.

It would sadden the couple if the cactuses were no longer there. They hinge their hopes for the species’ well-being on rain.

“We think saguaros don’t require just a single rainy season,” Ferguson said. “They need rain one summer to get going. They need rain that winter to survive the winter. Then they probably also need a second rainy season to really get established.”

In the drought-plagued 1940s and 1950s, Orum said, there was a similar decline in young saguaros. At the time, scientists weren’t sure whether the drought caused fewer young saguaros or if hungry cattle also were to blame.

But during the especially rainy years of the 1980s, Orum and Ferguson found 30 to 40 new saguaros each year across their acres.

The current decline of young saguaros in the park is not tied to cattle, so scientists figure drought is to blame.

After Orum and Ferguson retired from the University of Arizona in 2000, their love for the desert and saguaros motivated them to keep up the monitoring they’d been doing during their time at the university.

“It’s more important to us to be out here measuring cacti than figuring out how to invest our money, or lots of other things that people do with their time,” Ferguson said.

Besides, their careful scientific observation of the saguaros is key to learning the fate of the cactuses. Only monitoring will show whether saguaros decline or recover.

Orum said he and Ferguson won’t know for sure “until we’re 80 or 85 years old.”

Green lite: Tucson saves water with desert landscaping, synthetic grass

TUCSON – This used to be a city of lawns. Patches of Bermuda grass lined residential neighborhoods, kept green — even in blazing summer months — with diligent watering. Over the decades, that has changed. Most Tucson residents eschew lush lawns in favor of landscaping more in tune with the city’s desert setting — although that doesn’t necessarily mean there’s no green at all.

On a recent Friday morning, Hector Mendoza and his crew from the Artificial Grass Superstore, unfurled a patch of synthetic lawn on the driveway of a house in Oro Valley, a suburb of Tucson.

It was a little before 8 a.m., but they’d been at it for a few hours already.

“We like to start as early as possible,” Mendoza said. “Today’s going to be 109 (degrees) so we try to beat the heat as best we can.”

Over the next eight hours, his team would transform the backyard of this house from a dirt lot into an artificial green oasis.

Business these days is good, Mendoza said. Most of his customers come to him for one reason.

“Just the cost of the water and (lawn) maintenance,” he said. “We don’t foresee any cost on water going down.”

Since the 1980s, Tucson residents have replaced their green lawns with decomposed granite and opted for such plants as paloverde trees and cactuses that can endure drought and extreme heat. (Vanessa Barchfield/Arizona Public Media)

Whether or not they go the artificial route, Tucsonans have been ripping out their grass for the past four decades.

“It starts in the ’40s and ’50s, when we had a growth in Tucson, but not a lot of investment was made in infrastructure,” said Fernando Molina, a public information officer for Tucson Water.

During the 1970s, people who moved here from other parts of the country feel water stress for the first time.

“People were coming home at 4 o’clock, 5 o’clock, turning on their irrigation systems, probably doing their laundry as well,” Molina said. “Putting a big burden on the distribution system. And we simply couldn’t pump the water fast enough and deliver it to areas and meet these high demands.”

Tucson Water responded by launching a public information campaign called Beat the Peak, complete with television ads and jingles aimed at persuading residents to water their lawns less and at different points in the day.

“The original slogan was ‘Never Water Between Four and Eight,’” Molina said.

The Tucson City Council entered the fray in the late ’70s, adopting a new rate structure for water use: As people used more water, the unit cost would go up.

That move proved so unpopular all council members who voted for it were recalled. But the rate structure remains in effect today. Molina called the rate structure instrumental in nudging Tucsonans to change their landscaping.

“The desert-landscaping ethic has really taken hold here,” he said. “We are 10 years ahead of most communities in Arizona in terms of even thinking about that and 20 years ahead in terms of doing something about it.”

And that has driven down Tucson’s per capita water use from about 160 gallons per day in 1980 to just more than 120 gallons per day in 2017 — a 25 percent drop.

Pima County Master Gardeners, part of the University of Arizona’s Cooperative Extension service, is one of several organizations that promote low water-use landscaping and xeriscaping.

“The seven principles of xeriscape are common-sense things like design, using desert adapted plants, having an efficient watering system,” the program’s Eric Johnson said. “Those kinds of things that are no-brainers to longtime Tucsonans and really help to have a beautiful garden and help save a great deal of water.”

Johnson stressed that xeriscaping does not mean zero-scaping. And the Pima County Master Gardeners exists to teach residents about the desert’s rich landscaping options.

Even with no grass on the ground, landscape architect Steve Grede's home garden is an oasis of green in downtown Tucson. (Vanessa Barchfield/Arizona Public Media)

“One of the most visible ways we do that is with our demonstration garden that we have out here,” he said. “We like to think that it’s the biggest master-gardener demonstration garden in the Southwest.”

Visitors to the garden get ideas for their own yards.

“One is hesitant to be the only one on their street to take out a lawn and put in a rock and very different form of landscape,” said Steve Grede, a Tucson landscape architect.

“But in Tucson, it really took hold and it took hold in a major way,” Grede said. “So much of landscape is based on fashion.”

Although he’s an expert on desert landscaping, Grede said he “did have a very small lawn area that I stopped planting over a year ago, and I’ve just let it go totally dormant.”

His motivation for losing his lawn is closely linked to the water-rate policy implemented in the late-’70s.

“I am eager to bring my water bill down,” he said, but his reasoning went beyond his wallet. “It’s my sense of responsibility living in a desert environment. I would like to be a little bit more in harmony with this desert environment.”

This story is part of a collaborative series from the Colorado River Reporting Project at KUNC, supported by a Walton Family Foundation grant, the Mountain West News Bureau, and Elemental: Covering Sustainability, a new multimedia collaboration between public radio and TV stations in the West, supported by a grant from the Corporation for Public Broadcasting.