Desert Bees Have a Secret: How to Survive a Decade of Drought
Acluster of leafcutter bees are foraging for nectar and pollen on an unseasonably hot May morning in Bandelier National Monument, in northern New Mexico. Tiny, with few bright markings, they don’t look like bees at first — more like dark-colored buzzy insects.
But Olivia Carril is excited to spot them on penstemon plants, whose pale purple flowers have bright magenta stripes that guide the leafcutters down their long tubes to the nectar, past the anthers for a dusting of pollen. She scoops a handful of bees into her net, then quickly transfers them to glass vials.
Until Carril, an independent scientist and co-author of a field guide to North American bees, began her survey a year ago, it was unknown how many bees were in Bandelier: Just two species had been documented in one part of the monument, which climbs from lush riparian zones to piñon-juniper foothills to alpine forests. But in just a year, she has added at least 46 species to the list.
The public often hears stories of bees at risk, with honeybees threatened by colony collapse disorder and the first U.S. mainland bee, the rusty patched bumblebee, listed as endangered in 2017. But scientists like Carril are showing that the picture is more complicated for native bees, raising a host of questions about widespread pesticide use, habitat loss, and climate change.
Desert bees have a unique set of strategies to survive harsh conditions. And bees are most diverse in arid environments the world over, suggesting their persistence during past eras of drought. Will their strategies prove sufficient in an era of anthropogenic climate change? Is there time to learn more about native bees before it’s too late?
Karen Wright documents New Mexico’s bees from the edge of the Chihuahuan Desert at the Sevilleta National Wildlife Refuge. Her study is one of the longest-running bee surveys in the world: It began in 2002 and is entering its 17th year.
Despite the critical role bees play in diverse ecosystems, huge swaths of the U.S. remain unsurveyed. Out of some 4,330 North American and Hawaiian native bee species (a quarter of them found in New Mexico), there’s sufficient data to assess only 1,437, according to the Center for Biological Diversity.
When Wright started working at the Sevilleta in 2000, she was fascinated by the dramatic changes in the plant community in response to rain and other factors. And she was curious about the many species of bees that depended on them. How were they managing to survive when the desert landscape changed so drastically from year to year?
Now the assistant curator for the Texas A&M insect collection, she has identified nearly 300 species at the Sevilleta, and she says each is unique, with different tolerances to changing conditions — “so some of the bees are more resilient than others to drought.”
She also made promising discoveries, like a mason bee endemic to the Rio Grande Valley that hadn’t been collected in nearly 100 years — she describes it as “gorgeous bright blue,” with red hair. And she has identified 11 new species in the 360-square-mile wildlife refuge, with a dozen more undescribed. As she says, “You don’t have to go to the Amazon to find new species.”
But the Sevilleta has endured a decade of drought, and Wright has also documented the disappearance of some species of bees, which she says may mean local extinction. To know for sure, she’s waiting for this drought cycle to end. And no one knows when that will be.
Most bee studies last just three years, she says — too short to show long-term trends. “These continuous long-term studies are so important for really understanding how the landscape changes, how the bees and the flowers recover after drought,” Wright says.
But by the time the long-term data is available, Wright says, climate change may be “so bad that those effects are already permanent.”
Still, she hopes her study will outlast the “the tragedy of the drought,” “so I can really tell a whole story.” With more time, “maybe I can show the beauty of the recovery and the resilience of the desert.”
Bee scientists have lots of questions about biology, diet, nesting, survival strategies … and few answers. In her survey of bees at Bandelier National Monument, Olivia Carril hopes to reveal a more complete picture by documenting the plants they visit. At a bright yellow aster, she nets a species even though she’s already collected it, because it’s visiting a different plant. “If you want to talk about the plant pollinator network,” she says, “the plant part is as important as the bee part.”
Despite two extreme wildfires in the past two decades, Carril’s data for 2017 showed bees were both abundant and diverse in burn scars. Once the tree canopy is denuded by fire, understory plants are able to take advantage of sunlight and space, and plant diversity may increase, she says. Carril says bees are opportunistic, and “flowers and bees go together.”
This year will be a test for the resilience of New Mexico’s diverse environments. Eighty percent of the state is in severe to exceptional drought, and models of climate change suggest drought intensity will increase across the state.
At Carril’s high-elevation survey site in Bandelier, the landscape changes to hummocks of grass and scattered ponderosa pines, many with bark singed black. She surveys the abundant dandelions and quickly locks on a gooseberry bush buzzing with activity. “I am about to go collect a whole bunch of bees,” she says with a laugh, and pauses a beat before swooping in with her net.
The gooseberry, dense with tiny white flowers loaded with nectar, is full of bumblebees, quick gray digger bees, mining bees, and other “generalist” bees that aren’t picky about their food. Since it’s so dry this spring, there are fewer plants in bloom, and not as many bees to catch. Still, Carril counts more than 30 in her vials at the end of the day. “If this were peak bee season and this were how many bees I got, I think I’d be pretty disappointed,” she says, “but for not seeing many flowers in bloom today, I think we’ve done remarkably well.”
The arid Southwest is one of the hotspots of bee diversity in the world, with an abundance of “specialist” species, bees that rely on just one group of plants — generally a common, widespread group like prickly pear or sunflower. Around the world, there’s a higher proportion of specialist bees in arid environments than in humid ones. But scientists don’t know why.
“One interpretation is that to survive in really hot, unpredictable parts of the desert you need to be able to be synchronized with that plant very well,” says Bob Minckley, a professor of biology at the University of Rochester. He has led long-term studies of bees in the Southwest, including those that specialize on mesquite trees, which tap into groundwater and don’t require rain to bloom.
Since their adult stage is so short, often just six weeks, specialist bees must time their emergence to coincide with the bloom of their host plants. Those flowers can be short-lived too; “plants up here seem to flash,” Carril says. In northern New Mexico, evening primrose blooms briefly in May, and cholla cactus in June and July.
One theory to explain this synchronization is that specialist bees respond to the same cues their host plants do, like moisture. Then the bee larvae or pupae, usually in ground nests, emerge in time to feed on their preferred plant. Seventy percent of native bees are ground-nesters, and the vast majority are solitary, with each female building her own nest.
Bryan Danforth, an entomologist at Cornell University, travels from his lab in upstate New York to the Southwestern desert each summer. It’s “like paradise for a bee biologist,” he says. “There’s incredible things out there that are poorly studied.”
One of his studies of desert bees aimed to replicate exposure to rainfall in a lab setting. He found that larvae of a tiny ground-nesting desert bee did emerge in response to moisture. “It’s almost like bang, you get the high humidity, you get this pattern of emergence,” he says. His study also found evidence of bet-hedging: Some larvae became adults in one year and others in following years. This may be another critical strategy for desert bees, spreading the risk of emergence to minimize loss in drought years.
Another strategy may be spending the winter underground, as thick-skinned larvae or pupae. The bee larvae are like the seeds of annual plants that remain dormant until the right time to burst forth, Danforth says, a mirror of the very plants many bees depend on.
In an era of climate change and increasing drought, specialization may provide an advantage. While generalist bees that forage on a wide range of plants seem to emerge every year, specialists may wait out the years with poor conditions and low precipitation. Since droughts are unpredictable, the specialists might be the winners, Minckley says, “because they’ll come out or not come out in the right years.”
Still, it’s extremely difficult to know how bees are doing now, much less predict how they might respond to climate change in the future. The Southwest’s last extended drought occurred in the 1950s, but there’s very little information about bee communities before then. “That’s a big problem,” Minckley says. There’s very little baseline data, he says, and bee populations naturally fluctuate from year to year. “To see a downward trend would take a lot of sampling” and a lot of effort.
That’s one reason studies like Carril’s and Wright’s are important. Carril says she’s optimistic about bees’ responses to climate change. “It makes me really curious,” she says. “One thing I know about bees is they like dry and hot.”
Bryan Danforth acknowledges the remarkable adaptations of desert bees to unpredictability in their environment. But with climate change, “these bees are going to be pushed to their limits in terms of their ability to survive.”
At Carril’s high-elevation site, another gooseberry bush attracts a varied collection of bees nosing in its flowers. Carril wonders whether the charred stump next to it could be a home for a cavity-nesting bee. “If it’s too burned,” she says, “it’s probably disintegrating inside, probably not the best bee habitat.”
Suddenly a little black bee zooms down to the hole and disappears inside, then zips back out. Carril gasps in surprise, “Did you see that?”
A resourceful bee is making her nest in the blackened stump after all. Carril sits nearby, patiently waiting for the bee to return. “I’m gonna get comfortable,” she says. “This is worth it.”
Sara Van Note is an educator, writer, and audio producer based in New Mexico. She’s inspired by birdsong and accents, and fascinated by stories of resistance and resilience. She has also reported for PRI’s “The World,” NPR’s “Latino USA,” and The Christian Science Monitor.
Disclosure: Van Note is a part-time employee at the University of New Mexico School of Law; an unrelated department at the university supports Karen Wright’s bee survey in the Sevilleta National Wildlife Refuge.
In response to the concern about destructive sampling of bees (where bees are killed as a result of a study, which as pointed out in another comment, is necessary in many cases for identification), please see the study “The effect of repeated, lethal sampling on wild bee abundance and diversity”:
“We found that the standardized method for sampling bees, with specimens from 132 morphospecies, did not affect bee communities in terms of abundance, rarefied richness, evenness, or functional group composition. Thus, our results indicate that the bee communities we sampled are robust to such sampling efforts, despite removing an average of 2,862 bees per season.”
(PDF) The effect of repeated, lethal sampling on wild bee abundance and diversity. Available from: https://www.researchgate.net/publication/273890315_The_effect_of_repeated_lethal_sampling_on_wild_bee_abundance_and_diversity [accessed Jul 09 2018].
An interesting article.
In response to Stephen Buhner, it is often necessary to collect bees to make an identification.
I have written on this topic before in some of my many books. As usual this article, while highlighting a number of important points, misses the crucial one: researchers such as this one, often studying endangered bees, don’t “collect” bees, they kill them. The bee that had not been “collected” for 100 years . . . well, it won’t be doing any more pollinating, will it? The idea that someone “loves” bees and then kills them to promote the understanding and health of bees in complex ecosystems is, well, stupid. I am far from anti-science (which is the usual response to my point here) but i am very much an opponent of the behavior of many scientists. The number of researchers who damage complex ecosystems in their pursuits, adding by those actions to the problems they are studying, is very high. It is one of the severe problems within the scientific community (which comes from Francis Bacon) that nature must be “tortured” (Bacon’s word) to give up its secrets, further, that only by dissection can nature or its parts be understood. A holistic approach instead would use observation and photographs and long years of it instead, would approach with humility, and take as an axiom Aldo Leopold’s point: The first rule of intelligent tinkering is to save all the parts. When we approach nature in an attempt to understand it, we are approaching an organism some 4.5 billion years old. We are an organism some 100,000 years old (in our current form). We are embedded in an ecological, nonlinear, complex scenario, we in fact emerged as an expression of it. Such simple cut and dried reductive science as represented in this article and the researcher’s approach is in fact one of the great problems we face as a species. It is the source of a great many of the ecological problems we face and many innovations such scientists devise are in fact only responses to problems that their compatriots created in the first place. Simplistically, as an example, other scientists created the pesticides (based on reductive reasoning) that are one of the causes of bee declines across the world which bee scientists are studying and suggesting solutions for.
Thank you for this captivating piece of primary research in ecology ! In an era where the pursuit of investigative science is denigrated as irrelevant, when it is compared to the prevailing interest in research for strategic weapons and the development of new, expendable products and ‘improved’ business strategies for merchandising them, we can see how skewed human values have become. We have eclipsed the vital components in exchange for the various forms of distractions that can only yield temporary, competitive pursuits that feed egos, bank accounts, and political power drives. The restlessness we now see throughout modern human populations is related to this skewed pursuit. Just two days spent outdoors with a magnifying glass, binoculars, and a couple of identification books for plants, insects and birds, can reawaken our latent appreciation of how interdependent are all forms of Life, and how primary is the need to protect it through seeing for ourselves the beauty and vital role each component plays, and the importance of the surrounding matrix in which it is either nurtured or starved of what it needs for survival.
As a biology major, I discovered the world’s greatest treasures through the study of ecological relationships because it brought together all the sciences with the intent of gaining an understanding of the primary relationships seen out in the bush and in other natural biomes which support, not just humans, but all forms of existence. Valuing the complex Web of Life, from what is known to the inviting edges of the unknown, revivifies Life for the patient investigator with their senses alive to take it in. It can encompass the full range of involvement, from one’s backyard curiosity, all the way through intense academic studies with a particular focus. All of it is worthy. With an awakened appreciation of the dynamics involved in complex systems, it becomes obvious that we must protect the atmosphere that surrounds it and come to understand the role of climate change; experience the seas and the hazards of how plastics and toxic runoff are now decimating populations of living things unable to survive it; see how the pristine fresh water sources are being deeply polluted by industrial feedlots of hoofed animals, and battery caged chickens, and coal tailings and other industrial waste that is casually dumped within it by the increasingly blind policies of our regulatory agencies.
All of this reflects the call for revolutionary action toward a much deeper recognition of our responsibility in an environment that is rapidly being decimated.
It is a call for reorienting our spiritual perspectives toward a celebration of what this planet so remarkably provides all forms of Life, and that we as stewards are charged to protect it.
The Key Values of TRUTH, BEAUTY AND SCIENCE – Along with CURIOSITY
Thank you for the reminder.
Comment after studying ?
You all are awesome, the New Mexico Beekeepers Association is fantastic and they reach across the state even down to El Paso. It has been challenging getting bees through the winter, this past one particularly. Its my belief that these warm dry winters are causing bees to leave the hives more often in search of food, causing winter cluster size deterioration. The less bees clustering the more difficult it is to keep warm and therefore the winter lifecycle of the bees is skewed. We had numerous days above 50 degrees over the winter and the bees seemed as confused as their keeper. On a side note, I saw the most beautiful wildflowers I have ever seen in the Gila National Forest, in the middle of the largest charred landscape i have seen. It was amazing.
I had 4 hives and lost them all last winter. One honey still in the comb but some kind of mold. Another had honey in the comb but the bees had all vanished…I had last inspected in the fall preferring to not harvest 12 frames honey and leave it for the bees…gone, simply gone. The other with honey still in the comb was full with dead bees. Still stumped by this. Will begin again next year. Any thoughts?
Really appreciate this effort. In just south of SANTA Fe, NM & am very concerned about the loss in bee populations. In last six years have seen a huge decline in bee population in this area. Keep up the great work.