Collectors find plenty of bees but far fewer species than in the 1950s

Far fewer bee species are buzzing across Earth today, following a steep decline in bee diversity during the last three decades, according to an analysis of bee collections and observations going back a century.  

About half as many bee species are turning up in current collecting efforts for museums and other collections compared with in the 1950s, when surveys counted around 1,900 species a year, scientists report December 10 at That high diversity in collections endured for several decades, but then began to plummet around the 1990s, likely reflecting a real drop in global bee diversity, according to the study, which is under peer review. 

“This is the first study suggesting that bee decline is a global process, and that the most significant changes have occurred in recent years,” says Margarita López-Uribe, a bee evolutionary ecologist at Penn State who was not part of the new research. 

The new work evaluates global trends in bee diversity since the 1920s by tapping the database of the Global Biodiversity Information Facility. This international data-sharing network holds what López-Uribe describes as “the most comprehensive dataset of insect collection records worldwide,” including photos of bees in the field and of museum specimens dating back to the 18th century. Previous bee studies have reported falling populations, but evidence has often been limited to Europe and North America. Numbers of western honeybees (Apis mellifera) have been decreasing in North America and Europe (SN: 6/20/19), for example, but have increased in Asia, Africa and South America. For bees overall, though, the global situation was unclear.

Eduardo Zattara and Marcelo Aizen of the Pollination Ecology Group at the Biodiversity and Environment Research Institute in Rio Negro, Argentina, found that the number of instances of observing bees has climbed in recent decades, probably due to more researchers going into the field to document and study bees. 

But the number of observed species fell. In the 1950s, collectors added about 22,000 bee records per year, of about 1,900 species each year, for a global total of 5,600 species collected over the whole decade. After correcting for sampling effort, the researchers estimate that about 6,700 species would have been found in the wild. In the 2010s, collectors tallied an average of 860 species per year from an average of more than 37,000 observations per year, leading to an estimate of only about 3,400 species to be found worldwide in the wild.

ground nesting bee
This ground nesting bee (Pseudapis siamensis) native to Southeast Asia is among the bee species losing habitat due to urbanization and agriculture.Varat Sivayyapram

Declines in the number of species occurred on nearly every continent, starting at various points in the last four decades but largely in the 1990s on most continents. One exception was Australia and nearby islands, where the number of bee species estimated from observations spiked from about 300 to 500 in the 2000s. But species numbers in that region dropped back to 300 in the 2010s. Globally, thousands of bee species have become so rare that they are difficult to find or have gone extinct. 

These findings should convince people that bee diversity losses are not confined to specific regions, but “part of larger, worldwide trend,” says Zattara, who is now a visiting scientist at the Smithsonian National Museum of Natural History in Washington, D.C.

While the study provides an “invaluable” overview, the dataset is surely missing important insect collections from Asia, says bee biologist Natapot Warrit of Chulalongkorn University in Bangkok. He hopes the study encourages other researchers in the region to study and share data on pollinators. 

Bees and other insects such as butterflies and flies pollinate more than 75 percent of the most important crop types grown today, scientists say. But these pollinators face multiple threats including the expansion of monoculture crop cultivation, pesticides (SN: 1/17/18), climate change (SN: 9/24/15) and pathogens that can spread with the international bee trade (SN: 1/18/19). Researchers also have suggested bees may be at risk from power lines (SN: 11/12/19).

While their study reveals an ongoing “major global collapse in bee diversity,” the researchers aren’t trying to sound “gloomy or apocalyptic,” Zattara says. Rather, they hope the study prompts other scientists, policy makers and business leaders take action to reverse the decline.

Ancient kids’ DNA reveals new insights into how Africa was populated

Four ancient youngsters, one pair from around 8,000 years ago and another from about 3,000 years ago, have opened a window on humankind’s far older, far-flung African origins. 

Analyses of the west-central African children’s DNA indicate that at least three major human lineages —ancestral to either today’s central African hunter-gatherers, southern African hunter-gatherers or all other present-day people — genetically diverged from each other in rapid succession between roughly 250,000 and 200,000 years ago. 

A fourth, previously unknown human population also emerged in that time span and left a small genetic mark on modern western and eastern Africans, a team led by evolutionary geneticists Mark Lipson and David Reich, both of Harvard Medical School, reports online January 22 in Nature. That human line possessed a small amount of DNA from hominid populations that had originated before the rise of the human species, possibly Neandertals.

“This quadruple radiation [of human lineages] had not been identified before from DNA,” Reich says.

That genetic evidence from the long-dead kids fits a scenario in which different Homo sapiens populations emerged in different parts of Africa as early as around 300,000 years ago, followed by a mixing and mingling of populations across the continent (SN: 9/28/17).

A previous genetic study, led by evolutionary geneticist Pontus Skoglund of the Francis Crick Institute in London, identified a human population originating more than 200,000 years ago that was ancestral to later rainforest hunter-gatherer groups in western and central sub-Saharan Africa. The new study provides further evidence for that ancestral line: Ancient children in the new study carried a minority of ancestry from those ancient forerunners of rainforest groups.

Genetic data in the new study provide “the only ancient DNA record from so far west in sub-Saharan Africa,” Skoglund says.

Lipson’s group extracted DNA from four children buried at Shum Laka, a rock-shelter in northwestern Cameroon. Excavations there in the 1980s and 1990s yielded stone tools and other artifacts from hunter-gatherers spanning the last 30,000 years. The site also served as a cemetery for extended families. A total of 18 human skeletons, most from children, have been unearthed at Shum Laka. Some burials date to about 8,000 years ago, others to around 3,000 years ago.

excavation site
A 1994 excavation at a rock-shelter in Cameroon uncovered the skeletons of two boys buried around 8,000 years ago. DNA from these and other finds suggests that human populations in several parts of Africa genetically split from each other more than 200,000 years ago.Isabelle Ribot

The four Shum Laka children who yielded DNA — three boys and a girl — ranged in age at the time of death from around 4 to 15 years old.

Based on linguistic and archaeological evidence, researchers generally consider the region of Cameroon that includes Shum Laka to have been the place where Bantu languages, spoken by many Africans today, originated and spread across the continent’s southern half after around 4,000 years ago. The Bantu expansion is thought to explain why the majority of people in that swath of Africa now display close genetic connections.

Intriguingly, current Bantu speakers are not closely related to the Shum Laka children, the researchers say. The ancient kids inherited about two-thirds of their DNA from a previously unknown population distantly related to present-day West Africans. The rest of the genetic material came from the lineage outlined in the earlier Skoglund-led study that was ancestral to hunter-gatherers now living in central Africa. Present-day central African hunter-gatherers have a different ancestry from most Bantu speakers today. 

As a result, Bantu speakers across Africa likely didn’t descend from the ancient Shum Laka population, the researchers say. But other human groups could have lived in west-central Africa around the same time, including some who conversed in early Bantu tongues, Lipson and his colleagues speculate.

Another provocative new discovery concerns one of the Shum Laka youngsters, an adolescent male buried around 8,000 years ago. That boy possessed a rare set of Y chromosome gene variants, which are passed from father to son. It’s the first known ancient DNA from this unusually old paternal lineage. Today, this particular paternal lineage is found almost nowhere outside of two ethnic groups in western Cameroon today. Previous research suggests this male genetic line dates back to between 200,000 and 300,000 years ago, making it the oldest one known. It’s unclear why only one of the three ancient African boys in the new study came from that ancient male line of descent.

Fed by human-caused erosion, many river deltas are growing

River deltas, the fans of
sediment sweeping out from the mouths of rivers, are gaining ground.

Globally, delta land area increased by 54 square kilometers per year from 1985 to 2015,
scientists report January 23 in Nature.
A quarter of that gain is due to deforestation freeing soil from the grip of
tree roots, allowing rivers to carry more of it downstream.

Geomorphologist Jaap
Nienhuis of Utrecht University in the Netherlands and his colleagues examined
10,848 deltas to quantify humans’ impact. Three primary forces shape deltas:
rivers delivering sediment; tides pushing or pulling sediment; and waves
redistributing sediment along the coast. Humans exert a lot of control over how
much sediment a river carries: While deforestation feeds the flow of soil, dams
plug it up.

First, the team predicted
how delta shape would change over 30 years in a world without significant human
influence. It then compared those predictions to actual land area.

On balance, land gains due
to deforestation exceeded losses due to damming, the team found. In about 1,500
deltas, soil erosion due to deforestation increased sediment loads by more than
50 percent. Those changes were greatest among deltas in South Asia, Southeast
Asia and East Asia, where 57 percent of the new delta land area appeared over
the 30-year period.

Dams reduced
sediment supply by more than 50 percent in 970 other deltas. North America was
the only continent to show a net loss of delta area, partly due to damming
along the Mississippi River (SN: 4/4/18).

These gains and losses
occurred despite rising seas. But
much of the new delta area probably will be submerged by 2100, the team notes (SN: 9/25/19). Planned new dams and sand
mining for construction are likely to further erode land gains.

Stress turns hair gray by triggering the body’s fight-or-flight response

It turns out stress does turn hair gray, and now researchers know how.

Stress triggers the body’s fight-or-flight response, which in turn causes pigment-producing cells that give hair its color to go into a frenzy and dwindle in number, researchers report online January 22 in Nature. As these pigment cells disappear, so does the color.   

Gray hair has been linked to stress for centuries — think of U.S. presidents before and after holding office. But scientists didn’t understand how stress makes hair go gray. 

“It was satisfying to question a popular assumption … [and] to identify the mechanisms that now open up new areas of work,” says Ya-Chieh Hsu, a stem cell biologist at Harvard University. 

Hsu and her colleagues stressed mice by injecting them with a compound closely related to capsaicin, the active ingredient in chili peppers. Within five days, the rodents’ hair turned white. After eliminating the immune system and the stress hormone cortisol as causes of the color change, the team discovered that part of the animals’ nervous system was depleting pigment cells from hair. 

In hair follicles, cells called melanocyte stem cells color hair by converting into pigment-producing cells. The body can’t replenish the stem cells, so as these cells are used up, color vanishes. Sensory stress triggered a mouse’s sympathetic nervous system — which controls the body’s fight-or-flight response to stress — to release the neurotransmitter norepinephrine, the team found. That compound overactivates the reservoir of stem cells, setting off a flurry of conversion into pigment-producing cells. That, in turn, rapidly uses up the stem cells supply. 

It’s unclear why stress makes hair gray — an event also typically tied to getting older. But the work raises questions about whether stress-related graying is the same as aging, and lays the foundation for exploring other ways that stress affects the body (SN: 1/11/16), the researchers say. 

Phosphorus, a key ingredient of life, has been found in a newborn star system

For the first time, phosphorus, a key ingredient of life, has
been pinpointed in a cloud of gas and dust surrounding a newborn star.

Astronomers spotted a bright infant star shooting powerful jets of energy that created cavities in the gas and dust cocoon from which it formed. Different types of molecules in the cloud, including two simple phosphorus-bearing ones — phosphorus monoxide and phosphorus mononitride — were detected along the cavities’ walls, researchers report in the February Monthly Notices of the Royal Astronomical Society. Ultraviolet radiation from the newborn star helped form these molecules, the team suspects.

“Essentially, the young star is digging away at its natal
cloud,” says Maria Drozdovskaya, an astrochemist at the University of Bern in
Switzerland. Though phosphorus has been spotted around young stars before, its
exact location had never been pinpointed, Drozdovskaya says. Her team showed
that phosphorus monoxide dominated the dust regions closest to the infant

Molecules of phosphorus monoxide were also detected in a
comet in our solar system, the team reports, helping link faraway star-forming
regions where the molecules are created all the way to our part of the galaxy.

The findings add to evidence that comets may have helped deliver
phosphorus, which is essential to DNA and many key organic chemicals, to the
early Earth.

Observations of the young star were made using the Atacama Large
Millimeter/submillimeter Array,
or ALMA, an enormous collection
of radio dishes in Chile’s Atacama Desert. With its high-resolution instruments, ALMA was able to look in
detail at the star, found in a star-forming region known as AFGL 5142 located about
7,000 light-years away from Earth.

phosphorus in the earliest phases of a star’s life doesn’t necessarily mean it sticks around for long enough to
become incorporated into planets. So the researchers turned to evidence closer
to home, taking a second look at data from the European Space Agency’s now-defunct
Rosetta spacecraft, which studied
the comet 67P
/Churyumov-Gerasimenko from 2014 to 2016 (SN: 8/6/14).

are thought to
be pristine relics from the solar system’s past. Rosetta had already detected phosphorus as well as the simplest
amino acid glycine

in the atmosphere of comet
67P (SN: 5/27/16). But clued in by the presence of
phosphorus monoxide in the protostellar cloud, the spacecraft’s scientists looked
at their data again and found that phosphorus monoxide was the main form of
phosphorus in the icy body.

“It’s clearly telling us that comets contain the ingredients
of life in their most basic form,” Drozdovskaya says.

Though essential for life, most of the phosphorus on Earth
is locked up in minerals in its crust. Organisms tend to get the amount they
need through their diet. Phosphorus
monoxide, however,
has the advantage of being soluble in water, making it far more biologically
available than phosphorus locked in minerals, says study coauthor Víctor Rivilla
of the Arcetri Astrophysical Observatory in Florence. If comets delivered
phosphorus to the young Earth in the form of phosphorus monoxide, perhaps that helps
explain how early life was able to access the element.

It’s still unclear exactly how the phosphorus molecules were
created or if comets actually delivered them to Earth. “As much as we’re making
enormous progress — and this paper is an example of that — there are still
these giant gaps,” says George Cody, a geochemist at the Carnegie Institution
for Science in Washington, D.C., who was not involved in the work.

A sample return mission that collects ice from a comet and brings
it to terrestrial laboratories would allow scientists to do much more detailed
analyses of such simple molecules and perhaps start to fill in a few details,
he says. While missions are under way to retrieve
samples from asteroids
(SN: 1/15/19),
NASA’s most recent comet sample–retrieval proposal, the Comet Astrobiology Exploration Sample Return
(CAESAR), was not selected in the agency’s last round of funding.