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Not All Hydropower Is Climate Considerate Annie Sneed | December 13, 2019
Solar. Wind. Hydropower. These renewable energy sources are all much better for the climate than fossil fuels, right? Well, yes for wind and solar. But it turns out that the picture for hydropower is more complicated than we think.
A new study by the Environmental Defense Fund analyzed the climate impacts of 1,500 hydropower facilities across the globe. That accounts for about half of hydropower generation worldwide. The researchers looked at whether the facilities behave as a greenhouse gas sink or as a source. To figure this out, they investigated all the different components that help determine a hydropower facility’s greenhouse gas emissions.
“There are so many factors that contribute to greenhouse gas emissions from hydropower—but essentially the majority of greenhouse gas emissions arise from the reservoir itself, as vegetation and soils are submerged underwater in the dam that is used for the hydropower generation.”
Ilissa Ocko, a senior climate scientist at the Environmental Defense Fund and co-author of the study. As the submerged vegetation decays, it releases methane or CO2.
“The larger the surface area of the reservoir, the more greenhouse gases are going to be emitted from that reservoir. Also the temperature plays a role as well—how warm the reservoir is will affect how much greenhouse gases are produced and emitted from the reservoir.”
Through their analysis, Ocko and her co-author Steven Hamburg, also with the Environmental Defense Fund, discovered that the climate impacts of hydropower run the gamut. The good news is that some facilities perform just as well as wind and solar. But shockingly, more than 100 facilities are actually worse for the climate than fossil fuels. The study is in the journal Environmental Science & Technology. [Ilissa B. Ocko and Steven P. Hamburg, Climate Impacts of Hydropower: Enormous Differences among Facilities and over Time]
This finding doesn’t mean we should forget about hydropower.
“But we just need to be careful to make sure that we have climate benefits…there are a lot of situations where hydropower can be on par with wind and solar. So it really depends on the specific facility.”
Source: Scientific American https://www.scientificamerican.com/podcast/episode/not-all-hydropower-is-climate-considerate/ [Rephrase 1, 02:33]
Why some whales are giants and others are just big Jonathan Lambert | December 12, 2019
[Time 2] Sophisticated sensors suction-cupped onto the backs of whales are helping biologists answer two long-standing questions: Why are whales so big? And why aren’t they bigger?
Being big in general boosts whales’ ability to reach more food for less effort, helping them exploit the riches of the deep sea that are beyond the reach of many other creatures. By estimating the energy used — and gained — when foraging for 13 species of whales and porpoises, scientists have shown that how big the creatures get is influenced by feeding strategy and prey availability.
The sizes of toothed whales like orcas, which use echolocation to hunt for individual prey, appear to be constrained by how much food they can grab during a dive, researchers report. That’s not the case, however, for blue whales and other filter feeders, which tend to be much larger than their toothed cousins. Filter feeders alive today aren’t constrained by food availability, which may mean they might be limited by their biology. Or the animals could be on their way to evolving to be even bigger, according to a study in the Dec. 13 Science.
“This is a fascinating study,” says Samantha Price, an evolutionary biologist at Clemson University in South Carolina who wasn’t involved in the research. Biologists have been thinking about the evolution of bigness for a long time, she says, “but this paper, through incredible effort, actually got some data about these hard-to-study behaviors.”
In the last 5 million years, whales have become larger than ever before, and the blue whale grew into the largest known creature in the history of life, says Jeremy Goldbogen, a comparative physiologist at Stanford University. Changes in glacial cycles, wind and ocean currents, he says, have intensified upwellings of nutrients in special pockets of the ocean, creating sparse, but absurdly dense patches of tiny crustaceans and fish and other animals — whale food. [311 words]
[Time 3] Being large has helped whales exploit these food bonanzas in a few ways. Bigger creatures can travel farther using less energy per unit of mass, helping whales cross wide swaths of barren ocean to reach upwellings. Larger bodies also support larger lungs, buying bigger whales more time to feed during dives.
Simply put, bigger whales were thought to be more efficient at finding food, Goldbogen says. But without a detailed accounting of energy gained from food versus energy expended from diving and hunting, this idea had remained mostly speculative, he says. “We just didn’t know much about what these animals were actually doing underwater.”
So Goldbogen and a team of international researchers enlisted the help of technology-packed sensors, temporarily affixed via suction cup to the backs of more than 100 individuals from 13 species of cetaceans. Over a decade, the team tracked more than 10,000 feeding events of creatures as small as 50-kilogram harbor porpoises to 150,000-kilogram blue whales. “It was no small task,” Goldbogen says.
The tags, which housed pressure sensors, accelerometers, hydrophones and cameras, relayed a daily diary for the whales. The researchers could tell when filter-feeding giants opened their mouths to lunge at swarms of krill, or when sperm whales echolocated an octopus. All together, these data allowed the researchers to estimate how much energy different types of whales expend per dive.
Those tags were combined with sonar readings of prey density, as well as stomach dissections of stranded whales, to paint a detailed picture of different whale diets. That allowed the researchers to calculate an energy budget for each species. In other words, the team could estimate how much of a caloric bang a whale gets for its exertion buck, revealing the relationship between foraging efficiency and size. [292 words]
[Time 4] Toothed whales, like the titular sperm whale of Moby Dick, use echolocation to hunt for individual prey, usually squid or octopus (SN: 8/5/16). The researchers found that being big helps these creatures dive deeper and access these higher-calorie prey. But after a point, these whales’ foraging efficiency wanes with increased size. While every once in a while, they might find a giant squid — a big energy payoff — there just isn’t enough such prey in the ocean for the whales to get any bigger, given the energy needed to dive and hunt, Goldbogen says.
In contrast, bulk filter feeders, which target dense aggregations of tiny krill and other crustaceans, only get more efficient with size. The whales get a huge infusion of calories — calculations suggest more than 10 million calories, Goldbogen says — from a single gulp, which takes comparatively less effort than chasing down a squid. Rather than being limited by a lack of prey, blue whales and other filter-feeding whales may instead be limited by their biology, though the study wasn’t designed to determine what that physical limit might be. It may not be possible physically to engulf more krill than the animals currently do.
Alternatively, the size of these ocean giants might not be limited at all. The creatures could be on their evolutionary way to becoming even bigger, as long as populations of krill stay abundant. “Perhaps, millions of years from now, we’ll see even bigger ocean giants,” Goldbogen says. [242 words]
Source: Science News https://www.sciencenews.org/article/why-some-whales-are-giants-others-are-just-big
A biochemist’s extraction of data from honey honors her beekeeper father Tina Hesman Saey | December 13, 2019
[Time 5] WASHINGTON — One scientist’s sweet tribute to her father may one day give beekeepers clues about their colonies’ health, as well as help warn others when crop diseases or pollen allergies are about to strike.
Those are all possible applications that biochemistry researcher Rocío Cornero of George Mason University in Fairfax, Va., sees for her work on examining proteins in honey. Cornero described her unpublished work December 9 at the annual joint meeting of the American Society for Cell Biology and the European Molecular Biology Organization.
Amateur beekeepers often don’t understand what is stressing bees in their hives, whether lack of water, starvation or infection with pathogens, says Cornero, whose father kept bees before his death earlier this year. “What we see in the honey can tell us a story about the health of that colony,” she says.
Bees are like miniature scientists that fly and sample a wide variety of environmental conditions, says cell biologist Lance Liotta, Cornero’s mentor at George Mason. As bees digest pollen, soil and water, bits of proteins from other organisms, including fungi, bacteria and viruses also end up in the insects’ stomachs. Honey, in turn, is basically bee vomit, Liotta says, and contains a record of virtually everything the bee came in contact with, as well as proteins from the bees themselves.
“The information archive in honey is unbelievable,” Liotta says. But until now, scientists have had a hard time studying proteins in honey. “It’s so gooey and sticky and hard to work with,” he says. Sugars in honey gum up lab equipment usually used to isolate proteins.
So Cornero developed a method to pull peptides — bits of proteins — out of honey using nanoparticles — a feat no other researchers have previously managed, Liotta says. Once extracted from the honey, the peptides are analyzed by mass spectrometry to determine the order of amino acids that make up each fragment of protein. Those peptides are then compared with a database of proteins to determine which organisms produced the honey proteins. [333 words]
[Time 6] A group of high school students working at George Mason for the summer collected 13 honey samples from Virginia, Maryland. Two additional samples came from Cornero’s hometown of Mar del Plata in Argentina. The Argentine honey was from the last batches her father collected from his bees.
Proteins from bees, microbes and a wide variety of plants were among the components of the honey. Peptides in honey from one sample came from several bacteria, including some that normally live in bees’ guts and a few disease-causing varieties. Proteins from viruses and parasites that infect bees, including deformed wing virus and Varroa mites, which have been implicated in colony collapse disorder, were also found in the sample. Those results could mean bees from that location may have trouble surviving the winter when the insects’ immune systems are less able to fight infections.
Cornero also determined by looking at pollen and plant proteins in the honey that bees had pollinated a variety of plants, including sunflowers, lilacs, olive trees, red clover, potatoes and tomatoes. By analyzing pollen peptides, scientists may one day be able to learn whether claims that certain honey is made from wildflowers, clover or orange blossoms are really true.
What’s more, counting pollen peptides in local hives could, for example, give allergy sufferers a better idea of when hay fever is likely to flare in their area, Cornero says. The researchers also found plant virus proteins in the honey, an indication of the types of diseases that may be stalking local crops.
Next, Cornero hopes to develop a rapid protein test that would allow beekeepers to plunge a dipstick into honey and rapidly gauge their hives’ health. “Having my dad as a beekeeper, I know how beekeepers work, and it would be a great way to honor his work,” she says. [302 words]
Source: Science News https://www.sciencenews.org/article/biochemists-extraction-data-honey-honors-her-beekeeper-father
Frankincense trees—of biblical lore—are being tapped out for essential oils Rachel Fobar | December 13, 2019
[Paraphrase 7] On a starlit night long ago, as the story goes, three wise men brought gifts to baby Jesus in a stable. One was gold, the others frankincense and myrrh. Frankincense, like myrrh, was highly prized—thought to be worth its weight in gold—but it wouldn’t have been hard to find: Trees that yield the fragrant resin were widespread in the lands of the Bible and beyond.
Two millennia later, Anjanette DeCarlo and a team of Somalians spent a sweltering day hiking to what they thought was a virgin stand of frankincense-producing trees in the mountains near Yubbe, a town in Somaliland. But, DeCarlo says, when they arrived, after traveling more than four hours by car and another four hours on foot, “we were absolutely in shock.”
DeCarlo, an ecologist and director of a project called Save Frankincense, based in Somaliland—a self-governing region northwest of Somalia that isn’t recognized by foreign governments—hadn’t expected to find tree after tree whose trunks, from top to bottom, were marred by cuts.
Frankincense, woodsy and sweetly aromatic, is one of the oldest commercial commodities, spanning more than 5,000 years. Today, thousands of tons of it are traded every year to be used by Catholic priests as incense in thuribles and by makers of perfumes, natural medicines, and essential oils that can be inhaled or applied to the skin for their purported health benefits.
Most frankincense comes from about five species of Boswellia trees, found in North Africa and India, but also in Oman, Yemen, and western Africa. The trees look gnarled and knotty, like a desert bonsai. To collect frankincense, harvesters make incisions into the trunks and scrape out the oozing sap, which hardens into frankincense resin.
According to DeCarlo, the trees should be cut no more than 12 times a year to keep them healthy. But in that mountain forest in Somaliland, she counted as many as 120 incisions in a single tree. The resin that leaks out of the cuts acts like a scab, protecting the wound so it can heal. It’s the same with our bodies, she says. If you get cut once, “you’re OK, right? You put a band-aid on it….But if you get cut, you get cut, you get cut, and you’re cut…well, you’re going to be very, very open to infection now. Your immune system is going to take a big hit trying to save you, and your immunity’s going to crash.” She adds, “It is the exact same thing with a frankincense tree.”
During the past decade or so, the market for essential oils—worth more than $7 billion in 2018 and expected to double in value by 2026—has boomed, putting greater pressure on frankincense trees. Aromatherapy used to be a “healers’ niche,” says Tim Valentiner, vice president of global strategic sourcing for the essential oil company doTERRA, but now it’s more mainstream. He says the company, which was founded in 2008, doubled in size year-on-year at the beginning. (DoTERRA funds much of DeCarlo’s research into sustainable frankincense harvesting.)
Just how badly Boswellia trees are doing is largely unknown—population studies are difficult in the remote, war-torn areas where these species often grow. The International Union for Conservation of Nature, which evaluates the conservation status of plants and animals, has assessed one of the primary frankincense species, Boswellia sacra, as near threatened. But that was back in 1998.
Frankincense trees aren’t covered under the Convention on International Trade in Endangered Species of Wild Fauna and Flora, the global treaty that regulates cross-border trade in plants and animals, but experts have argued that Boswellia species meet the criteria for protection.
National laws vary widely. In Somaliland, for example, it’s illegal under xeer—traditional law—to overharvest trees. Some of Oman’s frankincense trees are located in a UNESCO World Heritage Site and are protected by law. In other countries, however, few or no laws cover frankincense, Bongers says.
Even where laws exist, Valentiner says, they may not amount to much because remoteness of frankincense trees makes policing them impossible. “This is the ends of the Earth,” he says. “These are extremely rural and rugged areas to access.”
First signs of trouble In a study in 2006, Frans Bongers, an ecologist at Wageningen University & Research, in the Netherlands, sounded early warning. His study showed that by the late 1990s, Boswellia papyrifera trees in Eritrea were becoming increasingly hard to find. This summer, Bongers co-authored a new paper predicting a 50-percent reduction in Boswellia papyrifera within the next two decades. This species—found mainly in Ethiopia, Eritrea, and Sudan—accounts for about two-thirds of global frankincense production.
His team discovered that the trees aren’t regenerating: In more than half the populations they assessed, they didn’t find a single young tree. The culprits are cattle grazing on saplings, uncontrolled fires, and overtapping—cutting a tree too many times. “There’s a very high mortality rate in the old trees,” he says, which leads to weaker trees that produce fewer and lower-quality seeds.
Even though the study focuses on one species, the paper warns that all Boswellia species are threatened by habitat loss and overexploitation. Boswellia are found almost exclusively in regions with a harsh, arid climate that are plagued by conflict and poverty, and selling the resin may be the only source of income for many people in these areas, leading to overtapping, Bongers says. “Local people want to make a living. When I talk to people, they think that there is no problem because the trees are there, and if they tap, they get it, so who cares? It’s about short-term—taking care of your family.”
For the villager trying to scrape out a living from frankincense trees, the “biggest problem,” according to Ahmed Dhunkaal, a harvester and researcher in Somaliland, is the middlemen who buy resin and broker it to big companies. These traders often exploit vulnerable harvesters. They claim they’re taking the frankincense on loan but then never pay for it, leaving families impoverished. “People are angry,” Dhunkaal says.
Osman Degelleh, the former director general and current development advisor to Somaliland’s Ministry of Trade, says the previous government planned to create a body dedicated to managing frankincense and resins, but that never materialized. He says the key is to foster small-scale frankincense suppliers who harvest trees sustainably and support their communities.
“We have big companies who are like sharks,” Degelleh says. Wealth isn’t evenly distributed across the supply chain of harvesters, middlemen, and sellers. “The onus is on the government to do something about that.” While the big companies are enormously wealthy, he says, harvesters “are earning peanuts.” [1102 words]
Seeking solutions Gerben Boersma, CEO of Three Kings Incense, a Holland-based supplier of incense to Catholic churches around the world, says frankincense prices have been going up in recent years even as the quality of the resin has gone down. Makers of frankincense-based products are compensating for the scarcity by mixing in high-quality essential oils and other things, such as sandalwood and flower blossoms.
The long-term solution to shortages, Boersma says, is to revert to old, more sustainable ways of harvesting frankincense. “When you grow a tree, I think it takes 25 years before it starts supplying its first incense. So you have to find some crazy person who’s willing to spend all of that time and have that patience to work like that. And that’s getting more and more difficult.”
Bongers helped develop guidelines for how to tap trees sustainably, such as by allowing them a full recovery year for every few years of tapping. He also recommends fencing and firebreaks to protect forests from wildfires and cows that overgraze saplings. He acknowledges that encouraging people in difficult circumstances to implement such measures is challenging. “I’m not sure that these guidelines are very well studied, let’s put it that way,” he says.
Because enforcement is so difficult in the remote, resource-poor areas where frankincense grows, Bongers believes that consumer demand for responsibly sourced products will spur change for the good of frankincense forests.
Some companies—including doTERRA, which sells 36 products containing frankincense, and the cosmetics company Lush, which sells 16—cater to more informed customers. They’re actively advertising that their frankincense is ethically sourced. (National Geographic has not independently verified company practices and supply chains.)
So much effort goes into making essential oils, says Kevin Wilson, director of public relations for doTERRA, that consumers have to understand that pure, sustainably sourced frankincense won’t come cheap. “If a bottle of frankincense is selling for $9 or $10 at a local grocery store, they can probably be sure that may not be the pure product,” he says. DoTERRA’s 15-milliliter bottles (imagine a bottle one twenty-fourth the size of a 12-ounce soda can) sell for about $90.
For Gabbi Loedolff, African hub coordinator for Lush’s buying team, selecting suppliers who care about sustainability largely revolves around growing new trees. “We’re really in this mindset of moving toward regeneration, so how can you actually create a surplus….And that’s certainly what we’re working on trying to figure out for frankincense.” Loedolff says she and other company representatives make a point of traveling to source forests to see how the harvesting is done, and they select suppliers who show commitment to sustainability.
Some researchers and harvesters, including DeCarlo and Dhunkaal, say that growing frankincense trees commercially on plantations would help, rather than relying exclusively on wild trees.
Dhunkaal has established a nursery of Boswellia carterii in Somaliland. Using his own money and donations from doTERRA and Lush, he built a greenhouse, collects clippings from wild trees, plants the clippings in his nursery, and pays men to water the saplings by hand. “Propagation is the best solution,” he says. He also provides training to frankincense harvesters to help discourage overcutting of trees in the wild.
If nothing changes, DeCarlo says, consumers have to ask themselves: Are we willing to lose frankincense in a few generations? “We’ve loved frankincense for a long time,” she says. "What I don’t want to see is that we love these trees to death.” [1675 words in all]
Source: National Geographic https://www.nationalgeographic.com/animals/2019/12/frankincense-trees-declining-overtapping/
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发表于 2019-12-18 19:02:09
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