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Is Hemp Really a Green Miracle Plant?

Science

Production of hemp was banned in the United States in 1937 under the Marihuana Tax Act.

A strain of Cannabis sativa, its low concentrations of tetrahydrocannabinol (THC) mean it won't get you high. The internet is abuzz, though, with claims that it's a green fix for a host of environmental ills.


Last year, the U.S. legalized hemp production under the 2018 Farm Bill and now farmers can finally grow their crop on an industrial scale. But can it really revolutionize everything from the textile industry to construction?

Researchers suspect some of the hype originated with a hemp lobby that's been sloppy with the science in its struggle to get the plant legalized. Still, studies also suggest that, with investment, it could replace some less sustainable materials.

So which claims stand up and which fall flat?


Claim one: Hemp was the first crop grown over 12,000 years ago.

Most evidence suggests humans first started domesticating plants around 10,000 years ago in Mesopotamia, but there isn't much evidence that hemp was grown quite that early.

Still, the history of humans and hemp is indeed long and intertwined. Archeological findings suggest it was grown in China more than 4,000 years ago to make paper, cloth and rope, and also for its oil.


Claim two: Hemp could be used in 25,000 products.
Hemp is certainly a versatile plant in that the various parts, from the stem to the flower, can theoretically be used "to house and clothe yourself," according to Lawrence B. Smart, a professor at Cornell University's School of Integrative Plant Science in New York State who is researching the potential of cultivating the plant on an industrial scale.

It's also a great gluten-free and soy-free source of protein, and full of omega 3 and 6 oils usually found in fish, making it suitable both as a dietary supplement for vegans and as animal feed, Smart added.

"I think that claim of multiple uses including fiber and medicine is valid," he told DW. The question is whether those are "more cost-competitive or better or more sustainable than the ones in the market we're currently using."

Claim three: Hemp biofuels could power a green transport revolution.

Hemp as a biomass crop — its stems are high in cellulose — or hemp oil as biofuel, could compliment other renewable energy sources. But like other energy crops, there are inherent problems with growing on a mass scale. Despite claims that it doesn't need fertilizer, hemp, like corn, would require a lot of nitrogen.

"I just don't think we've done the proper life-cycle assessments to say hemp offers any advantages over using corn biofuels," said Smart. "It does produce a reasonable yield per acre but other crops are far more sustainable."

Smart's research group at Cornell is looking into a number of potential bioenergy crops. So far, their research suggests that willow, a perennial plant, could be more sustainable than an annual like hemp. That's because it can be planted once and then harvested for wood chips without disturbing the soil for 25 to 30 years. Every time a field is tilled or plowed, it releases carbon into the atmosphere.

The oil crushed from hemp seeds can go into everything from salad dressings to biofuels.

Claim four: Hemp grows in poor soil and doesn't require pesticides.

Another common claim is that hemp essentially grows itself. But because it wasn't cultivated on a large scale during the 20th century, there are few studies to show whether or not it grows easily in poor soil.

Initial smaller-scale tests in Italy and the U.S. show promising results on hemp extracting toxins from soil. Researchers also say because of its fast growth — when planted in the right conditions — it doesn't necessarily need herbicides.

Hemp also contains cannabinoids and terpenes, compounds that may deter insects. But Smart says people should be wary of claims that pesticides are never required.

"We've found a number of insect pests that will damage [hemp] and quite a few diseases, including some new species of fungi that are being defined," Smart said. Pennsylvania State University's agricultural analytical services lab also found that pests like aphids, mold and slugs can damage hemp.

"If you plant a little 20-by-20-foot garden plot, it's very unlikely that you'll experience the full range of pests and pathogens that you would expect on 20,000 acres," Smart added. Industrial farming of any monoculture crop leads to environmental problems, so it also comes down to how a crop is grown.

Claim five: Hemp could replace oil-based plastics and we could live in hemp houses.

Companies like Australian-based Zeoform and Kanesis in Italy are producing small amounts of hemp bioplastic. But right now, producing hemp plastics is complicated, energy-intensive and expensive, so it isn't going to usurp the petroleum-based varieties in the near future.

Still, hemp is proving a popular alternative to fiberglass for use in compressed panels — carmaker BMW is using hemp in its door panels — and as a sustainable building material.

The deceptively named "Hempcrete" isn't a replacement for concrete but an insulation material suitable for timber-framed houses. Most popular in France, it's pricier than conventional alternatives, but Pete Walker, a professor at the University of Bath's civil engineering and architecture department, says it has advantages.

"It's a renewable resource," Walker said. "You can grow the hemp in four months and then you're taking carbon dioxide out of the atmosphere and locking it in this plant material." Its breathable structure also regulates a building's temperature and humidity, reducing energy consumption, he added.

Claim six: Hemp consumes a quarter/half the amount of water cotton does.

Recent comprehensive studies on cotton versus hemp are difficult to come by. One of the most extensive reports, which was published in the Stockholm Environment Institute in 2005, compared the two natural fibers with polyester, a synthetic material.

The study concluded that cotton needs around 50 percent more water in a growing season than hemp. Unlike hemp, cotton requires a lot of irrigation and is most frequently cultivated in parts of the world that are water-scarce, like Uzbekistan.

But it's not as simple as swapping one fiber crop for another. Hemp, while extremely durable, is also expensive and energy-intensive to work into a soft, wearable fabric. And its long fibers mean the process is completely different from working with short-fibered cotton, so the industry would essentially have to "retool" to make the switch.

Claim seven: The U.S. constitution was written on hemp.

The National Constitution Center and fact-checking website Politifact both completely refute one of the quirkier claims about hemp circulating on the internet. The U.S. Constitution, the Declaration of Independence and the Bill of Rights are all written on parchment, which is treated animal skin.

But Constitution Center says drafts of these documents might well have been made on hemp paper, as the plant was widely cultivated in North America for rope and sails at the time. Founding Father Thomas Jefferson and the country's president George Washington grew hemp.

Reposted with permission from our media associate DW.

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A net-casting ogre-faced spider. CBG Photography Group, Centre for Biodiversity Genomics / CC BY-SA 3.0

Just in time for Halloween, scientists at Cornell University have published some frightening research, especially if you're an insect!

The ghoulishly named ogre-faced spider can "hear" with its legs and use that ability to catch insects flying behind it, the study published in Current Biology Thursday concluded.

"Spiders are sensitive to airborne sound," Cornell professor emeritus Dr. Charles Walcott, who was not involved with the study, told the Cornell Chronicle. "That's the big message really."

The net-casting, ogre-faced spider (Deinopis spinosa) has a unique hunting strategy, as study coauthor Cornell University postdoctoral researcher Jay Stafstrom explained in a video.

They hunt only at night using a special kind of web: an A-shaped frame made from non-sticky silk that supports a fuzzy rectangle that they hold with their front forelegs and use to trap prey.

They do this in two ways. In a maneuver called a "forward strike," they pounce down on prey moving beneath them on the ground. This is enabled by their large eyes — the biggest of any spider. These eyes give them 2,000 times the night vision that we have, Science explained.

But the spiders can also perform a move called the "backward strike," Stafstrom explained, in which they reach their legs behind them and catch insects flying through the air.

"So here comes a flying bug and somehow the spider gets information on the sound direction and its distance. The spiders time the 200-millisecond leap if the fly is within its capture zone – much like an over-the-shoulder catch. The spider gets its prey. They're accurate," coauthor Ronald Hoy, the D & D Joslovitz Merksamer Professor in the Department of Neurobiology and Behavior in the College of Arts and Sciences, told the Cornell Chronicle.

What the researchers wanted to understand was how the spiders could tell what was moving behind them when they have no ears.

It isn't a question of peripheral vision. In a 2016 study, the same team blindfolded the spiders and sent them out to hunt, Science explained. This prevented the spiders from making their forward strikes, but they were still able to catch prey using the backwards strike. The researchers thought the spiders were "hearing" their prey with the sensors on the tips of their legs. All spiders have these sensors, but scientists had previously thought they were only able to detect vibrations through surfaces, not sounds in the air.

To test how well the ogre-faced spiders could actually hear, the researchers conducted a two-part experiment.

First, they inserted electrodes into removed spider legs and into the brains of intact spiders. They put the spiders and the legs into a vibration-proof booth and played sounds from two meters (approximately 6.5 feet) away. The spiders and the legs responded to sounds from 100 hertz to 10,000 hertz.

Next, they played the five sounds that had triggered the biggest response to 25 spiders in the wild and 51 spiders in the lab. More than half the spiders did the "backward strike" move when they heard sounds that have a lower frequency similar to insect wing beats. When the higher frequency sounds were played, the spiders did not move. This suggests the higher frequencies may mimic the sounds of predators like birds.

University of Cincinnati spider behavioral ecologist George Uetz told Science that the results were a "surprise" that indicated science has much to learn about spiders as a whole. Because all spiders have these receptors on their legs, it is possible that all spiders can hear. This theory was first put forward by Walcott 60 years ago, but was dismissed at the time, according to the Cornell Chronicle. But studies of other spiders have turned up further evidence since. A 2016 study found that a kind of jumping spider can pick up sonic vibrations in the air.

"We don't know diddly about spiders," Uetz told Science. "They are much more complex than people ever thought they were."

Learning more provides scientists with an opportunity to study their sensory abilities in order to improve technology like bio-sensors, directional microphones and visual processing algorithms, Stafstrom told CNN.

Hoy agreed.

"The point is any understudied, underappreciated group has fascinating lives, even a yucky spider, and we can learn something from it," he told CNN.

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