The 90210 reboot was just the latest attempt to monetize memory in popular culture. In 2019 alone, shows like Cobra Kai, Veronica Mars, Will and Grace, and The Conners have joined films like Rambo: Last Blood, Star Wars: The Rise of Skywalker, a live-action Lion King, and another Terminator in recalling stories and characters that first resonated 15 to 40 years before. Retrospective series like The Toys That Made Us take an exhaustive inventory of the plastic that populated store shelves in the 1980s and 1990s. Retro consoles like the NES Classic are gift-wrapped and doled out along with retro pop music compilations. One of the few non-sequel or remake movie hits of 2018 was Bohemian Rhapsody, an original film that nonetheless traded in on the cultural currency of Freddie Mercury, who died in 1991. Nostalgia is so pervasive that it could practically introduce a unit of measurement—Jason Priestley leaning into a locker might provoke a five, while Ralph Macchio in a karate gi could be an eight. Entertainment seems primed to appeal to children—not actual kids facing adolescence, but those lurking inside the minds of adults. Increasingly, researchers are trying to better understand why nostalgia seems to be having a moment and how these exposures affect us neurologically. It turns out that dwelling on the past may be helping us to contextualize the present and prepare for the future. Picture this: It’s late at night. You are out of college but have not yet embarked on a definitive career path. Bills are piled up on the table, a monument to adult responsibilities. Stress, anxiety, and student loans occupy your thoughts. On a social media page, you spot an advertisement for an old television show you liked. That brings you to YouTube, which has videos of Saturday morning cartoons you remember. For the next few hours, you drift from one clip to the next, happily regressing to a time when obligations were few and far between. That’s nostalgia: a bittersweet longing or yearning for one's past. (Its counterpart, historical nostalgia, is having an affection for a different era, one you might not actually have lived through.) While that DuckTales episode might make you smile, it’s not so much the adventures of Scrooge McDuck and his nephews as the personal memories it conjures that bring you to a relaxed state. “Having a nostalgic episode means you’re going to feel good, calm, at peace,” says Krystine Batcho, a professor of psychology at Le Moyne College in Syracuse, New York. “You stop feeling anxious. Your stress levels drop. You get a warm, soft, fuzzy feeling. Your brain is reviving old memories when you were a kid watching a show and smelling chocolate chip cookies baking in the kitchen.” According to Batcho, this attraction to the past is somewhat paradoxical. We are a forward-looking and future-driven culture, obsessed with the latest technology. So why get hung up on history? It could be because we’re accelerating too quickly. Smart phones get more sophisticated every year. Things change so fast that returning to a static frame of mind offers comfort. “People want to go back to the feelings they had when they believed life was better,” Batcho tells Mental Floss. “It triggers associational memories. You remember aspects of life from back when you first watched a show.” A movie may be worse than you remember, but it remains tethered to a time when you enjoyed an uncomplicated state of mind and a life largely free of commitments. That predictability is key. A memory can become distorted, and details could get muddled, but a happy recollection is going to be the same every time. Fundamentally positive memories are often stripped of negativity. “It’s comforting because you’re the master of that memory,” Batcho says. “You know your own lived-in past perfectly, but you have no idea what the future is going to be.” When you view an old television show or movie or listen to favorite music, it’s often as a coping mechanism. The desire for nostalgia tends to spike during and proceeding transformative life events—a marriage, a job, a death—because it offers stability and a peaceful remembrance of a time when life was not so stressful. That’s why sources of nostalgia are identified with childhood and why it’s often 10 to 20 years before those pangs of memory kick in. By that time, you’ve experienced a milestone in your life that might compel you to look back. MarkPiovesan/iStock via Getty Images Context and comfort make nostalgia a generally agreeable and positive emotion, but it wasn’t always thought of that way. In the 17th century, Swiss physician Johannes Hoffer defined nostalgia as a mental disorder, one suffered by Swiss soldiers dispatched to foreign territories who were homesick and dwelled on the details of their old lives. When it invites negative thoughts, then nostalgia can become bittersweet. More often, however, it’s literally rewarding. Several years ago, Mauricio Delgado, researcher at Rutgers University who studies reward processing in the brain, returned to his former university to give an alumni talk. Walking the campus for the first time since graduating, Delgado found himself processing a flood of positive memories. He left feeling good about his visit, and he began to wonder what nostalgia would look like if it could be visualized neurologically. “I thought there could be some reward value to this,” Delgado tells Mental Floss. “I wondered if it evoked similar processes in the brain.” With his team, Delgado published a study in the journal Neuron in 2014 that provided some tangible and fascinating evidence of how we process fond recollections. After tasking his subjects with recalling positive life experiences—a vacation to Disney World, for example—Delgado observed their brains' activity through a functional magnetic resonance imaging (fMRI) scanner. The subject would hit a button when they began to recall the memory, then hit it again when they stopped. They would also summon memories they felt neutral about—grabbing groceries or shopping for shoes. As they evoked a positive memory, the brains of his subjects lit up in a very specific way. “They tended to recruit brain systems involved in reward,” Delgado says. The brain’s processing of a reward happens in the striatum and prefrontal cortex, areas rich in dopamine receptors and active when people are enthusiastic about receiving good news or earning psychologically or tangibly positive assets like food or money. Nostalgia and those mental visits to the past offered neurochemical benefits not unlike a winning lotto ticket or receiving a “like” on Instagram. In another study, Delgado had subjects exposed to stress, then recall a positive memory. The act of recollection dampened the cortisol response, leading to a stress-alleviating effect. While these studies were not targeted to pop culture, one can glimpse the net result. Popular media is a conduit for pleasant memories, and pleasant memories produce positive neurological changes. “It’s reminiscing, and nostalgia is more like a television show from a past era,” Delgado says. “But nostalgia is what connects them.” In another fMRI study, some subjects passed on an opportunity for a financial reward for a neutral memory in order to continue drawing positive memories from the past. Making use of their internal time machine and the soothing state it offered was more valuable to them than money. Nostalgia has been recognized by name since Hoffer’s time, but it seems as though the past several years have seen an popular emphasis on recalling content to provoke that reward response. The 1970s were not bountiful with reboots of I Love Lucy, Gunsmoke, or other material from the 1950s. What makes the 21st century unique in this regard? Why is a show's cancellation no longer a guarantee that it will never return? jakkapan21/iStock via Getty Images Gerber also doesn’t discount the influence of mass media on our perceptions of time. “Media purposefully gives generations their own identities—Baby Boomers, Generation X," he says. These assigned categories make it easier to feel out of time when a new generation—like Millennials—comes along to remind an older population that their hairstyles, music, and fashion are no longer current, making them hyperconscious of the past they left behind. Media makes it hard to forget: It’s easy to examine your feelings about Woodstock when hundreds of articles celebrating its 50th anniversary abound. With age encroaching, a desire to retrieve those memories grows. “It’s an emotional cushion for dealing with change,” Gerber says. Nostalgia also relies heavily on social media, where collective recollections can be easily summoned by posting an old advertisement for a fondly remembered toy, game, or Starter jacket. “Now that more and more people don’t live near friends and relatives, it’s become a way to keep close to someone at a distance,” Batcho says. Nostalgia can also mend relationships, if one party has positive connotations with something that used to be shared as a couple. That Sopranos binge with an ex could stir feelings of forgotten emotion. “Nostalgic memories can remind you that you love a person,” she says. While nostalgia often separates generations, it can also bring them closer together. “Part of what we see happening is that it allows for intergenerational connections,” Batcho says. She cites the fact that her adult son was in college and wondering which career path to pursue when he remembered how often his mother watched St. Elsewhere, the NBC television series set in a hospital that aired from 1982 to 1988. “He felt this kind of warm and fuzzy feeling about hospitals and realized it came from watching me watch the show,” Batcho says. “It’s like secondhand nostalgia.” Her son became a doctor—a decision he based in part on those memories. Nostalgia often kicks in when enough time has passed to experience a major life event, which usually takes years from the time life consisted of cereal and Lunchables and when you need to think about a wedding. (Or a divorce.) But everyone’s relationship to the past is relative. Breaking Bad went off the air in 2013. In October, a follow-up film, El Camino, picks up where the series left off. Is that nostalgia? If you experienced a major milestone in the six years in between, maybe. Batcho notes that nostalgia tends to drop off as we get older. In adulthood, we cope with the crises of the present by remembering the past. In middle age and into our third acts, we’re busy with an independent life, kids, and a career. Later, we realize there’s more time behind us than in front of us, and our perspective changes again. Nostalgia at this late stage can once again grow bittersweet. We recall a past we cannot reproduce. There’s one further drawback to nostalgia. Like any pleasant stimulus, we can experience too much of it and become desensitized. After scoring record ratings for its debut, BH90210 kept dropping from week to week, eventually losing 60 percent of its viewers for its next-to-last episode. There seems to be a limited desire to check back in with Beverly Hills High. “There is a saturation point,” Batcho says. “Once you satiate your need for nostalgia, it loses its value. Like a fine wine, it’s best enjoyed in appropriate amounts. It’s supposed to be a visit.” It takes just moments for the fire to reduce their iconic profiles to molehills of ash. A team of officials from the North Carolina Wildlife Resources Commission watches the whole scene unfold. They aren’t there to put out the fire—instead, they stoke it by skimming the grass with handheld drip torches [PDF]. When the patch of wilderness before them is completely charred, they let themselves relax: Their job is complete. These prescribed burns—which replace fires that used to happen naturally, and recreate the conditions in which the plants originally evolved—are essential to the Venus flytrap’s wellbeing. Going to such lengths might seem strange, given that anyone looking for a Venus flytrap to decorate their dorm room windowsill or manage a fly infestation can find one easily: They’re available for less than $6 a pot at big box hardware chains, and for $10 to $30 at independent plant stores. But in the wild, the plant can only be found in one spot: a 75-square-mile area of North and South Carolina. That accounts for less than a third of species's historic range. Only 302,000 Venus flytraps remain there, down from 4 million in the 1970s. In the face of such decline, scientists have petitioned to put the plant on the Endangered Species List. And while prescribed burns aid in the Venus Flytrap’s survival, they’re not enough to guarantee it. Not when the plants are also threatened by land development, climate change … and poachers. Many of the greatest minds in history have been captivated by the Venus flytrap. Thomas Jefferson made several attempts to acquire its seeds, and in 1804, he finally planted them in a pot. But the plants are finicky: Venus flytraps thrive in habitats with damp, low-nutrient soil and lots of sunlight. The swampy coastal plains of the Carolinas have exactly the soil flytraps need, and without the boggy conditions of the Carolina coast, Jefferson's flytraps likely never poked past the soil. Seventy-one years later, in his book Insectivorous Plants, naturalist Charles Darwin described the flora, writing: “This plant, commonly called Venus' fly-trap, from the rapidity and force of its movements, is one of the most wonderful in the world.” You don’t need to be immersed in the botanical world to understand the flytrap’s appeal. The carnivorous plant is different from a fern or succulent; it moves and interacts with its environment, placing it in a special category between plant and pet. It rests with its leaf blades open, perfuming the air with a sweet nectar that lures insects. The inside of the trap contains six short, bristly hairs that are sensitive to motion. When prey disturbs two of these hairs within a short span of time—or if it brushes against the same hair twice—it triggers the hinged leaf blades. The tooth-like cilia trimming the jaws mesh together, ensnaring the meal as acidic juices inside the trap start to digest it. The unsettling process has enamored humans for centuries. "I think [carnivorous plants] have a lot more personality compared to normal plants, even if they are just normal plants," Josh Brown, owner and operator of San Francisco's Predatory Plants, tells Mental Floss. "Venus flytraps in particular are very dynamic. They move faster than any other plant their size, and people find that very compelling." Jordan_Sears/iStock via Getty Images In 1956, North Carolina passed legislation granting the Venus flytrap state protection. But even with its protected status, it was still legal to collect the plants from the wild under special circumstances. If someone had a permit and the land owner’s permission, they could pick flytraps from private property. Some plant sellers took this route, while others skipped the legal process and simply strolled onto state land with a shovel and a bucket. On the off chance they were caught, the punishment was a small fine. In 1981, there was a breakthrough that should have ended Venus flytrap poaching for good. Looking to remove some of the pressure from wild populations being targeted by poachers, William Carroll, part of the botany department of the University of North Carolina, cloned Venus flytraps in his laboratory for the first time. It was nothing like trying to grow flytraps in a home garden. In a sterile petri dish, the specimen thrived. “You can just take a piece of Venus flytrap and put it in a solution of agar, which is a seaweed-derived gel with some nutrients in it, and it will just start growing after a short period of time,” Brown says. Some plants carry pathogens—which contaminate tissue culture, impeding healthy cell growth—that make it hard to raise them in a sterile lab. Venus flytraps don’t have this problem, and in the age of cloning, sellers can use leaf clippings from a single plant to propagate unlimited Venus flytraps for pennies apiece. For entrepreneurs with a stake in the Venus flytrap market, the cloning was a stunning success. But it didn't stop the poachers. On November 1, 2015, two men emerged from the tall grass of North Carolina's Orton Plantation looking exhausted. They were boxed in by police officers, and after volleying across the field a few times, Scottie Stevenson, 44, and David Lewis, 23, stopped running and accepted whatever penalty awaited them. Hands raised, they approached the authorities and asked for a bottle of water. At that point, it wasn’t yet clear what the pair was guilty of. Law enforcement had been called to investigate a trespassing complaint, but the way the men fled upon their arrival suggested the crime was more severe. It took a police dog less than 10 minutes to locate the source of their panic: Discarded in the grass was a backpack stuffed with 1025 Venus flytraps along with the machete used to harvest them. Stevenson and Lewis were among the first people charged with violating a 2014 law designed to protect Venus flytraps. Prior to the new legislation, Venus flytraps had the protection of the state law passed in the 1950s and not much else. Even if poachers plucked hundreds of them from federal land—as many of them did in the 1990s and 2000s—the strictest penalty they faced was a $50 fine. North Carolina upgraded Venus flytrap poaching from a misdemeanor to a Class H felony on December 1, 2014. That means that poaching a single plant can now send someone to prison for months—and each plant that gets stolen is treated as an additional offense. After Stevenson and Lewis were arrested, they were held on a $1 million bond—an amount normally reserved for murder suspects. They were ultimately charged and convicted with one felony count. More recently, in March 2019, a poacher was charged with 216 felony counts—one for each Venus flytrap he took from the Green Swamp Preserve. It’s too early to say if the law is an effective deterrent for poachers, but conservationists have their doubts. “I think some of the poachers aren’t aware that it’s a felony to poach Venus flytraps in most of the North Carolina counties where it occurs,” Johnny Randall, the director of conservation at the North Carolina Botanical Garden at Chapel Hill, tells Mental Floss. Flytrap poachers are typically locals, often from families that have been collecting the plants for generations. “An ordinary person would not wander out through a wet pine savanna or the areas where these Venus flytraps occur," Randall says. "There are canebrake rattlesnakes, lots of biting insects. It’s not for the faint of heart to go out into these areas. The poachers are people who have grown up in this kind of environment, so they’re familiar with it.” Poachers usually enter the areas where Venus flytraps grow carrying machetes and pillowcases, and according to Randall, one person can harvest 500 plants in an hour—so a single raid can deal significant damage to local flytrap populations. And according to Randall, “The poor fellows who are being paid $.25 cents per plant are just trying to eke out a living in economically depressed areas of North Carolina, so even though they are breaking the law, these poachers, they’re not the real bad guys.” So who are the bad guys? Experts suspect that, in most cases, these local poachers are doing the dirty work for larger buyers and seeing just a fraction of the profits, though exactly which forces are driving the Venus flytrap black market remains unclear—especially given the plant's ready availability. okfoto/iStock via Getty Images Don Waller, a conservation biologist at the University of Wisconsin-Madison, suspects rare plant collectors overseas are behind many poaching crimes. Even though they’re identical to plants grown in labs, wild Venus flytraps may be more valuable in the eyes of certain buyers. “Interestingly, it's European collectors who are kind of fanatics about having a wild, collected plant,” he says. “They are willing to go on the dark internet and seek out these poached plants which they consider superior for some reason to commercially propagated plants.” While potentially devastating to Venus flytrap populations, poaching isn’t the main culprit behind the species’s decline. Conservationists agree that other environmental issues, like habitat loss, are bigger threats—that, and a lack of fire. The Wilmington, North Carolina, region—which sits at the center of the Venus flytrap's range—has undergone rapid development in recent years. Many of the wet savannas that once sustained vibrant flytrap populations have been replaced by golf courses and shopping centers. "The populations now are fewer than they used to be, and they tend to be more separated from each other by roads or inhospitable habitats,” Waller says. “Any time you fragment a population it becomes more vulnerable to local extinction." The Venus flytrap's home is no longer the safe environment it once was, which means simply replenishing swamps with flytrap clones isn't enough to sustain wild populations. But the biggest problem for the species, according to conservationists, has to do with fire. The plant's habitat is technically a swamp, but after a few days of baking in the sun, the sandy soil there becomes dry enough to support forest fires. Regular blazes are vital to this ecosystem, and to ecosystems around the world: They clear out debris and leave behind empty, fertile land that supports new plant growth. For centuries, if a bolt of lighting or the heat from the sun sparked a fire in the woods, the blaze burned until it fizzled out naturally. In some parts of the continent, Native Americans even ignited their own controlled burns as a way to manage the land. This changed when the first European colonists arrived in North America. Forest fires were seen as destructive forces that needed to be contained, and while fire suppression did save lives and property in many cases, it also disrupted the natural cycle of the environment. Venus flytraps were among the species hit hardest by the practice. When people started extinguishing natural fires in the Carolina region without allowing them to spread, taller shrubs were free to flourish and smother the ankle-high plants. Bespalyi/iStock via GettyImages “A large fraction of its population could be vulnerable, even to a meter or two of sea rise,” Waller says. Rising temperatures could also soon make their current habitat inhospitable: “These guys will need to move North if they are to match their current climate environment, and it’s not easy for them to move if their populations are smaller and more isolated from one another," he adds. Unlike most animal species, flytraps can't flee immediate threats. Luckily, conservationists are coming up with some creative solutions to help save them. The Venus flytrap may be vulnerable, but it isn't doomed. Establishing more nature preserves like the Green Swamp is one way to protect the flytrap’s habitat from future development projects. And once those areas are set up, wildlife managers can keep the land healthy by burning it. In the Green Swamp Preserve, periodically setting the ground on fire has become a normal part of the conservation plan. After plotting out where the burn will happen, officials pick a day with the perfect weather conditions (not too windy, not too dry) to ignite the supervised blaze. The flytraps burn up with the rest of the shrubbery, but when the next generation emerges from the soil, they’re able to thrive without having to compete for sunlight with thick, unruly brush. In Waller’s view, one of the most effective ways to ensure the species’ survival is to grant it federal protection. He's one of the scientists at the head of the movement to add Venus flytraps to the Endangered Species List. In 2016, he led a petition to get the species recognized and launched an online campaign promoting the cause. It’s not the first time scientists have tried to garner protection for the plant: It was considered for listing in the early 1990s and rejected by the U.S. Fish and Wildlife Service due to lack of evidence. But scientists are hoping things will be different this time around. “It's declined rapidly since the 1990s when the Fish and Wildlife Service considered it for listing," Waller explains. "So that was the basis for our petition: That this is a plant that is not hypothetically in trouble but getting rapidly into trouble now and needing the protection of the Endangered Species Act.” According to the Act, species are considered endangered if they’re at risk of becoming extinct throughout all or a large part of their natural range. The Fish and Wildlife Service is currently considering the Venus flytrap for protection for the second time. If it makes the list, the federal government will have to identify the critical habitats for the species and extend special management and protection to those areas. That could mean funding existing nature preserves, funding the creation of new nature preserves in vulnerable flytrap habitats, and ceasing any federal activities that would cause the species harm. Dale Suiter, an endangered species biologist with the FWS, tells Mental Floss that research is being conducted to see if the plant qualifies. “We’re currently working with the North Carolina Natural Heritage Program, and they are conducting a status survey which means they are trying to revisit as many populations as possible over this growing season and next growing season [...] After we get the results of that two-year study that we’ll start to evaluate the data and try to make a decision on what to do with the species.” However, the success of the species in the marketplace could present a stumbling block. “There are people who don’t think the plant should be listed as endangered, either because they think the plants are doing fine, which they are not, or because they realize there are huge numbers of these plants raised in captivity,” Waller says. “And if you can buy a plant at your local hardware store or nursery, what business does it have being on the Endangered Species List?” Indeed, adding the Venus flytrap to the Endangered Species List will need to be managed carefully. The listing of a common houseplant does come with potential drawbacks: If conservation laws don’t differentiate between Venus flytraps propagated in labs and plants grown in the wild, some people in the carnivorous plant business fear they could see their livelihoods disappear. “If it was made illegal in the U.S., that would probably lead to it being wiped out in the wild, because that would increase the black market value of it tremendously,” Joel Garner, who runs the online shop Joel's Carnivorous Plants, tells Mental Floss. “The Venus flytrap is one of the most mass-produced plants in the U.S., so you’re shutting down a pretty big market if you were to make that illegal. It would kind of be a situation where good intentions produced the exact opposite results you were trying to get." An endangered designation for the species wouldn’t automatically kill the industry, however. Pitcher plants—another carnivorous plant that’s popular with buyers—are extremely endangered, but shops can still sell them as long as they can prove they were grown in a lab or a nursery. Even with these provisions, Venus flytrap sellers may be wary of the red tape they’d have to navigate under stricter conservation laws. Waller is aware of this possibility, and he’s already proposed potential fixes. In a paper published in the Carnivorous Plant Newsletter [PDF], Waller and co-author Thomas Gibson encourage commercial growers and authorities to work together to create a habitat conservation plan before any new laws are passed. The plan they suggest takes something that’s been a detriment to efforts to protect the Venus flytrap in recent decades—its commercial popularity—and turns it into a strength. By adding a $.25 to $.50 surcharge to every plant that’s sold, sellers could generate revenue to fund conservation efforts. The paper estimates that such a program could raise millions of dollars a year toward acquiring new flytrap habitats and maintaining existing preserves. And it would come with an added bonus: each pot would include a tag telling buyers their purchase helps protect the species in the wild, raising awareness of the problem with the people most likely to care. “The public is very enthusiastic about Venus flytraps,” Waller says. “They buy them in great numbers, they kill them sometimes, and feed them insects in the meantime. What a remarkable plant.” No. In fact, under normal conditions (prior to human-caused fires) the Amazon [rain]forest is in a steady state. Oxygen is produced by photosynthesis and consumed by decay. If these were out of balance, then the mass of wood in the Amazon must change. That means if the Amazon were to disappear today, instantly (e.g. we harvested all the wood and used it to build houses) then the oxygen and carbon dioxide in the atmosphere would continue on at the same level. Until, that is, the wood rots. Then the carbon dioxide levels would increase. Except for the biomass decrease from human-caused fires, the biomass of the Amazon has not been changing. That means that no net carbon dioxide is being removed from the atmosphere, so no net oxygen is being released from carbon dioxide. Recently the Amazon biomass has been changing due to fires. When that happens, the wood and other carbohydrates in the trees combine with oxygen and produce CO2 and H2O. Thus the burning of the rainforests contributes to global warming. But under normal situations, when the biomass of the Amazon is not changing, there is no net production of oxygen or carbon dioxide. Incidentally, many writers who don’t understand this—and mistakenly think that the Amazon produces net oxygen—double their error by using a backward metaphor. They refer to the Amazon basin the "lungs of the world," but lungs are the organ that remove oxygen from the air and replace it with carbon dioxide, not the other way around. Where did the 20 percent figure come from? The best guess is that ecologists have calculated that 20 percent of the photosynthesis of the world takes place in the Amazon basin. But so does 20 percent of the consumption. This post originally appeared on Quora. Click here to view.