Environmental Science Articles

Article / Updated 09-01-2022

Celebrate everything that is beautiful about our planet by reconnecting with nature, learning more about the natural environment, or picking up a new eco-friendly habit or two. April 22 is Earth Day — a world-wide celebration commemorating everything that makes our blue-marble planet unique and beautiful, and all the things we can do to protect it. Starting all the way back during the environmental movement of the 1970s, Earth Day has grown to become a powerful motivator for individuals and companies alike to become more environmentally aware and responsible. From local volunteer cleanups to nation-wide conservation initiatives, this year is no different, with numerous events happening at both the grassroots and state levels. Want to join in on the celebration? Find Earth Day events in your area, by visiting https://www.earthday.org/ The First Earth Day Did you know... In response to public outcry to the Santa Barbara Oil Spill of 1969, U.S. Sen. Gaylord Nelson organized a nationwide "teach-in" about environmental issues to take place on April 22, 1970. More than 2,000 colleges and universities, 10,000 public schools, and 20 million citizens participated. Aside from volunteering or donating to an eco-friendly cause, there are plenty of other ways to celebrate Earth Day — here are just a few. Plant a healthy diet You’ve probably already heard about the massive environmental impact that animal farming has on the planet. It is second only to fossil fuels in terms of contributing to human-made greenhouse gas emissions, the cause of climate change. And, while the jump from a traditional omnivorous diet to a full-blown vegan one is not something most people can accomplish overnight, cutting down on red meat is a great first step. Something as simple as committing to meat-free Mondays can have a significant influence on your health and the environment. Get started by taking a crack at one or two of our favorite plant-based recipes found in Plant-Based Diet Cookbook For Dummies. Channel your inner green thumb You don’t need to become an expert horticulturist to help save our planet. Simply buying local or better yet, growing some of your own food can help reduce your carbon footprint — not to mention, teach you valuable transferable skills like diligence and patience. Plus, there’s just something so satisfying about working with your hands, especially if you’re used to working in front of a screen all day. You can start by growing some common herbs like rosemary or thyme. They are fairly resilient and, depending on where you live, can even be grown indoors. If you lack the space to garden, look for farmers markets in your area or, better yet, join a community garden, these gardens are becoming increasingly popular, even in the most urban of cities. Don't worry if you have no previous gardening knowledge — beginner-friendly resources, such as Gardening Basics For Dummies, will help you get there. You can also find a farmers market near you using the USDA National Farmers Market Directory. Stay informed It’s no secret that our planet is in grave danger as a result of climate change. But, contrary to what you may feel after reading all the increasingly worrisome headlines, you must remember — there’s still hope. And, while the biggest contributors of climate change, like animal farming and fossil fuel burning, may seem so far removed from your daily life, you’d be surprised how much of a difference you as an individual can make. Staying informed is perhaps the easiest way to help environmental causes. As an informed citizen, you have the power to choose more wisely what products to buy, what companies and practices to support, and even who you vote for in the next election. Don't know where to start? Check out Climate Change For Dummies to help you navigate this complex topic. More ways to greenify your life There’s always something more we can do to reduce our environmental impact on the planet, but that should not discourage us from taking action — after all, every little bit counts. One small change in your daily routine today will lead you to more and more lasting changes in the future. If you’re ready to explore even more ways to go green, check out Green Living For Dummies for a more comprehensive guide to sustainable living. From the team at Dummies, we wish all our fellow earthlings a happy and green Earth Day.

Article / Updated 08-11-2022

Environmental science is all about finding ways to live more sustainably, which means using resources today in a way that maintains their supplies for the future. Environmental sustainability doesn’t mean living without luxuries but rather being aware of your resource consumption and reducing unnecessary waste. Reduce household energy use. Energy conservation is itself a source of energy. Here are several simple ways to reduce your household energy use: Turn off appliances and lights that you’re not using. Install energy-efficient appliances. Use a programmable thermostat that lowers or raises the temperature when you’re not home. Set your thermostat lower than usual in the winter and bundle up. Open windows to allow a breeze instead of turning on the air conditioning. Hang clothes to dry instead of using the dryer. Use an electric teakettle rather than a stovetop kettle to boil water. Replace incandescent light bulbs with compact fluorescent bulbs (CFLs). Eat locally. A powerful way to live more sustainably is to eat locally. The convenience of supermarkets has changed how people think about food. You can stroll through aisles stocked with fruits, vegetables, and other products from all over the world any time of year. But these products consume huge amounts of fossil fuel energy to get from those global locations to your corner supermarket. Dispose with disposables. Previous generations didn’t dream of single-use razors, forks, cups, bags, and food storage containers, but these days, you can find a plastic version of almost any object and then throw that object away after you use it. Many of the environmental health issues today stem from toxins released into the environment by trash. Even trash that’s properly disposed of, such as that in a landfill, requires careful monitoring to ensure that dangerous chemicals don’t enter the surrounding environment. When you make a purchase, consider the item’s life expectancy: How long can the item be used? Will it have more than one use? When you’re done with it, will it end up in the trash? Start investing in reusable products for the items you most often throw away. Plant seeds. Try growing your own food. Simply plant a few seeds in a corner of your yard or in a container on your porch or windowsill. You don’t need acres; a few square feet on a patio, along the driveway, or in a window box can provide enough space to grow edible herbs, fruits, and vegetables. Recycle. Recycle as much as possible! If your neighborhood or apartment complex doesn’t offer recycling pickup, either find a drop-off location or request the curbside service. Buying products labeled post-consumer lets companies know that recycling is the way to go! For other items, such as CFLs, batteries, cellphones, and electronics, find an appropriate recycler. Be sure to ask electronics recyclers where these materials go for recycling and avoid companies that ship electronic waste overseas for unregulated “recycling” and salvage operations. Goodwill Industries International is one place that accepts electronics for responsible recycling. Resell and donate items. Items that you no longer need can get an extended life through resale and donation. By extending the life of any product, you help reduce dependence on disposable or cheaply made single-use products that end up in landfills. Try reselling clothing and children’s things through a secondhand or consignment retailer or consider donating them to a nonprofit resale organization (such as Goodwill) or charity organization (such as the Salvation Army or American Cancer Society) that will redistribute them to those in need. Drink from the tap. Dependence on bottled water has added more than a million tons of plastic to the waste stream every year. One reason people rely on bottled water is because they believe it’s safer and better tasting than tap water. But most municipal water supplies in the U.S. provide safe, clean, fresh water (and many bottled waters are just bottled from city water supplies anyway). If you don’t like the flavor of your tap water, consider the one-time investment in a filtration system. If you like the convenience of bottled water, purchase refillable bottles and keep one in your fridge, one in your car, and one at the office. Encourage your employer to install filters and offer glasses or reusable bottles at work, too. Save water. An easy way to live more sustainably is to conserve household water use. Consider installing water-efficient toilets or dual-flush toilets that let you choose whether to use a full flush (for solid waste) or half-flush (for liquid waste). Newer clothes washers can automatically sense the smallest level of water needed for each load. Smaller changes, such as switching to water-saving shower heads and adding aerators to your sink faucets, are also effective ways to significantly reduce household water use. To conserve water outdoors, use landscaping adapted to your local environment. When buying plants, look for drought-tolerant species and varieties and be sure to plant them in proper soil and sun conditions to reduce their need for excess watering. Set up sprinkler systems so they don’t water the sidewalk, the driveway, and other paved, impermeable surfaces. Rely less on your car. Using fossil fuels to support one person in each car on the road is clearly no longer sustainable. Investigate mass transit options in your town or city, such as a bus system, a light rail train system, or carpool and vanpool services for commuters. When traveling close to home, walk or ride your bike. Purchase fair-trade products. When you purchase items that are imported from all over the world — particularly coffee, cocoa, sugar, tea, chocolate, and fruit — look for the fair-trade certification. This designation tells you that these items were grown using sustainable methods of agriculture and that local people are receiving fair prices for the goods they produce. Items that don’t have the fair-trade certification may have been produced unsustainably and may be the product of exploitative labor practices that don’t benefit the local people.

Article / Updated 04-18-2022

Tornadoes are nature's most violent storms. Nothing the atmosphere dishes out is more destructive. They can sweep up anything that moves. They lift buildings from their foundations. They make a swirling cloud of violently flying debris. They are very dangerous to all living things, not only because of the sheer power of their winds, but the missiles of debris they create. Wind measuring instruments are destroyed by tornadoes, although according to reliable estimates, their winds can exceed 250 miles per hour. Flying at those speeds, pieces of straw can penetrate wood. According to most scientists, the top wind speeds in the strongest tornadoes are about 280 miles per hour. In an average year, 1,200 tornadoes are reported in the United States, far more than any other place in the world. On average, tornadoes cause 80 deaths in the U.S. every year and 1,500 injuries, although averages don't mean very much when it comes to these storms. In 1998, for example, 130 people died in tornadoes in the U.S., including 42 who were killed in an outbreak in central Florida and 34 who died in a single tornado in Birmingham, Alabama. Most human casualties are people in mobile homes and vehicles. The deadliest single tornado struck on March 18, 1925. In three and a half hours, it traveled 219 miles through Missouri, Illinois, and Indiana, killing 695 people. Most tornadoes, nearly 90 percent, travel from the southwest to the northeast, although some follow quick-changing zigzag paths. Weak tornadoes, or decaying tornadoes, often have a thin ropelike appearance. The most violent tornadoes have a broad, dark, funnel-shape that extends from a dark wall cloud of a large thunderstorm. There have been reports of some tornadoes that practically stand still, hovering over a single field. Others crawl along at 5 miles per hour. But the average tornado travels 35 miles per hour, and some have been clocked at more than 70 miles per hour. A tornado in 1917 traveled a record 293 miles. The average width of a tornado's path is about 140 yards, although some have been reported to be more than a mile wide. Most tornadoes occur between 3 p.m. and 9 p.m., although they have been known to strike at all hours of the day or night. They usually last only about 15 minutes, although, some have been known to stay on the ground for hours. Tornado Alley The size of the place known as Tornado Alley expands through spring and summer as heating from the sun grows warmer and the flow of warm moisture from the Gulf of Mexico spreads farther north. An area that includes central Texas, Oklahoma, and Kansas is the hard core of the season, but before it is over, as Figure 1 illustrates, Tornado Alley extends north to Nebraska and Iowa. Figure 1: Tornado Alley. It shrinks and swells over time, but there is only one Tornado Alley. Nowhere else in the world sees weather conditions in a combination that is so perfect for these storms. Here's what makes the storms of Tornado Alley so bad: Beginning in spring and continuing through summer, low-level winds from the south and southeast bring a plentiful supply of warm tropical moisture up from the Gulf of Mexico into the Great Plains. From down off of the eastern slopes of the Rocky Mountains or from out of the deserts of northern Mexico come other flows of very dry air that travel about 3,000 feet above the ground. From 10,000 feet, the prevailing westerly winds, sometimes accompanied by a powerful jet stream, race overhead, carrying cool air from the Pacific Ocean. Sometimes, the winds form a convective cap lid of warm air over the Plains that the rising air is eventually able to break through and explode upward into the sky. These are the ingredients for the most severe thunderstorms and most powerful twisters — sharp differences in temperatures at different levels, big contrasts in dryness and moisture, and layers of powerful winds that are blowing from different directions at different speeds. Forecasting Weather forecasters in Tornado Alley have a pretty good idea of the menu of conditions that are necessary to make severe thunderstorms, and they're pretty good at being able to forecast that severe thunderstorms are on the way. They can say that large hailstones and strong winds are likely, and a tornado is a possibility during the next several hours or the next day or two. But they can't forecast a tornado. The question of which of the conditions on the menu for severe thunderstorms actually causes tornadoes to form in these storms remains one of the most difficult mysteries of weather science. A severe thunderstorm that causes a tornado can look exactly like a severe thunderstorm that does not cause a tornado. Weather researchers have been working on the problem for years, chasing tornadoes all over the countryside, and still it is one of those things that is not well understood. The presence in the area of supercell thunderstorms really puts pressure on forecasters in local weather service field offices. The national Storm Prediction Center in Norman, Oklahoma, is on the phone giving advice, but the buck stops in the local office. The local forecasters know that a lethal tornado could come spinning down out of the dark cloud at any moment, but they can't be sure until they see it show up on a Doppler radar screen or a funnel is actually observed. Warning the public Billions of dollars have been spent in the last several years on research and computer modeling, radars and satellite technologies, and high-speed communications. Progress has been made. On average, when tornado warnings were issued in 1994, communities had six minutes to react. By 1998, the average lead time for warnings had stretched to 12 minutes. Television meteorologists and other media outlets play vital roles in such weather emergencies, continuously broadcasting the locations and predicted paths of tornadoes. Many lives are being saved by the increased public awareness and the lengthening time of advance warning that is available. In fact, the longer lead-time has reached the point where people are rethinking the idea of public shelters for tornadoes. As minutes are added to advance warnings, now it may be possible for people in harm's way to rush to a shelter before a tornado hits. More than 15,000 severe storm and tornado watches and warnings are issued by the National Weather Service every year. Most of the time, they are accurate. Sometimes, they are missed. Occasionally there are false alarms. The successes are taken for granted and often overlooked in the details of a tornado disaster. The failures and the false alarms seem to be remembered forever. Perfectly reasonable people who will forgive you for missing the rain on their picnic now have a different attitude. When it comes to tornadoes, they want perfection. Lives and limbs What are the odds of a tornado crossing your path? Even in Tornado Alley, the odds are against such an unhappy occasion. When it happens, of course, it's a disaster — but still, the odds are high against it. People think about tornadoes in tornado country the way people in the Southeast think about hurricanes and people in California think about earthquakes. It's part of the background of daily life that you really don't give very much thought to, because chances are, it's not going to happen. The five-dollar word for this is complacency — a self-satisfied unawareness of danger — and somebody is always getting on their high horse about it. The truth is, day in and day out, most people have other things to worry about that just seem more real. And it's just human nature to be optimistic, and to think things are going to turn out for the best. But it leaves you open for some terrible surprises once in a while, which is kind of sad, when you think about it. Government people in the disaster business and American Red Cross relief workers who deal with victims of these storms see this sense of surprise on people's faces all the time. A tornado watch or a warning? Don't confuse a watch with a warning. There is a big difference. Here is what they are about: Tornado watch: When National Weather Service forecasters issue a tornado watch, they are making a forecast that tornadoes are possible in your area. It's time to remain alert to signs of approaching storms and to make sure that you are prepared for an emergency. Tornado warning: This is an emergency message. A tornado has been sighted in your area, or weather radar indicates one is present. Now is the time to get to safety, to put your emergency plan into action. Tornado dos — and don'ts! The National Weather Service and the American Red Cross have put together these basic tips about tornado safety: Seek shelter immediately, preferably underground in a basement or in an interior room on the lowest floor, such as a closet or bathroom. Stay away from windows. Get out of your car or your mobile home and seek shelter in a sturdy structure. In the open, lie flat in a ditch or depression. Protect your head from flying debris. Do not try to outrun a tornado in your car. Do not seek shelter under a bridge over overpass. The idea that these are safe shelters is just plain wrong.

Cheat Sheet / Updated 04-12-2022

The ocean is big — really, really big — both as a body of water and as a topic. It encompasses physical characteristics, its ecosystems and inhabitants, its influence on climate and weather, the sustainable use of its resources, and much more. This Cheat Sheet touches on a few key topics.

Cheat Sheet / Updated 04-07-2022

Environmental science is a field of study focused on Earth’s environment and the resources it provides to every living organism, including humans. Environmental scientists focus on studying the environment and everything in it and finding sustainable solutions to environmental issues. In particular, this means meeting the needs of human beings (and other organisms) today without damaging the environment, depleting resources, or compromising the earth’s ability to meet the resource needs of the future. A sustainable solution to an environmental problem must be ecologically sound, economically viable, and culturally acceptable. This Cheat Sheet summarizes some key aspects of what environmental scientists study.

Cheat Sheet / Updated 03-08-2022

This Cheat Sheet describes how and why greenhouse gases are formed, investigates some important global warming terms, uncovers the negative impacts of climate change, and offers solutions you can implement in your everyday life to alleviate rising greenhouse gas emissions. Although climate change is connected to ugly futures, melting icecaps, rising sea levels, soaring temperatures, worsening hurricanes and monsoons, and the list goes on, it’s also a link to a better future. Climate change is opening doors for the development of new types of fuels, leading the shift to reliable energy sources, and creating a vision of a greener tomorrow.

Cheat Sheet / Updated 03-01-2022

Who doesn’t talk about the weather? But, if you know the meanings of some key weather words, you can talk even more fluently. And clouds provide scope for imagination and help in predicting and anticipating weather changes.

Cheat Sheet / Updated 02-16-2022

Global warming is already changing the environment, the economy, and people’s ways of living. The changes aren’t over, either, and the more that changes around the world, the more critical it is to understand this complex and important issue. The following describes how and why greenhouse gases are formed, investigates some important global warming terms, uncovers the negative impacts of climate change, and offers solutions you can implement in your everyday life to alleviate rising greenhouse gas emissions. Although global warming is connected to scary scenarios featuring soaring temperatures and worsening hurricanes and monsoons, it’s also a link to a better future. Global warming is opening doors for the development of new types of fuels, leading the shift to reliable energy sources, and creating a vision of a greener tomorrow.

Article / Updated 04-20-2021

Osteichthyes (pronounced ah-stee-ick-thees) is a class of about 28,000 fish characterized (in most forms) by a bony skeleton, scales (some without), paired fins, a single pair of gill openings supported by bony gill arches each covered by an operculum, jaws, a mouth with many teeth, a swim bladder (air-filled sack) for buoyancy, paired nostrils, and external fertilization of eggs. Bony fish are generally broken down into two groups: Ray-finned fish: Ray-finned fish have fins supported by spines; the fins are moved by muscles in the body of the fish that do not extend into the fins. They (usually) have a pair of pectoral fins and a pair of pelvic fins, along with dorsal, anal, and caudal fins, and most look like, well, a fish — their bodies are oval-ish and tapered at each end. They breathe primarily through gills. And they have a lateral line — a row of organs that sense changes in water pressure, movement, and vibrations (kind of like the sensitive hairs in our inner ears) which helps them find prey and not become prey themselves. Lobe-finned fish: Lobe-finned fish have rounded fins (shaped more like your earlobes), which are supported by muscles and articulated bones (bones that meet to form joints). In other words, their fins are more like hands than typical fish fins, though the end of each fin has thin, bony structures that fan out from the core of the fin. These fins are thought to be the precursors of amphibian legs and feet. Lobe-finned fish also have two dorsal fins (instead of one), and they have both gills and lungs (though they’re not functional in certain species), which enables some of them to breathe on land or under water. As your mother told you when you experienced your first heartbreak, there’s always more fish in the sea. With bony fish, that means 28,000 species and counting. We can’t possibly cover them all, so we kept this discussion brief by describing the two groups (ray-finned and lobe-finned) and highlighting the common, the cool, and the weird in each group. Ray finned Actinopterygii (ray-finned fish) are, by far, the largest and most diverse group of bony fish. They include anchovies, angelfish, barracuda, catfish, cod, eels, flounder, flying fish, frogfish, gars, grouper, grunt, halibut, herring, hogfish, jacks, lionfish, mackerel, marlin, minnows, mullet, needlefish, perch, piranha, pompano, porgy, sailfish, sardines, sea bass, sea trout, seahorses, shad, sheepshead, snappers, snook, sole, sturgeon, swordfish, tarpon, triggerfish, toothfish, tuna . . . we could go on but we think you get the idea. But let’s look at some notable members of the group. Imagine an award show with categories for the smallest, biggest, fastest, and so on: Smallest: Stout infantfish are barely as long as the width of a pencil — females max out at about 8.4 millimeters long, while males grow to only 7 millimeters. They’re also the smallest and lightest of all known vertebrates. If you ordered a pound of stout infantfish from the menu, you’d get a plate of roughly 500,000 fish! Largest: The sunfish (Mola Mola) can grow to be over 2,268 kilograms (5,000 pounds). They live in warm water and look like a swimming fish head that has been smushed. Fastest: The black marlin has been clocked at a maximum speed of about 129 kilometers per hour (about 80 mph). Longest: The giant oarfish is a long serpent-looking pelagic fish up to eight meters (26 feet) long. They’re silver with a red mohawk looking fin. They cherish their privacy and are rarely seen alive. Coolest: The Antarctic icefish lacks hemoglobin in its blood, making it clear and less susceptible to freezing, sort of like anti-freeze, which is useful for any fish living in the frigid waters off Antarctica. Due to this lack of hemoglobin, they have huge hearts and almost four times the amount of blood as other fish. Weirdest couple: Female anglerfish have it going on! Living in the dark, deep ocean, these ladies have a dangling dorsal fin tipped with luminescent skin, which functions as a fishing rod protruding from the center of their head ending in a glow-in-the-dark lure just in front of their huge mouth full of teeth. And she has all the guys attached at the hip, seriously. Male anglerfish are usually much smaller than the females. When a male finds one of these lovely ladies, he attaches himself to her as a permanent parasite. After a while, he loses his eyes and all his organs except his testes, physically fusing his body with hers. Talk about a Stage 4 clinger! Females can carry around multiple mates. Cutest: Seahorses get by on their looks. Remember when we said most ray-finned fish look like fish? Well, seahorses are one of those exceptions. They swim around upright with what looks like a little armored body and quick moving fins. They have a tubular snout used for eating plankton and fish larvae. And it’s the male seahorses that carry around the fertilized eggs in a special pouch until they hatch — how adorable is that?! Father of the year: Speaking of caring fathers, the jawfish is a paternal mouthbrooder, meaning he holds the fertilized eggs in his mouth till they hatch (see the following figure). Every so often, he spits them out, a practice called churning, which keeps the eggs aerated, hydrated, and clean, thereby increasing the chances that more will hatch. All the while, he doesn’t eat a thing. Fortunately for him, the incubation period for the eggs is only five to seven days. Friendliest: Yep, fish can be friendly, and a perfect example is the grouper. Because of their large size (the goliath grouper can grow to be almost 800 pounds), these fish are not really scared of anything and are naturally curious. We have had many encounters with grouper fish over the years, and honestly, they are the Golden Retrievers of the sea. The grouper in the following figure actually took Ashlan on a tour of his home, following her along her entire dive and nudging her when she wasn’t paying him enough attention. Longest living: Orange roughy, brightly colored and slow moving, can live up to 200 years — that is, unless they’re eaten (by us). The problem with eating orange roughy is that they don’t reach sexual maturity until the age of 20, so they’re exceedingly susceptible to over-fishing, and they’re caught using the super destructive fishing method of bottom trawling. If you need another reason not to eat them, they’re often full of heavy metals, such as mercury, because they live a long time and bio-magnify toxins into their tissue. So next time you are at a restaurant and they offer you orange roughy as a special, just say no and feel free to tell the waiter (and the chef) why. Honestly, most people, even in restaurants, don’t know how bad and destructive catching some of these fish is. A little schooling goes a long way. Lobe-finned Sarcopterygii (lobe-finned fish) are a group of only eight living species with lobe-shaped fins, two dorsal fins, gills, and lungs (which aren’t functional in certain species). They’re broken down into two classes — coelacanths and lungfish. Coelacanths Thought to have gone extinct 66 million years ago with the dinos, a coelacanth was spotted at a fish market in 1938. Two extant (living) species are now recognized — the West Indian Ocean coelacanth and Indonesian coelacanth. Referred to as a living fossil, many scientists see them as a possible link between sea creatures and four-legged land animals, such as salamanders, newts, and lizards. Living as deep as 2,000 feet, these carnivorous fish sleep in caves during the day and hunt for prey (mostly octopus, squid, and cuttlefish) at night. They grow to be about 6 feet long and weigh up to about 200 pounds. In 2010, Laurent Ballesta led a confidential Gombessa expedition in Jesser Canyon, Sodwana Bay, South Africa, to capture the very first pictures of the coelacanth taken by a diver (–120 meters). This was possible thanks to the South African diver Peter Timm, who was the first to face the mythical fish locally named Gombessa. Discover more in the book, Gombessa, Meeting with the Coelacanth. Coelacanths have lungs during their embryonic development that stop developing as the fish grows and are barely noticeable (and non-functioning) in adults. They also have a rostral organ in their snout that’s part of an electro-sensory system and a hinged skull that enables the back of the skull to tilt up to enlarge the opening of the mouth. Lungfish As their name implies, lungfish can breathe air. Yep, they have either one or two lungs (depending on the species) to extract oxygen from the air, and they also have gills to extract oxygen from water. These are freshwater fish that live in rivers and lakes in Australia, Africa, and South America. And they’re big — most species growing up to 1.2 to 2.1 meters (4 to 7 feet) long. Lungfish have horrible eye sight, but their great sense of smell, lateral lines, and sensitive touch (with their pectoral and pelvic fins) make up for it. African lungfish can also go into a deep sleep (estivation) for up to two years — a slimy sleeping beauty.

Article / Updated 04-20-2021

Elasmobranchii (pronounced ee-laz-mo-brank-ee-ee) are a familiar subclass of fish that includes some of the most misunderstood and maligned creatures in the world—sharks, skates, and rays. They’re characterized by a rigid dorsal fin (the top fin) and have four to seven pairs of gill slits to breathe. They’re all carnivorous, feeding on everything from large marine mammals to small crustaceans, and they lack a swim bladder, equipped instead with an oily liver to maintain buoyancy. In contrast to the teeth of most vertebrates, which are locked into sockets in the jaw bones, elasmobranch teeth are attached to the jaw with fleshy tissue. Many species have rows of teeth that continue to be replaced—some may go through as many as tens of thousands of teeth in a lifetime. Selachiia: Sharks Sharks go way back. The first evidence of sharks dates to the Ordovician period 400 to 450 million years ago! Approximately 450 species of fish have the honor of being classified as sharks, and they range in size from about 20 centimeters (eight inches) to 12 meters (40 feet) long. They’re all predators and feed mostly on fish, seals, and whales, but some sharks, such as the whale sharks and megamouth sharks, feed on tiny plankton. Baby sharks are called “pups,” but even before they’re born, they’re not all sweet and cuddly. Some baby sharks eat their brothers and sisters who are growing slower while still inside their mother (talk about sibling rivalry!). Other species of sharks create extra eggs for the growing pups to consume. Both are examples of intrauterine cannibalism. Some scientists believe this practice is “survival of the fittest” to keep the species strong. The smallest of sharks is the dwarf lantern shark. Lantern sharks, as their name implies, are bioluminescent—able to produce their own light, which they use to ward off predators, blend in with the lighter background above them, and communicate when swimming in schools. On the other end of the size spectrum is the whale shark, which can grow as long as 40 feet and weigh up to 40 tons (see the following figure). While this whale shark could easily gulp down prey larger than humans, it prefers feeding on tiny plankton. So, the biggest fish in the sea eats some of the smallest food. Bull sharks, so named because of their short, blunt snout, wide body, and aggressive temperament (and because they often head-butt their prey before eating them), are unique in that they can live in freshwater or marine environments, sometimes swimming far upstream into a river or tributary (see the following figure). Among sharks, they pose perhaps the most serious threat to humans mostly because they like to swim in the same places humans do, not because they find humans particularly tasty. Mako sharks (see the following figure) are perhaps the fastest of the species and one of the fastest fish on the planet, attaining speeds of up to 74 kilometers (45 miles) per hour, fast enough to chase down its favorite food — the speedy tuna. The hammerhead shark gets the award for being the weirdest looking with an eye on either end of its mallet-shaped head. They feed mostly on small fish, octopus, squid, and crustaceans and can grow up to six meters (20 feet) long and weigh as much as 450 kilograms (about 1,000 pounds). Depending on the species, they are either solitary or school in enormous numbers. No section on sharks would be complete without mention of the baddest shark prowling the oceans — the great white shark, which can grow up to 6 meters (20 feet) long and weigh more than 2.5 tons (see the following figure). They have a varied diet of fish, crustaceans, seals, sea lions, other sharks, and even small-toothed whales such as orcas. Where do they live? Wherever they want. But seriously, you can bump into one just about anywhere the water temperature is between 12 and 24 degrees Celsius (54 and 75 degrees Fahrenheit). Some people are terrified of sharks and won’t even take a dip in the ocean because of them, but we love sharks. I (Ashlan) am particularly fond of them for their beauty, size, power, athleticism, diversity, and for all they do to keep our oceans healthy. We really want you to love and respect them, too . . . and, if you fear them, to stop being afraid. Sharks have far more reason to fear (and hate) us humans than we have to fear them. Yes, Jaws scared the “carp” out of all of us, and to his dying day Peter Benchley (who wrote the book) felt horrible for this. He later became a huge shark activist, but the damage had been done. Generations of readers and moviegoers were scared out of their swimsuits of sharks, especially the great white, and unnecessarily so. Sharks are not vicious murderers just waiting for you to wade past the buoys or paddle your surfboard or paddleboard overhead. Certainly, some animals kill for fun — namely dolphins, house cats, killer whales, leopards, honey badgers, and, of course, humans. But the vast majority of predators, including sharks, eat only when necessary. And, like many predators, sharks carefully calculate their return on investment—whether they’ll expend more energy attacking a healthy surfer or an injured seal, for example. That’s why sharks smell for blood. They’re on the prowl for the wounded and the sick, and they can go long stretches without eating, so they can afford to be picky eaters and wait for the right opportunity to come along. Nothing personal, but you’re not the first choice on their menu. In fact, scientists believe that shark attacks happen as a case of mistaken identity. Sharks can only tell what you are with their mouth (no hands to feel ya with) which is why most attacks are a single bite and release and thus not usually fatal. The sharks quickly realize that you aren’t their normal prey and they move on. Still afraid? Then check out the following table to put your chances of dying from a shark attack in perspective. Gauging the Risk of Death from Shark Attack Cause of death Average annual deaths in the U.S. Car accident 44,757 Gun deaths 36,000 Accidental poisoning 19,456 Falling 17,229 Bike accident 762 Air/space accident 742 Excessive cold 620 Sun/heat exposure 273 Bee, wasp, hornet stings 62 Lightning 47 Train accident 24 Dog attack 16 Fireworks 11 Spider bite 7 Snake bite 5 Shark attack 1 Not only are sharks much less dangerous than many people think, they also play a vital role in maintaining a healthy ocean. As apex predators, they keep the population of their prey in check, strengthen the gene pools of their prey, and reduce the spread of disease by eating the sick, weak, and injured. Lions, tigers, bears, and other apex predators perform the same service, but they don’t get the horrible rap that sharks do (and they also attack people every once in a while, just sayin’). Sharks also protect plants and help preserve plant-based ecosystems by reducing the populations of the animals that graze on those plants. And they do their part to sequester carbon. Philippe and I swim with all types of sharks all over the world. From dozens of Great Whites off Mexico, swarms of Grey Reef Sharks in the Marshall Islands, to Whale Sharks in La Paz and huge Great Hammerheads in the Bahamas — never once have we felt scared or threatened. But we are always cautious and respectful when we’re in the water with these extraordinary predators. The ocean is their home, not ours. Unfortunately, every year, sharks are killed for their fins and their meat — about 100 million a year (but that number could actually be anywhere between 63 million and 273 million sharks killed each year). On average, that means about 11,400 sharks are slaughtered every hour, whereas four people in the whole entire world die from shark attacks per year on average. Sharks have far more to fear than we do. Batoidea: Rays Rays are a group of about 500 species that live in ocean waters worldwide. They look like a shark that has been smushed into a pancake in the outline of a kite (see the following figure). While sharks propel themselves with their tail, rays propel themselves with elongated wing-like pectoral fins. Some rays have a whip-like tail tipped with a venomous barb. A ray’s mouth is usually on the underside of its body and, when viewed from certain angles, looks as though it’s smiling. Instead of pointy teeth like sharks, rays have evolved rounded teeth they use to crush and grind their prey, mostly mollusks, crustaceans, and small fish. Another difference from sharks is that rays have their gill slits underneath their body as opposed to the sides and take in water to breathe through large openings (spiracles) on the upper surface of the head. In addition, most rays have their eyes on top of their head. Most are benthic (bottom dwelling) but some species such as the manta ray are epipelagic (free swimming). Like sharks, males have a clasper they use to mate with the female which then almost exclusively gives birth to live young. Finally, rays are almost all marine. Rays are a diverse group that includes electric rays, stingrays, manta rays, and more. In this section, we cover a few of our favorites. Electric rays have a rounded body and range in length from less than 30 centimeters (1 foot) to about 2 meters (6 feet). They’re equipped with two large electric organs positioned on either side of their head that are capable of delivering a 220-volt shock — more than sufficient for stunning prey and fending off predators. They generally feed on small fish and invertebrates, so you’re pretty safe unless you happen to step on one. The largest ray is the giant manta ray, shown in the following figure, which has a “wingspan” of up to nearly 9 meters (30 feet). They’re commonly referred to as “devil rays” because of the two special flaps at the front of their heads called cephalic lobes, but devil rays are very sweet. They feed mostly on plankton, using those devilish horns to direct more water and food into their mouths. Eagle rays have beautiful spotted skin that produce the appearance of dappled sunlight as they swim through the water. Unlike most rays, they have a very long pronounced tail and have been known to launch themselves out of the water in dramatic displays, spinning and flipping in the air. Last on our list of rays is the most unique of the group—the sawfish, also referred to as a carpenter fish. Granted, it looks more like a shark, but its mouth and gills are positioned on its underside, and it has wing-like fins characteristic of a ray. Its coolest feature is its long snout rimmed with exposed teeth. Batoidea: Skates Skates are members of the same subclass as rays, and they look like rays, but they have a few key differences. While rays are more diamond shaped, a skate’s body is more triangular or rounded, and they often have a pointy nose. Skates also have thicker, wider tails with sharp spikes that run along the middle of the tail and up their backs (no barb at the tip). Skates have small teeth to eat prey, in contrast to the rounded teeth rays use to crush and grind their food. While rays swim in both shallow and open water, skates typically hang out near the bottom and often hide in the sand. Also, instead of live births, skates lay eggs in a leathery case called a mermaid’s purse. Unfortunately, skates are struggling to survive. The International Union for Conservation of Nature (IUCN) listed the common skate as an endangered species in 2000 and as a critically endangered species since 2006.