A Connecticut village in autumn is ablaze with the brilliant colors of turning leaves. Every year, many vacationers visit the state to enjoy its scenic countryside and to explore its many picturesque villages and historic sites.
Credit: © Corbis Bridge/Alamy Images

Fall means pumpkins, colorful leaves, and crisper weather. It also means the end of summer. What causes the seasons to change? The four seasons result from the tilt of Earth’s axis of rotation and the planet’s motion around the sun. The axis slants at an angle of 23 degrees 27 minutes in relation to the plane of Earth’s orbit. As a result, Earth’s Northern and Southern hemispheres tilt toward or away from the sun during different times of the year. Some people mistakenly believe that seasons result from Earth moving closer to or farther from the sun at different times of the year. But Earth orbits at nearly the same distance from the sun throughout the year. The small changes in distance that do occur have little effect on Earth’s weather.

Tomorrow, September 23rd, at 2:50 a.m. Eastern Time, the autumnal equinox marks the beginning of autumn in the Northern Hemisphere. In the Southern Hemisphere, where the seasons are reversed, the event is called the vernal equinox and marks the start of spring. The word vernal means of spring. An equinox is either of the two moments each year (the other is in March, again changing the seasons) when the sun is directly above Earth’s equator. On the days of the equinoxes, all places on Earth receive approximately 12 hours of sunlight. Today, the sun rose at 6:43 a.m. Eastern Time and will set at 6:53 p.m.—a total of 12 hours and 10 minutes of daylight. The term equinox comes from a Latin word meaning equal night. The equinoxes occur at different times of day each year on March 19, 20, or 21 and on September 22 or 23.

The time interval from the March equinox to the September equinox is longer than that between the September equinox and the next March equinox. This time difference results from the Earth’s elliptical (oval-shaped) orbit around the sun. Our planet moves faster in its orbit when it is closer to the sun. The distance between the Earth and the sun is shortest in January. Therefore, the Earth completes the semicircle from the September equinox to the March equinox faster than it does the opposite semicircle.

Astronomers also use the term equinox for either of two imaginary points where the sun’s apparent path among the stars crosses the celestial equator. The celestial equator is an imaginary line through the sky directly over the equator.

After the autumnal equinox, the weather cools and nights become longer than days, and days continue to shorten until the winter solstice. The weather then warms and daylight begins its recovery toward the summer solstice in June. The winter solstice is technically the shortest day of the year, and the day of the summer solstice enjoys the most sunlight.

An adult spotted lanternfly resting on a stem.
Credit: © Jay Ondreicka, Shutterstock

What is red and black and spotted all over? The spotted lanternfly! While these insects look like harmless butterflies or moths, they are damaging multitudes of trees. They have become an invasive pest in the United States.

What is an invasive species? Invasive species are animals, plants, and other living things that spread rapidly in new environments where there are few or no natural controls on their growth. They crowd out native species, putting them at risk of extinction. They also cause billions of dollars in damage each year to agriculture, fisheries, forestry, and public health.

The spotted lanternfly is native to eastern Asia, including China, India, and Vietnam. The first spotted lanternfly detected in the United States was in Pennsylvania in 2014. The insect’s eggs were probably brought to the country in overseas shipments. People have unintentionally transported egg masses on vehicles, crops, and other items, spreading spotted lanternflies to more places in the United States.

Well, what is the spotted lanternfly? The spotted lanternfly is a type of insect called a planthopper. It feeds on a variety of host plants.

Adult spotted lanternflies grow up to 1 inch (2.5 centimeters) long. The adult has forewings that are gray with black spots. The hind wings are red with black spots and partly black and white on the ends. The insect’s abdomen is yellow with black bands. Nymphs (young) are 1/4 inch (0.6 centimeters) to 1/2 inch (1.4 centimeters) long. Nymphs are black with white spots, developing red patches as they mature.

Nymphs hatch in May and jump from plant to plant before developing wings. The lanternfly molts to its mature form in July. Adults can only fly short distances. Adult spotted lanternflies die with the first few freezes of winter. The eggs of the lanternfly survive the winter and hatch in late spring.

Spotted lanternfly egg masses on a tree in spring in Berks County, Pennsylvania.
Credit: © Amy Lutz, Shutterstock

Female spotted lanternflies attach egg masses in rows on tree bark and various other surfaces from September through December. They cover the egg masses with a waxy, mudlike secretion. They can lay two egg masses a year, each containing 30 to 50 eggs.

How are these little insects killing trees? The spotted lanternfly has a piercing-sucking mouthpart that enables it to feed on the sap of trees and plants. Spotted lanternflies most commonly feed on the Ailanthus, also called the tree of heaven. However, they feed on over 70 different plant species. While feeding, the lanternfly secretes a sugary substance called honeydew. This secretion attracts other insects to the tree and creates an ideal environment for a fungus called sooty mold to grow. The sooty mold can cause a plant to rot, killing trees and reducing crops. The spotted lanternfly poses a threat to apple and grape crops as well as commercial logging in the United States.

To combat the further spread of the insects, experts recommend removing egg masses from trees. They also advise checking such items as vehicles, camping gear, firewood, building materials, and outdoor furniture for insects and egg masses before moving them.

The Swedish environmental activist Greta Thunberg (holding sign) marches in a 2019 protest organized by students. As a teenager, Thunberg became known for her boldness in confronting adult politicians for their inaction on climate change due to global warming.
Credit: © Alexandros Michailidis, Shutterstock

This Saturday, April 22, is Earth Day, an annual observance to increase public awareness of environmental issues. Each year on Earth Day, millions of people throughout the world gather to clean up litter, protest threats to the environment, and celebrate progress in reducing pollution.

Earth Day began in the United States. In 1969, the U.S. Senator Gaylord A. Nelson suggested that a day of environmental education be held on college campuses. The following year, the lawyer and environmentalist Denis Hayes, then a recent graduate of Stanford University, led hundreds of students in planning and organizing the observance of Earth Day on April 22, 1970. About 20 million people participated in this celebration.

The observance of Earth Day in 1970 helped alert people to the dangers of pollution and stimulated a new environmental movement. That same year, Congress created the Environmental Protection Agency to set and enforce pollution standards. Congress also passed the Clean Air Act of 1970, which limited the amount of air pollution that cars, utilities, and industries could release. Other new environmental laws soon followed.

One modern champion for the environment is the Swedish activist Greta Thunberg. She has worked to convince politicians to take action against climate change due to global warming. Global warming is an observed increase in Earth’s average surface temperature. As a teenager, Thunberg became known for her boldness in confronting adult politicians for their inaction on climate change. She has called upon leaders to reduce emissions of greenhouse gases, mainly carbon dioxide. Such gases trap heat in the atmosphere, warming the planet’s surface.

Thunberg was born in Stockholm, Sweden, on Jan. 3, 2003. She was diagnosed with autism spectrum disorder at a young age. As a child, she showed an interest in environmental issues. She convinced her family to reduce their carbon footprint by becoming vegan and giving up air travel. Carbon footprint is a measure of the greenhouse gas emissions associated with human activities.

In 2018, at the age of 15, Thunberg protested for action on climate change outside the Swedish parliament, inspiring other student protesters. Together, they organized school strikes to demand action on climate change. In August 2019, Thunberg sailed across the Atlantic Ocean from Plymouth, in the United Kingdom, to New York City, in the United States, on a “carbon neutral” voyage. Thunberg sailed aboard a yacht that got its electric power from solar panels and underwater turbines. While in the United States, she addressed the United Nations as part of its Climate Action Summit. During her speech, she announced that she and a group of other children were filing a lawsuit against five nations not on track to meet their emission-reduction targets under the Paris Agreement. The Paris Agreement is a global treaty designed to fight global warming.

Thunberg is the author of several books on climate change activism. No One Is Too Small to Make a Difference (2019) is a collection of Thunberg’s speeches. Our House Is on Fire (2020), a memoir by Thunberg and her family, tells how Thunberg’s personal struggles led her to become an activist. Thunberg’s best seller The Climate Book (2023) explains how the climate is changing and calls on society to adopt effective strategies to slow climate change.

Lava fountains and flows illuminate the area during the Mauna Loa volcano eruption in Hawaii, U.S. November 30, 2022.
Credit: © Go Nakamura, Reuters/Alamy Images

That’s a whole lotta lava! Mauna Loa, the world’s largest active volcano, erupted on November 27, 2022, and it hasn’t stopped. Mauna Loa is in Hawaii Volcanoes National Park on the island of Hawaii. It rises 13,677 feet (4,169 meters) from sea level to its peak. That is about 12 Eiffel Towers standing on top of each other! At the top is Mokuaweoweo, a crater. But wait, there is more! The Kilauea, a volcano that lies on the southeastern slope of Mauna Loa, is also erupting. The two volcanoes are creating a dual eruption that has continued since late November.

Mauna Loa, meaning long mountain, spans about half the surface of Hawaii’s Big Island. It covers 10.5 miles from the base to the summit. It hasn’t erupted in 38 years! Most volcanologists consider any volcano that has erupted in the last 10,000 years or so to be active. Some of them use the term dormant to describe an active volcano that is not currently erupting or showing signs of a coming eruption. Volcanologists label a volcano extinct if there is strong evidence it will never erupt again.

Mauna Loa’s continued eruption has shot lava into the sky and down the slope of the mountain. The lava flow is dangerously close to a pivotal highway on the Big Island. Daniel K. Inouye highway connects the eastern and western halves of the island. As the lava flow galumphed at a rate of 40 to 60 feet an hour, officials activated the National Guard to the scene on Tuesday, 9 days after the eruption began. Officials have a plan for shutting down the highway if the lava gets much closer.

Scientists can predict the behavior of volcanic eruptions by looking at past eruptions. There is plenty of data on Kilauea since it has erupted off and on since the mid-1950′s. Kilauea erupted in 2018 engulfing around 700 homes in lava and spewing volcanic ash 30,000 feet into the air. While scientists know what Kilauea is capable of, they do not have much information on Mauna Loa.

Mauna Loa’s longest eruption lasted 18 months in 1855-1856. Most of the lava produced by eruptions comes from rifts (cracks) in the mountain’s sides, not from the peak crater. In 1926, lava destroyed a coastal settlement. Parts of other settlements were buried in 1950. A 1984 eruption sent lava flowing to within 4 miles (6.4 kilometers) of the city of Hilo.

Engineer at a wastewater treatment plant
Credit: © kittirat roekburi/Shutterstock

In 2020, at the start of the global COVID-19 pandemic, officials began testing wastewater for the virus. This tool soon helped officials track where the virus was spreading and whether cases were dropping in certain communities. What is wastewater and why is it used to track viruses? Wastewater comes from residential purposes such as bathing, laundry, and dishwashing. Most of the water in our homes is used to carry away wastes. This water, and the wastes it carries, is called sewage. Recently, scientists have employed this water for another purpose –virus tracking! It might not wear a cape, but it is helping officials prepare for outbreaks and provide information for residents on COVID-19, monkeypox, and polio. All three of these viruses are spreading in the United States.

In most U.S. cities, a piping system under the streets carries away the sewage from homes, factories, hotels, and other buildings. A system of pipes that carries sewage from buildings is called a sanitary sewerage system. Sewage has a bad odor. But more important, it contains disease-producing bacteria. Most cities have treatment plants that clean sewage water and kill the bacteria in it. The treated water can then be returned to a river, stream, or lake.

Almost all of the sewage in the United States undergoes some type of sewage treatment. Only a little of the sewage is dumped untreated into rivers. The dumping of untreated sewage causes serious problems for the environment and for cities downstream that take their water from the same rivers. Untreated sewage looks and smells foul, and it kills fish and aquatic plants.

Water treatment can also help scientists and disease experts track harmful viruses. Lately, officials have been testing wastewater for COVID-19, monkeypox, and polio. Officials are trying to control the spread of viruses to prevent epidemics. An epidemic is an outbreak of disease that attacks many people at about the same time. An epidemic may last a few hours, a few weeks, or many years. A disease that spreads throughout the world is pandemic. Public health agencies are responsible for the control of epidemics. Immunizations can prevent epidemics of some infectious diseases. Vaccines are available for COVID-19, monkeypox, and polio. Other epidemics are prevented by maintaining clean food and water supplies, or by controlling insects and other animals that spread disease. Informing people about the causes of epidemics and methods of prevention is crucial in the control of epidemics.

The next time you walk by a smelly sewer, remember not all heroes wear capes or smell good. When you see the case numbers or affected areas, tell your family and friends we have our wastewater and many dedicated scientists to thank!

The sun produces heat from nuclear reactions deep inside it. All life on Earth depends on this heat.
Credit: NASA/SDO

This summer, the entire globe experienced a heat wave. Western states in America experienced a record-breaking heat wave in late August and early September of 2022.

A heat wave is a period over which the temperature rises well above normal for a particular region. Heat waves may be less dramatic than such natural disasters as hurricanes, earthquakes, or tornadoes, and heat waves tend to cause less damage to property. However, heat waves rank among the deadliest extreme weather.

The varying nature of local climate makes it difficult to establish a simple definition of a heat wave. The temperatures of a heat wave must be hot relative to the average temperatures at a place during a particular time of year. For example, a temperature of 90 °F (32 °C) during the summer is not out of the ordinary for the northern African country of Sudan. However, it would be an exceptionally high temperature for the northern U.S. state of Alaska. Meteorologists agree that high temperatures must persist for more than one full day to be considered a heat wave.

This chart can be used to determine the heat index (HI), a number that describes how people are affected by the combination of temperature and relative humidity. As the temperature and relative humidity rise, the heat index increases. The higher the index, the greater the likelihood that people will develop heat-related illnesses. The risk of illness is low when the index is below 80 °F.
Credit: World Book chart by Linda Kinnaman

Heat waves are sometimes accompanied by high relative humidity. Relative humidity is the amount of water vapor in the air compared with the amount the air can hold at saturation. High relative humidity interferes with the human body’s ability to cool itself through the evaporation of sweat. Thus, high humidity can make a heat wave more uncomfortable and dangerous. Some weather agencies make use of a measure called the heat index, which factors in relative humidity to give a measure of how hot the air feels.

Heat waves are generally created by areas of high air pressure. Meteorologists call these areas highs or anticyclones. Warm highs bring high temperatures and air that contains little moisture. These highs are large weather systems that may affect a region for an extended time. In the summer, a warm high sometimes stalls over North America, for example, causing a heat wave.

The high temperatures of a heat wave can cause dehydration and hyperthermia in people and in animals. Dehydration is a condition in which the body loses too much water. In severe cases, dehydration can lead to a fast heartbeat, low blood pressure, shock, and death. Hyperthermia is a condition that occurs when the body becomes overheated. Forms of hyperthermia include heat exhaustion, heat cramps, and heatstroke (also called sunstroke). Heatstroke is a serious condition that can cause permanent neurological damage and death.

Elderly people, infants, and people with long-term illnesses may suffer heatstroke more readily than others during a heat wave. Hyperthermia can be particularly dangerous for people with long-term medical conditions. Such conditions as asthma, diabetes, heart failure, and high blood pressure place the body’s organs under stress. The added stress from hyperthermia can induce heart attack, breathing failure, and other fatal medical events among such people.

The complexity of diagnosing heat-related deaths has made it difficult for experts to track the toll of heat waves. The World Health Organization estimated that heat waves killed more than 166,000 people between 1998 and 2017. Another study found that approximately 500,000 heat-related deaths occurred worldwide between 2000 and 2019. Despite the uncertainties, experts agree that heat waves are deadly. In 2003, for example, Europe suffered a catastrophic heat wave in which some 70,000 people died.

Heat waves can also put stress on electric power and water services. People’s use of air conditioning strains the electrical grid. Power plants may need more water for cooling. People may also use more water to try to keep cool. When demand for electricity exceeds generating capacity, officials may have to reduce voltage to prevent a blackout. Such a reduction, called a brownout, may damage electrical equipment or cause the equipment to operate less efficiently. High temperatures also buckle pavement and warp railroad tracks.

Drought kills crops. Two farmers examine a Kansas corn field that has been affected by a drought in 2012. Climate scientists suspect such droughts might become more common in some areas due to the effects of global warming.
Credit: © Mashid Mohadjerin, The New York Times/Redux Pictures

Heat waves are dangerous to plants and animals as well. Excessive temperatures can kill animals that cannot find ways to keep cool. Prolonged heat can wither plants. Droughts usually accompany heat waves, compounding the danger to living things. Heat waves and droughts dry out the ground and plants, increasing the likelihood and severity of wildfires.

A Russian firefighter sprays water on a wildfire in the Ryazan region, southeast of Moscow. In 2010, a devastating wave of wildfires wept across Russia following a record-setting heat wave.
Credit: AP Photo

Data suggest that heat waves are increasing in duration, frequency, and intensity. The time of year in which heat waves occur is also expanding. Most climatologists think that climate change brought about by human-caused global warming is driving these changes.

People must exercise caution during heat waves to avoid health problems. Experts advise wearing light-colored, loose-fitting clothing when outdoors and avoiding going out during the hottest part of the day. People should drink fluids regularly but avoid beverages with alcohol or caffeine, which can contribute to dehydration.

People who are homeless or who live in homes without air conditioning are particularly vulnerable to heat waves. During a heat wave, local governments may open air-conditioned cooling centers where people can stay to cool down.

People can help to protect their community during a heat wave. They can air condition their homes only to what temperature is necessary, conserving power. People might be asked to limit water use at certain times to prevent drops in their community’s water pressure. They may be asked to conserve water if the heat wave is accompanied by a drought. Because heat waves increase the risk of wildfires, people may be prohibited from starting fires outdoors.

South African DJ Black Coffee
Credit: © WENN Rights/Alamy Images

July is Disability Pride Month. Behind the Headlines will feature people claiming their disability and excelling. Claiming disability means actively accepting their condition and integrating it into their identity.

Over thirty years ago, the world-renowned DJ Black Coffee was in a taxi accident during celebrations for the release of South African activist Nelson Mandela from prison. He suffered an injury that permanently paralyzed his left arm. Black Coffee is the stage name of Nkosinathi Innocent Sizwe Maphumulo, a South African disc jockey (DJ) and music producer. He creates electronic dance music (EDM). Black Coffee is known for his futuristic, tribal, and jazz-inspired sounds.

Maphumulo was born on March 11, 1976, in Durban, South Africa. Maphumulo grew up in Mthatha, in the Eastern Cape. Maphumulo later studied jazz music at the Durban University of Technology. Black Coffee earned one of two spots for South African artists in the Red Bull Music Academy in Cape Town in 2003. The academy is a traveling EDM festival and workshop. Maphumulo released his first album, Black Coffee, in 2005. His breakthrough hit was the single “Happiness” (2005).

Black Coffee began making appearances at nightclubs and music festivals. His other albums include Have Another One (2007), Home Brewed (2009), Africa Rising (2012), and Pieces of Me (2015). He released the EP Music is King in 2018. EP stands for extended play and is a type of musical recording that includes several songs but is not considered a full-length album. In 2022, Black Coffee won a Grammy award for best dance/electronic album for Subconsciously (2021).

Black Coffee has spoken out about how he stopped wearing his arm brace due to bullying and also rarely shows his left arm in public. Black Coffee has honed the hands-on skill of disc jockeying.

Sea Grass
Credit: © Rich Carey/Shutterstock

The world’s largest living thing has been hiding beneath the waves of Australia’s Shark Bay for thousands of years. But it is not some giant shark or other ancient nightmare—it is a patch of sea grass the size of a city.

Sea grass is a flowering ocean plant that somewhat resembles grass on land. It even forms large underwater meadows. Sea grass is different from seaweed, which is actually a type of algae.

Sprawling sea grass meadows carpet the bottom of Shark Bay, off the Western Coast of Australia. They serve as a habitat for fishes and other animals and grazing pasture for manatee-like dugongs. Recently, scientists conducting genetic studies of these meadows made a startling discovery.

The scientists, from the University of Western Australia, discovered that vast patches of Shark Bay sea grass are all clones of a single individual. Clones are offspring that are genetically identical to their parents. Sea grass clones itself by growing shoots from its root system that develop into new plants. These plants are capable of surviving on their own, but often remain interconnected. In many ways, the meadows function as a single individual—the largest organism (living thing) on Earth.

Similar discoveries have been made on land. In Utah, a colony of quaking aspen trees known as Pando shares a genetic identity and underground root system. The result is a single organism covering just over 100 acres (40 hectares) of land. A similar colony of mushrooms, known as the Humongous Fungus, covers more than 2,000 acres (800 hectares) in Oregon. Shark Bay’s monster meadow dwarfs these landlubbers at a staggering 50,000 acres (20,000 hectares). That’s about the size of the city of Cincinnati, Ohio.

Evidence suggests that the sweeping swath of sea grass is some 4,500 years old. The plant’s genetic makeup may hold the key to its longevity. The species, known as Poseidon’s ribbon weed, is actually a hybrid of two other plants, and it has two complete sets of genes. Such a condition, a form of polyploidy, is generally deadly in animals. But it can be harmless in plants or even beneficial. Scientists think that all those extra genes may have given the ribbon weed the genetic resources necessary to survive thousands of years of changing climate.

However, there’s no guarantee that the gargantuan grassland will continue to survive. Global warming is raising the temperature of Earth’s oceans, posing a threat to virtually every organism living there. Sea grass meadows may be a particular point of concern because, like coral reefs, they provide habitat for a wide variety of species, making them hotbeds of biodiversity (the diversity of living things).

Tulips are colorful garden flowers that bloom in the spring. Tulip leaves and the flower stem grow directly out of a bulb.
Credit: Derek Fell

Spring has sprung! Sunday, March 20th, was the vernal equinox, the official marker of the spring season in the Northern Hemisphere. The equinox occurs when the sun is directly above Earth’s equator. When the sun is in this position, all places on Earth receive approximately 12 hours of sunlight. The term equinox comes from a Latin word meaning equal night.

The equinoxes occur on March 19, 20, or 21 and on September 22 or 23. In the Northern Hemisphere, the March equinox marks the start of spring and is often called the vernal equinox. The position of the vernal equinox is called the first point of Aries. The word vernal means of spring. The September equinox marks the beginning of autumn and is called the autumnal equinox. The seasons are reversed in the Southern Hemisphere.

The equinoxes are the two moments of the year when the sun is directly above the equator. As Earth moves in its orbit around the sun, the position of the sun changes in relation to the equator, as shown by the dotted lines in this diagram. The sun appears north of the equator between the March equinox and the September equinox. It is south of the equator between the September equinox and the next March equinox.

The time interval from the March equinox to the September equinox is longer than that between the September equinox and the next March equinox by several days. This time difference results from the earth’s elliptical (oval-shaped) orbit around the sun. The earth moves faster in its orbit when it is closer to the sun. The distance between the earth and the sun is shortest in January. Therefore, the earth completes the semicircle from the September equinox to the March equinox faster than it does the opposite semicircle.

Historically, the year began with spring in many cultures. Evidence of this practice in ancient Rome remains part of the modern calendar. Counting March instead of January as the first month of the year, we find that September, October, November, and December are the seventh, eighth, ninth, and tenth months. The prefixes sept-, oct-, nov-, and dec- come from the Latin words for 7, 8, 9, and 10.

Spring looks different around the world. The Northern Hemisphere has spring weather from late March through May. In the Southern Hemisphere, spring weather begins in September and lasts through November. The number of daylight hours increases during spring, particularly in the polar regions, and the temperature rises. Nature awakens in spring. Flowers bloom, and hibernating animals leave their winter sleeping places. Many cultures have festivals that celebrate the arrival of spring. Find your own way to celebrate spring this year. Spring is a new beginning, enjoy the flowers, longer days, and warmer weather!

Brontosaurus.
Credit: © Emiliano Troco

Sauropods were the most spectacular of the dinosaurs. Their long necks supported small heads that took in needles and leaves. Despite such a nutrient-poor diet, they reached sizes and lengths unparalleled in any other terrestrial (land-dwelling) animals. How—and why—did they get so large? A recent study may have discovered a lead to unraveling the physiology of these amazing animals. 

Over tens of millions of years, the arrangement of the continents has shifted through the action of plate tectonics. Geologists can trace how a location has moved over the face of Earth to determine its paleolatitude. The paleolatitude is the position of a point on the Earth’s surface in relation to the equator at a time in the distant past. Both latitude and paleolatitude are measured on a scale of 0° (the equator) to 90° (the poles). Higher latitudes experience cooler temperatures and less sunlight in winter. 

Dinosaurs reigned during the Mesozoic Era—a time of warmer climates. Despite the planet being largely ice-free, regions near the poles still faced cold winters and weeks or months without sunlight. Nevertheless, dinosaurs have been found at high paleolatitudes, including in Antarctica and Alaska. At least some of these dinosaurs remained there through the winter. 

Sauropod fossils, however, are conspicuously absent from these polar locations. No sauropod fossil has been discovered from a paleolatitude higher than about 65°. Instead, these chilly climates were strictly occupied by meat-eating theropods and some plant-eating dinosaurs called ornithischians. 

Some paleontologists (scientists who study prehistoric life) suspected the absence of fossils suggest that sauropods preferred warmer climates. But others thought that sauropods might not have fossilized well near the poles for some reason, or that the fossils are still waiting to be discovered. 

A team led by Alfio Alessandro Chiarenza of the University of Vigo in Spain analyzed the paleolatitude of all the places where sauropod fossils have been found. The team published their findings last month in the scientific journal Current Biology. They determined that the absence of sauropods at high paleolatitudes was not due to incomplete sampling. Chiarenza’s team used models of the Mesozoic climate and found that sauropods preferred savanna-type habitats. Sauropod ranges were tightly constrained by the lowest predicted temperature. 

Why didn’t (or couldn’t) sauropods brave the cold? They might have cooled down too quickly, despite their massive sizes. Many theropods—and possibly some ornithischians—had downy or hairlike feathers that could be used to keep them warm. Sauropods lacked any such insulation. Furthermore, a sauropod’s long necks and tails might have lost heat quickly when exposed to bitter-cold winds. 

Sauropods buried their eggs in the earth to keep them at a stable temperature. But this method probably would not have kept the eggs warm enough in cold climates. In contrast, theropods sat on their eggs and ornithischians covered their eggs in rotting plants. Both of these approaches could keep the eggs warm even in cold climates. 

Chiarenza’s team proposes that sauropods did not possess as high of a metabolism as theropods and ornithischians. Historically, scientists have classified animals as endothermic (“warm-blooded”) or ectothermic (“cold-blooded”). Endothermic animals tend to produce more of their own body heat, while ectothermic animals tend to rely more on their environment for heat. This is a false division, since every animal is somewhat reliant on its environment for heat. But animals classified as endothermic can usually survive in cooler temperatures. Reptiles, the classic endotherms, are concentrated near the equator. 

In many ways, this makes a lot of sense. A lower metabolism would have enabled sauropods to survive on less food. Their huge size would cause them to lose less heat to their environment, much like a well-insulated building. Growing evidence suggests that the ancestor of dinosaurs and crocodilians (a group of reptiles) had a high metabolism, but crocodilians “slowed down” when dinosaurs took over most environmental niches. A similar changed might have occurred in sauropods as well, enabling them to attain colossal sizes. Sometimes slow and steady wins the race.