Throughout Earth’s history, biodiversity has gradually increased. Yet as you know, at the same time, many species have gone extinct. No mastodons are lumbering down your street or pterodactyls are flying through the air. In fact, of the billions of species that have lived on the planet, 99 percent have gone extinct. It is a natural part of life on Earth.
Species become extinct for a number of reasons. Some are natural extinctions, called “background extinctions.” These happen when species can’t adapt to changes in their environment. The changes include habitat loss, the evolution of a new species, temperature or precipitation changes, or disease.
Other species have disappeared because of mass extinctions. These were natural events that happened suddenly, causing many species to die off in a short period of geologic time. There have been five mass extinctions in Earth’s history.
ESSENTIAL QUESTION
What are the threats to biodiversity today?
Scientists warn that we are currently experiencing another mass extinction. No asteroids are headed our way, but conditions on Earth are changing so rapidly that some species cannot adapt. As a result, current extinction rates are 1,000 to 10,000 times higher today than the normal background rate of extinction. The cause? Humans.
Since the evolution of modern humans some 200,000 years ago, our population has swelled to more than 7 billion. As our numbers have grown, our species has transformed the earth to meet our needs. But with an ever-growing population, we have a greater and greater impact on the earth and on biodiversity.
A million years from now, what will the geologic record show about the impact of man? Watch this TED-Ed video for a closer look at the ways the new age of mankind, the Anthropocene, will be part of the geologic record.
Ted-Ed human impacts
CLIMATE CHANGE
Climate change is often in the news. Scientists are very concerned about the effects climate change is having on the planet and its biodiversity. During the earth’s 4.5-billion-year history, the climate has changed many times, from ice ages to periods when the earth’s climate was mostly tropical. The problem today, though, is that the rate of climate change is too fast. And it’s the result of human activity.
Bizarre Biodiversity
Seahorses: Unlike other species, the male seahorse, not the female, is responsible for the babies! He carries the developing embryos around in a pouch, much like that of a kangaroo.
greenhouse effect: when the presence in the atmosphere of gases such as carbon dioxide, water vapor, and methane allow incoming sunlight to pass through, but then trap that heat.
One cause of climate change is the burning of fossil fuels. People want energy to drive their cars and power transportation, heat and cool homes, produce electricity, and run factories. In our modern world, most of that energy comes from fossil fuels. However, these fuels emit gases as they are burned.
These gases, such as CO2, work like a greenhouse, trapping heat in the earth’s atmosphere— that’s why it’s called the greenhouse effect!
Deforestation is another cause of rising CO2 levels in the atmosphere. Trees and plants naturally capture and store carbon. The removal of trees has reduced the amount of carbon being taken out of the atmosphere. Carbon dioxide levels in the atmosphere have varied over geologic time. Some CO2 is necessary to keep our planet warm. However, today the levels are at an all-time high. Because of this, scientists predict that in the twenty-first century, the average temperature around the globe will rise between 2 and 5.2 degrees Fahrenheit (1.1 to 2.9 degrees Celsius).
This power plant at Apollo Beach, Florida, is releasing greenhouses gases into the atmosphere.
That rise in temperature may not seem like a lot—it might even sound nice to have warmer days. But think about it like this. You have on a hoodie and jeans and maybe a hat, too. You are comfortable—not too hot, not too cold. Then, someone cranks up the heat. Suddenly, you are sweating and shedding layers. Or you move to another room that’s cooler. Or open a window to cool the room back down.
As a human, you are able to adapt quickly. Other species? Not so much. Trees in the rainforest of South America, for example, are gradually growing farther uphill to stay in a climate they are adapted to. But the change is happening too fast for them to keep up.
One impact of global warming is melting polar ice. The melting of sea ice will disrupt many polar species, including polar bears, which depend on the ice for hunting. In addition, as the ice melts, sea levels will rise, flooding many island and coastal habitats. These areas will simply be under water, putting all species in these locations at risk. Tigers are one species that stand to lose almost all of their breeding grounds as sea levels rise.
Polar bears depend on the ice because it serves as a platform from which to hunt for their favorite food—seals.
credit: Dr. Kathy Crane, NOAA Arctic Research Office
TED-Ed has put together an archive of short informational videos that can teach you more about our changing climate. There are videos on renewable energy, the buildup of CO2 in our atmosphere, animals’ ability to adapt to climate change, human impacts in the geologic record, and more.
TED-Ed Changing Climate
ocean acidification: the process by which the ocean absorbs carbon dioxide from the atmosphere, and through a series of chemical reactions, becomes more acidic.
coral bleaching: a sign of poor health in coral that happens when algae in the coral die or lose their color.
Climate change will also result in hotter temperatures, which threaten the survival of African wild dog pups, which are heat-sensitive. Rising temperatures mean shrinking water supplies, which affects many different species— including humans. Weather patterns are changing, too, causing more extreme weather events in many parts of the world.
Increased CO2 levels affect marine life as well. The ocean naturally absorbs CO2 from the atmosphere, where it dissolves. In the process, chemical reactions turn the CO2 into an acid. But with more CO2 in the atmosphere, more CO2 is being absorbed by the oceans, and our oceans are becoming too acidic.
Coral bleaching at Mariana Islands, Guam
credit: David Burdick
Because of ocean acidification, many shelled marine species can’t produce hard, healthy shells. Species such as clams, oysters, and mussels are threatened. Coral reefs are, too. Corals are actually animals that together form a community called a reef. Ocean acidification is causing coral growth to slow, and the corals’ skeletons are weaker. Without healthy skeletons and shells, many species, including coral, are more vulnerable to predators and erosion.
DID YOU KNOW?
Unless humans make changes, more than half of Earth’s marine species may be at risk for extinction by the year 2100.
Coral reefs are also affected by higher water temperatures, which cause a loss of microscopic algae, the main food source of coral. This results in coral bleaching. The earth has already seen a steady decline in the number of healthy coral reefs. If coral reefs disappear, the many marine species that depend on coral reefs for food and shelter may disappear as well.
POLLUTION
When you think of pollution, what comes to mind? Perhaps you think of piles of litter along a street. Or a brown cloud spewing out of the smokestack of a factory. Or maybe an oil spill in the ocean. These are just a few examples of the many types of pollution that result from human activity. And each one affects biodiversity.
Pesticides in Honey
Bees are an extremely important part of the world’s ecosystems. Not only do they pollinate flowers and crops, they also produce honey. Yet their numbers have been dropping significantly. This is partly due to climate change and habitat loss. Pesticides also affect bee populations. Scientists have even discovered traces of toxic pesticides in honey. When bees collect nectar from flowers or plants treated with chemicals, the pesticides go back to the hive with them.
agriculture: growing plants and raising animals for food and other products.
runoff: produced when water picks up wastes as it flows over the surface of the ground. Runoff can pollute streams, lakes, rivers, and oceans.
single-use: describes an item that is made to be used only one time and then thrown away.
microplastic: a tiny piece of plastic less than 0.2 inch in size.
An algae bloom
credit: Eric Vance, U.S. EPA
Pollution is any material or substance that comes into an environment and is poisonous or can cause harm. Similar to litter, smoke, and oil spills, many types of pollution are easy to see. But many serious pollution threats to biodiversity cannot be seen.
The fertilizers and pesticides used in agriculture are one threat that is gaining more attention. Pesticides do a great job of getting rid of pests, but they also kill other insects as well as beneficial microbes in the soil. Then, the harmful chemicals make their way into the soil and the water, affecting fish and other organisms.
And while some fertilizers and animal waste are not directly toxic, they are full of nutrients that upset the balance of nearby and downstream habitats. Nitrogen fertilizers have caused many “dead zones” in the earth’s oceans and other water sources.
A dead zone is an area where nitrogen has created an overgrowth of algae—an algae bloom. Some of the algal blooms are toxic, killing fish and marine birds and mammals. Whether directly toxic or not, when the algae die and decompose, the process takes up all the oxygen in the surrounding water. With little or no oxygen, most marine life cannot survive.
A beach in Hawaii covered in plastic debris.
credit: U .S. Fish and Wildlife Service Headquarters (CC BY 2.0)
The earth’s oceans have growing numbers of dead zones. One of the largest forms every spring along the Gulf of Mexico in the southern United States as a result of fertilizer runoff from farms far upstream in the Missouri and Mississippi watersheds.
Another source of pollution that goes unnoticed, especially in the ocean, is plastic trash.
Plastic has become a big part of our lives. Much of the plastic produced, however, is single-use plastic. That means you use it once and throw it away—think of plastic bottles, bags, and utensils. Unfortunately, only a small percentage of plastic gets recycled. The rest ends up in landfills or makes its way into the ocean. Even worse, plastic never decomposes. As time passes, it does break down into smaller and smaller pieces, called microplastics, but it never fully goes away. This has become an enormous problem for marine life. The problem is so bad that huge garbage patches have formed in the world’s oceans. These patches are places where ocean currents bring the trash together in gigantic swirls that cover millions of square miles.
Does this look like a jellyfish to you? It does to a sea turtle!
credit: Ben Mierement, NOAA NOS (ret.)
DID YOU KNOW?
Every year, approximately 9 million tons of plastic trash go into the ocean.
The issue of plastic trash in the ocean affects more than 700 marine species. Some species get tangled in discarded fishing nets. Others, such as sea turtles, eat the plastic by accident. Unfortunately, a plastic bag floating in the ocean looks a lot like a jellyfish—the turtles’ favorite food.
The Laysan albatross on Midway Atoll in the North Pacific also mistakes plastic trash for food. Sadly, they bring this plastic “food” back to their young. On the atoll, the stomachs of dead birds are found to be full of plastic trash.
Plastic trash in our oceans is one of the greatest threats facing biodiversity in the sea. And plastic bottles are one of the leading sources of this trash. Every minute, 1 million of these bottles are bought around the world. But less than 10 percent are recycled. Learn about the origin of these bottles and what happens when they aren’t disposed of properly.
Ted ed plastic bryce
The birds starve to death with a full stomach.
Plastic pollution affects the entire food chain. Even if an organism ingests plastic and isn’t harmed right away, the plastic itself is toxic. The toxins have effects on a species’ reproduction, health, and survival skills. Then, when another species comes along and eats the first, they are taking in microplastics and toxic chemicals, too. This happens all the way up the food chain to humans. A study by a university in Belgium found that people who eat seafood regularly eat up to 11,000 bits of microplastic per year!
HABITAT LOSS AND FRAGMENTATION
As the human population grows, more and more of the earth’s land surface is converted for human use. Some of this is for development—houses, grocery stores, cities, roads, and more. Much of it is for agricultural uses to feed growing populations.
Every time land is converted for human use, other species are killed or pushed out. Can you imagine a bear knocking on your door and saying, “Hey, get out. Time to move on.” The bear moves into the kitchen, mountain lions make dens in the basement, and birds take over the attic. And you are out of a home.
Garbage Patches
In the world’s oceans, there are five large swirling masses of trash called garbage patches. How does this happen? Most of the trash originates on land and makes its way into the sea. Sometimes, cargo ships lose their loads, which dumps more debris into the ocean. The debris is then caught up in ocean currents. Where these currents meet, the water swirls in a gigantic spiral, concentrating the debris in one place. These garbage patches are not solid islands of plastic, but places in the ocean where the trash is concentrated. It’s like a thin soup with flakes of plastic and the occasional larger chunks of plastic. The largest patch is the Great Pacific Garbage Patch. It is estimated to be more than twice the size of Texas.
fragmentation: the act of breaking something into smaller sections or pieces.
over-exploitation: the hunting or taking of a natural resource (such as animals or trees) faster than the population can reproduce, which often leads to extinction.
poaching: the illegal hunting and killing of animals.
medicinal: having properties that can be used to treat illnesses.
When species lose their habitat, they must adapt or move.
Otherwise, they will die. Think about what might have lived on the very spot your home or school is on now. What was the native habitat?
Habitat destruction has become the leading cause of biodiversity loss around the world. Can you imagine a world without orangutans in the wild? That’s exactly what is happening. Orangutans are on the brink of extinction because their habitat in Indonesia and Malaysia is being cleared for palm oil production and other agricultural uses. This type of deforestation is occurring around the world, including in the old-growth forest of the Pacific Northwest. The deforestation results in the loss of tree species as well as the plants and animals in that ecosystem.
DID YOU KNOW?
Humans have converted 37 percent of Earth’s land surface to agricultural uses.
An orangutan in Indonesia
credit: Tim Laman (CC BY 4.0)
As humans continue to convert land, we divide natural ecosystems into smaller and smaller pieces. This fragmentation restricts species to living in smaller areas. The fragments are cut off from other fragments and may not provide species with enough space to roam, eat, and find a mate.
OVER-EXPLOITATION
Another threat to biodiversity is over-exploitation. Humans are hunting some species faster than those species can reproduce.
Illegal wildlife trade is a type of over-exploitation that occurs around the world. Also called poaching, this occurs when animals are hunted or captured even though they are protected. Pangolins, a scaly anteater, are one of these animals. They are killed for their scales. In China and Vietnam, it is believed that these scales have medicinal value.
Similarly, sharks are killed for their fins to make shark-fin soup in Asia. The demand for shark fins is so great that many shark species are at risk for extinction, and as many as 100 million sharks are killed each year. Elephants are killed for their ivory tusks, rhinos for their horns, and tigers for their fur.
An adult pangolin with a baby
credit: U.S. Fish and Wildlife Service Headquarters (CC BY 2.0)
People who keep track of elephant populations noted a 30-percent decline in African elephants between 2007 and 2014. The fear is that if the poaching continues at that rate, these elephants will be extinct by the year 2040.
Over-exploitation affects many other species as well. People trade exotic birds as pets. Plants are illegally traded, too. People commit these crimes because the demand is huge and the money is good. Yet this wildlife trade is considered one of the greatest threats to endangered species.
Even common species with large populations can quickly suffer from over-exploitation.
Bizarre Biodiversity
Red Crab: This land crab that lives only on islands in the Indian Ocean migrates in masses (about 15 million!) from the forest to the ocean.
credit: DIAC images (CC BY 2.0)
The ocean, for example, was once thought to hold a never-ending supply of fish. Off the coast of Newfoundland, Canada, people made their living fishing for cod for more than 500 years. But as technology improved and human populations grew, larger and larger catches were harvested.
By 1992, the cod population was only 1 percent of what it was in the 1980s. To try to fix the situation, all cod fishing was banned. More than 20 years later, the population had recovered a little, but was still only 25 percent of 1980s levels. Many species have gone extinct due to this type of over-exploitation, including the passenger pigeon, the Steller’s sea cow, and the Pinta Island tortoise.
DID YOU KNOW?
Noise and light pollution are also affecting species, including birds, sea turtles, and whales.
Magnified Microbiome!
Indoors
Humans have explored ecosystems around the planet, but ones that we still don’t know much about are the ecosystems within our own homes!
Microbes are everywhere indoors—on doorknobs, floors, light switches, toilet seats, counters, sinks, your pillow, and more. Even the air is full of microbes. One cubic meter of indoor air has up to 10 million cells of bacteria! But as you’ve learned, most of these microbes are not bad. These helpful microbes are needed to maintain healthy environments.
Researchers have discovered that humans have a complicated relationship with the microbes in our homes. Home microbiome studies are looking into these organisms we share our homes with to understand the role they have in human health. And while the microbes affect us humans, the research has already found that the people living within a home affect the microbes there. When someone leaves a house for a few days, taking their microbes with them, the microbe community in the home changes.
Invasive species can threaten biodiversity, too. Sometimes, humans bring species from one place to another, either accidentally or on purpose. Species introduced from somewhere else don’t always cause harm to an ecosystem. However, when an introduced species upsets an ecosystem’s balance and decreases ecosystem function, it is considered invasive.
This happens when the new species finds itself in an ecosystem with few predators. It might do well against native species in the competition for food and other resources. It might also reproduce quickly. Often, native species have no defenses, can’t escape, or cannot adapt. The result is that the entire food web is altered and ecosystem function decreases.
Zebra mussels on a native mussel
credit: U.S. Fish and Wildlife Service
Ever since humans began to travel the globe, species of plants, animals, bacteria, and other organisms have traveled with them. The zebra mussel is a species native to Russia that made its way to the United States as a hitchhiker on the hulls of ships. First discovered in the United States in 1982, the tiny zebra mussel is causing great problems for the ecosystems of the Great Lakes and rivers of the country. They attach themselves to and damage native mussels, filter out algae that native species use for food, and gum up any water filtrations or intake systems on the river or lake.
DID YOU KNOW?
The brown tree snake was accidentally introduced to the island of Guam at the end of World War II and has since wiped out the native bird population.
Another type of invasive species that is proving to be especially deadly is disease. Again, species evolve and adapt to their environment through time. But when a new disease is introduced, species do not have the defenses to fight the disease.
One example is the chytrid fungus that affects amphibians. Humans have helped spread the fungus around the world through the wildlife trade, causing one of the largest wildlife extinctions ever seen. The fungus is responsible for extinction of hundreds of species of frogs and other amphibians.
More than any other species that has come before us, humans have had an enormous impact on Earth and on biodiversity. Technology has increased our ability to transform the planet to meet our needs. And as the human population continues to grow, so does our impact.
In fact, as the human population increases, species diversity decreases.
By the year 2050, the human population on Earth is expected to reach 9 billion. Meanwhile, more than 23,000 species around the world are at risk for extinction. That includes more than 40 percent of all amphibians, 33 percent of reef-building corals, and 13 percent of birds. The question becomes, what can we do about it?
ESSENTIAL QUESTION
What are the threats to biodiversity today?
WANTS VS. NEEDS
In the modern world, we tend to use the word “need” quite a bit. But as a species, how much do we truly need? Let’s take a look.
›Create a two-column table. Label the first column “needs” and the second column “wants.”
›Begin by considering what you think the definition of “need” is. What is the definition of “want” in comparison?
›Now, think carefully about what you, as a human, need for basic survival. List these things that you absolutely cannot live without. If you are being honest, this “needs” column will have only four or five items.
›Now, list things in your life that you want in the “wants” column.
›As you look at your list, do you think that the needs of all humans are the same? How about the wants? Was there a time when your needs were not met? What did you do? How do humans respond when their needs aren’t met?
›Compare your list with lists made by family, friends, or classmates.
Consider This
Now, consider plants and animals in nature. What do they need to survive? Do different species have different needs? Are other species’ needs different from yours? How do humans’ wants interfere with the needs of other species?
When humans drill for and transport oil, sometimes oil spills in the ocean. When these disasters happen, millions of gallons of oil are released into the sea, affecting all biodiversity. Birds are some of the many victims. Start a scientific method worksheet and predict how you think birds’ feathers might be affected by an oil spill and how that, in turn, might affect the bird.
Caution: Wear gloves to handle the feathers.
›To understand how oil affects birds’ feathers, find some loose feathers and clean them.
›Put some oil, such as olive oil or bike oil, on the feathers and rub it in. Then, drop water on the feathers. What happens? How would a bird be affected if all its feathers were coated in oil? What would happen to the bird?
›Try to clean the oil off the feathers. What happens if you use cold water? Hot water? Try adding dish soap to the water—does that help? What else can you try? What does this tell you about the difficulty of cleaning up large oil spills in the ocean?
DID YOU KNOW?
After oil spills, countless volunteers turn out to rescue affected birds. They use Dawn dishwashing liquid to remove the oil from birds’ feathers!
Consider This
Investigate further to learn how oil spills affect birds to see if your prediction was correct. Then, research recent oil spills to learn how the entire ecosystem was affected. Does the ecosystem recover? How long might that take? Can you come up with some creative solutions to help birds after an oil spill? Use your feathers to investigate solutions.
Ideas for supplies: pots, soil, plant seeds, vinegar
Acid rain is one of the many problems resulting from pollution in the air. Acid rain forms when water vapor combines with chemicals in the air from burning coal and fossil fuels, from manufacturing, or from other smoke. The precipitation falls as acid rain. Start a scientific method worksheet. What do you predict that the effects of acid rain might be on biodiversity?
›Label three pots as #1, #2, and #3. Plant the same type of seeds in each pot. Use fast-growing seeds such as beans or peas. Use the same type of soil for each pot as well.
›Water plant #1 with 100-percent water. Give plant #2 a mix of about 90-percent water and 10-percent vinegar. Finally, water plant #3 with a 50-50 mix of water and vinegar.
›Which plant do you think will grow the fastest? Which will be the healthiest? Make your predictions and record them in your science journal. Make observations every day and take notes in your science journal.
DID YOU KNOW?
American wildlife ecologist and author Aldo Leopold (1887–1948) once noted, “We abuse land because we regard it as a commodity belonging to us. When we see land as a community to which we belong, we may begin to use it with love and respect.”
Consider This
Were your predictions correct? How was the growth of each plant similar? How were they different? Now think about plants in nature. How are they affected by acid rain? Can they adapt to this change? Consider the rest of the food chain. How might other species be affected by acid rain? How might ecosystems be affected? How does acid rain affect humans?
WORDS TO KNOW
acid rain: precipitation that has been polluted by acid.
