Category extinction

WHY IS THE FORESTS OF THE MARINE WORLD UNDER THREAT?

A type of algae, kelp is crucial for thriving ecosystems the world over. However, kelp forests are shrinking. But, why? Let’s find out

Most types of seaweed or marine algae grow along the coasts in shallow waters, where they can attach themselves to rocks, shells, or the sea floor. A root-like part called holdfast anchors them firmly and prevents them being washed away by strong waves or currents. A soft, flexible stem-like frond with outgrowths similar to leaves emerges from the holdfast. Though they carry out photosynthesis, algae are not plants as they don’t have true roots, stems, leaves, or flowers. Marine algae can be green, brown, or red in colour. Red algae are delicate and feathery and prefer warm tropical seas. Small green algae are found everywhere in shallow waters. Brown algae called giant kelp grow in cool waters at depths ranging from 15 to 40 mt.

Extraordinary ecosystem

A kelp forest is one of the most valuable and productive: ecosystems on Earth. Kelp forests are found all over the world-the west coasts of North and South America, the southern tip of Africa and Australia, and off islands near Antarctica. In North America, kelp forests are found on the Pacific Coast from Alaska to California. A forest of kelp is home to a variety of creatures. They live and forage for food among its broad blades. The kelp provides shelter not only from predators. but also from storms. Mammals and birds that thrive in kelp forests include seals, sea lions, whales, sea otters, gulls, terms, egrets, and herons. Sea otters have an especially beneficial bond with kelp. Mother otters wrap their babies in kelp to keep them from drifting away while they go hunting. Adult otters also find the dense kelp canopies a secure place to snooze. The otters return the favour by eating sea urchins that dine on kelp. Kelp forests can shoot up in no time, growing up to 30 cm a day. Some species attain heights of over 45 mt!

Kelp farming is a big part of the billion-dollar global seaweed-farming industry. Kelp renders sea water less acidic. This enables kelp farmers to raise shellfish, which require low acidity. Kelp and mussels are grown on floating ropes, which also support baskets of scallops and oysters. One kelp farm can produce 40 metric tonnes of kelp and a million shellfish per hectare per year! As with other species of seaweed, kelp is used in many products,) including shampoos and toothpastes, as well as a wide range of foods such as salad dressings, puddings, cakes, dairy products, and ice cream. It is also employed in pharmaceuticals and in the manufacture of fireproof and waterproof textiles.

Urchin attack

The waters off the coast of northern California are home to lush forests of bull kelp. Since 2013, the population of purple sea urchins that feast on the kelp, has exploded, destroying almost 90 % of the kelp forest. Sea stars prey on purple urchins and keep their numbers in check. However, a mysterious disease killed off huge numbers of sea stars, leaving sea urchins to thrive. Sea snails (called red abalone) and red sea urchins, both of which are raised for meat and feed on bull kelp, died from starvation. Commercial red sea urchin and red abalone fisheries located on America’s northwestern coast have closed down as a result.

Fact file

• Kelp forests are the ocean’s lungs just as trees are the Earth’s lungs. They absorb carbon dioxide and give out oxygen.

• Warming seas along the Australian coast have wiped out huge swathes of kelp forest.

•Extremely hot weather is harmful to kelp forests. Strong storms can wipe out large areas by uprooting the plants from the sea floor.

• There are 18 species of edible kelp, including kombu widely used in Japanese cuisine.

•Kelp is rich in calcium and Vitamin K.

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WHAT IS MEAN BY EXTINCTION?

The dying out or extermination of a species is what is referred to as extinction. When species are diminished because of environmental factors or because of evolutionary changes in their members, extinction occurs. While rates of extinction have varied largely, human activities, deforestation, habitat loss, over-hunting, pollution and climate change have meant that the present-day extinction rate is many times more than what it was previously.

About 541 million years ago, a great expansion occurred in the diversity of multicellular organisms. Paleobiologists, scientists who study the fossils of plants and animals to learn how life evolved, call this event the Cambrian Explosion. Since the Cambrian Explosion, there have been five mass extinctions, each of which is named for the geological period in which it occurred, or for the periods that immediately preceded and followed it.

The first mass extinction is called the Ordovician-Silurian Extinction. It occurred about 440 million years ago, at the end of the period that paleontologists and geologists call the Ordovician, and followed by the start of the Silurian period. In this extinction event, many small organisms of the sea became extinct. The next mass extinction is called Devonian extinction, occurring 365 million years ago during the Devonian period. This extinction also saw the end of numerous sea organisms.

The largest extinction took place around 250 million years ago. Known as the Permian-Triassic extinction, or the Great Dying, this event saw the end of more than 90 percent of the Earth’s species. Although life on Earth was nearly wiped out, the Great Dying made room for new organisms, including the first dinosaurs. About 210 million years ago, between the Triassic and Jurassic periods, came another mass extinction. By eliminating many large animals, this extinction event cleared the way for dinosaurs to flourish. Finally, about 65.5 million years ago, at the end of the Cretaceous period came the fifth mass extinction. This is the famous extinction event that brought the age of the dinosaurs to an end.

In each of these cases, the mass extinction created niches or openings in the Earth’s ecosystems. Those niches allowed for new groups of organisms to thrive and diversify, which produced a range of new species. In the case of the Cretaceous extinction, the demise of the dinosaurs allowed mammals to thrive and grow larger.

Scientists refer to the current time as the Anthropocene period, meaning the period of humanity. They warn that, because of human activities such as pollution, overfishing, and the cutting down of forests, the Earth might be on the verge of—or already in—a sixth mass extinction. If that is true, what new life would rise up to fill the niche that we currently occupy?

Credit : National geographic 

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WHAT SPECIES ARE ON THE BRINK OF EXTINCTION?

Can you believe that at least one in five reptile species in the world are threatened with extinction? Yes, that is what the first major global assessment of the world’s cold blooded creatures reveals. Let’s look at the findings.

At least one in five reptile species are threatened with extinction, including more than half of turtles and crocodiles, according to the first major global. assessment of the world’s so-called cold-blooded creatures.

Catastrophic declines in biodiversity across the world are increasingly seen as a threat to life on Earth- and as important as the interrelated menace of climate change.

Threats to other creatures have been well documented. More than 40 percent of amphibians, 25 percent of mammals and 13 percent of birds could face extinction. But until now, researchers did not have a comprehensive picture of the proportion of reptiles at risk.

HOW MANY SPECIES ASSESSED

In a new global assessment. published in the journal Nature, researchers assessed 10,196 reptile species and evaluated them using criteria from the International Union for Conservation of Nature (IUCN) Red List of threatened species.

They found that at least 1,829. 21 per cent were either vulnerable, endangered or critically endangered. “It’s just overwhelming the number of species that we see as being threatened,” said co-author Neil Cox, who manages the IUCN-Conservation International Biodiversity Assessment Unit and co-led the study. “Now we know the threats facing each reptile species, the global community can take the next step…. and invest in turning around the often too under-appreciated and severe biodiversity crisis.”

TOOK 15 LONG YEARS

Young said the reptile assessment. which involved hundreds of scientists from across the world, took around 15 years to complete because of a lack of funding.

“Reptiles, to many people, are not charismatic. And there’s just been a lot more focus on some of the more furry or feathery species of vertebrates for conservation,” he said. Researchers hope the new assessment will help spur international action to halt biodiversity loss. Almost 200 countries are currently locked in global biodiversity talks to try to safeguard nature, including a key milestone of 30 percent of Earth’s surface protected by 2030.

“Through work like this, we advertise the importance of these creatures. They’re part of the tree of life, just like any other and equally deserving of attention,” Young said.  AFP. Crocodiles and turtles were found to be among the most at-risk species, with around 58 percent and 50 percent of those assessed found to be under threat respectively.  Crocodiles are killed for their meat and to remove them from human settlements. Turtles are targeted by the pet trade and used for traditional medicine. The Komodo dragon of the Indonesian islands is threatened with extinction, researchers say.

WHERE ARE THEY FOUND?

Threatened reptiles were largely found concentrated in Southeast Asia, Western Africa, northern Madagascar, the Northern Andes and the Caribbean. Reptiles restricted to arid habitats such as deserts, grasslands, and savannas are significantly less threatened than those in forest habitats, the study says.

THE KING IS IN DANGER

Another well-known species at risk is the fearsome king cobra, the world’s largest venomous snake. It has been classified as vulnerable, indicating it is very close to extinction”, according to the research. “It’s a real iconic species in Asia and it’s such a shame that even widespread species such as this are really suffering and in decline”. Logging and deliberate attacks by humans were among the biggest threats to the snake.

WHAT ARE THE THREATS THEY FACE?

Agriculture. logging. invasive species and urban development were found to be among the threats to reptiles, while people also target them for the pet trade or kill them for food or out of fear.

Climate change was found to pose a direct threat to some 10 per cent of reptile species. Longer-term threats such as sea level rise, or indirect climate-driven dangers such as fire, and from things like disease also have an impact.

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WHY DO CREATURES GO EXTINCT?

Extinction is when an entire population of a particular creature disappears from Earth. Though it sounds drastic, extinctions are quite common in Earth’s history. Scientists believe that 99 per cent – over five billion species that ever lived – have become extinct since the beginning of life. This could have happened due to reasons of lack of food or disastrous events like asteroids hitting Earth. In recent times, the speed at which species are becoming extinct has increased due to human activity.

The most common cause of extinction is a sudden, serious change in a species’ habitat. A habitat is the surroundings in which an animal lives. Animals can rarely survive such sudden change. Their food supply may be wiped out. They may also lose shelter or other things that they need to survive.

Many things can change a species’ habitat. Floods, fires, droughts, volcanoes, and other natural events may be causes. People also change the environment in ways that drastically affect animals. People clear forests and drain wetlands. They build dams that disrupt the flow of rivers. They build cities on land that animals need to survive. They also create harmful pollution.

Some changes that cause extinction affect only a small area. Others are large enough to affect the entire world. A fire or other local event may cause the extinction of animals that live only in that region. A sudden change in the global climate might wipe out an animal species that lives in many parts of the world.

People can cause extinctions more directly as well. Some species have been hunted to extinction. The passenger pigeon is one example of this. Humans killed millions of the birds over many years. The last one died in the early 1900s.

Dinosaurs first appeared on Earth about 215 million years ago. They were the most important land animals for more than 150 million years. By 65 million years ago, however, the dinosaurs had died out.

Many scientists believe that a large asteroid, or rock from space, caused this mass extinction. When the asteroid hit Earth, the impact caused drastic changes. Thick dust and other materials blocked the sun. Temperatures dropped, and plants could not grow. The dinosaurs could not survive the cold temperatures and lack of food. But early species of birds and mammals did survive.

Credit: Kids Britannica

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