Are We Facing the Sixth Mass Extinction? How Climate Change Is Driving Species to the Brink

Are We Facing the Sixth Mass Extinction? How Climate Change Is Driving Species to the Brink

KAKALI DAS

For most of Earth’s long history, life has risen, flourished, and disappeared in powerful cycles. Around 66 million years ago, dinosaurs ruled the planet. They were strong, diverse, and widespread.

Yet a sudden environmental disaster, most likely caused by a massive asteroid impact, changed the climate so drastically that they could not survive. Their extinction marked the end of an era. However, this was not the only time life on Earth faced such a crisis.

Over the nearly four billion year history of life on Earth, the planet has experienced five major mass extinctions, collectively known as the Big Five.

The first, the Ordovician Silurian extinction about 440 to 450 million years ago, was caused by severe global cooling and falling sea levels that wiped out nearly 85 percent of marine species.

The Late Devonian extinction, which occurred around 372 to 359 million years ago, unfolded over a long period of environmental instability, likely linked to oxygen loss in the oceans and significant climate shifts.

The most devastating event, the Permian Triassic extinction about 252 million years ago, is often called the Great Dying, when massive volcanic eruptions triggered extreme global warming and led to the disappearance of around 90 to 97 percent of all species.

The Triassic Jurassic extinction around 201 million years ago was also associated with intense volcanic activity and climate change, clearing the way for dinosaurs to rise and dominate the Earth.

Finally, the Cretaceous Paleogene extinction about 66 million years ago, caused mainly by a large asteroid impact, brought an end to the age of dinosaurs along with many other forms of life.

Extinction itself is a natural process. Scientists estimate that, on average, about ten percent of species disappear every one million years. This gradual change is part of evolution. Some species adapt and survive, while others cannot adjust to changing conditions. But mass extinction is very different. It happens when a very large number of species disappear within a relatively short period in geological time. In such events, up to seventy to ninety percent of species can vanish. These are rare and catastrophic moments in Earth’s history.

The largest of the Big Five occurred at the end of the Permian period about 250 million years ago, often called the Great Dying. During this event, around ninety seven percent of land species and about eighty five percent of marine species became extinct. The causes were linked to massive volcanic activity that lasted for millions of years. Enormous eruptions released huge amounts of volcanic ash, dust, and gases into the atmosphere. At first, the dust blocked sunlight and caused global cooling. Later, large amounts of carbon dioxide released by the volcanoes created a powerful greenhouse effect. Global temperatures rose by about thirteen degrees Celsius over several hundred thousand years.

This extreme warming caused serious damage. Ocean currents slowed down. Oxygen levels in the oceans dropped. Carbon dioxide dissolved in seawater, making the oceans more acidic. Many marine organisms could not survive in these harsh conditions. On land, plants and animals also struggled as temperatures changed rapidly. A chain reaction of environmental changes led to the collapse of ecosystems. Life eventually recovered, but it took millions of years.

Scientists studying these past events have discovered that rapid temperature changes were a key factor in mass extinctions. In some cases, temperatures changed by about ten degrees Celsius over one million years. That may sound slow, but in geological terms, it is very fast. Species need time to adapt. When change happens too quickly, they cannot evolve fast enough to survive.

Today, many scientists warn that we may be entering a sixth mass extinction. Unlike the previous five, this crisis is not caused by volcanoes or asteroids. It is mainly driven by human activities. Deforestation, pollution, overfishing, habitat destruction, and the burning of fossil fuels are placing enormous pressure on life on Earth. Climate change, caused by greenhouse gases such as carbon dioxide, is one of the most serious threats.

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The International Union for Conservation of Nature, known as the IUCN, regularly assesses the risk of extinction for species around the world. According to its latest Red List data, more than forty eight thousand species are now facing the threat of extinction. This number has increased sharply over the past few decades. Approximately sixteen thousand species are directly affected by climate change. These numbers are alarming and suggest that biodiversity loss is happening at an unprecedented rate.

The Secretary General of the United Nations, Antonio Guterres, has warned that humanity is turning nature into a weapon of mass extinction. He has said that we are treating the planet like a toilet, using and polluting it without thinking about the consequences. His words reflect growing global concern that human actions are pushing ecosystems beyond their limits.

Climate change affects species in many ways. Rising temperatures alter habitats and disturb natural cycles. Some animals and plants are adapted to very specific conditions. When those conditions change, survival becomes difficult. For example, coral reefs are highly sensitive to temperature. Corals live in a close relationship with tiny algae that provide them with food and colour. When ocean temperatures rise, corals become stressed and expel these algae. This process is called coral bleaching. Without the algae, corals turn white and can die if the stress continues.

Scientists predict that even if global warming is limited to one point five degrees Celsius above pre industrial levels, seventy to ninety percent of the world’s coral reefs could disappear. If temperatures rise by two degrees, up to ninety nine percent may be lost. Coral reefs support a vast number of marine species. Their loss would have serious consequences for fish populations and for millions of people who depend on them for food and income.

The Arctic region is another area experiencing rapid change. Temperatures there are rising about three times faster than the global average. Arctic sea ice has been shrinking dramatically. Satellite data collected since 1979 show a clear decline in both the thickness and extent of sea ice. In recent years, winter sea ice has reached record low levels. Scientists predict that in the future, summer sea ice could disappear completely.

Polar bears depend on sea ice to hunt seals, their main source of food. As the ice melts earlier in spring and forms later in autumn, polar bears have less time to hunt. This affects their health and their ability to reproduce. In parts of Canada, the polar bear population has declined by about fifty percent over the past forty years. Studies show that if sea ice breaks up one month earlier than in the past, a large percentage of pregnant females may fail to reproduce successfully.

Climate change also affects mountain ecosystems. In high altitude regions, many plant species grow only in narrow temperature ranges. When temperatures rise, snow melts earlier in spring. This can dry out the soil and change growing conditions. In some Japanese mountain ranges, annual average temperatures have risen by more than one degree over the past several decades. As a result, certain alpine flowers have disappeared from areas where they once covered the ground. Other plants that prefer warmer and drier conditions are spreading.

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These changes can disturb relationships between species. Many alpine plants depend on insects such as bumblebees for pollination. When warmer temperatures cause plants to bloom earlier, but insects do not change their life cycles at the same speed, a mismatch occurs. Flowers may bloom before pollinators are active. This can reduce reproduction for both plants and insects. Such disruptions can spread through the food chain and affect birds and other animals.

Biodiversity is closely linked to ecosystem services, which are the benefits humans receive from nature. These include clean air, clean water, food production, and disease control. Healthy ecosystems with high biodiversity are generally more stable and better able to resist disturbances. When biodiversity declines, these services can weaken.

One example is pollination. Bees and other pollinators are essential for the production of many fruits and vegetables. The Food and Agriculture Organization estimates that more than seventy five percent of global food crops depend to some extent on pollinators. However, many bee species are declining due to habitat loss, pesticide use, and climate change. Rising temperatures can alter the timing of flowering and reduce food sources for bees. In some regions, farmers have reported that bees stop pollinating during periods of extreme heat. When natural pollination fails, farmers must do the work by hand, which is time consuming and costly. Yields can decrease, affecting food supply and income.

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Climate change can also influence the spread of diseases. Diverse ecosystems often help regulate infectious diseases by limiting the spread of pathogens. When biodiversity decreases, disease carrying organisms may multiply more easily. Changes in temperature and rainfall patterns can expand the range of insects that carry diseases. Migratory birds may change their routes and timing due to climate shifts, potentially altering the spread of avian diseases.

Unlike past mass extinctions, which occurred over thousands or millions of years, the current rate of extinction is extremely fast. Scientists estimate that species are disappearing at a rate one hundred to one thousand times higher than the natural background rate. This rapid pace leaves little time for adaptation. Evolution requires generations. When environmental change happens within decades, many species cannot adjust.

Human activities are leaving clear marks on the planet. Studies of ocean floor sediments show traces of micro-plastics and radioactive materials from nuclear tests beginning around the mid twentieth century. Ice cores drilled from Antarctica contain tiny bubbles of ancient air. By analysing these bubbles, scientists can measure past levels of carbon dioxide. The data show a sharp increase in carbon dioxide since the industrial revolution. The chemical signature of this carbon indicates that it comes mainly from burning fossil fuels.

Efforts to combat climate change are increasing worldwide. Renewable energy sources such as wind power are expanding rapidly. However, even well intended solutions can have unintended effects. Wind turbines can pose a threat to birds, especially large species like eagles. In some areas, hundreds of birds die each year from collisions with turbine blades. Offshore wind farms can also affect seabirds by altering their flight paths and feeding patterns. This highlights the need for careful planning to balance climate action with wildlife protection.

To protect biodiversity, conservationists are working on multiple fronts. Protecting natural habitats is essential. Establishing protected areas can help preserve ecosystems and give species space to survive. Reducing greenhouse gas emissions is crucial to slow climate change. Sustainable farming, responsible fishing, and reducing pollution are also important.

Some scientists are developing new methods to safeguard genetic diversity. One such approach is cryopreservation, in which living cells and tissues from endangered species are stored at very low temperatures. These frozen samples can potentially be used in future research or breeding programs. By preserving living cells rather than only preserved specimens, scientists hope to keep open the possibility of restoring genetic lines that might otherwise be lost. While such projects act as a final safety measure, experts emphasize that preventing extinction in the wild is far more important.

The idea of a sixth mass extinction may seem distant or abstract to many people. But extinction is not only something that happens in textbooks or far away places. It can occur quietly in local environments. A small butterfly found only in a limited region may disappear due to habitat destruction or climate shifts. When that happens, an entire unique genetic history is lost forever.

Everything in nature is connected. The disappearance of one species can affect many others. For example, the extinction of wolves in certain regions led to an increase in deer populations. Overgrazing by deer damaged vegetation, which in turn affected other plants and animals. Such cascading effects show how delicate ecological balance can be.

The future depends on the actions we take today. Governments, scientists, communities, and individuals all have roles to play. Reducing carbon emissions, conserving forests, protecting oceans, and supporting sustainable practices are essential steps. Education and awareness are also important. When people understand that biodiversity supports their daily lives, they may be more willing to act.

Mass extinctions in the past reshaped life on Earth. Each time, life eventually recovered, but the process took millions of years and created entirely new ecosystems. Humanity cannot assume that it will escape the consequences of large scale biodiversity loss. Our food systems, economies, and health are deeply tied to the natural world.

We are living in a critical moment. The evidence shows that climate change and other human activities are driving species toward extinction at an alarming rate. While the situation is serious, it is not hopeless. The same human intelligence and innovation that have altered the planet can also help protect it. By learning from the past and respecting the limits of nature, we may still prevent the sixth mass extinction.

If future generations look back at this time, they may see it as the period when humanity faced a great challenge and chose to act responsibly. Whether in one hundred years or one million years, the story of our era will depend on the decisions we make now. Protecting biodiversity is not only about saving other species. It is about preserving the delicate web of life that sustains us all.

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