On the Brink of Extinction? Special Edition - IMPACTS: Climates Change the World

Key Concepts

• Mass Extinction: A significant decrease in the biodiversity of Earth, occurring when a large percentage of species go extinct within a relatively short geological timeframe.
• The Big Five: The five most severe mass extinction events in Earth’s history.
• Sixth Mass Extinction: The current ongoing extinction event, largely driven by human activity.
• Biodiversity: The variety of life in the world or in a particular habitat or ecosystem.
• Greenhouse Effect: The process by which certain gases in the Earth's atmosphere trap heat, leading to a warming of the planet.
• Ocean Deoxygenation: The reduction in oxygen levels in the ocean, often caused by warming temperatures and increased nutrient runoff.
• Phenological Mismatch: A disruption in the timing of biological events (e.g., flowering, insect emergence) due to climate change.
• Dilution Effect: The idea that higher biodiversity can reduce the spread of infectious diseases.
• Cryopreservation: The process of preserving cells, tissues, or organisms at very low temperatures.
• IPS Cells (Induced Pluripotent Stem Cells): Adult cells that have been genetically reprogrammed to behave like embryonic stem cells.

The Looming Sixth Mass Extinction: Lessons from the Past and Actions for the Future

Introduction

For nearly 4 billion years, life on Earth has experienced periods of both flourishing and catastrophic loss. Five major mass extinction events, known as “The Big Five,” have dramatically reshaped the planet’s biodiversity. However, scientists now warn that we are on the brink of a sixth mass extinction, unique in its primary driver: human activity. Currently, over 48,000 species are threatened with extinction, a fourfold increase in just 25 years. This crisis is fueled by environmental destruction, pollution, and, critically, climate change accelerated by greenhouse gas emissions. The International Union for Conservation of Nature (IUCN) reports approximately 16,000 endangered species are already affected by climate change. As UN Secretary-General Antonio Guterres starkly stated, “Humanity has become a weapon of mass extinction. We are treating nature like a toilet.” This necessitates a critical examination of past extinction events to inform present-day conservation efforts.

Understanding Past Mass Extinctions

Dr. Yab Atsushi, chief curator at the National Museum of Nature and Science in Tokyo, explains that while extinction is a natural process (approximately 10% of species go extinct every million years), mass extinctions represent a dramatically accelerated rate, reaching 70-90%. These events are triggered by rapid environmental changes stemming from both extraterrestrial and terrestrial phenomena.

A prime example is the Permian-Triassic extinction event, occurring around 250 million years ago, which wiped out 97% of land creatures (including Cotlerinkus, a Permian mammal ancestor) and 80-86% of marine species. This extinction was largely driven by massive volcanic activity. This activity released enormous amounts of volcanic dust, gas, and lava over millions of years. The initial effect was global cooling due to dust blocking sunlight, followed by long-term warming caused by the greenhouse effect of released carbon dioxide. Sea surface temperatures rose by approximately 13°C over 800,000 years, ocean currents slowed, leading to deoxygenation, and increased carbon dioxide dissolved in seawater caused ocean acidification. These cascading effects created an uninhabitable environment for countless life forms.

Dr. Yab emphasizes that past extinctions occurred over relatively short periods, with temperature changes happening at rates of around 10°C over 1 million years. This rate is a key factor in understanding the severity of these events and provides a benchmark for assessing the current crisis.

The Sixth Mass Extinction: Human-Driven Crisis

Unlike previous mass extinctions, the current crisis is directly attributable to human activities. The IUCN identifies environmental destruction and overexploitation of natural resources as major threats, with climate change acting as a significant accelerator. The number of species facing extinction has surged in recent years, highlighting the urgency of the situation.

The golden toad of Costa Rica, declared extinct in 2004, serves as a poignant example. Despite inhabiting a protected nature reserve free from deforestation and pollution, the toad succumbed to extinction primarily due to successive extreme droughts linked to climate change.

Coral reefs are also facing a catastrophic decline. Rising sea temperatures cause coral bleaching, weakening the coral and often leading to death. IPCC reports predict that even limiting global warming to 1.5°C will result in the loss of 70-90% of the world’s coral reefs, with a potential loss of 99% at 2°C. Mako Island in Japan provides a firsthand view of this devastation.

The Arctic is warming at three times the global average rate, threatening the polar bear, the largest land carnivore. The loss of sea ice, the polar bear’s primary hunting ground, is leading to a decline in their nutritional status. Studies show a 50% decline in the bear population in western Hudson Bay, Canada, over the past 40 years, and projections indicate that a one-month earlier spring sea ice breakup could lead to a 40-73% failure rate in female reproduction.

Interconnectedness and Cascading Effects

Dr. Onuma Manabu highlights the interconnectedness of ecosystems and the potential for cascading effects. The increasing deer population in Japan, due to the extinction of wolves, is causing significant damage to endangered plant species through overgrazing. This illustrates how the loss of one species can disrupt the entire ecosystem.

A critical point raised is that the current extinction rate is 100 to 1,000 times higher than the natural background extinction rate, solely due to human activities. This rapid pace prevents species from adapting through evolution, a process that historically accompanied past extinction events.

The concept of “phenological mismatch” is also crucial. Rising temperatures are causing plants to bloom earlier, while insects, like bumblebees, are not emerging at the same time, disrupting pollination and threatening both species. This disruption extends to animals that feed on these plants and their predators, creating a cascading effect throughout the ecosystem.

The Dilution Effect and Emerging Infectious Diseases

Dr. Onuma further explains the “dilution effect,” where higher biodiversity can regulate the spread of infectious diseases. As biodiversity declines, the risk of zoonotic diseases (diseases that jump from animals to humans) increases, as exemplified by the COVID-19 pandemic. This underscores the importance of biodiversity conservation for human health.

Safeguarding the Future: Conservation and Cryopreservation

Addressing the crisis requires a dual approach: mitigating climate change and actively conserving biodiversity. However, even well-intentioned conservation efforts can have unintended consequences. Wind power, a sustainable energy source, poses a threat to birds, with golden eagles and black-legged kittiwakes facing significant mortality rates from collisions with wind turbines. Initiatives like creating artificial nesting structures for kittiwakes are being explored, but their effectiveness remains uncertain.

Dr. Onuma’s “Time Capsule Project” at the National Institute for Environmental Studies represents a final safeguard. This project cryopreserves cells and tissues of endangered species, preserving their genetic diversity for future generations. The project has successfully cryopreserved cells from 127 endangered Japanese species and aims to reach 385. They have even created IPS cells from endangered bird species, offering potential for future breeding programs. While Dr. Onuma hopes this technology will not be needed for species recovery, it serves as a crucial backup plan.

Conclusion

The evidence is clear: the sixth mass extinction is not a distant threat, but an ongoing crisis unfolding before our eyes. The interconnectedness of ecosystems, the rapid pace of extinction, and the human-driven nature of the crisis demand urgent action. As Dr. Onuma powerfully stated, “Extinction is not a future story. Extinction is happening next to us.” Preventing this catastrophe requires a fundamental shift in our relationship with nature, prioritizing conservation, mitigating climate change, and recognizing the vital role biodiversity plays in sustaining life on Earth. The future of our planet, and indeed our own survival, depends on it.