The Next Species

1. Earth's History is Marked by Mass Extinctions, and We May Be Causing the Sixth.

And now scientists suggest that a sixth mass extinction may be under way, given the known species losses over the past few centuries and millennia.

Five major extinctions. Earth's 600-million-year history of complex life includes five catastrophic mass extinction events, wiping out over 75% of species each time. These include the Ordovician (86% loss, glacial cycles), Devonian (75% loss, cooling/warming), Permian (96% loss, supervolcano), Triassic (80% loss, warming/acidification), and Cretaceous (76% loss, asteroid/volcano). Each had multiple causes, like the Permian's Siberian Traps volcano causing warming, ocean acidification, and acid rain.

A new extinction event. Scientists warn we are entering a sixth mass extinction, driven by human activity. Our population surge and environmental destruction are causing species numbers to plummet at an unprecedented rate. Some estimates suggest we could reach mass extinction levels within just three centuries if current trends continue.

Rapid human impact. From a geological perspective, humanity's destructive impact has been incredibly fast. If Earth's history were a 24-hour day, we only appeared in the last few seconds, yet we've already caused damage comparable to past geological epochs.

2. Life is Resilient: Extinction Clears the Board for Evolutionary Renewal.

Extinction is a powerful creative force, says Douglas H. Erwin, a paleobiologist at the Smithsonian Institution.

Recovery follows collapse. Despite the devastation of mass extinctions, life has always recovered. The Permian extinction paved the way for dinosaurs, and the Cretaceous extinction opened the door for mammals and eventually humans. Survivors of these bottlenecks rapidly diversified and evolved into new forms, filling the newly emptied ecological niches.

Evolutionary creativity. From the wreckage, life undergoes bursts of evolutionary creativity. The early Triassic, following the Permian extinction, saw the rise of active, mobile species dominating over the passive, anchored life forms that preceded them. This period also saw the emergence of new body plans and ecological relationships.

Nature's persistence. Examples like the recovery of ecosystems after volcanic eruptions (Mount St. Helens, Krakatoa) or in human exclusion zones (Chernobyl, Korean DMZ) demonstrate nature's remarkable ability to rebound when human pressure is removed. While individual species may be fragile, life itself is incredibly resilient and will find a way to persist and evolve.

3. Humanity's Footprint: Rapid Growth and Resource Depletion Drive Environmental Collapse.

Our massive overpopulation and accompanying decimation of earth’s natural resources, if pursued unabated, may lead to man’s own demise.

Unprecedented population surge. Human population growth has accelerated dramatically, especially in the last two centuries. It took 200,000 years to reach 1 billion (1800), but only 200 more to reach 7 billion (2011). Projections show 9 billion by 2045, a surge with unimaginable risks and side effects.

Resource decimation. This population boom is coupled with a massive increase in resource consumption. As developing nations industrialize, their demand for food, energy, and goods rises, straining finite resources. This unsustainable trajectory is depleting natural capital at an alarming rate.

A deadly virus. From nature's perspective, humanity has become a deadly virus. Our activities, from land use to pollution, are decimating natural resources and driving other species to extinction. This self-inflicted damage, if unchecked, could ultimately lead to our own demise.

4. From Soil to Sea: Our Actions Are Dismantling Earth's Life Support Systems.

The combined human impact on land surfaces during the past few hundred years is as large as that which occurred during the last ice age.

Soil degradation. Agriculture, while fueling population growth, has severely degraded the soil needed for future food production. Practices like monoculture and reliance on inorganic fertilizers decrease biodiversity and pollute the land. Overgrazing and fire suppression promote invasive woody plants, further reducing fertile grasslands.

• Southern US cotton farming eroded inches of topsoil.
• Phosphorus mining creates toxic waste and pollutes waterways.
• Nitrogen fertilizers reduce plant species diversity.

Water stress. Water resources are under immense pressure from overuse and pollution. Rivers like the Colorado are drying up before reaching the sea due to upstream consumption. Urbanization and agriculture deplete groundwater and surface water sources.

• Las Vegas relies heavily on the shrinking Colorado River.
• Proposed pipelines threaten underground water reserves.
• Dams alter river ecosystems and fish habitat.

Ecosystem services lost. These degraded environments lose vital "ecosystem services" provided by diverse species, such as water purification, soil generation, pollination, and climate regulation. Losing these natural functions weakens our own life support systems.

5. The Unseen Threat: Biodiversity Loss Fuels Disease and Undermines Our Health.

About 60 percent of all infectious diseases that affect humans are “zoonotic,” meaning they reside in animals that act as reservoirs for the disease.

Zoonotic diseases rise. Disturbing natural habitats and reducing biodiversity increases the risk of zoonotic diseases jumping from animals to humans. When diverse species are lost, the remaining, often more resilient, species can become more efficient reservoirs for pathogens.

• Ebola and HIV/AIDS linked to bushmeat hunting.
• Lyme disease risk increases in fragmented forests with fewer predators.
• SARS linked to civets and fruit bats after habitat disturbance.

Dilution effect lost. Biodiversity provides a "dilution effect." With more animal species, diseases are spread among a variety of hosts, some less efficient at transmitting the pathogen to humans, thus reducing overall risk. Losing this diversity concentrates disease in fewer, more effective carriers.

Antibiotic resistance. Our reliance on antibiotics, particularly in animal agriculture, is creating drug-resistant "superbugs." Overcrowded conditions in confined animal feeding operations necessitate antibiotic use, which then enters the environment and food chain, undermining our ability to treat infections.

• Low-dose antibiotics in animal feed select for resistant bacteria.
• Resistant bacteria found in waterways and even on beaches.
• Common diseases like gonorrhea and tuberculosis are becoming multidrug-resistant.

6. Oceans in Peril: Acidification, Warming, and Overfishing Reshape Marine Life.

The oceans of the world are beginning to absorb the increasing levels of CO2 we harbor in our atmosphere.

Acidification's impact. The ocean absorbs atmospheric CO2, forming carbonic acid and increasing acidity. This threatens marine life, especially creatures with calcium carbonate shells or skeletons like krill, clams, and coral.

• Krill embryos fail to develop in highly acidic water.
• Shells of sea snails dissolve in acidic conditions.
• Coral reefs, vital fish breeding grounds, are dissolving and bleaching.

Warming and low oxygen. Warmer waters hold less oxygen, and climate change may be slowing ocean circulation, expanding "oxygen minimum zones." These zones are uninhabitable for many marine species, compressing their habitat and making them more vulnerable to fishing.

• Low-oxygen zones are expanding globally.
• Tropical fish are squeezed into narrow surface layers.
• Permian extinction saw oceans go stagnant and lethal.

Overfishing's devastation. Industrial and artisanal fishing have severely depleted fish stocks worldwide. We are the top marine predator, hunting fish and other marine life to the brink of extinction.

• Global fish catches peaked in the 1980s and are declining.
• Deep-sea fishing targets slow-reproducing species like orange roughy.
• Shark populations have plummeted due to fin trade.

7. Predators Under Siege: Removing Apex Species Disrupts Ecosystems Globally.

Over the last 600 million years, during most of the extinction events, predators were the last to go.

Top-down disruption. Unlike past extinctions where predators were often the last to go after plants and herbivores collapsed, humans are uniquely targeting apex predators first. This top-down removal has cascading effects throughout ecosystems.

Ecological consequences. Removing predators allows prey populations to explode, leading to overgrazing and habitat destruction.

• Sea otters control urchins, protecting kelp forests. Without otters, urchins decimate kelp.
• Wolves control elk, allowing willow and aspen forests to recover in Yellowstone.
• Islands without predators see prey populations boom, leading to forest degradation.

Targeting large carnivores. Humans hunt large predators for various reasons: valuable parts (tusks, fins, horns), competition with livestock, or perceived danger.

• Sharks are killed for fins, threatening ancient species.
• Lions, tigers, and other large cats are hunted, reducing their numbers.
• This selective pressure is altering the balance of nature.

8. The Population Bomb: Our Numbers and Appetites Strain Planetary Limits.

If the world continues to grow as it has in the last fifty years its population could reach 27 billion by the year 2100, which is unsustainable.

Exponential growth. Human population growth has been exponential, particularly since the Industrial Revolution. This rapid increase, coupled with rising consumption per capita, puts immense pressure on Earth's finite resources.

• Population doubled from 1 billion to 2 billion in 130 years (1800-1930).
• Doubled again from 2 billion to 4 billion in 44 years (1930-1974).
• Reached 7 billion by 2011.

Unsustainable consumption. If everyone lived like middle-class Americans, the Earth could only support about 2 billion people. The desire for higher living standards globally exacerbates resource depletion.

• Livestock consumes five times the grain as the US human population.
• Meat consumption rises with economic development.
• Wars have historically been fought over food and resources.

Approaching limits. We are rapidly approaching or exceeding the planet's carrying capacity for humans at current consumption levels. Running out of vital resources like fertile land, phosphorus, and water could lead to widespread conflict and collapse.

9. Human Evolution Isn't Dead; It's Accelerating, Driven by Culture and Technology.

Their belief is that evolution is now happening about one hundred times faster than the long-term average of our species’ existence.

Evolution continues. Contrary to the idea that human evolution stopped, genetic changes are accelerating, particularly in the last 10,000 years since the advent of agriculture. This is partly due to larger populations providing more opportunities for mutations and stronger selective pressures from new environments and diseases.

Cultural selection. Cultural and technological innovations are driving new forms of selection.

• Lactose tolerance spread rapidly with dairy farming, providing a nutritional advantage.
• Adaptations to high altitudes (barrel chests, faster breathing) evolved quickly.
• Resistance to epidemic diseases developed in dense agricultural populations.

Rapid genetic change. Studies show significant genetic changes in human populations in just the last few thousand years. Different groups are adapting to local conditions, diets, and lifestyles, leading to genetic divergence.

• 7% of human genes evolved in the last 5,000 years.
• European Jews show genetic adaptations linked to historical occupations and isolation.
• Humans are getting taller, living longer, and changing physically due to improved conditions.

10. Beyond Earth: Mars and Technological Futures Offer Potential, and Peril.

Interplanetary travel could be a major force for human change.

Mars colonization. Mars is often considered a potential escape if Earth becomes uninhabitable. It has water ice, essential elements for life, and a day length similar to Earth's. Colonization faces immense challenges:

• Extreme temperatures and low atmospheric pressure require sealed habitats.
• High radiation levels necessitate underground living.
• Gravity differences could make return to Earth difficult for those born on Mars.

Technological transformation. Future technologies could fundamentally alter humanity.

• Genetic engineering could allow for "designer children" with selected traits.
• Cloning could lead to multiple copies of individuals.
• Mind uploading could transfer consciousness to software or machines.

AI risks. The development of advanced artificial intelligence poses an existential risk. AI could rapidly surpass human intelligence, potentially leading to unintended or hostile outcomes that outcompete or eliminate humanity.

11. Nature's Enduring Power: Life Will Recover, Even After We're Gone.

Nature will survive.

Life finds a way. Regardless of the scale of human-caused destruction or our own fate, life on Earth is incredibly resilient. Plants, animals, birds, reptiles, fish, fungi, and bacteria will survive, adapt, diversify, and proliferate.

Recovery takes time. While nature can rebound quickly in localized disasters (volcanoes, exclusion zones), recovery from a mass extinction event takes millions of years. The early Triassic, after the Permian extinction, was a "ghost town" for millions of years before new species diversified.

New forms emerge. The species that survive a bottleneck will move into abandoned spaces and evolve rapidly with less competition. The future Earth, without humans, would see new ecosystems dominated by different sets of players and rules, potentially including larger animals returning.

12. The Choice: Unprecedented Change or Facing the Consequences of Collapse.

But in making that request, we are asking humans to do something that no other species has ever done: constrain its numbers voluntarily.

The Gause experiment. Humanity's population trajectory resembles Georgii Gause's experiment with microorganisms: rapid exponential growth followed by a potential crash when resources are exhausted. Our lack of natural competitors has allowed this unchecked expansion.

Avoiding the crash. To avoid a catastrophic collapse, humanity must voluntarily constrain its numbers and resource consumption. This requires a fundamental shift in behavior and values, moving away from the instinct to grow and consume without limit.

A turning point. History shows humanity is capable of dramatic shifts in consciousness and behavior, such as the rapid abolition of slavery or the rise of women's rights. Whether we can achieve a similar transformation to live sustainably with nature remains the critical question for our future.

Last updated: May 4, 2025