The Sixth Mass Extinction Is Underway

By Melissa Immel 

“I’ve watched the expansion of human activities drive population after population to extinction.” – Paul R. Ehrlich

The sixth mass extinction is here, and humanity’s long-term existence is far from guaranteed. That unsettling realization is what a team of researchers found in their new study, published in the journal Science Advances. Among the authors are Paul R. Ehrlich, Bing Professor of Population Studies and Professor of Biological Studies at Stanford University, and Anthony D. Barnosky, Professor of Integrative Biology and founder of the Barnosky Lab at the University of California, Berkeley. 

Even using conservative assumptions, the research team found an extremely rapid rate of biodiversity loss over the last several centuries, revealing that the sixth mass extinction is already in progress. Fortunately, through intensified conservation efforts and other changes in behavior, we likely have the ability to avert the ultimate crisis, but the timeframe for action is quickly escaping. 

According to Barnosky, we have lost 50% of terrestrial vertebrate wildlife, which includes amphibians, reptiles, mammals, and birds, in the last 40 years. We have also fished approximately 90% of the big fish out of the sea. “Continue at that rate,” Barnosky said, “and the sixth mass extinction is virtually assured in about three human lifetimes, if not before.” 

“The benefits we’re losing are both practical and emotional,” said Barnosky. Coral reefs are in danger of disappearing by the end of this century, due to combined effects of climate change, fishing pressures, and pollution. On the practical side, Barnosky explained, if coral reefs disappear, we will lose 25% of all ocean species and 10% of the world’s fisheries, resulting in hundreds of millions of poor people to go hungry, which leads to severe social unrest and global problems. On the emotional side, said Barnosky, we are doing to nature the equivalent of if we went into the world’s most famous museums and destroyed all of the Rembrandts, Van Goghs, Picassos, etc. “Each species is one-of-a-kind, one of nature’s irreplaceable works of art,” said Barnosky.

Barnosky cited several other examples of rapid biodiversity loss. If poaching is continued as it has been for the past decade, there will be no more wild elephants on the planet in just the next two decades. Tigers, lions, gorillas, and other iconic large mammal species are at risk of a similar fate. Amphibians such as frogs and salamanders are being hit hard as well. “In California, our state mammal, the grizzly bear, is already extinct, and our state tree, the coast redwood, state amphibian, the red-legged frog, and state reptile, the desert tortoise, are threatened with extinction,” Barnosky pointed out.  

Ehrlich emphasized the fact that population losses in certain areas of the world have dramatic effects as well. If we were to wipe out honeybees in North America, we would lose 15 to 18 billion dollars economically, and our food would be dramatically less nutritious. White-nose syndrome is currently wiping out bats in North America, and bats wipe out mosquitoes that carry diseases, which have the potential to wipe out humans. According to Ehrlich, such population losses are serious extinctions, but are not recorded as such. “Civilization is utterly dependent on the species of the planet,” Ehrlich said. 

As the crisis stands today, the chances of civilization persisting are zero, said Ehrlich. If we decide to act, research estimates that there is a one to ten percent chance of humanity existing by the years 2100 to 2200; however, Ehrlich said, “we’re doing essentially nothing.” 

Starvation is a serious side effect of climate disruption. As we add more carbon dioxide to the atmosphere, the nutritional value of grains tends to drop, said Ehrlich. Increasing population rates contribute to the problem as well. The world’s population is growing by 75 million people every year. “Our biggest threat,” Ehrlich said, “is trying to feed two and a half billion more people in the next 30 years.” Ehrlich’s controversial book, The Population Bomb, published in 1968, describes the dangers of overpopulation. Today, he continues to fear what will happen if global population rates do not decline. 

Ehrlich and Barnosky each laid out some of the most important and effective steps we can take to help slow these trends, their approaches somewhat different but clearly overlapping.

Ehrlich focused on the following priorities as most urgent:

  • Give equal rights and opportunities to women everywhere, resulting in decreased birth rates
  • Give modern contraception and access to safe abortions to every heterosexual, sexually-active person, resulting in less unwanted births and saving the lives of millions of women
  • Engage in redistribution, as too many people have far too much, and too many people have not nearly enough 
  • Cease dependence on fossil fuels immediately 

According to Barnosky, we should prioritize the following four solutions:

  • Replace fossil fuels with clean energy as soon as possible
  • Ensure that our agricultural footprint does not increase and take over lands that are currently supporting other species
  • Economically value nature as a long-term investment rather than a bottomless checking account 
  • Stabilize the human population at numbers that do not exceed ten billion 

In his readable and optimistic book Dodging Extinction, Barnosky outlines further strategies for dealing with the looming threat of the sixth mass extinction. 

The frustration and constant worry that scientists like Ehrlich and Barnosky face is undeniably apparent. The scientific community has spoken out on these issues repeatedly, Ehrlich said, but no real action has been taken. “My worry,” Barnosky said, “is that issues like the extinction crisis will not come on people’s radar screen fast enough to deal with the problem. We have a short window of opportunity where we can still step in and guide the planet where we want it to go. Global problems by their very nature take a couple of decades to fix. If we don’t start moving in the right directions now, it will soon be too late to avoid the worst-case scenarios.” 

Despite the dim outlook on humanity’s future, Barnosky is “guardedly optimistic.” “If people understand and recognize the gravity of the problems we face as a global society, we are remarkably good at fixing them,” said Barnosky. “Everyone needs to be scared,” cautioned Ehrlich. In summary, Ehrlich is “optimistic about what we could do, but pessimistic about what we are doing and will do.” 

“We know what needs to be done,” Ehrlich said. 

Melissa Immel is a recent graduate of the University of California, Santa Barbara with a bachelor’s degree in political science. UCSB is home to the Lambda of California Chapter of Phi Beta Kappa.