In her 2015 book 'The Sixth Extinction', author Elizabeth Kolbert sounds the alarm about humans imperiling the Earth in the current 'Age of Man' - dubbed the Anthropocene.
Kolbert observes that humans have transformed more than half the ice-free land on Earth. We've dammed or diverted most of the world's major rivers; our fertilizer plants and legume crops fix more nitrogen than all terrestrial ecosystems combined; and our planes, cars, trucks, and power stations emit about a hundred times more carbon dioxide than volcanoes do. These kinds of changes have led to atmospheric warming, ocean warming, ocean acidification, sea level rise, deglaciation, desertification, eutrophication, species extinction, and other unwanted events.
Kolbert continues the theme of human-caused destruction in this book, which describes transformations that have had unforeseen repercussions. Kolbert also recounts proposed 'fixes', many of which seem as chancy as the original alterations.
To gather data, Kolbert traveled widely and interviewed scientists, engineers, and other experts. Kolbert's narrative is detailed and filled with scientific explanations, statistics, and personal observations. There are also light moments, like the time Kolbert was body-slammed by a jumping carp or lunched on a tasty New Orleans po-boy sandwich.
I'll provide a brief description of some of the changes Kolbert describes. For additional examples, specifics and anecdotes, I'd encourage you to read the book.
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Kolbert's first example is the Chicago Sanitary and Ship Canal (CSSC), essentially a man-made river that was created to re-route Chicago's waste so it doesn't enter Lake Michigan - which is Chicago's source of drinking water. Instead, the CSSC carries effluent the other way, so it flows into the Des Plaines River, and eventually reaches the Mississippi River and the Gulf of Mexico.
This huge 'river reversal' upended the hydrology of roughly 2/3 of the United States and is forcing a whole new round of interventions, like electrification of the CSSC. These new interventions are necessary to prevent migration of the Asian carp - a VERY aggressive invasive species - from the CSSC to the Great Lakes.
Invasive Asian Carp
Asian Carp jumping out of the water
The Asian carp themselves are an example of human folly. They were originally imported from China to the southern United States, to keep aquatic weeds in check. The carp soon spread north, and it's feared that, if they reach the Great Lakes, the carp will outcompete native species and disrupt the Great Lakes ecosystems.
Electric Fish Barriers are designed to keep Asian Carp out of the Great Lakes
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Kolbert next details the erosion of the state of Louisiana. On maps, Plaquemines Parish looks like a muscular arm extending into the Gulf of Mexico, with the Mississippi River running down its center. But seen from the air, the parish looks very different, very emaciated, with only thin strips of land along the river. The fact is, Plaquemines Parish is eroding, as is the entire coast of Louisiana. Kolbert notes, since the 1930s Louisiana has shrunk by more than 2000 square miles.
Historic Plaquemines Parish
Erosion of Plaquemines Parish
The reason is the thousands of miles of levees, flood walls and revetments built to manage the Mississippi River. This system, built to keep southern Louisiana dry, prevents sediment from replenishing the land along the Louisiana coast. The land constantly erodes, and when - sediment doesn't replenish it - disappears completely.
Mississippi Levee
Once again, new interventions are necessary to repair the damage, and various redresses have been proposed. One suggestion is to pump sediment from the Mississippi River, transport it by pipes, and spread it over the land. This would cost about $30,000 per acre. Another idea is to punch holes in the levees along the Mississippi, and gate and channelize the openings, to divert sediment back onto the land. This would be a VERY complex and difficult project.
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Kolbert then addresses Devil's Hole, a Nevada geologic formation located in a detached unit of Death Valley National Park. Devil's Hole cavern contains a pool that's home to the only naturally occurring population of the endangered Devil's Hole Pupfish.
A Devil's Hole Pupfish has an average length of 2.3 cm (0.9 in)
The fish have evolved to thrive in the high temperature, low oxygen environment of Devil's Hole, and can't survive anywhere else. In an attempt to boost the pupfish population, scientists have built a concrete simulation of Devil's Hole, and monitor it carefully.
Author Elizabeth Kolbert working with scientists in 2019 to count pupfish numbers at Devil's Hole
Humans haven't always tried to preserve species, however, but rather the exact opposite. Kolbert notes that man has caused the extinction or near-extinction of many animals, such as Wild Turkeys, Eastern Elk, Passenger Pigeons, Bison, Woolly Mammoths, Woolly Rhinos, Mastodons, North American Camels, Moa Birds, Dodo Birds, Red Rail Birds, and many more. These losses extend across all continents, all oceans, and all taxa.
Flocks of Passenger Pigeons once darkened the skies
Extinct North American Camels
Conversely, humans have boosted the populations of other (perhaps less desirable) animal species, termed synanthropes, that benefit from human habitats. These organisms include raccoons, American crows, Norway rats, Asian carp, house mice, and many species of cockroach. 😝 Ditto for some plants, called apophytes, that grow in abandoned fields.
Humans inadvertently create hospitable environments for house mice
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One of the world's most serious problems is the devastation of coral reefs. The warming oceans have caused coral bleaching, which happens when corals expel the symbiotic green algae that live in their tissues. Without the algae, the corals turn white and die.
As a possible solution to the problem, some biologists suggest artificially breeding hardier corals in a kind of 'assisted evolution.' Other suggestions include pumping deep water to the surface, to cool the reefs; and cloud brightening, to reflect sunlight back into space.
Cloud brightening has been proposed to help save coral reefs
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Another blunder perpetrated by humans was the importation of Cane Toads from South America to Australia, to control pest beetles on sugar cane crops. The toads, which are toxic, spread far beyond the original habitat and are now a major problem.
Cane Toad
Sketch showing the spread of Cane Toads in Australia
Many species that eat cane toads have crashed, including Fresh Water Crocodiles, Yellow-Spotted Monitor Lizards, Northern Blue-Tongued Lizards, Water Dragons, Common Death Adders, and the Northern Quoll - a cute marsupial.
The Water Dragon population crashed
The Northern Quoll population crashed
Suggested remedies include editing the Cane Toads' genome using a technology called CRISPR, to make the animals less toxic; and genetically engineering “daughterless” toads, turning the pests all male and destroying their populations.
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Among the biggest problems facing humanity is global warming, caused by humans injecting carbon into the atmosphere. This problem began in the late 18th century, when the steam engine kick-started the industrial revolution.
The industrial revolution resulted in massive amounts of carbon being spewed into the atmosphere
Higher temperatures have caused droughts, storms, heat waves, wildfires, rising sea levels, increased melt-off of Antarctica, and more.
Global warming causes huge changes in the environment
Scientists believe we've already emitted so much carbon into the atmosphere that we must not only curb emissions, but must remove carbon to keep temperatures at safe levels. One proposed solution is to suck carbon out of the air and inject it into the ground, where it forms stone. Another proposed remediation is to add a mineral called olivine to the oceans, which would induce the seas to absorb more carbon. These solutions are difficult to implement and very costly.
Carbon dioxide injected into basalt forms stone in about two years
A more draconian proposal to reduce global warming is called solar geoengineering. The idea is to inject a gazillion reflective particles - such as microscopic diamonds or sulfates - into the stratosphere, so less sunlight will reach the planet.
Solar geoengineering has been suggested to help reduce global warming
On an aesthetic note, this would change the appearance of the sky, which would look white instead of blue.
Solar geoengineering might result in a white sky
Solar geoengineering has been variously described as dangerous beyond belief; a broad highway to hell; unimaginably drastic; and also as inevitable. (This sounds like the script of a disaster movie to me.)
For all these proposed solutions we must ask "Do humans have the right to do this? And will it work? And what is the alternative?"
In this narrative Kolbert presents an alarming picture of the future of Earth if we humans don't take immediate steps to address the problems we've caused. Everyone should read this book.
Rating: 4.5 stars
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