Chapter 7: We Are Killing Life

From the moment Homo sapiens first burst out of Africa and began spreading across the planet in search of new food some 50,000 years ago, we hunted most megafauna to extinction, which created chaos for ecosystems across the planet. Within a few thousand years of the first humans entering North America, 75% of all large species—including mammoths, mastodons, giant sloths, American cheetahs, and American lions—were gone. Versions of this same story had previously transpired in Europe, Asia, and Australia. The only exception was Africa, where local species had co-evolved with us.

Here is another one of many examples from more recently: there were roughly 60 million bison in North America before the Europeans arrived. By the early 1900s there were fewer than 200 bison remaining. We humans hunted them to near extinction and did the same thing to grizzly bears, mountain lions, wolves, elk, pronghorn, beavers, and sea otters. Thankfully these species survived, but others (the passenger pigeon, great auk, Carolina parakeet, and ivory-billed woodpecker) were not so lucky.

I wish I could say these days were behind us. But they are not. Consider tuna. It is a big business, worth around $40 billion per year, and makes up an estimated one-quarter of global seafood trade. Here in the United States we eat over 600 million pounds of canned tuna every year (those numbers do not include sushi or filets)! This results in overfishing of tuna that has decimated their populations. Fishing pressure drove the population of Pacific bluefin tuna to right under 3% of its historic size. Not only are we pushing tuna to the edge of extinction, but we are also harming and killing other sea creatures in the process. As an example, longline fishing, one of the techniques used to catch tuna, kills an estimated 250,000 loggerhead turtles and leatherback turtles annually, both of which are critically endangered. The fishing industry calls this collateral damage “bycatch,” and throws it back in the ocean to rot. Estimates suggest that bycatch amounts to a shocking 38 million tons of sea creatures and 40% of all fish caught every year. Thanks to bycatch and overfishing in general, we have reduced fish populations by anywhere from 50 to 90%, depending on the species. All this because we like to eat tuna.

Many of the species described above—including tuna—are known as keystone species. A keystone species is one that has low functional redundancy, meaning if it disappears from its ecosystem there are no other species that can fill that specific niche. They hold entire ecosystems intact. When they die, so too does the life that relies on them. By killing megafauna and other keystone species, we have indirectly harmed and killed many other species that relied on them for survival.

Consider a case study in Yellowstone National Park involving the gray wolf, which is a keystone species in that region. By the mid-1900s, gray wolves had mostly been hunted to extinction in the lower 48 states of the US. Intensive surveying of Yellowstone National Park from 1975 to 1977 failed to find a single wolf. But thanks to the Endangered Species Act of 1973 (one of the most important laws in history in terms of conservation), awareness about the importance of wolves increased. As a result, in the mid-1990s the Fish & Wildlife Service began reintroducing wolves back into Yellowstone. The changes that ensued were profound. The wolves hunted elk, which had a cascading effect on the health of plants. Without such heavy, unrestrained elk predation, various plant species were able to rebound, especially willows, aspen, cottonwood, and berry-producing shrubs. Wolf kills provided scavenge opportunities for eagles and ravens. Their populations grew. Berries from the bushes fed a growing number of bears and supported the resurgence of six different species of songbirds. Wood from willows, aspens, and cottonwoods helped the beavers and enabled their populations to rebound. The beavers created new dams, thus changing the path along which the streams flowed. Water flow slowed and stream sediment decreased. Populations of trout and other fish rebounded. Slowing water also meant that more water percolated into the land, which benefited trees, and thus herbivores. As bird, beaver, trout, and herbivore populations increased, so too did populations of predators. More kills released more nutrients for plants. Plant life surged and with it so did populations of insects, more birds, and new herbivores. Species that had not been seen in the area for many years reappeared. Entire terrestrial and aquatic ecosystems began to heal. Overall soil fertility increased and life continued to explode, in both diversity and abundance. All this because a keystone species—the gray wolf—was reintroduced into its native habitat.

This only scratches the surface of the full effects, most of which are not yet known. Researchers are still learning about new outcomes and connections. This makes me think of the quote by Frank Edwin Egler: “Nature is not more complex than we think, it is more complex than we CAN think.”

Here is more about this case study:

Case study about wolves in Yellowstone

Not only have we obliterated life directly through hunting and indirectly through the eradication of keystone species, but we have also done so through habitat destruction. All terrestrial life needs forests and grasslands to live their lives. When we destroy these places—as we have been doing over the past 10,000 years—we destroy their ability to feed, find shelter, and reproduce. There are many ways we destroy habitat. One is by completely clearing an ecosystem using bulldozers and other large machinery. We also destroy habitats when we split them apart. This is called fragmentation, and it happens when we build roads, railroads, fences, and other structures that cut through tracts of land and divide ecosystems indiscriminately. This happens across the planet. Here are some real-life examples:

Most life needs uninterrupted wild space in which to live and travel. Consider the red wolf, which used to thrive here in North Carolina and across the southeastern United States. They need as many as 80 square miles to survive. There are very few places in North Carolina with enough space to allow for such range. As a result, red wolves must cross highways, travel around cities, and find a way under fences or go around them. They must also avoid being shot by farmers. Sadly, red wolves have not been able to survive such conditions. As of October 2023, there are currently 11 known red wolves remaining in the wild in North Carolina.

There is another highly damaging form of habitat destruction, which is the introduction of something called an invasive species. Invasive species are non-native species that cause widespread harm and destruction when introduced to a new ecosystem. Here is a recent example:

Before 1900, the American chestnut was a common native species in North America, particularly in the Appalachian Mountains, where it provided food and shelter for many insects, birds, and mammals. They were referred to as the redwoods of the East Coast due to their incredible size and maturity. In 1904, some folks brought a Japanese chestnut tree to the United States. Unbeknownst to them, this tree carried a tiny fungal pathogen called chestnut blight. Within the year, experts found this pathogen in American chestnut trees in the Bronx Zoo. It was fully lethal; the American chestnut had not evolved any defense that could withstand this fungus. Within 35 years, it swept across the country and decimated huge population of American chestnuts, killing somewhere around 4 billion trees. Populations of plants, insects, birds, and mammals that relied closely on the American chestnut all suffered as a result. Some species—such as the chestnut ermine moth and the phleophagan chestnut moth—went fully extinct. The accidental introduction of the invasive chestnut blight caused incomprehensible damage to life and ecosystems across the US.

During our expansion across the globe we carried seeds, rats, insects, and germs, to name a few. Some of these had profound impacts on the new ecosystems into which we entered. Especially today, with increased global trade comes the increased movement of potential new invasive species. Burmese pythons in the Everglades, emerald ash borer, fire ants, zebra mussels, kudzu, feral swine, European starlings, and Asian carp are a few from a long list of highly invasive species that have created ecological disasters here in the United States. This is happening all over the world at an increasing pace.

The World Wildlife Fund’s Living Planet Report 2018 published the following data: we’ve seen a 60% decline in the population size of birds, reptiles, mammals, fish, and amphibians (on average) in the past 40 years. In 2004 the International Union for Conservation of Nature (IUCN) reported that the current rates of extinction for birds, mammals, and amphibians were at least 48 times greater than natural extinction rates. A widely cited paper published in the Proceedings of the National Academy of Sciences calls this massive loss of life a “biological annihilation” that represents a “frightening assault on the foundations of human civilization.”

In what amounts to mere minutes on the Cosmic Calendar, we humans have killed an unimaginable amount of life through hunting and habitat destruction. According to Paul Martin, an expert on this topic, virtually all animal extinctions in the past 50,000 years were caused by humans. We are pushing life on this planet to the brink of existence.

Sadly, there is no end in sight. We cut down and fragment forests and grasslands to make way for new agriculture, neighborhoods, and development every day. With that comes the eradication of more keystone species, soil loss, and diminishing fresh water. Continued globalization perpetuates the introduction of more invasive species that wreak havoc. Collectively, this results in more and more carbon being released into the atmosphere.