The Next Species: The Future of Evolution in the Aftermath of Man

by Michael Tennesen

  Gilly’s team did catch sierra mackerel and yellowtail, but neither fish was of the same size or in the same numbers as Steinbeck and Ricketts had reported.

  Steinbeck and Ricketts got a look into the future, though they didn’t realize it at the time, when they boarded a shrimp trawler off Guaymas on the mainland side of the Gulf and witnessed the unintended consequences of the fish species that came up with each net. Though the fishermen tried to separate the shrimp from the rest of the catch and tossed back the unwanted fish, most of these died belly-up in the water. Today shrimp trawling is recognized as the single most ecologically damaging activity in the Gulf.

  Sharks, particularly the enormous schools of hammerheads that once circled the sunken islands, or seamounts, in the middle of the Gulf, have declined in size and number. The same is true with manta rays: they have been replaced with smaller mobula rays than the ones seen by Steinbeck and Ricketts. Steinbeck wrote of the attempted landing of a number of huge manta rays, but the rays always broke the line, even when it was three inches thick. And Steinbeck and Ricketts noted several other species of squid but not Humboldt.

  Though Gilly never saw the abundance of marine life that Steinbeck had witnessed, he found his own vision when he got to San Pedro Mártir Island, an area known for hosting many sperm whales. Since sperm whales eat Humboldt squid, Gilly figured there must be a lot of squid, and this was the reason for taking this detour, which had not been a part of Steinbeck’s journey. He was looking for baby Humboldt squid, something nobody had ever found in the Gulf. Satellite data had told him there was an intense tidal upwelling event (tides bringing the rich waters of the deep up toward the sea surface), and he guessed that the forward edge of this rich marine zone might harbor tiny squid larvae. On his second net tow, he found two baby squid a quarter of an inch long. But there was more.

  It was a place where “all the life was, plankton, fish, squid, and whales,” reported Gilly. The biologist and his team were greeted by a nonstop squid review, with Humboldt squid darting in toward the boat and flashing their underbellies in attempts to lure small schooling fish near the surface. The show continued until after midnight.

  They didn’t set anchor, since the sea was more than 3,300 feet (1,000 meters) deep, so they simply drifted all night. At one point, large sperm whales were lounging at the surface with fins exposed, some in pairs, showing their flukes before diving. Gilly had never seen a sperm whale before, yet he knew they were hanging out because Humboldt squid, their favorite food, were there in abundance.

  Said Gilly, “We had come to the Sea of Cortez to discover how things might have changed since 1940—and here on the open water was the most dramatic ecological change witnessed during the entire trip, the apparent arrival of two major predators far offshore from the rocky reefs that were scoured by Ricketts and Steinbeck. This was a profound and qualitative change—an ecological regime shift.”

  It was the apex of a new evolution, one made up of squid and sperm whales, which had replaced the vision of tuna, marlin, sailfish, sharks, and other finfish that Steinbeck and Ricketts had seen only seventy years earlier.

  The Gulf of California was not the only place experiencing ecological change due to low-oxygen waters. Beginning in 2002, low-oxygen water from off the North Pacific shore had slipped up over the continental shelf and moved inshore, killing off bottom-dwelling marine creatures off the coast of California, Oregon, and southern Washington. Gilly and others have been watching these findings, too. These low-oxygen events normally arrived in the late-summer months.

  In 2006, Pacific waters off Oregon went into an anoxic (no oxygen) condition, killing off many organisms. Submersible vehicles put into the water recorded dead fish strewn across the bottom. Surveys revealed near complete mortality of bottom-dwelling creatures. Continental shelf waters off the Pacific Northwest are from twenty to fifty miles across. They lie beneath the California Current, which is one of the richest marine ecosystems in the world, though this system will be in jeopardy if low-oxygen events grow in size and frequency.

  Waters flowing south along the shore tend to bank clockwise in the northern hemisphere and counterclockwise in the southern hemisphere, an effect caused by the rotation of the earth on its axis. Off the US Pacific coast, prevailing northwest winds push surface water away from the coast, and cold, nutrient-rich waters at depth are pulled up to replace it. This greatly increases the productivity of coastal marine environments.

  Though many fish stocks are down off the California coast, marine mammals are doing well. Part of this may be the result of their adapting to consume squid and other creatures in the deeper sea. To get to these depths, whales, dolphins, seals, and sea lions all had to pass through a unique event in evolution. In prehistoric times, ancestors of these mammals came out of the sea as fish, lost their gills, and evolved lungs to breathe air. But they returned to the sea when competition from land animals increased, and they had to learn to survive underwater again, only this time breathing air. They currently use a host of neat breath-holding tricks, since the deep ocean is not a friendly place for air breathers. Gilly says that studying sperm whales is difficult, so scientists study other diving marine animals as proxies for whales.

  DEEP DIVERS

  Back in the 1960s, scientists generally thought animals might dive to 325 to 650 feet (100 to 200 meters), but researchers at the Scripps Institution of Oceanography in San Diego, California, recorded a Weddell seal in McMurdo Sound off Antarctica that dived to 1,970 feet (600 meters).

  Since then, emperor penguins, leatherback sea turtles, northern elephant seals, bottlenose whales, and sperm whales have met and surpassed that record. In a world where the oceans may no longer hold enough oxygen for gill-breathing fish, breath holders might still have a chance at survival.

  Elephant seals are a great example of an adaptable breath-holding mammal. And since they come out of the water only twice a year for extended stays, they are a lot easier to follow by attaching tags and transmitters while on land in order to record dives. Northern elephant seals have recovered from near extinction and number nearly one hundred thousand animals in the North Pacific. They utilize a unique set of evolutionary adaptations on their deep dives. Their heart rates at the surface are about 120 beats per minute, but while diving they can reduce that to 30 to 35 beats. They have even been recorded as low as 2 beats per minute—the edge of cardiac arrest in a human. Unlike man, most of the oxygen in diving elephant seals is stored in myoglobin in the muscle and hemoglobin in the blood instead of the lungs. They have higher concentrations of hemoglobin in the blood and larger blood volumes than most animals.

  Elephant seals have streamlined bodies that glide through the water as if they were traveling on a layer of ball bearings. In a paper in Nature in 2011, biologists at the University of California, Santa Cruz, reported that one elephant seal dove to 5,765 feet, then a record for the species. That’s the equivalent of more than three Empire State Buildings stacked on top of one another, with the seal plummeting from the top of the uppermost building to the basement of the bottom building before coming back to the surface, a distance of over two miles. Aside from the two or three months of the year that they come out on land to mate or to molt, they are mostly underwater, not really a diving animal but more of an animal that occasionally surfaces.

  All the elephant seal’s air passages, including the lungs, collapse flat and become airless between 350 and 700 feet (100 and 200 meters). With no air in these spaces, there can be no exchange of gas (particularly nitrogen), and thus elephant seals avoid the blood chemistry imbalances such as the bends (nitrogen bubbles) and rapture of the deep (nitrogen poisoning) that plague human divers.

  On these dives, the elephant seal’s face looks like a prune. Researchers like to paint up Styrofoam mannequins, put lipstick on them, color their eyes, and send them down 300 feet just for kicks. They come back looking like shrunken heads. But the dives are worth it to the elephant seals, said University of California biologis
t Burney Le Boeuf: “The deep-scattering layer, the top of the oxygen minimum zone, is where most of the biomass in the ocean is concentrated. These animals are diving to the center of the richest part.”

  But it’s dark down there. Cameras attached to these animals come back with images of a black screen. Some fish are bioluminescent, like lantern fish, a favorite of Humboldt squid in the Sea of Cortez. Whales and seals may swim below their prey and in daylight hours look back up at their silhouettes. The animals are well adapted for this territory. The enormous eyes of the elephant seal help it see in the dark. Whales may do one better than elephant seals, using natural sonar systems to locate their prey. The nose of the sperm whale constitutes a quarter to a third of its total weight and may contain the most powerful sonar system in the natural world.

  Deep divers have a virtual monopoly on their prey at those depths, and they also avoid two deadly predators that spend most of their time at the surface: great white sharks and killer whales. For the most part, elephant seals are attacked when getting in and out of the waters on the islands they visit twice a year—for a month or two in winter to breed and for a month or less in summer to molt. They spend the rest of the year in the water on long northern migrations of up to thirteen thousand miles. They dive almost continuously on these trips, each dive lasting twenty minutes or more, after which they spend two or three minutes at the surface, taking in oxygen and letting out CO2, before they head back down. These are incredible adaptions for an animal that breathes air.

  Without these threats, diving can be almost an autopilot affair. Sperm whales and elephant seals sleep as they dive, closing one eye while half of the brain naps and the other side keeps vigilant, then switching back and forth. Plus, once they get down to those depths, the escape responses of prey are a lot slower, allowing deep divers to wander around as if they were at an all-you-can-eat buffet.

  But once again the remarkable Humboldt squid has another adaptation in its bag of tricks. Gilly worked on a study with biologist Julia Stewart and found that Humboldt squid, both off Monterey Bay and in the Gulf of California, sometimes power-dive to depths of up to one mile—right through the oxygen minimum zone—and remain there for long periods of time, sometimes all day, before powering upward again. This trick is possible because the oxygen minimum zone is really a layer, and oxygen starts going up again at depths of more than about 3,500 feet because of deep ocean currents that bring oxygen to deep waters. “These extraordinary dives by Humboldt squid may be escape responses triggered by the presence of groups of foraging marine mammals. The squid simply dive down, hang out for several hours, and then pop back up, hoping to find the predators gone,” says Gilly. Only squid seem to navigate these low-oxygen zones so effortlessly. Seals and whales have to come back up for air, but squid can move up and down without it.

  Most fish, however, are limited to shallower waters, where they are the target of marine mammals and man, the latter responsible for diminishing fisheries. According to the World Wildlife Fund, the Gulf is the source of nearly 75 percent of Mexico’s total annual fish catch, but overfishing (both industrial and artisanal) is contributing to dramatic declines in sharks, rays, and finfish. The global decline in fish catches, combined with rising demand, is leading to a global fishery crisis that threatens the Gulf of California as well as the rest of the world.

  Humanity doesn’t limit its impacts to fish most commonly found on menus. Exotic sea creatures from turtles to manta rays to marine mammals are being hunted to extinction. Shark numbers, for example, have declined by 80 percent, with one-third of shark species now at risk of extinction. The top marine predator is no longer the shark; it is us.

  It has been ten thousand years since most humans lived as hunter-gatherers. Fish are the last wild animals that we hunt in large numbers. And yet we may be the last generation to do so. On average, people eat four times as much fish now as they did in 1950.

  In the late 1980s, the photographer George H. H. Huey and I went to the end of Baja to do a story on the shark fishermen there, who complained of fewer and smaller shark catches. When I interviewed a number of marine biologists about this, no one could imagine that these great open-ocean species could diminish. Even Rachel Carson couldn’t imagine fish stocks diminishing. But all that has changed.

  Humboldt squid could beat the odds against other marine creatures. Their numbers are expanding at sea, while ocean fish populations are contracting. In a relatively short period of time, this squid has learned to adapt to climate change and alterations of oxygen content in the water, conditions that are fatal for many other animals.

  Gilly has a lot of respect for this animal: “If someone wanted to design an ocean predator for the future, this would sure be it.”

  What evolutionary adaptations will we need to survive our future?

  Part III

  NO-MAN’S-LAND

  8

  THE END

  THE LOSS OF THE diversity of life on earth has implications for man that we appear ready to ignore. Mammals, reptiles, birds, amphibians, and fish possess what are called “ecosystem services,” functions they perform that are crucial to the well-being of nature and Homo sapiens. Their loss is our loss. Without their survival, ours is in question. It’s why some scientists believe man won’t survive a mass extinction, because of all the ecosystem services we will lose in such an event.

  We’ve seen how diversity of forest animals can help protect us from disease, but this is not nature’s only gift for our survival. Other living things, like plants, insects, and microbes, play vital roles in our lives as well. One of those valuable roles is creating clean water. New York City’s drinking water, which is naturally cleansed on its 125-mile journey from the Catskills to the city, is an example. Many of the system’s best purifiers lie beneath the forest floor: in the fine roots of the trees filtering the water, and in microorganisms in the soil that break down contaminants. These natural processes in the watershed absorb as much as half of the nitrogen coming into the waterways from auto emissions, fertilizers, and manures. In the wetlands section of the water’s travels, cattails and other plants also help filter nutrients as they trap sediment and heavy metals.

  New York’s system of waterways owes its existence in part to an epidemic of Asiatic cholera, which in 1832 killed nearly one in fifty of the city’s inhabitants and prompted more than half the population to leave town. New York City politicians quickly launched the construction of a major drinking water system by damming the east and west branches of the Croton River, forty miles upstate in Westchester and Putnam Counties, and then built aqueducts to channel that water to reservoirs in downtown Manhattan.

  But New Yorkers were still thirsty. So the city’s Board of Water Supply looked farther out of town to the Catskill Mountains. Today, New York City’s source is the Catskill/Delaware Watershed, named after the two rivers that have delivered water to the city for most of the twentieth century. The watershed provides drinking water to nearly ten million people, and for a long time its supply has been kept clean by natural filtration. But in 1986 the US Congress amended the Safe Drinking Water Act, which was originally passed by Congress in 1974 to protect public health by regulating the nation’s public drinking water supply. The amendment pressed New York City to build a $6 billion to $8 billion filtration system. Instead the city proposed protecting this valuable watershed by buying land as a buffer and a natural filter while upgrading sewage treatment plants.

  But housing development got in the way. Roads and homes started to appear in the Catskill/Delaware Watershed, and New York City politicians procrastinated on their land purchase proposal. To get things going, Robert F. Kennedy Jr., son of the late senator, then the attorney for New York’s clean water advocate, Riverkeeper, solicited a real estate agent who estimated that it would cost only $1 billion to buy every acre in the Catskill/Delaware Watershed, several billion dollars less than a filtration system. The real answer, Kennedy told one reporter, was to “stop development. That’s w
hat you have to do, but nobody wants to say it.”

  Kennedy kept pushing the city on Catskill land purchases, taking film crews into one faulty hospital treatment plant, showing how sewage and wastewater were leaking out into the New York system. The New York Post reported that the Croton reservoir had been shut down due to pollution by sewage, but a New York City spokesman countered that it had been shut down by “organic material.” The late-night television host David Letterman joked that the story “scared the organic material out of me.”

  New York City reacted by putting severe restraints on development, new sewage plants, paved surfaces, and farming activities in the watershed, but local residents countered with lawsuits alleging they were being asked to shoulder the cost of New York’s drinking water. The battle ended in a compromise in which the city promised to spend $1.5 billion to buy up land and to construct and repair necessary storm drains and sewage systems. The EPA put off the New York City requirement to build a drinking water filtration system for another five years.

  Today the city does everything to guarantee the safety of its water, including following urban sales of Pepto-Bismol and Imodium, both dysentery medicines, to help monitor water quality. Inspectors look for outbreaks of disease caused by single-celled parasites such as Giardia lamblia and Cryptosporidium parvum in the city’s water supply. Giardia can cause cramps and diarrhea, but just one cyst of Cryptosporidium can lead to severe illness or death in people with weakened immune systems.

  Right now nature is producing the correct amounts of plants, forests, cattails, earthworms, and soil bacteria to keep these and other illnesses out of New York. But if we keep destroying species, the biological equilibrium of these natural systems won’t be there to offer its first line of defense.