The Next Species: The Future of Evolution in the Aftermath of Man (23 page)

Censuses of wildlife at Fukushima found that the abundance of birds, butterflies, and cicadas had decreased; bumblebees, grasshoppers, and dragonflies were not affected; and spiders actually increased in abundance—possibly because the insect prey they normally fed on were weaker and easier to catch. Eventually insects will start to drop off. Small mammals, reptiles, and amphibians remain quite low, but cleaned-up areas of the exclusion zone could start attracting them later. Scientists believe that mutations will appear as insects and animals cycle through more generations.

What concerns some biologists is the radioactivity that washed into the ocean. Japan is on the migratory route of multiple marine species in the North Pacific, including tuna and sea turtles. Right now the Fukushima accident site has the stronger effects of the initial explosion and release of radioactive, short-lived isotopes, whereas some of those initial effects of radiation at Chernobyl have disappeared.

Guns, bombs, and radioactive waste aren’t the greatest things for wildlife, but they are better than burgeoning populations of humans consuming every last inch of open space. They keep people, concrete, and asphalt at bay by giving the plants some ground to grow on. Still, man has many less obvious ways of destroying wildlife habitat: Just
look to our oceans.

T
HE OCEAN COVERS
71 percent of the earth’s surface and contains 97 percent of the planet’s water. There are massive amounts of energy stored up in its ponderous waves, occasionally unleashed by storms and earthquakes. Life got started beneath its surface, and it still offers an elegantly evolved storehouse of creatures within its churning waters, though its abundance was greater before we built boats and headed out to sea.

Despite its enormous significance to humans, we know as much about this underwater world as we do about Mars. The ocean is a no-man’s-land of weakly controlled international agreements. It’s the last frontier. The last place where we still hunt wild game in significant amounts. The last place we still harvest wild creatures with only rudimentary ideas about their limits.

Overharvesting the sea is not our only dilemma, as we must also deal with a legacy of pollution festering within it. The oceans of the world are beginning to absorb the increasing levels of CO
₂
we harbor in our atmosphere. This heightens the acidity, and
lowers the pH of ocean waters, which is bad for krill, the preferred food source of a number of whales that feed in the high-latitude areas of both the Arctic and the Antarctic. But it gets more exact. Biologists also believe
that ocean acidity
decreases the ability of whales to hear the mating calls of others. Both of these effects could be catastrophic for whale populations.

I got to see firsthand the importance of human changes to the marine environment when I accompanied Adam Pack, associate professor at the University of Hawai’i at Hilo, aboard the
Kohola II
to the mating and calving grounds of the humpback whales off the Hawaiian Islands. Just a few minutes out of Lahaina Harbor on the island of Maui, a huge humpback whale leapt out of the water, its entire body hanging in the air momentarily before crashing into the ocean, the spray soaking all the researchers on our boat.

But Pack’s attention wasn’t focused on the breaching behemoth. Instead, he was observing a group of whales roiling at the ocean surface farther off. Soon our boat was just outside
a ring of male humpback whales surrounding a lone female.

Pack, dressed in a wet suit, slipped over the side of the boat with a video camera while several of his students and I watched from above. More than ten thousand humpbacks migrate annually from their winter feeding grounds off Alaska and the North Pacific Rim to Hawaiian waters. Surrounding this lone female, the males butted heads and slashed each other with their fins in an effort to position themselves next to her as the principal escort—the one who gets to mate with the female whale first when she becomes receptive.

Studies by Pack and colleagues have shown that the larger females prefer larger males. On this day it seemed that fewer than half of the males swimming in this dangerous circle were juveniles. Still, this is a lot when you consider how much they sacrifice to get here, and how little they are rewarded. Juveniles come here to watch; they don’t have access to the females. They are basically traveling six thousand miles from southeastern Alaska to Hawaii—a trip that will cost most of them one-third of their entire body weight due to fasting—to attend a very expensive school on mating behavior.

Biologists aren’t quite sure why these whales make this long trek. It may be that Hawaiian waters are warmer and calves don’t
need such a thick layer of fat around them at birth. Or perhaps it is the fact that there are fewer predators, particularly killer whales, in Hawaiian waters. A study by John Calambokidis with the Cascadia Research Collective, in Olympia, Washington, found that more than 25 percent of humpbacks examined had tooth marks on them from killer whale attacks. But humpback whales take these risks for the chance to mate.

Males advertise themselves to females not only with their size but also with their song, an important part of reproduction. Though juveniles are excluded from mating, they still get to sing. Scientists at the Australian Marine Mammal Research Centre in the 1990s recorded two males singing a particular song one year that was different from the other eighty singers recorded off Australia. And the next year more males were singing that song. The following year all the males were singing that song. A couple of whales had started a musical trend, a form of culture. But ocean acidification may be affecting their song as well as their food.

Humpbacks are adaptive animals. Researchers at the Alaska Whale Foundation have witnessed humpbacks diving below schools of krill or fish and blowing bubbles around the schools, essentially herding them into a tighter group, after which the whale comes up beneath the group, its mouth open wide to capture everything possible.

At one time scientists held the idea that the ocean might be a legitimate sink for growing amounts of CO
₂
on land. Some scientists were even looking for ways to improve the uptake of CO
₂
by the sea, but it turned out the
ocean was doing a good job of taking in CO
₂
all by itself. CO
₂
in the ocean reacts with the water to form carbonic acid, and this leads to increased ocean acidity. The result is that the oceans are 30 percent more acidic than before. And there are consequences to pay.

Acidification of ocean water is bad for krill, the preferred food source of a number of whales. Studies from the Australian Antarctic Division show that most krill embryos exposed to high levels of acidification (2,000 parts per million) did not develop and none hatched successfully. Cold waters absorb more CO
₂
than warmer waters. Southern ocean carbon dioxide levels could rise to 1,400 parts per
million by the year 2100, three and a half times higher than current rates closer to the equator. This could devastate marine life.

Ocean creatures that wear their skeletons on the outside, such as shrimp, clams, and coral, will find that an increasingly acidic environment could start dissolving those shells. Krill look like tiny shrimp whose skeletons are wrapped around their bodies like a thin suit of armor. These exoskeletons protect them from the elements, but ocean acidification could destroy that protection.

Plus, acidification interferes with the ability of whales to hear others sing. Researchers at the Monterey Bay Aquarium in California found that acidification reduces the ability of the sea to absorb low-frequency sound. This amplifies the ambient noise level from currents, animals, and man, making it more difficult to hear whale sounds, which are broadcast at similar frequencies. The ocean absorbs at least 12 percent less sound now than it did in preindustrial times. And this is projected to rise to 70 percent in 2050.
As the ocean gets noisier, whale sounds may get muffled—a critical component of their mating system.

Humpbacks and other whales evolved from the same terrestrial animals that gave rise to sheep and deer. About 60 million years ago these animals moved back into the sea, slowly evolving the ability to drink salt water as their nostrils moved higher up their foreheads until they became blowholes. Their ancestors spawned different lineages of marine mammals, including whales. Some, like killer whales, preyed on different marine mammals, including other whales; others, like the humpback, evolved fine, fibrous combs called baleen in their mouths to filter shrimp, krill, and other creatures that traveled in large schools.

Though originally from the ocean, they were
unable to get their gills back: “Evolution doesn’t move backwards,” said Hans-Dieter Sues when I visited him. So whales had to learn to breathe air only at the surface. They gradually lost their legs, though some whales still have small vestiges of legs near their tails. That any animal could go through such an enormous range of changes is testament to evolution’s incredible ability to morph its creatures.

Commercial whale hunting in the first seven decades of the twentieth century reduced their numbers by over 99 percent. From pre-whaling estimates of 250,000 animals, humpback whales had been nearly hunted to extinction, with only about 2,000 then remaining. In 1970, they were put on the endangered list, and since then humpback numbers have rebounded to more than 20,000 in the North Pacific. But acidification could change that progress, particularly since acidification goes hand in hand with warming (both caused predominantly by CO
₂
).

Warming could result in a loss of polar ice. Some biologists refer to it as the
“Atlantification” of the Arctic. A loss of sea ice could affect Arctic whale natives like ivory-white belugas and the single-tusked narwhals, which look like unicorns. These two whales lack a prominent dorsal fin—the main fin located on the back of fishes and certain marine mammals—which makes it easier for them to hunt under the ice. But as the ice cover melts, killer whales—whose prominent dorsal fins have foiled their ice cap hunting so far—could have free rein over the Arctic natives. Killer whales might target bowhead whale calves, while minke whales could provide increasing competition for food to all.

The prospect of a polar-ice-free future concerns many researchers. Gretchen Hofmann, a marine biologist at the University of California at Santa Barbara, makes annual visits to McMurdo Station in the Antarctic to study the effects of acidification. She likes to go down in the southern hemisphere’s spring, and she told me: “There are twenty-four hours of daylight but the ice is still strong enough for us to move around on it and support our weight.”

McMurdo is a coastal station at the southern tip of Ross Island, about 850 miles (1,360 kilometers) north of the South Pole. It is a snow-covered island surrounded by frozen seas and rimmed by jagged mountains. The annual temperature is zero degrees Fahrenheit (minus 18 degrees Celsius), but it can get even colder with the wind-chill factor. Many scientists wear
“ice cream suits”—big, thick coveralls that cover the whole body—but Hofmann likes her layers better: a down jacket, topped by a layer of polar fleece, topped by another layer of polar fleece, topped by a parka to cut the wind.

She says
the worst thing about McMurdo is the food. “It’s all from cans. You get used to having fresh vegetables in Santa Barbara. But down there, there’s nothing fresh, and your food habits get worse and worse. All of a sudden you realize, ‘I’m living on Pringles!’ ”

Hofmann spends about a month or two each year doing her research and teaching classes. She claims the Antarctic is a special land of snow and ice, but the poles are more affected than other areas by acidification as well as global warming, because colder water holds more CO
₂
. Hofmann also works in the South Pacific island of Moorea and along the California coast.

Off Antarctica and off Palmyra Atoll in the mid-Pacific, Hofmann and her coworkers have found that the increase in seawater acidity caused by greenhouse gas emissions is still within
the bounds of natural pH fluctuation. But areas in California such as at the mouth of the Elkhorn Slough in Monterey Bay and off La Jolla, at the top of San Diego Bay, are already experiencing acidity levels that scientists had expected wouldn’t be reached until the end of the century. Hofmann believes ocean acidification in the open ocean may still be tolerable for marine organisms, but that those animals living in tidal, estuarine, and upwelling regions may be functioning at the limits of their physiological tolerance.

Curt Stager, author of
Deep Future: The Next 100,000 Years of Life on Earth
and a professor at Paul Smith’s
College, has studied the Eocene climatic optimum, an interglacial period that began about 50 million years ago. During this time average global temperatures rose 18 to 22 degrees Fahrenheit (10 to 12 degrees Celsius) above today’s mean temperature for several million years.

But what interests Stager most is a brief spike in rising temperatures, called the Paleo-Eocene thermal maximum (PETM), that for approximately 170,000 years forced this world into an extremely warm state, another 10 degrees Fahrenheit (5 to 6 degrees Celsius)
hotter, on top of an already warming world that resembles our own extreme-emissions scenario in climate models. To date, humans have sent 300 gigatons of fossil carbon into the atmosphere. During the PETM there were at least 2,000 gigatons in the atmosphere from causes that yet remain unclear.

As greenhouse gas concentrations rose, they warmed and acidified the deep sea enough to wipe out bottom-dwelling creatures and burn a red layer into the ocean floor. Sediment cores show that it took thousands of years for the worst of it to subside. The PETM might have reduced the nutritional value of plants, stunted the growth of mammals, and encouraged insects to attack plants more vigorously. During the PETM, mammals were extremely small, about half the size of their counterparts during the periods before and after.