The Next Species: The Future of Evolution in the Aftermath of Man (25 page)

A study by Cathy Lucas, a marine biologist at the University of Southampton, UK, predicts that jellyfish concentrations are regulated by decadal fluctuations and that the rise in the 2000s is part of the normal ups and downs that last peaked in the 1970s. But another study, conducted by researchers at the Institut de Recherche Pour le Développement in France, speculates that overfishing is the cause. Researchers at the Institut compared two major ecosystems along the Benguela Current, which flows along the southwestern coast of Africa. Off Namibia, where commercial fishing regulations are lax, jellyfish are spreading in coastal waters. But off South Africa about 600 miles (1,000 kilometers) south, where fishing has been tightly controlled for sixty years, jellyfish populations are stable.

José Luis Acuña, at the Universidad de Oviedo in Spain, studies jellyfish, which he says are an increasing problem in some parts of the Mediterranean. He claims that despite the fact that jellyfish are
slow-moving, drifting animals with no vision to help them spot prey, they do as well as some sighted, fast-moving fish, when you factor in their much lower metabolisms that don’t require as much food, and their large body sizes, which are achieved by the addition of a good amount of water.

Jellyfish are ancient, dating back 600 million to 700 million years or more. That’s three times the age of the first dinosaurs. Acuña speculates that jellyfish have survived and will continue to thrive in the future by evolving large, water-filled bodies that can come in contact with more prey. Although larger bodies are less efficient, collecting your prey while drifting through the water beats the high-energy costs of hunting it down. He sides with those who think that
overfishing is promoting the presence of jellyfish in ocean waters. Without eyes, jellyfish seem to be able to handle human polluted environments
better than fish.

Jellyfish are adaptable, perhaps even more than humans. Our strategy has been to go after food, metals, and fuel with full and furious fervor, whereas jellyfish have evolved a much more passive strategy of gently moving though the water, taking only what they need, and limiting their expenditure of energy. We’ve moved in ways that are exhausting our available resources, while jellyfish glide through the water, carefully limiting their costs. Which has the best outlook for the future? In a structured competition, it would be hard to think we could outlast the jellyfish.

Is the future of the ocean one filled with jellyfish and squid? Perhaps. But both of these creatures bear the markings of “weedy species”—those that rush in after a catastrophe. They are like the new grasses that sprouted up near Mount St. Helens in places where the volcanic eruption had blown the trees down. Or the early Triassic scallop
Claraia
that moved in after the Permian extinction. They are quick to take over disturbed areas and to go through large population explosions, but those explosions are not made to last.

If the pressure from man continues at current rates, we will indeed trash the oceans. The world’s fisheries are already at an extreme point. At a recent symposium for the American Association for the Advancement of Science, I heard one European scientist say that we should eat fish only on major holidays “like Americans now do with turkey.”

Despite the best efforts of environmental groups like the World Wildlife Federation, the future does not look bright as long as man is in the picture. However, if we were to take a sabbatical or perhaps an early retirement, the ocean would return in due time. And we’re not talking about returning to conditions as they were before the first European explorers. To resurrect life as it was in its prime, we need to go back much further.

Says Olazul’s science director Frank Hurd, “Most fisheries managers try to rebuild ecosystems to what they saw fifty years ago. But if you want to know what virgin nature really looked like in the Americas,
you don’t go back fifty years, or even five hundred years, you go back before the first human ever appeared.”

What would that look like? Man has altered the oceans so thoroughly that it’s hard to imagine. Callum Roberts in
The Unnatural History of the Sea
offers up Captain Edmund Fanning’s first visit to Palmyra Atoll in the Pacific Ocean in 1798 as his best attempt to describe it. Captain Fanning was headed from the Juan Fernández Islands, off the coast of Chile, to Canton, China, with a boat full of fur seal pelts. Fanning and his men from Stonington, Connecticut, had spent four months off Chile taking fur seals for their pelts. Palmyra, in the middle of the Pacific, was the halfway point of their journey.

Late on a hot June night, Fanning’s men, who’d sighted breakers ahead and worried there were hidden obstacles under the water, awoke the captain. What the men had seen was an atoll of islands circling a bay wreathed in foam from the ocean swells, which were exploding against the coral beneath. Fanning and
his crew struggled to find calm waters on the downwind side of the atoll, where they dropped anchor. They awoke the next morning to encounter about fifty islets surrounding three lagoons. The shores were fringed by coconut palms and coconuts lay all over the beaches, untouched by man.

Fanning and a few of his crew took a rowboat to investigate. While rowing into the bay, he was astounded at the abundance of fish. Ravenous sharks grabbed at the rowboat’s rudder and oars, “leaving thereon many marks of their sharp teeth and powerful jaws.” As they entered the bay, the sharks were replaced by multitudes of fish that were less rapacious but even more plentiful.

The men went ashore for coconuts while Fanning stayed with the rowboat to fish. He stood there with a harpoon and caught fifty mullet weighing about five to twelve pounds (two to five kilograms) in short order. He stopped, perhaps thinking the fish might spoil or the boat might sink under the weight of his men and the fish.

Today, Palmyra Atoll, 1,000 miles south of Hawaii, has passed through various international controls before the Nature Conservancy bought it in 2000. Though there is a small private-use airport
run by the conservancy, the island is mostly the same place that Fanning visited in 1798. Coral reefs that have grown on the rim of an ancient submerged volcano form the atoll. These vast submerged reefs support three times the number of corals found in the Caribbean and Hawaii.

Palmyra is one of the few places in the ocean where top predators dominate the underwater community. Dive into the water and sharks surround you, a site not seen often elsewhere. Palmyra has more apex predators—large fish like groupers, jacks, and sharks—than any other reef known to science. A diver stepping into this unique ecosystem is stepping back in time to when fishing had not yet affected the seas. The reefs support a complex web of life: not only sharks but pods of dolphins, manta rays, sea turtles, and thousands of tropical fish.

Do you want to peek at the ocean after man? Go visit Palmyra Atoll. The species may change going into the future, but everything else will probably be the same. A rise in the sea level might submerge the reef, but the reef will eventually return once mankind hits the road.

Prior to Fanning’s visit to Palmyra Atoll, there was no evidence of human contact. Fanning may not have appreciated what he was seeing, but it was something that today is extraordinarily unique.

Perhaps the greatest treasure of this magical place is its abundance of marine predators, which are currently under assault almost everywhere else in the world.

O
VER THE LAST
600 million years, during most of the extinction events, predators were the last to go. During the Cretaceous extinction, which knocked out the dinosaurs, the asteroid’s impact created clouds of gases and dust that blocked out light. This killed off the plants, which knocked off the plant eaters, and took out the predators, which ate plant eaters for lunch. Plants, plant eaters, and predators were the sequence then, but this time we’re attacking both ends. We’re killing off our plants, which are at the bottom of the food chain or “web,” as biologists prefer to call it, while at the same time going after predators, at the top of the web. We’re killing off predators first, either because they have valuable appendages (shark fins, rhino horns, elephant tusks) or because they take our domestic animals, or simply because, once in a while, they get one of us.

There are unique consequences for this top-down approach, says Jim Estes, professor of ecology and evolutionary biology at the University of California, Santa Cruz, when I visited with him at the Long Marine Laboratory on campus. He witnessed some of the top-down consequences in 1970 when, as a graduate student, he was sent to the Aleutian Islands between Alaska and Russia to study sea otters. One of his professors had urged him to address
the role of sea otters as predators
within the Aleutian ecosystem. “It
never dawned on me that that would be an interesting question,” says Estes.

The Aleutian Islands are a chain of volcanic islands that stretches from the Alaska Peninsula toward the Kamchatka Peninsula, creating the boundary between the Bering Sea and the North Pacific Ocean. This is an area of stormy seas where one is not likely to find cruise ships, rustic inns, or tourists. Amchitka Island within the chain was used as an airfield during World War II but is currently uninhabited. Northern sea otters were nearly wiped out by fur hunters here in the late nineteenth century but an international treaty in 1911 stopped the pillage. By the 1970s the northern sea otter had recovered over vast areas of its former range, but not all. This gave Estes a unique vantage point from which to understand the value of a predator within a maritime ecosystem by viewing islands with and without otters.

In the first weeks of the study, Estes piloted a boat around Amchitka, past submerged rocks and into foggy inlets, here and there diving under the icy waters to get a glimpse of what lay below. Around the craggy underwater shorelines, the seas were filled with kelp plants that grew up from the bottom offering a respite, nursery, and feeding grounds for a wealth of marine creatures. Kelp is one of the fastest-growing plants on earth: under ideal conditions it’s capable of growing up to two feet in a day and can reach 175 feet in height in a matter of months. Beneath the surface, the
kelp rises like an undersea forest. Large golden leaves attach to long thin stalks that sway with the movement of the currents.

Amchitka offered a robust, healthy ecosystem with predators in place, but Estes needed a comparative view. So he traveled to Shemya Island a couple of hundred miles west of Amchitka. Shemya had come under the same human assault that had wiped out the sea otters at Amchitka, but the otters hadn’t yet returned to Shemya. When Estes entered the water there, he found a different world from the one he’d found at Amchitka. To start, there was little or no kelp. Instead, he viewed an ocean bottom thick with urchins, small spiny, spherical creatures, the favorite food of otters. The role of the otter as predator
was immediately obvious. With otters, there were still some urchins present but they occupied hidden crevices and weren’t numerous enough to curtail the growth of kelp. Without otters, there was a thick covering of urchins and no kelp forest. Since then, Estes has spent a good deal of his professional career trying to understand that relationship.

Without otters, there was simply
no predatory pressure on the urchins, and without this pressure, urchin populations boomed. The problem was that urchins in sufficient numbers attacked the kelp holdfasts at the base of the plants, and this killed the kelp plants and the marine forests they created.

Estes visited New Zealand to understand what kept urchins at bay in those waters where there were no otters and never had been. The biologist found that southern kelp had developed a load of noxious compounds to make them unsavory to urchins. Off the Aleutian Islands, Alaska, and western Canada, the otter discouraged the presence of urchins all by itself. And with otters protected, the balance returned. Otters recovered to 75 percent of their original range in the Aleutians, as the kelp forests there grew thick and healthy.

But then, in the beginning of the 1990s, sea otter populations plummeted there once again. Their numbers, estimated at 55,000 to 100,000 in the 1980s, dropped to 6,000 by the year 2000. Some marine biologists blamed disease, others blamed increased ocean temperatures from climate change, and still others pointed their fingers at industrial fishing. But one day in 1991, Brian Hatfield, a US Geological Survey biologist working with Estes, came into one of their field offices in the Aleutians and said he thought he’d just seen a killer whale take a sea otter, but he wasn’t sure. “He came back a few days later,” says Estes, “and this time he was positive.”

Estes didn’t bite at first. Pollution, industrial fishing, and disease were still the favored culprits of the otter decline back then, but all of these options would have left a weakened, scrawny population of otters, and the otters in the Aleutians were fit and fat. Pollution, industrial fishing, and disease would have weakened the otters through
sickness and poor health. But killer whales reduced the population of otters to such low levels that food was no longer a limiting factor, which was why these small furry creatures were so big and healthy.

Otters weren’t the only marine mammals in trouble in that region. Populations of Steller sea lions, northern fur seals, and smaller harbor seals were also collapsing, and their remaining populations appeared healthy as well. The case for the killer whales grew stronger.

Alan Springer, a researcher as the University of Alaska Fairbanks, approached Estes at a conference and showed him how killer whales depended on large whales as a food source, but post–World War II industrial whaling had removed half a million great whales—the killer whales’ natural prey—from the North Pacific. Prior to whaling, the North Pacific and the southern Bering Sea had an estimated 30 million tons of whales, but when the International Whaling Commission imposed a moratorium on whaling in 1985, only 3 million tons of whales survived. About 90 percent of whales in the North Pacific had been destroyed, and the killer whale was frantically trying to make up for the loss of food.