Moises Velasquez-Manoff

Did Asteroids Really Do in the Dinosaurs?

Sixty-five million years ago, a six-mile-wide asteroid slammed into what's now the Yucatán Peninsula in Mexico. The impact, 2 million times more powerful than the largest nuclear bomb ever detonated, gouged out a 112-mile-wide crater and sent mega-tsunamis thousands of feet high in all directions.

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Some Coastal Woes Begin Far Inland

In the early 1970s, Earl "Rusty" Butz, the US secretary of Agriculture, urged American farmers to plant crops "fencerow to fencerow." "Get big or get out," he told them. Farm subsidies followed and, as many small farms consolidated into fewer larger ones, the country transitioned into a new era of corporate-dominated agribusiness. With large-scale farming came the large-scale application of man-made fertilizers.

Around the same time, large algal blooms began appearing with increasing regularity in the shallow, coastal sea at the mouth of the Mississippi. The algae died and sank. As it decomposed, it sucked oxygen from the surrounding water. Areas along the ocean floor became oxygen-depleted, or hypoxic. Oxygen-dependent organisms that were able to, fled. Those that couldn't, suffocated.

The nation had a new problem, one that underscored how the ocean's problems can begin 1,000 miles inland: Fertilizer applied throughout the huge Mississippi watershed was creating a "dead zone" in the northern Gulf of Mexico. It's the second-largest such dead zone in the world, after the one in the Baltic Sea.

Scientists understand the causes and have proposed a bevy of possible solutions. A decade ago, state and federal agencies began to coordinate their efforts to address Gulf hypoxia. The effort got off to a strong start, but has since foundered for lack of funds.

"It's the tragedy of the commons," says Nancy Rabalais, executive director of the Louisiana Universities Marine Consortium in Cocodrie, La. "Things that a farmer doesn't know about he doesn't care about."

Since the widespread adoption of man-made fertilizers in the 1950s -- the innovation behind the "green revolution" -- fertilizer and pollution runoff has caused hypoxia to increase in many shallow waters. By one estimate, the number of dead zones worldwide has doubled every 10 years since the 1960s, to 170. The US has about 50 hypoxic areas affecting half its estuaries. As developing countries continue to adopt industrial-scale farming methods, many foresee the problem spreading.

The Gulf dead zone has grown steadily, doubling in average size between 1980 and 2000. Scientists expect it to get bigger. More fertilizer than ever is washing down the Mississippi due to the ethanol boom and heavy rains. This year scientists predict a Massachusetts-sized dead zone, nearly 20 percent larger than the previous record of 2002. Chronic hypoxia has completely altered places like Chesapeake Bay and the Black Sea. No one knows how the Gulf's hypoxic zone might affect the area's lucrative fisheries.

"We're ... playing roulette with the Gulf fisheries," says Doug Daigle, coordinator of the Lower Mississippi River Sub Basin Committee on Hypoxia in Baton Rouge, La. "The big fear is that we'll have a crash.... Once that happens, it's very hard to try to go back and fix it."

The problem, which embraces the 1.2 million-square-mile Mississippi watershed, spread across 31 states, is daunting. But a recent US Geological Survey report indicated that the fertilizer sources are relatively concentrated. Nine states contribute 75 percent of the nutrient runoff that ends up in the Gulf. Each year, $391 million worth of fertilizer washes down the Mississippi, according to the nonprofit Envi°©°©ron°©°©mental Working Group (EWG) in Washington.

Mitigation measures are relatively low-tech. Planting a buffer of certain crops - switch grass, for example - around farmland can cut nutrient-rich runoff. Wetland systems absorb nutrients in the water, which places a premium on wetland restoration. Changing when and how farmers fertilize also lessens runoff.

When polled, farmers say they would prefer the more diverse landscape implied by buffers and restored wetlands. Indeed, various programs exist at both state and federal levels to pay farmers to let land go fallow, or even restore it. But currently the incentives to plant crops -- including direct subsidies and high food prices -- are much greater than those for conservation. In the top polluting counties, EWG puts the ratio at 500 to 1.

"They're being paid to grow more and more corn rather than to implement these conservation measures," says Donald Scavia, professor of natural resources and environment at the University of Michigan, Ann Arbor. "You're concerned about fish in the ocean, and it's being driven by US farm and energy policy."

The only way to address the problem, say experts, is through a coordinated effort led by a central authority.

In 1997, the Environmental Protection Agency convened a task force to address the problem. Four years later, the group produced a comprehensive action plan aimed at halving the size of the hypoxic area by 2015. To do so, nutrients would have to be cut by almost one-third. (A later study found that a 55 percent cut would be required.)

Eight years later, some are calling it the "no-action plan." Individual states have moved to address their water quality issues locally, but the coordinated effort called for in the action plan has yet to emerge. Lack of money is the biggest obstacle, a fact noted in the in the 2008 Action Plan signed earlier this month.

"The goal was to achieve something like $2 billion per year to fight hypoxia," says Len Bahr, director of applied science in the Louisiana governor's Office of Coastal Activities in Baton Rouge, and a signatory on the 2008 plan. "None of that money has ever materialized."

"We don't really have the legal authority in place for anyone to fix this," says Catherine Kling, a professor of economics at Iowa State University, Ames. "And if you don't have that, you have to rely on voluntary" measures.

Ethanol production is likely to enlarge the dead zone. A March study in the Proceedings of the National Academy of Sciences found that if the US meets its stated goal of 15 billion to 36 billion gallons of corn-based ethanol by 2022, nutrient flow into the northern Gulf will increase by 10 to 34 percent. Without drastic changes in agricultural practices, the paper concludes, the Action Plan's goals are "practically impossible."

Already, last year farmers devoted a nearly California-sized tract of land to corn cultivation, a 15 percent increase over the previous year, and a 60-year high. Last year, the dead zone reached the third-largest extent ever observed.

Heavy rainfall throughout the Midwest this year has increased the Mississippi's discharge by 75 percent. While the river's fertilizer concentration is lower than last year's because of high water volume, it will dump 37 percent more nutrients into the Gulf. Loss of crops to floods may urge farmers to plant a second crop, sending more fertilizer downstream.

A study published earlier this year speculates that, after 30 years of excess nutrients, the Gulf ecosystem may be near a tipping point. The northern Gulf's sediments have become so saturated, the authors say, that the ecosystem is showing less resilience. Compared with 30 years ago, it takes a smaller nutrient load to cause the same size dead zone.

Some fishermen are worried, too.

"It has the potential to affect fisheries," says Ms. Rabalais. Fish can flee when an area turns hypoxic. But often the bottom-dwelling bivalves and worms that form an integral part of the ecosystem can't. "It reduces biodiversity," she says. And with each reduction, returning fish find the ecosystem less able to sustain them.

Others think the dead zone's potential impact on fisheries is being oversold. How oxygen-depleted waters affect an ecosystem depends on the ecosystem itself, says James Cowan, a fisheries oceanographer at Louisiana State University, Baton Rouge.

In Chesapeake Bay, for example, originally dominated by bottom-dwelling organisms like oysters, increased nutrient influx has restructured the food web. Low-oxygen waters can occupy up to 40 percent of the Chesapeake in summer, suffocating crabs, fish, and worms. Centuries of harvesting oysters, which once filtered excess nutrients from the water and so defended the bay against hypoxia, may have sent the ecosystem past a tipping point. Few oysters remain.

But at the mouth of the Mississippi, the ecosystem is already adapted to a harsh environment that includes large pulses of sediment and fresh water. Midwater organisms accustomed to these conditions dominate the ecosystem. The greater threat here, Dr. Cowan says, is loss of coastal wetlands that serve as fish nurseries. "For my money, that's the bigger concern," he says.

Where Have All the Fish Gone?

Early European explorers to the Americas encountered an astounding abundance of marine life. White beluga whales, now limited to the arctic, swam as far south as Boston Bay. Cod off Newfoundland were so plentiful that fishermen could catch them with nothing more than a weighted basket lowered into the water. As late as the mid-19th century, river herring ran so thick in the eastern United States that wading across certain waterways meant treading on fish. And everywhere sharks were so numerous that, after hauling in their catches, fishers often found them stripped to the bone.

"It completely bowled me over when I started reading some of these early accounts," says Callum Roberts, a professor of marine conservation at the University of York, England, and author of "The Unnatural History of the Sea," which tells much of this tale. "The picture painted is one of an abundance of life which is very hard for us to grasp today."

Hundreds of years of fishing -- and especially the last half century of industrialized fishing -- have drastically altered the oceans. Measured by weight, only 1/10th of the large predators that once swam the seas -- the big fish and sharks that shape the entire ecosystem -- is estimated to remain. And many of these changes have occurred relatively recently. Any middle-aged fisherman will wax nostalgic about the catches of just 20 years ago. Any marine scientist will glumly check off reefs they once studied that are now bleached and overgrown with algae as a result of overfishing and pollution, and the marine life that's simply disappeared.

"Today's oceans have got far less in the way of biomass than they used to," says Professor Roberts. "We're altering ecosystems in a way that reduces the level of productivity they can support."

After millenniums of a free-for-all, many foresee the era of open access to the ocean formally coming to a close.

World catches have steadily declined since peaking in the late 1980s. Everyone, from scientists to fishermen, is alarmed. And in the US, all quarters are pushing to develop solutions before the problem becomes unfixable. Fishermen and fishery managers are rethinking management to encourage stewardship. Scientists now say that fish stocks can't be viewed in isolation; they must be managed in the context of the greater ecosystem. Many, even some fishermen begrudgingly, realize the importance of having some areas completely off-limits to fishing in order to keep ecosystems healthy. And increasingly, a new argument is heard in the debate over fisheries: Marine ecosystems should be preserved not just for their economic value, but also because, like the wilderness preserved in the national forest system, they are part of humankind's natural heritage.

The debate comes at a time when, driven by both health trends and increasing prosperity in countries like China, demand for fish is rising. In industrialized countries, fish consumption doubled, to 27 million metric tons, between 1961 and 2003, according to the United Nation's Food and Agriculture Organization (FAO). Per capita, that's an increase of one-third, to 29.7 kg (65.5 lbs.) per person yearly. (Much of the increased demand is being met by a growing aquaculture industry.) In developing countries, fish continue to provide an important source of protein. The average African gets 17 percent of his protein from fish; for Asians, it's 26 percent. The typical North American gets only 7 percent of his protein from fish.

Fishery managers have a name for what can be removed without causing stocks to fall: the maximum sustainable yield. In theory, a well-managed fishery should provide free food -- save for the cost of catching it -- year after year.

And yet, even in the US where stocks are on balance in better condition than in other places, 41 of the 244 stocks for which the National Marine Fisheries Service (NMFS) has information are being fished at unsustainable levels, or overfished. Worldwide, one-quarter of fish stocks are overfished, says the FAO. Another 50 percent are fished to full capacity; they can sustain no more. According to one somewhat controversial analysis, if current fishing trends continue, all the world's fisheries will have collapsed by mid-century.

What happened? Daniel Pauly, director of the Fisheries Centre at the University of British Columbia, Vancouver, calls the combined cultural, technological, and economic factors "the march of folly."

It began with a long-held notion of the sea's endless bounty.

Until relatively recently, fishermen, fishery managers, and scientists alike thought the sea was so vast, so teeming with life, that human activity simply couldn't diminish it, Mr. Pauly says.

Until the advent of modern fishing technology in the 20th century, it couldn't.

"The sea was very large compared to the means we had to exploit it," Pauly says. But beginning with steam-powered trawlers more than 100 years ago, and ending with today's global-positioning navigational systems, technology has improved fishermen's reach and efficiency. "We essentially deployed our industrial armada against fish, and obviously we would win: It's a war against fish," says Pauly.

Technology made inaccessible fish accessible. Pristine areas used to constantly replenish adjacent areas that were fished, scientists hypothesize. But as technology let fleets fish in areas previously unfished due to remoteness or difficult undersea topography, this replenishment failed. Fish numbers fell, but better fishing technology concealed the trend. World catches remained stable or increased, suggesting healthy stocks.

Then, when local stocks began to collapse, fleets moved ever farther offshore, leading to what Robert Steneck, a professor of marine biology at the University of Maine, Orono, calls "roving banditry": High-seas fleets fishing stocks to collapse, then moving on. Many countries also subsidized their fleets, increasing capacity far beyond what the seas could absorb. Worldwide, the FAO estimates that by the 1990s, subsidies had pushed fishing capacity some 30 to 50 percent above what the oceans could sustain. (It has since fallen.)

"When the biomass goes down because of fishing, in a sense the stock has a message.... 'Leave me alone,' " says Pauly. "But subsidies, which contribute to the harvesting of fish, enable the fisher to ignore the signal of the stock."

In the US, which actively developed its domestic fleet throughout the late 1970s and '80s with low-interest loans and other programs, many thought that fishing overcapacity would self-correct. If fishermen were just another predator, once fish numbers dropped, fishers would, too. Equilibrium would be restored.

But the laws of economics led to a different outcome: "As stocks get rarer and rarer, their prices go up -- the so-called 'ratchet effect,' " says Steve Murawski, chief scientist at National Oceanic and Atmospheric Administration Fisheries in Silver Spring, Md. The incentive to catch the few remaining fish increases rather than decreases. "That wasn't well understood," he says.

Empty Oceans, a series on the state of the world's fisheries, will be appearing in the Monitor's environment section. For the full series, click here.

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