The grim harvest of "finning"—a wasteful practice that is reducing shark populations at an alarming rate.
     Imagine a bustling metropolis at noon. Amid the lunchtime commotion, an elderly man walks across a busy intersection. He collapses. Because this occurs in his hometown, blocks from his physician’s office, his medical history is readily accessible, and his current ailment is easily identified and treated. Now take the same man on vacation in a city halfway around the world. When he collapses, the situation is vastly different. His medical records cannot be obtained, and doctors can only treat the emergency by assessing his current state.
     Scripps professor Jeremy Jackson uses this analogy to illustrate the state of the world’s coastal ecosystems: they are currently in an emergency room, and there is not an accurate record of their history.
     A marine ecologist and geologist, Jackson set out two years ago to understand how coastal ecosystems are changing. Every marine ecosystem he had studied throughout his 30-year career had become almost unrecognizably different from when he had first studied them, and he wanted to know why. Thus, he assembled an international team of 19 marine researchers, who collected and analyzed archaeological, paleoecological, and historical data. (See "Just for the Record" to find out more about these sources of information.)
     In what has become a seminal study published as the cover story of the journal Science, Jackson’s research has provided a startling historical account of how vast populations of marine species have been decimated over centuries through a single and identifiable human act: overfishing.

An Inuit hunter
skinning a walrus.
     "I don’t think we need to document in exhaustive detail what happened to every species in the ocean, and I don’t think we could do it," Jackson said. "But the power of the result we came up with is that we saw a standard sequence of events everywhere we looked. That sequence was overfishing the biggest animals around, then focusing on smaller and smaller organisms that are lower and lower down the food chain."
     According to Michael Kirby, a Scripps postdoctoral fellow and a coauthor of the study, the participating scientists gathered on more than 10 occasions beginning in September 1999 to discuss evidence of centuries of overfishing in three marine areas: kelp forests, coral reefs, and estuaries.
     The team discovered that human impacts on marine ecosystems became evident hundreds and even thousands of years ago. In North America, for instance, overfishing was documented before the colonial periods, although these effects pale in comparison with those of modern overfishing.


Millions of tons of fish are caught annually for the aquaculture industry.
     "Essentially, by overfishing our coastal oceans for centuries, we are doing uncontrolled experiments and witnessing the transformation of the global coastal ocean," Jackson said. "We’re witnessing the disappearance of large organisms and the increasing ascendancy of small invertebrates and microbes throughout the coastal ocean. We don’t know how easy it is to reverse the process, assuming we have the will to do it.
     Removal of key predators from the oceans disrupts marine food webs, making coastal oceans more vulnerable to many problems emerging today, such as toxic blooms and disease outbreaks. Setting all of this within a historical context is absolutely vital if researchers are to fully comprehend the causes and results of change in our coastal oceans.
     "Responding only to current events on a case-by-case basis cannot solve the oceans’ problems because impacts of human disturbance are synergistic and have deep historical roots," Jackson said. "Many extinctions make ecosystems more vulnerable to other natural and human disturbances."
     Wolfgang Berger, a Scripps research paleogeologist and another coauthor of the report, has been studying sediments from the Santa Barbara Basin that date back more than 1,000 years.
     "We tend to be more familiar with historical records in terrestrial systems," Berger said. "If you don’t understand the time scale of changes to an ecosystem—whether it’s the chaparral on land or marine life in the sea—then you don’t really understand the ecosystem."

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