Past as Prologue
by Mary-Russell Roberson



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Ecology is the science of describing how plants and animals in a particular place interact with each other and their environment. Over time, the ecology of any place changes, and it's important to understand where the present lies on a continuum of change: Is the population of one species rising while another is falling? Is the plant community different than it was years ago? Have new species moved in?

Grinnell Survey Team
Joseph Grinnell (far right) and members of his survey team in Cedar Canyon in San Bernadino County, California, in 1938. Grinnell foresaw the need for historical ecology. (MVZ Archives)

Ecologists have often used their own lifetimes as a measure, comparing the current character of the woods or size of bird flocks to what they remember from childhood. But now, some are looking back further and, if possible, trying to quantify what they find. This relatively new field is called historical ecology.

To piece together an ecology that existed before they were born, the pioneers of this field are using many of the same sources as historians, including journals, maps, and other written records, as well as oral history accounts. For example, scientists and historians are using such diverse sources as the journals of 17th-century pirates and centuries-old European cookbooks to chart the rise and fall of various marine species.

At the University of Kentucky's Department of Forestry, scientists John Cox, David Maehr, and Jeffery Larkin wondered whether towns, creeks, and mountains named after animals could provide clues to the animals' ranges when the United States was being settled by Europeans. They used the Geographical Names Information System database maintained by the U. S. Geological Survey to map the occurrence and frequency of places named for any of 24 species—21 mammals, two reptiles (alligator and rattlesnake), and one bird (passenger pigeon).

Seven of these animals, including bear and deer, had names often applied to several different species, and were excluded from the results. For the remaining 17 species, the overlap between the animals' historical ranges and the distribution of places named for them was between 21 and 100 percent, with a mean of 83 percent. Javelina place names were most reliable with a 100 percent overlap—Javelina Canyon in Terrell County, Texas, is one example—most likely because their distribution was relatively small. Coyote had a 99 percent overlap, perhaps for the opposite reason: because they were so ubiquitous. Among the least reliable were place names containing the word "lynx": These overlapped with lynxes' historical ranges just 49 percent, perhaps because lynx were often confused with bobcats or because these cats are so secretive.

In a paper published in the journal Conservation Biology in 2002, the scientists concluded that place names in the United States do illustrate a drastic reduction in the ranges of most of these animals over the past few centuries. But although place names, pirate journals, and cookbooks can provide supporting evidence or highlight areas for further research, they cannot be relied upon in isolation. Wolverine, Kentucky, for example, is named for the Wolverine Coal Company, and not all Bear Lakes were necessarily frequented by bears.

When evaluating any source material, historical ecologists consider the fallibility of human memory and motivation. For example, several early European explorers to the Americas embellished their accounts with tales of oversize aggressive women warriors called Amazons. They may have been trying to impress others or sell more books, or perhaps it was just wishful thinking. To mine historical evidence for more accurate information, historical ecologists always look for ways to corroborate data.

The Lewis and Clark Journals

The earliest and most detailed account of the natural history of the American West was provided by the Lewis and Clark expedition. Meriwether Lewis, along with William Clark and the other members of the Corps of Discovery, were charged by President Thomas Jefferson to follow the Missouri River west from St. Louis in search of a good overland route to the Pacific Ocean. Jefferson also instructed the group to document "the names of the nations & their numbers; . . . the soil & face of the country, it's [sic] growth & vegetable productions, the animals of the country generally, & especially those not known in the U.S."

Meriwether Lewis
Meriwether Lewis. (Library of Congress)

The explorers left St. Louis in May of 1804, reached the Pacific in the fall of 1805, and returned to St. Louis in September of 1806, crossing rugged and unmapped ground that had not been systematically explored by European Americans. As directed by Jefferson, the Corps kept copious notes of its travels, describing in astounding detail just about everything it saw and counting and measuring whatever it could.

On Saturday, May 4, 1805, while camped in present-day Roosevelt County, Montana, Meriwether Lewis wrote,

I saw immence quantities of buffaloe in every direction, also some Elk deer and goats [pronghorn]; having an abundance of meat on hand I passed them without firing on them; they are extreemly gentle the bull buffaloe particularly will scarcely give way to you. …we saw many beaver some which the party shot, we also killed two deer today. much sign of the brown bear.

Daniel Botkin, professor emeritus in the department of ecology, evolution, and marine biology at the University of California, Santa Barbara, realized that he could use passages like this one from the Lewis and Clark journals to estimate the density of grizzly bear populations in the early 1800s. He counted 37 individual grizzlies mentioned over the course of about 1,000 miles during the westbound journey, which he calculated to be 3.7 grizzlies per 100 square miles. (He used square miles because he assumed the men could see about half a mile on either side of their route, giving a width of one mile to their 1,000-mile-long transect.) In his 1995 book, Our Natural History: The Lessons of Lewis and Clark, Botkin points out how strongly his results rely upon his assumptions. If, he says, he had estimated that the men could see one kilometer on either side of their route, instead of half a mile, he would have ended up with 5.7 grizzlies per 100 square miles. However, he notes that grizzly experts Frank and John Craighead estimated a similar density of the bears in Yellowstone during the 1950s through 1960s—between about three and five bears per 100 square miles.

Researchers at Oregon State University used the Lewis and Clark journals in a different way. As a doctoral candidate, Andrea Laliberte read them to find clues to the relationship between human settlements and wildlife abundance. "I was really impressed with the detail that [the Corps] recorded," Laliberte says, "considering they were on the river or horseback 12 hours a day, making camp every night, hunting their own food."

Laliberte, now a rangeland remote-sensing scientist at the U.S. Department of Agriculture's Jornada Experimental Range in Las Cruces, New Mexico, tracked nine different species in the journals: deer (a generic term for both white-tailed and mule deer), elk, bison, pronghorn, bighorn sheep, grizzly bear, black bear, wolf, and beaver.

William Clark
William Clark. (Library of Congress)

She made a spreadsheet of the latitude and longitude of each of Lewis and Clark's 506 campsites, then noted for each day which species the men mentioned in their journals, general descriptions of the quantity of wildlife, the number of individual animals the expedition killed, and the presence of any human settlements within 50 kilometers (31 miles) of the campsite.
           
"Their observations were really reliable because they were living off the land," Laliberte says. The men needed wildlife for meat, buffalo robes, and leather to make moccasins and ropes. According to the journals, the party needed either four deer, one elk and one deer, or one bison per day. The daily records of animals killed corroborate that and give credence to the daily tally. In areas of sparse wildlife, such as the Columbia Basin in present-day Washington and Oregon, the company ate some of their horses and dogs. Lewis and Clark kept separate journals and several other men on the expedition did as well, so Laliberte was able to compare observations from several sources for most days.

Were Lewis and Clark seeing what America looked like before Columbus landed? Probably not. Smallpox and other European diseases swept the continent before Lewis and Clark did, killing millions of native peoples. There's no widespread agreement on a number, but some archeologists estimate that 90 percent of indigenous peoples may have succumbed to disease in the first couple of centuries after 1492. Lewis and Clark's journals mention abandoned Native American villages, pock-scarred Native Americans, and stories told by survivors about the diseases that ravaged their villages. Laliberte says, "The abundance that Lewis and Clark saw could very possibly be a rebound caused by lower human pressure."

Despite the fact that Lewis and Clark were traveling through land supporting a recently reduced population of humans, Laliberte and her advisor, William Ripple, found that the proximity of human settlement affected wildlife abundance and diversity. "In a nutshell," Laliberte says, "when there was a greater density of human settlement, the animal density was less and they saw fewer species. What's sort of surprising is that the human density was very low but I could make out those influences on the wildlife."

How Many Cod Swam in the Sea?

The Lewis and Clark expedition intended to document scientific information, but records and recollections originally valued for other reasons can also yield valuable scientific data. Historical ecologists studying cod are finding solid facts in 19th-century business documents and interviews with older fishermen.

Residents of eastern New England and Canada's Atlantic provinces have fished for cod and other groundfish, which live mostly on the sea bottom, for centuries. But in areas where fishermen of yore landed rich cod harvests, the nets of today's fishermen come up empty. In the 1990s, the area's cod fishery collapsed as a result of hundreds of years of continued harvesting, ever-more-efficient fishing techniques, and a population decline among the cod's prey. Cod still live in the northwest Atlantic, but there are too few to support a commercial fishery.

When cod migrate to their natal spawning grounds and gather in large schools, they do not feed, so they were not easily caught in the days when fishermen used only hooks and lines. But in the 1920s, fishermen began trawling the sea bottom with nets. Suddenly, what had been a protected stage in the cod life cycle became a vulnerable one—fishermen sought out the huge spawning schools and scooped them up.

Today, scientists are looking into ways to help cod populations rebound. First, they are trying to work out where and how the cod lived. "If you don't know what existed before, there's no way on Earth you can hope to restore it," says Ted Ames of Stonington, Maine. Ames is a lobsterman with a master's degree in biochemistry who received a MacArthur Fellowship in 2005. He used an ingenious combination of oral history, personal knowledge, and scientific evaluation to reconstruct spawning grounds and migration routes for cod in the Gulf of Maine in the 1920s.

cod
Atlantic cod. (NOAA)

Like his ancestors, Ames has spent most of his life as a commercial fisherman. He realized that older fishermen would have the knowledge he needed to begin reconstructing where cod lived decades earlier. "Fishing isn't a random poking around looking for something," Ames says. "Many of the shoals and fishing grounds have been known for centuries. What's happened traditionally in the coastal fisheries is, once an area was fished out, it ceased to exist—nobody had any continuing knowledge of it." Scientists call this phenomenon "ecological amnesia."

Ames identified fishermen who had worked in the Gulf of Maine between 1930 and 1960; most of them were in their 70s and 80s. Many had to be persuaded to share what they knew. "It's very touching, because that information was proprietary," Ames says. "[It] traditionally passed from father to son and rarely spread any further." Ames told them, "Number one, there are no fish there anymore, and number two, the sole purpose of what we're doing is to try to rebuild the population of cod and haddock along the coast so that we can again have a credible fishery—only this time, use it sustainably." He was able to interview 28 of the 32 fishermen he contacted.

Because he was asking people to rely on memories of events that occurred decades earlier, Ames developed several criteria for the data he collected: Before he identified any area as a historical spawning ground, it had to be reported independently by at least two sources, it had to be an appropriate depth for cod spawning (ten to 100 meters, or about 30 to 300 feet), and the bottom had to be an appropriate substrate for spawning—sand, gravel, or muddy gravel. He supplemented and corroborated his interviews with information from early U.S. Bureau of Commercial Fisheries reports and U.S. Fish & Wildlife Service bulletins.

"We recorded nearly a thousand square miles of historic spawning grounds that had hitherto been unknown to the scientific community," Ames says. About half of these spawning grounds are now abandoned; others are sparsely populated.

Ames also asked the fishermen about the relative amounts of fish they caught at various times of year. Using these data, he mapped spawning grounds and directions of movement of different cod subpopulations during the year. He says that recent tagging studies have so far corroborated his theories on the directions and timing of cod migration.

Although cod fishermen in the 1920s and '30s were able to make a living, the fishery was depleted even then. "That's part of the folklore of fish in these old fishing communities," Ames says. "The big collapse in the mid-coast area came somewhere around the turn of the century, somewhere between the 1880s and 1920." The development of trawling and other innovations extended commercial fishing of cod into the 1990s.

Other scientists are also using historical ecology methods to help pinpoint the timing of the big collapse. The Gulf of Maine Cod Project is codirected by historian Jeffrey Bolster and ecologist Andrew Rosenberg of the University of New Hampshire. With another colleague from the university, biostatistician Andrew Cooper, the interdisciplinary team is using various historical, ecological, and statistical methods to quantify cod populations off the coast of northeast North America over the past 400 years.

"There's an extraordinary debate going on today about rebuilding marine ecosystems," says Bolster. "How many fish do we want? How many fish did there used to be? How many fish can swim in the sea? How can fisheries managers begin to even think of making policies and aiming at targets if they don't know where they are aiming?"

To date, the group has analyzed data from schooners that worked the Scotian Shelf (just off the southern coast of Nova Scotia) between 1852 and 1859. These schooners sailed offshore twice a year on multiweek trips, and used baited lines to catch cod. Onboard logs documented the number and location of cod caught, how much fish by weight was sold at the end of the trip, and, often, how much cod nearby schooners caught. The federal government also paid each captain and crew a bounty based on the size of the ship. Using all of these sources allowed Bolster and his colleagues to check and cross-check the information.

The numbers show a clear pattern over time: "These guys watched their annual landings decrease about 50 percent from 1852 to 1859," Bolster says. In fact, by 1859, many of the schooners were abandoning the Scotian Shelf for different waters.

Using statistical population modeling methods, the Gulf of Maine Cod Project estimated the total biomass of cod on the Scotian Shelf in 1852 at 1.26 million metric tons. Today, the area is thought to support 50,000 metric tons of cod, just four percent of the 1852 estimate.

The group is now working with similar data from smaller boats that fished along the central coast of Maine in the 1860s. "We're astonished as to how many tons of fish were landed by these small boats," Bolster says. "They were catching fish in all sorts of places where there aren't any fish today."

Grinnell Resurvey Project

Nineteenth-century fishermen probably did not anticipate their logs' value to future ecologists, nor could Lewis and Clark have anticipated how their journals would one day be used. But in the early 1900s, California biologist Joseph Grinnell embarked on an immense documentation project expressly to produce an ecological record that would be useful to scientists yet unborn. You might call it "planned historical ecology."

Grinnell Resurvey Project
Scientists Jim Patton (standing) and John Perrine work on the Grinnell Resurvey Project. (Amanda Hawn/MVZ Archives)

Grinnell was the director of the Museum of Vertebrate Zoology at the University of California in Berkeley from its founding in 1908 until his death in 1939. A man of unusual foresight, he wrote in 1910, "I wish to emphasize what I believe will ultimately prove to be the greatest purpose of our museum, and this is that the student of the future will have access to the original record of faunal conditions in California and the west."

During the first four decades of the 20th century, Grinnell and others recorded 13,000 pages of meticulous field notes, collected and preserved thousands of specimens, and took 2,000 photographs documenting California's birds, mammals, reptiles, and amphibians. "These records were left explicitly for people to use in the future," says John Perrine, a wildlife biologist at the museum.

And that is just what is happening. The museum's current director, Craig Moritz, has launched an ambitious project to retrace Grinnell's steps to quantify how the ecology of California has changed during the 20th century, and to leave a record for future scientists. The Grinnell Resurvey Project is focusing first on the seven areas for which the Grinnell team gathered and distilled their observations into lengthy books.

Perrine says, "Our goal is to go back to the exact same spot on the map and use methods similar to theirs." The resurvey team is spending most of their time on small mammals and birds, as Grinnell did.

To survey birds, Grinnell and his colleagues walked a trail and at regular intervals wrote down all the bird species they saw or heard. "We can walk that same trail at the same time and same date [day of the year]," Perrine says. For small mammals, the Grinnell team set out traps; today's teams do the same, but release most of the mammals they identify.

Perrine is heading up the resurvey effort in the Lassen area—a 3,000-square-mile rectangle in northern California that includes Lassen Volcanic National Park—that began last summer. A team headed by Jim Patton, a retired biology professor and curator of the museum, surveyed the first area, which includes Yosemite National Park, from 2003 to 2006.

So far, the Yosemite data have yielded some interesting insights. Chief among them is that the ranges of some small mammals have changed in relation to elevation. For example, the ranges of the alpine chipmunk (Tamias alpinus), the pika (Ochotona princeps), and several other small high-elevation species have shrunk upward—they no longer live in the lower-elevation parts of their former ranges. Some other small mammals have enlarged their ranges by expanding up, with the result that there are four small mammals found in Yosemite today that were previously confined to lower-elevation areas along the boundaries of the park. "The most dramatic of those is the piñon [deer] mouse [Peromyscus truei]—a 25-gram [about one ounce] mouse with huge ears," Patton says. "The eastern part of the population has extended upward almost 2,000 feet. It's an extremely significant shift."

Is global warming driving these populations upward? There is some evidence of warming in the park, including the fact that the glacier on Mt. Lyell in Yosemite is about a third of the size it was a century ago. The range changes of the small mammals are consistent with what would be expected due to global warming, but, as John Perrine points out, "that doesn't mean that's what caused it. Figuring out cause and effect is always difficult." He is interested to see whether small mammals exhibit similar patterns of range change in other areas as the resurvey project continues.

The field data are already being used in diverse ways. Scientists are comparing the DNA of specimens from Grinnell's time to those of today to shed light on questions such as whether a species loses genetic diversity as its range shrinks, and are using past and present data to test computer programs that model global warming. They may also compare specimens to determine whether species have changed physically over time.

Chaos Crags
Chaos Crags in Lassen Volcanic National Park, California, was photographed in 1930 (top) as part of the original Grinnell Survey Project, and recently for the Grinnell Resurvey Project (bottom). (MVZ Archives)

Although it's dizzying to imagine how many research projects could be generated by the resurvey project, Perrine tries to stay focused on the data-collection process itself. He and Patton and others on the team know that future scientists are depending on them.

With that in mind, the resurvey project is not only duplicating Grinnell's work but improving on it, by adding modern equipment such as mist nets for catching birds and GPS for locating collecting sites, and by standardizing their methods. "We're mapping all of our sites to great detail, and including standardized habitat descriptions, with the goal that 20 or 100 years from now someone will be able to replicate exactly what we did," Patton says.

"Grinnell knew that his information would be used in ways he couldn't imagine," Perrine says. "That's something we try to keep in mind—researchers in the future will use this information in ways that we can't imagine. The best we can do is to be clear in our methods and leave them the best data possible."

Thanks to the foresight of Grinnell and his team, historical ecologists studying small mammals and birds of California in the 20th century have a wealth of accurate and reliable data. And when the Grinnell Resurvey Project wraps up in a decade or so, an almost unimaginable richness of data will be available and waiting for people who will use it in unimaginable ways.

—Mary-Russell Roberson is a freelance writer living in Durham, North Carolina. She and Kevin Stewart recently coauthored a new book, Exploring the Geology of the Carolinas: A Field Guide to Favorite Places from Chimney Rock to Charleston.


ZooGoer 3(2) 2007. Copyright 2007 Friends of the National Zoo. All rights reserved.



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