How has he transformed the scene?
If there is a path between the realms of pure and applied science, ecologist David Tilman helped to put it there. "I don't see any reason why you can't do top-notch science that is also relevant to environmental problems," notes this University of Minnesota Regent's professor.
"If there were a Nobel Prize for environmental science, Tilman would be a likely choice."
Robert Elde, Dean, College of Biological Sciences,
University of MN (in) UM News, 4/2010
His focus is on the questions that compel his research: Why are there so many species on earth? How are so many species able to co-exist? How does biodiversity—or the lack of it—influence ecosystems? How can human-caused environmental change be measured and mitigated? What actions must be taken now to preserve a living earth for future generations?
It is more than a lifetime's worth of questions, to be sure. But for Tilman—who marvels at complexity and loves a good puzzle—that's part of the attraction. He's nearly four decades into a distinguished career as an environmental research scientist, having received two premier international awards for his contributions to the field: the International Prize for Biology and the Heineken Prize for Environmental Sciences. He has twice been recognized as the 'most highly cited environmental scientist of the decade' by the Institute for Scientific Information, most recently for the years 1997-2007. An elected member of the National Academy of Sciences, he has published 2 books, 3 edited volumes, and more than 250 papers in peer-reviewed literature. Yet, in many respects, he feels he's just getting started.
For the record, let's just say it's a pretty good start.
On the basic research front, Tilman's work has contributed to numerous seminal advances in the theoretical basis, knowledge, and practice of his discipline. Early in his career, his PhD thesis from the University of Michigan aimed to redefine the very field he sought to enter, making the case for greater integration of the mathematical theory he loved. When A Test of Predictive Mechanistic Theory in Ecology was published in the journal Science in 1976, it was a revolutionary concept in a field then devoted largely to the observation and description of nature. Today, the predictive, mathematics-rich methodology espoused by Tilman is an established component of the discipline, and students of ecology learn to plumb their mysteries with tools akin to those of a physicist.
Tilman's basic research was instrumental in upending another long-standing paradigm in 1994, when he and collaborator John Downing published controversial findings in the journal Nature refuting the prevailing wisdom that diversity acted as a de-stabilizing force in eco-systems. In the landmark Biodiversity and Stability in Grasslands, Tilman and Downing put forth a new theory based on 12 years of data collected from study plots delineated within a natural grassland at the U of M's Cedar Creek Ecosystem Science Reserve. Greater diversity of species, they asserted, was associated with increased eco-system stability, and to no small degree. Even when subjected to the stress of extreme drought, plots with the greatest diversity of plant species were found to maintain a productivity level as much as 6 times greater than low-diversity plots under similar conditions. It was the first evidence-based theory for the key role of biodiversity in the functioning of ecosystems: a concept that had been suggested but not proven by such leading scientists and theoricians Drs. Paul Erlich and Edward O.Wilson.
Subsequent research by Tilman and other scientists around the world only reinforced the efficacy of the findings. Before the 1994 paper had even gone to press, Tilman and Downing embarked on another first of its kind experiment at Cedar Creek. This time, the diversity of vegetation would be a carefully controlled and managed variable. The investigators cleared twenty acres of land, then planted seed to create plots ranging in species diversity according to established criteria. Since that time, in what has become the longest term and largest controlled study on biodiversity in the world, the productivity of these plots has been measured on an annual basis. As in the earlier study, diversity has consistently been found to be positively correlated with productivity. Plots with the highest diversity have produced as much as 240% more in bio-mass (new growth of vegetation) annually than plots with plants growing in monoculture (single-species) conditions.
Even those closest to the research on biodiversity have been astounded. Imagine reaching into your pocket for a match and finding a blast furnace.
The work at Cedar Creek, together with independent studies by such respected researchers as Shahid Naeem at Columbia in the U.S. and Sir John Lawton in England, had the effect of opening whole new areas of scientific inquiry. In the eyes of scientists around the world, the earth's biodiversity came to matter in ways it had not previously. At the same time, the tendency of humans to simplify their environment took on new, more sobering, implications. If biodiversity represented such an essential powerhouse of productivity in nature—and a key source of ecosystem stability and resiliency—then humanity was squandering its own future in the wholesale transformation from prairies and forests to cornfields and lawns.
To contribute to such sea changes of understanding is the stuff of dreams for most research scientists. But the critical piece—and what distinguishes Tilman's career—is that he brings the full force of such insights to bear as actionable intelligence in the solving of environmental problems.
If ever there were a time for society to reap the rewards of its investment in modern ecosystem science, Tilman urges, it is now: and there is no better place to begin than with a re-imagining of agriculture. "Land clearing, greenhouse gases, habitat destruction, loss of biological diversity, pollution of surface waters—these are all costs of how we do agriculture," says Tilman. "There are ways we can do it better. There are ways, I'm convinced, that we can feed 9 or 10 billion people and have a wonderful, livable, sustainable earth that will provide people a thousand years in the future with a life at least as good as that which we've been able to enjoy."
His conviction is rooted in the real-world soil of the 5400-acre Cedar Creek Ecosystem Science Reserve in East Bethel, MN, site of investigations conducted by Tilman and an ever-changing assembly of University faculty, visiting scientists, graduate students and post docs. Founded in the 1930s, Cedar Creek was designated for funding by the National Science Foundation in 1982 as one of 11 Long Term Ecological Research (LTER) sites in the country. It is presently one of 26 such sites across the globe. As the Reserve's Director and Principle Investigator, Tilman is shepherding his own studies at the site while also serving the interests of fellow scientists working on such issues as carbon sequestration, nitrogen deposition, dynamics of eco-system function, and climatic warming. While not an ag experiment station per se, many of the discoveries and theoretical advances generated here have direct and exciting relevance to agriculture. With the ecologist's eye for pattern, Tilman is determined to connect the dots.
Consider, for example, a world in which biofuel is not produced by single-species crops of corn or soybeans, but by perennial <br />prairie plantings using a diversity of species. The kicker, as Tilman's studies at Cedar Creek have shown, is that these native perennial mixes are highly productive even when grown without irrigation, with little to no inputs of fertilizer or chemicals for control of pests/disease, on land that has already been disturbed—including land now considered unfarmable due to depleted or marginal soils. The power of bio-diversity would, in effect, be harnessed as an efficient and renewable energy source.
As Tilman notes, the societal benefits of a shift to such bio(diverse)fuel would include more abundant, cleaner water and a reduction in the greenhouse gases currently associated with both land clearing and excessive use of nitrogen fertilizer. Atmospheric carbon dioxide now contributing to air pollution and global warming would be sequestered as organic carbon in the vegetation and soil of these bio-diverse crops, at a rate of 2 tons per hectare (roughly 1600 lbs/acre). Perennial cover would reduce soil erosion, keeping soil on the land and out of surface waters. The most fertile agricultural land—land that has already been cleared—could be reserved for food crops. Further reductions in global nitrogen inputs could be accomplished on the five major food crops (corn, wheat, rice, barley, rye) without diminishing yields: simply through more strategic timing and dosing of applications. "Currently, only about 30-40% of the nitrogen we put on cornfields in the U.S. actually ends up in the corn," notes Tilman, with the remainder lost in spring run-off to creeks and streams. Potential benefits for farmers could include reduced costs for fertilizer inputs, reduced labor, more reliable yields, and—given a level playing field in the market—greater profit.
Add a health-conscious trend toward more modest consumption of red meat, and more of the global food supply could directly feed humans rather than going toward animal feed. Even as the earth's population increased, the pressure to clear land in the interest of agriculture would be vastly diminished. Remaining refuges of invaluable biodiversity in the world's undeveloped lands might be preserved.
The goal, says Tilman, is a win-win for farmers and society as a whole, over the short and long term. Any solutions must make economic sense in both developed and developing nations, taking into account the desperate conditions and limited options of subsistence farmers around the world: "We can't expect these farmers to pick themselves up by their bootstraps," says Tilman, "when they don't have boots."
There is an implicit invitation here, for human society: a window to a different and better future. Tilman is quick to say that he is an ecologist, not a social scientist. But he knows that the outcomes of such "next generation" approaches to agriculture—and any new practices guided by ecosystem science— will play out in the socio-political realm, where they will be subject to market demand, subsidies, political will (or lack thereof), and the often slow percolation of new scientific ideas through the cultural landscape. Ultimately, Tilman acknowledges, it's a matter of ethics: whether or not this generation feels an obligation to those that will follow.
For his part, Tilman is leaving no stone unturned in the effort to influence that pace of change for the greater good. He's taking every opportunity to communicate both the urgency of global threats to the environment and prudent remedial action as guided by modern eco-system science. In addition to his wide publication in the peer-reviewed literature (see selected bibliography) Tilman and his message have been featured in Time, Smithsonian, and Popular Science magazines, in the Washington Post and New York Times, in the major Dutch newspaper NRS Handelsblad and the local pop-culture weekly City Pages. He's done broadcast interviews with BBC World Service Radio, National Public Radio, and Tokyo Broadcasting System International. Within the academic community of the U of MN, he has taught literally thousands of students, advised 18 PhD candidates and mentored 21 post-doctoral researchers (and still counting). Outside of the University setting, he has advised on science policy and priorities for such entities as the National Science Foundation, the President's Committee of Advisors on Science and Technology, and the National Academy of Sciences. He founded Issues in Ecology, a publication dedicated to advancing communication among ecologists, the public, and governmental decision makers. Although based at the University of Minnesota, he has traveled across the country and around the world for over 300 speaking engagements.
In all instances he considers his role to be that of "an honest broker of what we know scientifically." Still, when Tilman speaks of the need to preserve the earth's natural capital, he speaks not only as a scientist but also as a man: one who feels a moral obligation as a citizen of the planet to leave an undiminished environment for the benefit of future generations. His own appreciation for nature grew out of countless boyhood hours spent outdoors, exploring the sand dunes along Lake Michigan that lay just outside the back door of his family's cottage. Later, as a young man of 20, he was one of a generation of college students whose consciousness was seared by national media images of a river so polluted it caught fire. It was 1969: ironically, Ohio's Cuyahoga River was ablaze in the same year that the United States showed its scientific prowess by putting men on the moon.
Today's generation has its own variation on the Cuyahoga, on a planetary scale, and it's own galvanizing images. Tilman is determined to see the prowess of modern eco-system science—in all its refined and exquisite mathematical splendor—demonstrated right here on earth. In the end, it is the ultimate practical matter to preserve the eco-system services upon which humanity relies for both survival and quality of life. Whether or not that reality will hit home with enough people—and the right people—in time to do any good, Tilman cannot be sure. But this man of science still manages to hold out more than a little hope, because he believes that people around the world have something essential in common. Says Tilman, "I think it's something deep in our evolutionary roots that people love nature."
