Songs of the Miner's Canary
Songs of the Miner's CanaryA rise in atmospheric carbon dioxide concentrations; creation of an ozone hole over Antarctica; increasing greenhouse gases trapping ever more efficiently the sun's radiant heat. We all have heard of these environmental changes, as well as dire predictions about their probable results: more cataracts and skin cancer, melting ice caps, rising oceans and decreasing fresh water, agricultural systems collapsing in the sweltering heat.
Yet taking these predictions seriously is neither easy nor pleasant. Everything within us tempts us to proclaim the earth's systems protective and nurturing for the indefinite future. The thought that our own bodies and the earth's living communities can withstand the onslaught of rapid human-generated change without being scathed comforts us and lulls us into complacency. If we have no proof that crop yields will decline in the Midwest, or that our scantily-clad youngsters will suffer by playing outside in the summer's sun, it's much easier to continue to act in the traditional manner: to escape the heat by driving the kids to the swimming pool and returning to our air-conditioned homes to relax (all the while producing greenhouse gases, using ozone-depleting CFCs, and risking exposing our kids to UV radiation in the process). Advocating long-term sustainability rather than short-term consumption or profit simply isn't a popular suggestion, especially given the present political climate.
Yet that is just what a careful look at the earth's living systems seems to be telling us to do. Their reactions to invisible environmental alterations are difficult to detect and even more arduous to prove. But recent research confirms that the earth's complex ecosystems are indeed serving as our miner's canaries. Although natural ecosystems are exceedingly complex, and although many of their processes remain cryptic, they are exhibiting behaviors that demonstrate how human actions are affecting life on earth in a myriad of subtle ways. Consider as examples the three following discussions, each of which links ongoing research by CGRER members to a recently discovered, significant alteration of the earth's natural ecosystems.
Gene Takle, a CGRER member and ISU atmospheric scientist, has been investigating fluctuations both in Iowa's mean temperatures and in climatic fluctuations. He is analyzing climatic data collected since 1900 in an attempt to determine whether significant temperature changes have already occurred in the Corn Belt. By feeding these data and expected alterations in atmospheric composition into his computer models, he also can spin out hypothetical midwestern climates of future years.
But even if temperatures warm a bit, what will this mean in terms of the earth's natural systems? While the human reaction might be to turn up the air conditioning, native species -- plants as well as animals -- would be forced to migrate to cooler climes. George Malanson, a geographer at The University of Iowa, is examining the potential future migration of midwestern trees by constructing computer simulations based on pollen data from the past 12,000 years. These data provide past rates of migration, which are then used to predict future movements across our modern fragmented landscape in hypothetical climates. He also is studying the response of treeline vegetation in the Rockies to climatic and geomorphic variables in an attempt to understand future upslope movement potentially stimulated by global warming.
Antarctic Ozone Hole - 1993
Research published this past June provided the first evidence that such plant migrations are not just theoretical: they are already occurring among some of the earth's most sensitive predictors, the tiny tundra plants of the uppermost Alps. Comparisons of modern and early 1900s records revealed that certain plants are currently migrating upslope from 3 to 12 feet a decade. This movement corresponds with a warming of about 1.5 F, and demonstrates that even moderately warmer temperatures here are already playing a significant ecological role -- potentially pushing the species in question upslope and off the mountain tops into extinction.
These complex interactions all feed into predictions of future atmospheric CO2 levels. CGRER botanist James Raich, along with Christopher Potter, have been attempting to better understand the CO2 -- soil emission link of the puzzle. Soil emissions vary significantly with seasonal moisture patterns, temperature, and land use patterns. Their model is the first to incorporate these important variables into calculations of soil CO2 emissions on the global scale, and thus allow incorporation of soil CO2 flux into more inclusive CO2 models. To derive a "global carbon budget," all of the complex CO2 interactions need to be accurately fed into a computer model. CGRER members O-Yul Kwon and Jerry Schnoor have just published a model that integrates the oceanic, atmospheric, and soil interactions into a single model for the first time. Their model will aid persons who are analyzing atmospheric CO2 changes and attempting to determine their probable results, and it will point out future research needs. Because of this new model's completeness, it also is being considered by the Intergovernmental Panel on Climate Change as a tool for guiding governmental restrictions on CO2 emissions in the future.
But are all these efforts to model CO2 changes worth the effort? True, CO2 is the most abundant greenhouse gas, but global warming concerns aside, how do changes in CO2 concentrations directly affect life on earth? Raising the levels of CO2 in the laboratory has been shown to stimulate the growth of some plants, and recent research demonstrates that this growth enhancement may already be going on in nature. Tropical forests which are otherwise intact are displaying substantially higher rates of turnover -- that is, higher death rates and faster recruitment of new individuals. Accelerating forest turnover rates, which have been detected around the world over the last 25 years, coincide with the buildup of atmospheric CO2 over the same time period, and that CO2 buildup is thought to be the causative factor. Speeding up the tropical forest turnover rate is significant: through selecting against slow-growing trees, it could decrease the biodiversity of these large, complex forests. Also, since the faster growers have less dense wood, the forests' CO@ storage capacity could decrease - which in turn would increase atmospheric CO2 concentrations even more.
Ozone declines now have been documented around the globe, and researchers are attempting to determine the extent of depletion in various locations. The accuracy of their measurements is critical to this effort. CGRER astronomers Steve Spangler and Jack Fix are developing a technique to use radio telescopes to improve the vertical resolution of ozone measurements. By examining absorption as well as emission lines from ozone, they expect to fine tune our knowledge of the altitude profile of ozone distribution and better trace changing ozone abundance in the future.
A significant ozone depletion trend of a fraction of a percent annually already has been recorded for Iowa, as well as for much of the northern hemisphere. CGRER members Kevin Crist and Greg Carmichael have been using satellite and ground-based measurements to evaluate the ground-level changes in UV radiation resulting from this ozone decline. Their computer simulations show that rural Iowa is indeed experiencing increasing amounts of UV radiation. Persons need fear exposure particularly in the summer during the middle of the day, when the sun is directly overhead.
The Grindelwald Glacier
Beth Jurkiewicz, a graduate student working with CGRER member Garry Buettner, has demonstrated how increased UV radiation might affect human health. Using a mouse model, she showed that UV radiation hitting skin stimulates the formation of free radicals, reactive chemical species that are known to lead to photoaging and skin cancer.
Researchers have demonstrated that other detrimental responses to UV radiation are already occurring among amphibians. The severe decline of many frog and toad populations has alarmed herpetologists since 1990, when this drop was discovered to be occurring around the world. Several causes of the decrease have been suggested, such as acidification of waters where they lay their eggs and pollution of these waters. Research published in March showed that the decline, at least for high-altitude species that lay their eggs in the open, is likely caused by increases in UV-B radiation. This radiation alters the structure of the frogs' genetic code, preventing it from carrying out its tasks of protein production and self-replication during cell division. As a result, the sensitive gelatinous eggs of these amphibians do not hatch successfully, and the populations are cascading downward. Iowa's amphibian expert, Professor Jim Christiansen, has hypothesized that this process might explain the recent disapperance of the previously-abundunt cricket frog in the northern tier of Iowa counties.
At times, the significance of individual bits of CGRER research may be viewed as inconsequential. We might wonder if a more accurate understanding of soil CO2 emissions really matters. Or whether a few more free radicals in our skin will do much to us, or if programs to predict plant migrations are worth the cost. We might be lulled into skepticism concerning the worth of frog songs in the summer, or doubt the crashing slump of a tropical tree if no one is there to hear it.
But once these research bits are tied to the bigger picture, their significance looms overhead. For what other species are exposed to, so are we. The frogs and tundra plants that are now reacting to environmental changes probably differ from us humans in quantity of dose rather than quality of response. They are simply extremely sensitive detectors of atmospheric distortions. Heeding their canary songs now will bode us well in the future.
And even if we humans were never to react to certain environmental changes, we will be affected by their perturbations. For each of nature's seemingly small reactions has the potential of cascading in ways that may never have been expected. As an example, consider the ongoing decline of migrant songbirds in temperate forests. Biologists had warned that populations of insects eaten by those birds could explode. But few expected the results of recent research, which demonstrated that a decrease in bird numbers also stresses forest productivity. Trees, in particular white oaks (which abundantly grace our Iowa woodlands), were shown to have twice as much insect damage to foliage when unprotected by songbirds, and they produced significantly fewer leaves in subsequent years. Thus a decline in songbird populations may assault the general health and integrity of our eastern forests and the strength of forest-based economies.
The need is greater than ever to collect the pieces of information that, when added together, create a complete picture of how we are changing our world. To bring researchers together in centers such as CGRER, where they can tie their ideas to those of others in related disciplines, linking cause to effect, and hoping that processes of change might also be discovered. To tie the atmospheric changes being measured by physical scientists and engineers to the rebounds of life on earth at all levels. These linkages of research and researchers endow CGRER with mission and point its direction.
Blaustein, A.R., P.D. Hoffman, D.G. Hokit et al, 1994. UV repair and resistance to solar UV-B in amphibian eggs: A link to population declines? Proceedings of the National Academy of Science, 91:1791-1795.Christiansen, Jim, Drake University, pers. comm.
Crist, K., G.R. Carmichael, and K. John, 1994. UV-B exposure and atmospheric ozone: evaluation of radiative flux to changes in ambient ozone. Journal of Hazardous Materials 37:527-528.
Grabber, G., M. Gottfried, and H. Pauli, 1994. Climate effects on mountain plants. Nature 369:448.
Jurkiewicz, B.A. and G.R. Buettner, 1994. Ultraviolet light-induced free radical formation in skin: An electron paramagnetic resonance study. Photochemistry and Photobiology 59: 1-4.
Kwon, O-Y and J.L. Schnoor, 1994. Simple global carbon model: The atmosphere-terrestrial biosphere-ocean interaction. Global Biogeochemical Cycles 8:295-305.
Malanson, G.P. and D.R. Butler, 1994. Competitive hierarchies, soil fertility gradients, and the elevation of treeline in Glacier National Park, Montana. Physical Geography 15:166-180.
Marquis, R.J. and C.J. Whelan, 1994. Insectivorous birds increase growth of white oak through consumption of leaf-chewing insects. Ecology 75:2007-2014.
Phillips, O.L. and A.H. Gentry, 1994. Increasing turnover through time in tropical forests. Science 263:954-957.
Raich, J.W., and C.S. Potter, 1995. Global patterns of carbon dioxide emissions from soils. Global Biogeochemical Cycles 9(1): in press.
Takle, E.S. and L.O. Mearns, 1995. Temperature means, extremes, and variability in the U.S. Midwest: Analysis of observed data and global and regional model results. Preprints, Ninth Conference on Applied Climatology, Dallas, TX, American Meteorological Society, 202-205.