00_cover_Biennial Report 05-06.qxd - INSTAAR - University of ...

altered by humans over the past 2000 years. Atmosphericmethane (CH 4 ) varied as expected over the past few centurieswhen methane concentrations in the atmosphere roseby nearly 300% and other greenhouse gas levels are knownto have increased sharply due to human influences. But theresults further back in time came as a shock. Measurementsof the stable carbon isotopes in methane ( 13 C of CH 4 )fluctuated much more than expected before the industrialrevolution. The gyrating ratio combined with other geochemicalmeasurements are evidence for massive fires set byhumans clearing land for agriculture and hunting for at least2000 years. A prominent feature is a huge drop in the 13 Cratio from ca. A.D. 1500–1600, and this was attributed todecreased grassland and forest burning by indigenous peoplesin the South and Central Americas, where populationwas devastated by diseases brought to the New World byEuropean explorers. The study is particularly importantbecause methane increases have had the second highestimpact on climate change over the past 250 years behindcarbon dioxide, accounting for about 20% of the warmingfrom all greenhouse gas increases. Methane is more powerfulthan carbon dioxide on a per molecule basis in slowingthe release of radiated heat away from Earth. Previous workby other groups indicates that methane emissions fromwildfires are likely to be higher during warm and dry periods,such as El Niño events, and may therefore increasewith future climate change.The paper was published in the September 9, 2005,issue of Science. Image: Central field tent at Law Dome,Antarctica, where drilling took place. Snow accumulation atLaw Dome is very high (greater than 1 m/year), enablingthe extraction of well-dated, high-resolution ice cores forgreenhouse gas analysis. (Photo: Vin Morgan, AustralianAntarctic Division, ACE, CRC).ENVIRONMENTAL ENGINEERSSTUDY POLLUTION OF COLORADOMOUNTAIN STREAMS BY MINES.Diane McKnight (INSTAAR and CEAE) andJeff Wong (CEAE) spoke with radio stationKUNC’s Gavin McMeeking about the pervasivepollution of Colorado mountain streams by mining andthe potential for remediation by environmental engineers.More than 19,000 abandoned mines in Colorado have pollutedmore than 7500 miles of streams (equal to the distancefrom Los Angeles to Sydney, Australia). This summerMcKnight and Wong are concentrating on Peru Creek inSummit County (Snake River Watershed). The creek’s bednear an abandoned mine is covered by metal oxides at alevel that prevents algal growth and is lethal to aquatic life.There are no stream insects and thus, no fish or riparianbirds. To help understand the transport of metals, Wong setup a salt injection tracer experiment that mimics the behaviorof some nonreactive solutes, such as zinc, and helps inquantifying how much iron oxide is being deposited.Undergraduate students in the CU Biomathematics Scholarsprogram based at INSTAAR participated in the downstreamsample collection. Computer modeling of the experiment’sdata will provide ideas for remediation, but much remains tobe learned and eventually millions of dollars will be neededto clean up this stream and many others. Ironically, anotherhurdle to successful remediation is the Clean Water Act,which mandates that any group working on remediationbecomes liable for the environmental damage. CongressmanMark Udall has proposed a “good samaritan” amendmentbut it has stalled in Congress. Two other INSTAAR gradstudents, Andrew Todd and Chi Yang (CEAE), are studyingthe combined effects of limited prey and metal toxicity onfish and birds in other less severely impacted stream reachesin the larger Snake River Watershed. The segment aired onKUNC on August 4, 2005.ANCIENT DIETS OF AUSTRALIANBIRDS POINT TO BIG ECOSYSTEMCHANGES. Gifford Miller led an internationalteam (INSTAAR, CarnegieInstitution, Australian National University,Wollongong University, and BatesCollege) to discover that the diet of twoflightless birds inhabiting Australia shifted soon afterhumans arrived ca. 50,000 years ago, coincident with arapid and dramatic shift in the ecosystem’s flora. Their discoveryis the best evidence yet that early humans may havealtered the continent’s interior with fire, changing it from amosaic of trees, shrubs, and grasses to the desert scrub evidenttoday. The researchers used isotopic studies of nearly1500 eggshell fragments of fossilized emu and Genyornisdating back 140,000 years. The analyses, which pinpointparticular plant groups ingested by the birds, indicated thatemus living before 50,000 years ago preferred nutritiousgrasses characteristic of milder temperatures and warm sum-Tents dot the skyline at FladeIsblink, a small ice cap at 81°Nin NE Greenland, summer 2006.Patterns in the surface hoardecorate the surface of the ice.Researchers from INSTAAR andthe Niels Bohr Institute at theUniversity of Copenhagen drilledthe ice cap. Photo: Bruce Vaughn(INSTAAR).RESEARCH MISSION | 11