Tag Archives: global environmental change

Mountain glaciers become sea water, frozen tombs uncovered

Over the past several decades, the rapid melting of mountain glaicers has been a primary contributor to rising sea levels. Estimates of the long-term contribution of non-polar glacial melting to sea level rise vary substantially, but most experts agree that the contribution will fall somewhere between a tenth and a third of a meter. A recent Nature Geoscience report used the World Glacier Inventory, a repository of information on >120,000 glaciers, to predict changes this century in all 19 non-polar regions containing mountain glaciers and ice caps. This study predicts that total glacial volume will reduce by 21 +/- 6% by 2100, though in certain areas the reduction may be as high as 75%. This will lead to dramatic changes in regional hydrology and serious water problems for people who depend on seasonal glacial melting for freshwater and irrigation (see my December post, “Fog harvesting for a thirstier world”).

Water shortages, sea level rise, and erosion and hydrologic changes resulting from mountain glacial melting all pose real and very apparent problems for human populations. Another fascinating result of glacial melting will not incite new environmental dangers, but is already leading to social unrest and conflict between scientists and indigenous populations. It turns out that in certain regions, tombs, bodies and ruins from ancient civilizations, once buried deep beneath the ice, are now thawing. The most prominent example of this is in the Central Asian Altai mountains, where over 700 tombs have been preserved for 2,500 years by ice or permafrost. Increasing ground surface temperatures are causing these tombs to thaw. Another example is the huge coastal cemetery near Barrow, Alaska, where sea ice loss is causing the coastline to erode at rates of up to 20 m/year, exposing generations of human remains. It is becoming apparent that glacial thawing will impact frozen archaeology worldwide, and will potentially lead to both great discoveries and great unrest.

Globally, some of the most fascinating human archaelogical discoveries have involved frozen remains. Freezing allows preservation of human tissue that would otherwise decay in several decades, and archaelogists are now using advanced molecular techniques to date such tissue and even extract ancient DNA samples. Archaeologists across the world are now clamoring to take advantage of newley exposed human remains that may only be valuable for a short period of time. This has already stirred anger amongst many indigenous populations, who do not wish to see their ancestor’s remains and a part of their cultural heritage uprooted and shipped off to a lab thousands of miles away for chemical analysis.

The problem essentially arises from the fact that there is currently no standard legal framework to mediate the interests of scientists, governments and indigenous people with respect to these precious archaeological repositories. Glacial retreat necessitates the creation of new laws and policies to address these concerns- and soon, if our mountain melting rate predictions are at all accurate.

Radick and Hock. 2011. Regionally differentiated contribution of mountain glaciers and ice caps to future sea-level rise. Nature Geoscience. In press.

Molyneaux and Reay 2011. Frozen archaeology meltdown. Correspondence . Nature Geoscience. In press.

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GeoChip: linking genetics with environmental processes

Over the past decade, environmental scientists have been casting a wider net in their attempts to understand complex environmental processes on a molecular scale. Once fascinating new line of research involves co-opting techniques developed by geneticists, largely for the biomedical industry, in order to understand how genes are important regulators of earth-scale processes as carbon and nitrogen cycling.

The GeoChip is a clear example of this search for new methods to answer old questions. Microbiologists  are working on remote Antarctic islands to understand some of the simplest nutrient cycling pathways in the world. The ecosystems they study are often composed of only a handful of fungal and microbial species. These simple food chains allow resarchers to contruct basic models of how energy and nutrients (such as carbon and nitrogen) are transferred.

This is where GeoChip comes in. GeoChip is a gene microarray chip designed to identify “functional genes” involved in important nutrient cycles. It allows the identification of genes in an environmental sample that regulate carbon fixation, decomposition, and atmospheric nitrogen fixation, to name a few.  Understanding what functional genes are available in a system allows scientists to both understand the potential of that system for cycling nutrients and better predict how that system will respond to environmental change.

Imagine a glass floor divided into hundreds of indentical squares. Each of these squares contains a different fragment of DNA, reconstructed by geneticists from known DNA sequences. When scientists want to probe an environmental sample for specific DNA sequences, they “wash” their sample over the floor. Fragments of DNA will stick to their complementary sequence on the floor, causing a square to light up. Scientists can “read” a GeoChip by identifying fluroescently lit spots where environmental DNA has attached. They use this information to develop a picture of the functional genes present in that system.

In Antarctica, GeoChip is already been used to answer important ecological questions. For example, scientists are finding that genes for nitrogen fixation, the crucial ecosystem process that produces plant-useable nitrogen in the soil, occur in lichen-rich areas. Lichens are believed to be among the earliest land colonizers, and the ability of lichen-dominated systems to add nitrogen to the soil may be an important finding in reconstructing the early colonization of terrestrial systems. Other findings include carbon-fixation genes in plots that lack vegetation, indicating microbial communities that are able to perform some sort of photosythesis in the absence of plants.

Citation:

Yergeau et al. 2007. Functional microarray analysis of nitrogen and carbon cycling genes across an Antarctic latitudinal transect. The ISME Journal 1: 163–179