Scientist in Action at Nuuk Basic
This week we had the unique opportunity to visit Nuuk Basic, a low-arctic long-term ecological monitoring station. The research station is part of the Greenlandic Ecological Monitoring (GEM) program, which also has a station in high-arctic northwest Greenland at Zackenburg. The goal of the GEM program is to study the effects of climate change on the terrestrial, freshwater, and marine environments of Greenland and more broadly the arctic using “cross-disciplinary” techniques.
Greenland Ecological Monitoring (GEM) program sites
Cross-disciplinary – it is kind of like double narwhal – what does it mean?
When I think of the term cross-disciplinary, I envision using one set of methodologies (i.e. ecology) to think about and answer questions in a different field (i.e. geology). Cross-disciplinary may or may not be synonymous with multi-disciplinary, inter-disciplinary, or trans-disciplinary; it may also just be used colloquially as a synonym. This is one very interesting questions that our Polar Environmental Change IGERT program at Dartmouth College is trying to think about and contribute to the discussion occuring in academia.
Badeso in the foreground (i.e. the lake with Arctic char) and Kobbefjord in the background
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The 2011 IGERT cohort spent one week camping outside of Kangerlussuaq in the same site the 2010 cohort chose last year. The first things we noticed upon arriving at our campsite were the incredible views of the Russell glacier, the Little Ice Age moraine, and the glacial meltwater lakes.
Google map of the area between the IGERT camp near the Russell glacier and the Kangerlussuaq fjord. Air temperatures drop as you drive up the road from Kangerlussuaq to the IGERT camp and the glacier, perhaps offering a gradient useful for studying climate change and insect outbreaks.
But as a close second we noticed that the woody shrubs at the site were all leafless and brown, and that there were many large Lepidoptera larvae (caterpillars) roaming in search of food. This place had experienced a recent caterpillar outbreak. The larvae that were left had no more food to eat, and they crawled up our tents and boots or into any warm microclimate. Northern wheatears and snow buntings came in to camp to eat this easy prey off the tents. Adult moths also flew around in large numbers and we picked them out of our hair and our coffee. We identified this Lepidoptera species as Eurois occulta, the Great Gray Dart moth known to defoliate the dwarf birch and grayleaf willow common in Greenland.
Caterpillars ate all of the birch and willow leaves around camp, leaving a brown world.
Eurois occulta larva
Eurois occulta adult
However, the entire landscape was not brown. Many hillsides with similar aspect and distance from the glacier experienced only moderate levels of herbivory and remained green. Farther from the glacier, back toward Kangerlussuaq and the fjord, the brown outbreak patches disappeared. Acting on a hot tip from Mike Avery, a PhD student in Eric Post’s lab at Penn State University, we searched for evidence that caterpillars were attacked by a pathogen – desiccated caterpillar corpses draped in the willow leaves. We found many of these corpses in non-outbreak areas farther from the glacier but did not see any close to the glacier where air temperatures are much cooler.
Some nearby hillsides, however, suffered only slight defoliation.
Closeup of moderate levels of herbivory.
Carcass of a larva infected by a pathogen.
Why are some hillsides completely brown while others remain green? This is a big question in ecology, and one possible answer is that caterpillars in defoliated areas lack “top-down” controls by predators such as birds, other arthropods, and pathogens. The caterpillar immune system can fight off infection by pathogens (fungal or viral) but this defense requires a high protein diet. In plants much of this protein is RuBisCO, a nitrogen-rich enzyme essential for photosynthesis, and the protein content of leaves is expected to decrease as air temperatures get warmer and the growing season gets longer. Perhaps caterpillars farther from the glacier had less resistance to pathogens because of lower protein content of leaves, or perhaps there are more natural enemies such as birds or arthropods in warmer areas. The birch/willow shrub tundra of West Greenland is a great ecosystem to test competing explanations for why insect herbivores sometimes outbreak and how climate change may alter the frequency and intensity of these outbreaks.
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We thought we’d discovered a new species until we were informed it was a DOUBLE NARWHAL. What does it mean?
Here’s the normal version, check them out on wikipedia. Narwhals are suspected to be particularly vulnerable to climate change because of their specialized sea ice habitat…perhaps the doubles are better suited, but I doubt it.
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