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Center for the Study of Origins talk: The origin of soil erosion across Iceland

Monday, April 29, 2019, 7:00PM - 8:00PM

Speaker

Áslaug Gerisdóttir

INSTAAR Affiliate and CSO visiting scholar

Location:

SEEC room S228 (Sievers Room)

Soil erosion has been severe across Iceland for centuries. A commonly held view is that soil erosion and landscape instability began with the settlement of Iceland ~874 CE. At that time, Iceland was described as having forests “extending from the shoreline to the mountains”, but as birch “forests” were cleared for agriculture and pastoral activities, the vegetation cover that once protected Iceland’s soils from erosion was compromised. Rapid population growth after 874 CE and the poorly consolidated nature of the ash-dominated soils resulted in widespread soil erosion, which has continued through today.

Against the argument that the origin of soil erosion in Iceland coincided with human agency are chemical proxies for temperature and hillslope erosion that are preserved in lake sediment across Iceland. Our records, derived from these chemical proxies in many lake sediment cores, suggest that soil erosion began several centuries before the acknowledged settlement of Iceland. We suggest these data reflect a threshold adjustment to cooling summers, which were a consequence of regular changes in Earth’s orbit, centuries before settlement. Widespread soil erosion was intensified several centuries after settlement, during the Little Ice Age 1300-1900 CE, when summer cooling was amplified by expanded Arctic Ocean sea ice and repeated Icelandic volcanism, with continued livestock grazing and deforestation. Information from historical accounts and results from climate proxies derived from the lake sediment are compared with the primary goal to separate the roles of climate (temperature, hydrology/storminess and sea ice), volcanism and humans in the onset and subsequent acceleration of soil erosion.