A paleoecological perspective on 1450 years of human impacts from a lake in southern Greenland

Abstract

A multiproxy sedimentary record from Lake Igaliku in southern Greenland documents 1450 years of human impacts on the landscape. Diatoms, scaled chrysophytes, and C and N geochemistry show perturbations consistent with recent agricultural activities (post-ad 1980), superimposed upon long-term environmental variability. While the response to Norse agriculture (~ad 986-1450) is weak, the biological response to the last 30 years of modern sheep farming is marked, with drastic changes in diatom taxa, δ 13 C and δ 15 N isotopic ratios, and a sharp increase in scaled chrysophytes. Indeed, current conditions in the lake during the last 30 years are unprecedented in the context of the last 1450 years. The dominant driver for recent changes is likely an intensification of agricultural practices combined with warming summer temperatures. Warm temperatures and agricultural disturbance together during Norse Landnám did not lead to the marked changes seen in the modern lake environment over the last 30 years. The synergistic response between increased climate warming and agriculture will likely have unanticipated effects. These findings confirm the sensitivity of Arctic lakes to external anthropogenic forcing and are the first analyses of their kind for the effects of agriculture in Greenland.

Long‐term dynamics in microbial eukaryotes communities: a palaeolimnological view based on sedimentary DNA

“…The previous studies based on the morphological remains (Perren et al . ; Millet et al . ) reported subtle changes over the last 1450 years and until 1980 AD.…”

“…In addition, there is evidence that Norse agriculture during this period had almost no impact on the trophic state of the Lake Igaliku, except subtle changes of its flora and fauna (Perren et al . ; Millet et al . ).…”

“…This lake has been preserved from the marked eutrophication. In Greenland, only two periods of agropastoral activities were inventoried: (i) the Norse settlement period between AD 986 and the middle of the 15th century (Arneborg et al 2011;Massa et al 2012;Guillemot et al 2015) and (ii) the recent occupation, since the 1920s, marked by moderate eutrophication around the 1980s (Austrheim et al 2008;Perren et al 2012;Millet et al 2014).…”

A multiproxy evaluation of Holocene environmental change from Lake Igaliku, South Greenland

“…Following the disappearance of the Norse *1450 AD, Igaliku was resettled during the 18th century (Arneborg 2007) and large-scale agriculture, based on sheep farming, was developed in the 1920s (Austrheim et al 2008). Consequently, the response to climate change over the last millennium was overprinted by land-use effects (Gauthier et al 2010;Massa et al 2012;Perren et al 2012). However, the consideration of humaninduced changes at Lake Igaliku in light of the entire Holocene ecosystem development provides new insights about their magnitude.…”

“…Yet, Holocene climate records show distinct differences between the outer and the inner coastal region elsewhere in Greenland (Perren et al this volume) and the inner fjord regions represent an important ecoclimatic zone, which is unique in Greenland. Existing paleoenvironmental archives from this inner fjord region have mainly been studied for the evaluation of Norse impact during the last millennium (e.g., Fredskild 1992;Edwards et al 2011) as has the Lake Igaliku site (Gauthier et al 2010;Massa et al 2012;Perren et al 2012). However, in addition to its archaeological significance, this lacustrine sequence situated in the Norse Eastern Settlement contains an archive of *10,000 years of natural climatic and environmental evolution in a critical location for paleoclimatic studies in the North Atlantic.…”