Search

During the last glacial–interglacial cycle, Arctic biotas experienced substantial climatic changes, yet the nature, extent and rate of their responses are not fully understood1–8. Here we report a large-scale environmental DNA metagenomic study of ancient plant and mammal communities, analysing 535 permafrost and lake sediment samples from across the Arctic spanning the past 50,000 years. Furthermore, we present 1,541 contemporary plant genome assemblies that were generated as reference sequences. Our study provides several insights into the long-term dynamics of the Arctic biota at the circumpolar and regional scales. Our key findings include: (1) a relatively homogeneous steppe–tundra flora dominated the Arctic during the Last Glacial Maximum, followed by regional divergence of vegetation during the Holocene epoch; (2) certain grazing animals consistently co-occurred in space and time; (3) humans appear to have been a minor factor in driving animal distributions; (4) higher effective precipitation, as well as an increase in the proportion of wetland plants, show negative effects on animal diversity; (5) the persistence of the steppe–tundra vegetation in northern Siberia enabled the late survival of several now-extinct megafauna species, including the woolly mammoth until 3.9 ± 0.2 thousand years ago (ka) and the woolly rhinoceros until 9.8 ± 0.2 ka; and (6) phylogenetic analysis of mammoth environmental DNA reveals a previously unsampled mitochondrial lineage. Our findings highlight the power of ancient environmental metagenomics analyses to advance understanding of population histories and long-term ecological dynamics.

We used subfossil mosses and peats to document changes in regional climate, cryosphere, and terrestrial ecosystems in the western Antarctic Peninsula at ~65°S latitude. We find that most peat forming ecosystems have initiated since 2800 cal B.P., in response to warmer summers and increasing summer insolation. The period at 900–600 cal B.P. was coldest as indicated by ice advance, abundance of kill ages from ice‐entombed mosses exposed recently from retreating glacial ice, and apparent gap in peatbank initiation. Furthermore, the discovery of a novel Antarctic hairgrass (Deschampsia antarctica) peatland at 2300–1200 cal B.P. from the mainland Antarctic Peninsula suggests a much warmer climate than the present. A warming and wetting climate in the 1980s caused very high carbon accumulation in a Polytrichum strictummoss peatbank. Our results document dramatic transformations of landscape and ecosystems in response to past warmer climate, providing a telltale sign for what may come in the future. The discovery of a novel Antarctic hairgrass (Deschampsia) peatland at 2300‐1200 cal yr B.P. suggests a warmer climate than todayAges of reexposed ice‐entombed mosses show ice advance at 900‐600 cal yr B.P. in the western Antarctic PeninsulaRapid carbon accumulation in a moss peatbank responded to warming and wetting climate in the 1980s

Detailed inventory of peatlands by aerial photography shows that peatlands with climatically sensitive localized islands of permafrost cover 17,505 km2within a broad band of occurrence in continental western Canada (Alberta, Saskatchewan, and Manitoba). Within this zone, 37.5% of the total area covered by bog, and 9.1% of total area covered by fen have localized permafrost landforms (frost mounds and/or internal lawns). Regional distribution of the presence/absence of localized permafrost peatlands relative to expansive peat plateaus (peatland completely underlain by permafrost) shows that a north to south landform gradient exists that is dominantly controlled by mean annual temperature. Percent cover of localized permafrost peatland in an area is best explained by the amount of total peatland cover that can support it. Localized permafrost is associated with collapse forms (internal lawns) throughout the range of its occurrence in western Canada. In some locations permafrost has completely melted, moving the current southern limit of permafrost north by 39 km on average, and by as much as 200 km.

Detailed inventory of peatlands by aerial photography shows that peatland with climatically sensitive localized islands of permafrost covers 17,505 km2 within a broad band of occurrence in continental western Canada (Alberta, Saskatchewan, and Manitoba). Within this zone, 37.5% of the total area covered by bog, and 9.1% of total area covered by fen have localized permafrost landforms (frost mounds and/or internal lawns). Regional distribution of the presence/absence of localized permafrost peatlands relative to expansive peat plateaus(peatland completely underlain by permafrost) shows that a north to south landform gradient exists that is dominantly controlled by mean annual temperature. Percent cover of localized permafrost peatland inan area is best explained by the amount of total peatland cover thatcan support it. Localized permafrost is associated with collapse forms (internal lawns) throughout the range of its occurrence in westernCanada. In some locations permafrost has completely melted, moving the current southern limit of permafrost north by 39 km on average, and by as much as 200 km. [ABSTRACT FROM AUTHOR]