Study Recreates Past to Understand Reaction of Arctic Wetlands to Climate Change in the Future

A recent study has used partly fossilized plants and single-celled organisms to explore the effects of climate change on the Canadian High Arctic wetlands and help foresee their future.

Compared to other regions on Earth, the Arctic is warming faster, which is resulting in the rapid transformation of the region’s ecology. So far there has been inadequate information on the reaction of Arctic wetlands to climate change and escalating global temperatures.

An international team of researchers led by the University of Leeds and the Geological Survey of Canada have recreated past moisture environments and vegetation histories to establish how three key types of Canadian High Arctic wetlands have reacted to warming temperatures over the last century.

Getting an insight into past ecological variations in this region allows for more accurate predictions of how future transforms, such as longer growing seasons and more water from ground-ice thaw, could impact the wetlands.

The research paper, published in Geophysical Research Letters, showed that under 21st century warming scenarios and with sufficient moisture, some Arctic wetlands may change into peatlands, forming new natural carbon storage systems and to a certain extent moderating carbon losses from degrading peatlands in southern regions.

High Arctic wetlands are important ecosystems and globally-important carbon stores. However, there are no long-term monitoring data for many of the remote regions of the Arctic – making it hard to determine their responses to recent climate warming. Reconstructing the ecological history of these wetlands using proxy evidence can help us understand past ecological shifts on a timescale of decades and centuries.

Thomas Sim, Study Lead Author and PhD Researcher, School of Geography, Leeds

Study co-author Dr Paul Morris, from the University's research [email protected], said: “Our findings show that these harsh and relatively unexplored ecosystems are responding to recent climate warming and undergoing ecosystem shifts. While some of these wetlands could transition into productive peatlands with future warming, the long term effects of climate change is likely to vary depending on the type of wetland.

“Although new productive peatlands may form in places such as the High Arctic, degrading peatlands in other areas are a major global concern. Every effort should be made to preserve peatlands across the globe – they are incredibly important component of the global carbon cycle.”

The team surveyed ecological responses to 20th century warming in the three types of High Arctic wetland: polygon mire, valley fen, and coastal fen. Plant macrofossils and testate amoeba – minute, single-celled organisms that reside in wetlands – along with radiocarbon dating were used as proxies for historic transitions in vegetation and moisture levels.

The study learned that all three wetland types – with the exclusion of a few sections of the polygon mire – have undergone ecosystem shifts that corresponded with an increase in growing degree days: a unit researchers apply to measure growing season length and warmth. The coastal fen site experienced a surge in shrub cover associated with warming, while sections of the polygon mire saw an increase in moss diversity.

The research also discovered that environmental factors other than warming temperatures may be influencing the variations in vegetation. The research states that grazing Arctic geese could have contributed to the latest shift from shrub to mosses in the coastal fen site. Arctic geese population have grown considerably and food competition at their summer nesting locates may be making them look for new grazing sites further north as they warm.

Our study highlights the complex ways in which climate change is affecting ecosystems and suggest that effects of climate warming will vary depending on wetland type. While we can clearly see that climate change is altering ecology across the Arctic wetlands, whether that will result in a transition to productive peatlands will be strongly influenced by the complex dynamics that govern the wetlands.

Dr Jennifer Galloway, Study Co-Author and Associate Professor, Aarhus Institute of Advanced Studies, Denmark and Geological Survey of Canada

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