Can plants help to prevent permafrost thaw?
Permafrost thaw, the melting of frozen soils caused by global climate change, could have potentially devastating effects on carbon dioxide levels within the earth’s atmosphere. Researchers at the University of Edinburgh are conducting novel research into the potential role plants could play in helping to prevent this thawing from taking place.
What is permafrost?
Generally found in boreal and arctic environments, permafrost (a permanently frozen layer of ground), stores large volumes of frozen carbon produced from dead plant matter. If thawed, the permafrost could release very large amounts of carbon dioxide into the earth’s atmosphere. A major concern is that this would cause further increases in global temperatures, which in turn could cause more permafrost to thaw, creating a vicious cycle. The more thawing there is, the more carbon dioxide that is released and the more carbon dioxide that is released, the more thawing there would be.
Professor Mathew Williams, who is a Head of the Global Change Research Institute in the School of GeoSciences at The University of Edinburgh, is also the lead investigator on the CYCLOPS project. The CYCLOPS team (including partners at the Universities of Exeter, Sheffield and Sussex) have focused on conducting novel research into the role that plants play in the prevention of permafrost thaw.
How could plants help?
Plant communitiies in permafrost environments, including trees, shrubs and mosses, play a vital role in controlling the temperature of soil, and therefore the presence of permafrost. Plants shade the soil from the warmth of sunlight, and their roots extract water leading to drier soils which are better insulators. Mosses in particular, act like effective down insulation, trapping air, which restricts the penetration of heat to the ground below. Even after their death, plants affect permafrost by creating organic soils that cover much of Northern latitudes. Like moss, if these organic soils are dry, they are excellent insulators.
A key goal of CYCLOPS was to better understand how variations in organic soil thickness, moss thickness and vegetation cover determines the presence of permafrost, and how deeply permafrost thaws each summer. Large uncertainties remain when trying to understand and predict rates of permafrost thaw and many climate models fail to incorporate key processes related to these ecological interactions.
The CYCLOPS project has therefore focused on investigating the role that different plant communities play in protecting permafrost and also looked to examine the effects of thawing in different ecosystems.
The role of fire
A further complexity is how climate warming interacts with fire. In a warmer world we expect to see more fires in high latitudes, similar to those in Canada in the summer of 2016. These fires burn away the vegetation, including moss and also organic soils. These types of changes to the land surface then result in a much deeper thaw of permafrost, and combined with warmer conditions, this may lead to the loss of permafrost more quickly than expected.
The study therefore also incorporated the effects of fire on permafrost ecosystems, particularly looking to evaluate how models of thaw reproduce the observed effects of fire.
An additional release of Methane
CYCLOPS is also exploring how a landscape changes after the loss of permafrost. These areas typically become wetlands, and can release large amounts of methane, a potent greenhouse gas. This knowledge is important for making predictions of the effect of permafrost thaw.
Implications of the Research
Results from this study will produce improvements in modelling, particularly the links between climate change, carbon cycling and fire disturbance across high latitudes. Data will be used to develop a process-based model of vegetation-soil-permafrost interactions and help to improve our understanding of the rates and potential consequences of permafrost thaw, and its links to land use change and fire. The model will be the first of its kind to simulate the biochemical feedbacks from carbon dioxide and methane in both wetland and free-draining environments.
This information is vital for global understanding of climate change, and also for regional adaptation and mitigation efforts. Thaw in permafrost areas is a significant issue for local communities due to its impact on land cover, hydrology, roads and buildings, and resource extraction.