This year’s UN Climate Change Conference (COP26) will be held in Glasgow in November, and now more than ever before, the pressure is on for world leaders to agree on climate action to keep global warming below 1.5°c. In the lead up to the conference, we’re asking our editors and authors to share their research at the interface of climate and ecology. In this post, our editor Jessica Royles from the Cambridge Centre for Climate Science shares her research on using Antarctic mosses as a tool to reveal the environmental conditions of the past.
Antarctic mosses are not amongst the usual tools that spring to mind for investigating climate change, but after four trips to Antarctica and countless hours slicing, examining, weighing, analysing, head scratching and plotting I am happy to report they can be very revealing about environmental conditions in the past.
At a handful of locations on the west side of the Antarctic Peninsula (the area nearest South America) deep moss banks have accumulated over thousands of years. The surface moss grows slowly, but, protected by permafrost, the organic matter beneath is very well preserved. Using an adapted ice-corer we extracted frozen moss peat cores from the surface down to the bed rock below – over 2.5 m in some cases. With limited meteorological recording and with no trees for dendrochronological analyses, these moss banks provide the longest biological palaeoclimate archives available in the region.
Mosses are well adapted to life in Antarctica as they can quickly activate photosynthesis and grow in the brief periodswhen conditions are suitable…and then rapidly shut down again when conditions change, which may be at the end of the season, or just a few hours later when another storm blows in.
Back in Cambridge, we sub-sampled the frozen cores into 1 cm sections. The moss fibres were amazingly well preserved and we also found penguin feathers embedded in sections over 1000 years old. The cores then underwent radio-carbon dating, for the development of age-depth models and species composition analysis. Two species (Chorisodontium aciphyllum and Polytrichum strictum) dominate the moss banks, and each core was formed by only one species, making them ideal material for palaeoclimate analysis. I extracted cellulose from the moss organic matter and we measured the stable carbon (13C/12C) and oxygen (18O/16O) isotope ratios. Colleagues at the University of Exeter used microscopic analysis to count the testate amoebae in the core.
The first core we collected and analysed was from Lazarev Bay on Alexander Island, which at 69oS is the southernmost known moss bank. Multiproxy analysis showed that carbon isotope discrimination and the testate amoebae population increased in line with changes in meteorological and ice core records in the late twentieth century (Current Biology 23:1702). Carbon isotope discrimination reflects the optimality of summer conditions for photosynthesis, whilst testate concentration reflects microbial population change and it was clear that these biological responses to recent climate change were unprecedented in the last 150 years, and this work was cited by the 2014 IPCC Working Group 2, Fifth Assessment Report.
From this initial site, we expanded our analysis spatially, with an in depth assessment of the past 150 years across a 600 km transect (Current Biology 27(11): 1616) ), and temporally, back in time over 4000 years to the base of the oldest cores (Geology 46(12): 1071-1074.). Both of these analyses showed fundamental and widespread changes in the terrestrial biosphere had occurred in response to warming, and indicated that terrestrial ecosystems are likely to alter rapidly under future warming scenarios.
All in all, these beautiful and fascinating moss cores, extracted from some of the most remote and vulnerable ecosystems on our planet, have revealed how unusual recent rapid climate change has been, and the significant impact it has already had on biological systems – especially those at the extremes of survival. Working in Antarctica depends on hard work, compromise and international collaboration, and these will be required all parties at the COP26 Glasgow summit if there is to be any chance of effectively reducing carbon emissions and limiting temperature rises to 1.5oC, outcomes essential to protecting vulnerable populations and ecosystems around the world.
For more information on this year’s COP26 meeting, read the handy BES Guide to COP26.
I completed my NERC funded PhD at the University of Cambridge and British Antarctic Survey, Cambridge, UK, and this work was then extended through a NERC funded post-doctoral project, in collaboration with the University of Exeter, UK.
Project members: Professor Pete Convey and Professor Dominic Hodgson (British Antarctic Survey)
Professor Dan Charman, Dr Matthew Amesbury, Dr Tom Roland (University of Exeter)
Professor Howard Griffiths (University of Cambridge)
Funded by: NERC