Evolution of wetlands since the Last Glacial Maximum Pirita Oksanen University of Bristol

Wetland synthesis - distribution, extent, type and accumulation Public database Maps Data – model comparisons Since ca BP Phase 1. Northern extratropics. Phase 2. Tropics.

Peatlands net sink of CO2 – vegetation sequesters from the atmosphere Wetlands net source of CH4 – methanogenesis in waterlogged environment ca. 5 million km2 natural wetlands over 1 million km2 irrigated cultivation Gt C in peat Tg CH4/a from natural wetlands ca. 40 Tg CH4/a from rice paddies estimates for the LGM Tg CH4/a

temperature, water table and vegetation control CH4 production and flux wide variation of CH4 fluxes both between and within wetlands and seasons Mean values (Aselmann & Crutzen -89) Bogs – 15 (1-50) CH4/m2/day Fens – 80 (28-216) Swamps – 84 (57-112) Marshes – 253 ( ) Floodplains – 100 (50-200) Lakes – 43 (17-89) Rice paddies – 310 ( )

Wetland vegetation plant functional types OPEN mosses with dwarf-shrubs and forbs – bogs and fens tall sedges and grasses (>1.5 m height) - fens and marshes low sedges and grasses - fens and other open wetlands open water WOODED (>5% tree cover) - bogs and fens wooded, evergreen broad-leaved wooded, evergreen needle-leaved wooded, seasonal broad-leaved wooded, seasonal needle-leaved FORESTED (>40% tree cover) - swamps forested, evergreen broad-leaved forested, evergreen needle-leaved forested, seasonal broad-leaved forested, seasonal needle-leaved

Mires today, sites with bottom dates Previous databases used: Oksanen 2005, Gorham et al. 2005, McDonald et al. 2006, PAIN. Lappalainen et al. 1996

Basal peat dates – BP Continental and ice-sheet outlines by Patrick Bartlein, University of Oregon

Mires at BP Experimental ice-sheet data by W.R Peltier, University of Toronto

Mires at BP

Mires at BP

Mires at 9000 BP

Mires at 6000 BP, sites with basal peat dates Continental and ice-sheet outlines by Patrick Bartlein, University of Oregon

Mire initiation in arctic/boreal regions >21000