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. 21 000 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 • 400-500 Gt C in peat• 100-150 Tg CH4/a from natural wetlands• ca. 40 Tg CH4/a from rice paddies• estimates for the LGM 80-110 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 (137-399)• Floodplains – 100 (50-200)• Lakes – 43 (17-89)• Rice paddies – 310 (179-438)

~INLAND WETLANDS~

BOGS

SWAMPS

FENS

OPEN WETLANDS

MARSHES

SPRINGS GEOTHERMAL WETLANDSFLUVIAL

LACUSTRINE

Open Wooded

Raised Blanket

Aapa

Rich Oligotrophic

Eutrophic Mesotrophic

Wooded

Paludifying forestSwamp forest Cloud forest

Raised Rich

Open

Eutrophic Mesotrophic

Shrub-swamp

Shrub-marsh

Carr Alder thicket

Palsa mirePolygonal mire

Wet tundra

High palsa mire Plateau palsa mire

Sloping mire

Wet meadow

Saline/brackish AlkalineFreshwater

Flooded meadow Sedge marsh

Terrestrialising lake

~COASTAL/MARINE WETLANDS~

INTERTIDAL MARSHES INTERTIDAL SWAMPS

AQUATIC BEDSINTERTIDAL FLATS

Salt marsh Salt meadow Salting

Raised FreshwaterBrackish

Mangrove Nipah

Tidal freshwater swamp forest

~HUMAN-MADE WETLANDS~

AGRICULTURAL

ARTIFICIAL LAKES

CANALS

EXCAVATIONSRice field Wet meadow

Pond Reservoir

Wastewater treatment

Thermokarst lake

Wet moor

Oligotrophic

Alpine wet meadow

~NOT WETLAND~

DRIED PEATLAND BURIED PEATLAND

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 50 000 – 21 000 BP

Continental and ice-sheet outlines by Patrick Bartlein, University of Oregon

Mires at 13000 BP

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

Mires

at 11000 BP

Mires at 10000 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

0

50

100

150

200

250

300

350

400

450

mire initiation cases

cumulative/ 5

0 2000 5000 8000 11000 15000 >21000