the value of peatland rewetting for reducing ghg emission · -ghg emissions and the feasibility of...
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The value of peatland rewetting for reducing GHG emission
Hlynur Óskarsson Agricultural University of Iceland
- Extent of peatland draining in Iceland- GHG emissions and the feasibility of restoration- Our research at Mávahlíð, Western Iceland
Outline
Icelandic peatlands
- Original coverage estimated as 9000 km2
- Minerotrophic and dominated by vascular plants
- By far the largest ecosystem carbon reservoir
Peatland draining
Length of drainage ditches excavated yearly during the period 1942-1993
Length of drainage ditches excavated yearly during the period 1942-1993
Length of drainage ditches excavated yearly during the period 1942-1993
Estimate of wetland drainage
• Drained for cultivation = 576 km2 (~15%)• Drained and never cultivated = 3.424 km2 (~85%)
• > 75% disturbed• ~ 45% fully drained
Less than 80% of the drained areas are cultivated, some areas are used for grazing but a large fraction is currently not in use
349 Gg eq-CO2 / yr (N2O)
1615 Gg CO2 / yr (Fossil fuel use in 2010 = 1992 Gg CO2 )
440 Gg C / yr
400.000 ha drained
UN default value: 1,1 ton C / ha / yr
1. Negative greenhouse gas balance
Drained, but not in use – is that acceptable?
2. Peat erosion taking place
3. Water quality issues
4. Areas declining in fertility
5. Loss of habitat for wetland species
Drained, but not in use – is that acceptable? - No
Rewetting possible?
Hestur rewetted siteSmall GHG study 2000-2
• Comparative study of three sites – undrained, drained and rewetted
• Simultaneous measurement campaigns (8) – CO2, CH4, N2O
y = 500,43Ln(x) - 2135
R2 = 0,5679
y = 404,29Ln(x) - 1506,2
R2 = 0,7127
y = 412,29Ln(x) - 1585,9
R2 = 0,7432
0
200
400
600
800
1000
1200
1400
1600
1800
2000
0 200 400 600 800 1000 1200 1400 1600 1800 2000
PAR
mg
CO
2 m
-2 h
r-1
Endurheimt
Framræst
Óraskað
Log. (Endurheimt)
Log. (Framræst)
Log. (Óraskað)
CH4 efflux
y = 0,4783e0,2186x
R2 = 0,4464
y = 0,59e0,2035x
R2 = 0,5756
y = 0,0143x + 0,0316
R2 = 0,0248
-5,0
0,0
5,0
10,0
15,0
20,0
-2 0 2 4 6 8 10 12 14 16 18
Soil temperature
mg
CH
4 m
-2 h
r-1
Restored
Drained
Intact
Expon. (Restored)
Expon. (Intact )
Linear (Drained)
y = 96,513e0,1801x
R2 = 0,7551
y = 29,315e0,2306x
R2 = 0,7741
y = 45,078e0,1898x
R2 = 0,6739
0
200
400
600
800
1000
1200
1400
1600
1800
2000
-2 0 2 4 6 8 10 12 14 16
Soil temperature (-10cm)
mg
CO
2/m
2 /hr
DrainedIntactRestored
GHG Flux g / m-2 / yr-1 Natural mire Drained site Restored site
CO2 respiration 1154,1 2525,8 1211,1
CO2 uptake -1677,6 -1613,0 -1541,8
CO2 NEE -523,5 912,8 -330,7
CH4 (CO2-eq) 382,9 17,0 357,1
N2O (CO2-eq) 4,4 33,2 1,6
SUM total CO2-eq -136,2 963,0 28,1
Restoration holds promise because in most areas no alteration has taken place other than the excavation of the ditches and research indicates that peatland restoration establishes the former GHG balance of the peatland
A recent report from the Ministry of the Environment on options for reducing GHG emissions concludes that wetland restoration is a feasible option and that large areas (~ 1000 km2) could be restored without having negative effects on other land-use, such as agriculture
In 2007 Iceland and Belarusproposed to the UNFCCC thatwetland restoration be acceptedas “new activity” under the Kyotoprotocol.
At the climate summit in Cancún2010 / Durban 2011 negotiatorsagreed that in a future climateagreement it should be possiblefor countries to reduce theiremissions by rewetting drainedpeatlands
Mávahlíð research site
DitchRoad
Thanks to: Rannveig Ólafsdóttir, Guðrún Óskarsdóttir, Stefanía L. Bjarnadóttir Snorri Þorsteinsson and Jón Guðmundsson
Funded by: ISAL Iceland
Mávahlíð research site
DitchRoad
• ~ 3 ha in size• Drained in 1977• Never ploughed• 936 mm & 3,3°C
• Ave. depth 2,45 m• % C 31,3• C/N 17,3• Bulk density 0,24
Mávahlíð research site
DitchRoad
Weekly measurements of:
• GHG• Soil water table• Soil temperature• NDVI
Mávahlíð research site
DitchRoad
Continuous measurements of:
• Soil water table• Soil moisture• Soil temperature• PAR• Air temperature• Precipitation
Mávahlíð research site
DitchRoad
Weekly samples for measurements of:
• POC• PON• DOC• DON• (CO2 )• (CH4)
y = 44,372e0,263x
R² = 0,8347
0
500
1000
1500
2000
2500
0 2 4 6 8 10 12 14 16
Soil temperature
mg
CO
2m
-2hr
-1
y = -735ln(x) + 2961,1
R² = 0,8075
-2500
-2000
-1500
-1000
-500
0
500
0 100 200 300 400 500 600 700 800 900
mg
CO
2m
-2hr
-1
PAR
-35000
-25000
-15000
-5000
5000
15000
25000
35000
0 50 100 150 200 250 300 350 400
Day of Year
GPP
ER
NEE
DitchRoad
Mávahlíð research site - July, 2012
CO2 respiration flux 2012
2012
0 50 100 150 200 250 300 350
mg
m-2
h-1
0
200
400
600
800
1000
1200
1400
1600
1800
Drained Rewetted
CH4 flux - 2012
DOY - 2012
0 50 100 150 200 250 300 350
mg
m-2
h-1
-0,2
-0,1
0,0
0,1
0,2
0,3
0,4
0,5Drained Rewetted
CO2 respiration flux 2012-13
2012 2013
0 100 200 300 400 500 600 700
mg
m-2
h-1
0
500
1000
1500
2000Drained Rewetted
CH4 flux 2012-13
2012 2013
0 100 200 300 400 500 600 700
mg
m-2
h-1
-2
0
2
4
6
8Drained Rewetted
Reduction in emission following rewettingCO2-eq - 2012
2012 - DOY
160 180 200 220 240 260 280 300 320
mg
m-2
h-1
0
100
200
300
400
500
Reduction in emission following rewettingCO2-eq - 2013
2013 - DOY
140 160 180 200 220 240 260 280
mg
m-2
h-1
-200
0
200
400
600
800
Photosynthetic CO2 flux vs PAR
PAR
0 200 400 600 800 1000 1200 1400
mg
m-2
h-1
-3500
-3000
-2500
-2000
-1500
-1000
-500
0
Drained Rewetted
Conclusions• Rewetting the site was successful – WTL at the surface • Almost immediately some reduction in soil respiration – increased with time• CH4 efflux slower to respond but very significant increase in in second season• Photosynthetic uptake of CO2 approx.15% less on rewetted site