The value of peatland rewetting for reducing GHG emission. Hlynur Óskarsson Agricultural University of Iceland

Transcription

1 The value of peatland rewetting for reducing GHG emission Hlynur Óskarsson Agricultural University of Iceland

2 Outline - Extent of peatland draining in Iceland - GHG emissions and the feasibility of restoration - Our research at Mávahlíð, Western Iceland

3 Icelandic peatlands - Original coverage estimated as 9000 km 2 - Minerotrophic and dominated by vascular plants - By far the largest ecosystem carbon reservoir

4 Peatland draining

5 Length of drainage ditches excavated yearly during the period

6 Length of drainage ditches excavated yearly during the period

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8 Length of drainage ditches excavated yearly during the period

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11 Estimate of wetland drainage > 75% disturbed ~ 45% fully drained Drained for cultivation = 576 km 2 (~15%) Drained and never cultivated = km 2 (~85%) Less than 80% of the drained areas are cultivated, some areas are used for grazing but a large fraction is currently not in use

12 Drained, but not in use is that acceptable? 1. Negative greenhouse gas balance UN default value: 1,1 ton C / ha / yr ha drained 440 Gg C / yr 1615 Gg CO 2 / yr (Fossil fuel use in 2010 = 1992 Gg CO 2 ) 349 Gg eq-co 2 / yr (N 2 O)

13 2. Peat erosion taking place

14 3. Water quality issues

15 4. Areas declining in fertility

16 5. Loss of habitat for wetland species

17 Drained, but not in use is that acceptable? - No Rewetting possible?

18 Hestur rewetted site Small GHG study Comparative study of three sites undrained, drained and rewetted Simultaneous measurement campaigns (8) CO 2, CH 4, N 2 O

19 2000 m g C O 2 m -2 h r y = 500,43Ln(x) R 2 = 0,5679 y = 412,29Ln(x) ,9 R 2 = 0,7432 y = 404,29Ln(x) ,2 R 2 = 0,7127 Endurheimt Framræst Óraskað Log. (Endurheimt) Log. (Framræst) Log. (Óraskað) PAR

20 CH 4 efflux 20,0 Restored Drained mg CH4 m -2 hr -1 15,0 10,0 5,0 Intact Expon. (Restored) Expon. (Intact ) Linear (Drained) y = 0,4783e 0,2186x R 2 = 0,4464 y = 0,59e 0,2035x R 2 = 0,5756 y = 0,0143x + 0,0316 R 2 = 0,0248 0, ,0 Soil temperature

21 Drained Intact Restored y = 96,513e 0,1801x R 2 = 0,7551 mg CO2/m 2 /hr y = 29,315e 0,2306x R 2 = 0,7741 y = 45,078e 0,1898x R 2 = 0, Soil temperature (-10cm)

22 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

23 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

24 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 km 2 ) could be restored without having negative effects on other land-use, such as agriculture

25 In 2007 Iceland and Belarus proposed to the UNFCCC that wetland restoration be accepted as new activity under the Kyoto protocol. At the climate summit in Cancún 2010 / Durban 2011 negotiators agreed that in a future climate agreement it should be possible for countries to reduce their emissions by rewetting drained peatlands

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27 Mávahlíð research site Thanks to: Rannveig Ólafsdóttir, Guðrún Óskarsdóttir, Stefanía L. Bjarnadóttir Snorri Þorsteinsson and Jón Guðmundsson Funded by: ISAL Iceland Road Ditch

28 Mávahlíð research site ~ 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 Road Ditch

29 Mávahlíð research site Weekly measurements of: GHG Soil water table Soil temperature NDVI Road Ditch

30 Mávahlíð research site Continuous measurements of: Soil water table Soil moisture Soil temperature PAR Air temperature Precipitation Road Ditch

31 Mávahlíð research site Weekly samples for measurements of: POC PON DOC DON (CO 2 ) (CH 4 ) Road Ditch

32 y = 44,372e 0,263x R² = 0,8347 mg CO 2 m -2 hr Soil temperature

33 500 PAR mg CO 2 m -2 hr y = -735ln(x) ,1 R² = 0,

34 GPP ER NEE Day of Year

35 Mávahlíð research site - July, 2012 Road Ditch

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38 CO 2 respiration flux Drained Rewetted mg m -2 h

39 CH 4 flux ,5 0,4 Drained Rewetted 0,3 mg m -2 h -1 0,2 0,1 0,0-0,1-0, DOY

40 CO 2 respiration flux Drained Rewetted 1500 mg m -2 h

41 CH 4 flux Drained Rewetted 6 mg m -2 h

42 Reduction in emission following rewetting CO 2 -eq mg m -2 h DOY

43 Reduction in emission following rewetting CO 2 -eq mg m -2 h DOY

44 Photosynthetic CO 2 flux vs PAR mg m -2 h Drained Rewetted PAR

45 Conclusions Rewetting the site was successful WTL at the surface Almost immediately some reduction in soil respiration increased with time CH 4 efflux slower to respond but very significant increase in in second season Photosynthetic uptake of CO 2 approx.15% less on rewetted site