Deltares – Utrecht University – Geological Survey of the Netherlands
Double Trouble: subsidence and CO2respiration due to 1,000-years of Dutchcoastal peatland cultivation
Gilles Erkens, Michiel J. Van der Meulen, Hans Middelkoop
As published in Hydrogeology Journal, 2016
24 mei 2016
Swampy areas
Berendsen 2005
The peaty history of The Netherlands
Orange - coastal peats
Brown - upland peats
after Visscher 1949
Palaeogeography800 A.D.Vos (2010)
24 mei 201624 mei 2016
What happened with The Netherlands?
Photo: H.J.A. BerendsenPhoto: G. Erkens
BEFORE AFTER
Photo: D. HendriksPhoto: G. Erkens
Berendsen 2005
The history of human impact in Dutch peatlands
1: Drainage
2: Excavation
After Wetenschappelijke Atlas van Nederland
Drainage of peat causes subsidence
Drainage = oxidation of peat = land surface loweringVan de Ven, 1993
900 AD
1050 AD
1250 AD
2000 AD
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Drainage and mining of peat bogs
Zoning
A- drained
B- Excavated andreclaimed
C- Excavated andnot reclaimed
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Research question and Approach
Research question: How much land subsidence occurred due to drainage andexcavation during the last 1000 years?
Essential information:i) Elevation of current land surfaceii) Elevation of land surface 1000 years ago
Main presumption:All land elevated presently under MSL used to be elevated at or above MSL.
24 mei 2016
Input 1: elevation of current land surface
Input data: digital elevation model ofThe Netherlands (AHN)
• Laser altimetry data (LIDAR)• Nation-wide• High-resolution of 1 x 1 x 0.05 m
We excluded:i) Upland peatlands
(above 1 m + MSL1000)ii) Areas of open wateriii) Lowland with no peat in
subsurfaceiv) Tectonic subsidence
(30 cm in 1000 years)
Disclaimer:All estimates and assumptions in this studyare conservative!
Van de Plassche,1982
MSL1000 =
~ 0.3 m -MSL
24 mei 2016
Input 2: elevation of land surface 1000 AD
Input:palaeogeographical and
palaeobotanical reconstructions• Based on core-derived and
historical information• Nation-wide• Low resolution
Two types of peat are distinguished:i) Domes (bogs)
(elevated 2 m + MSL1000)ii) Planes (fens)
(elevated 0.8 m + MSL1000)
Subsidence calculations:Subtracting present-day land surface from
the 1000 AD land surface
Peat bogs and fens 800 A.D.after Pons (1992)
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Results (i): total subsidence
Subsidence values because ofanthropogenic land use:
i. On average: 2.0 mii. Maximal: ~8-10 m
This resulted in:i. 56 % of the Dutch coastal plain
being below MSLii. The need for continuous pumpingiii. Reversal of drainage systems
Steps to obtain CO2 respiration:i. Calculate lost volume of peatii. Calculate carbon content of the lost
peat (using bulk density)
24 mei 2016
Results (ii): volumes
Landscape type Area(km2)
Height(m)
Volume(km3)
Older peat (below MSL1000) 6661 - 8.3Bogs(above MSL1000)
best estimate 4360 2 8.6range - 1 - 4 4.1 – 15.7
Fens(above MSL1000)
best estimate 3534 0.8 2.9range - 0.5 – 1.5 2.1 – 6.0
Total best estimate 7895 - 19.8range - - 14.5 – 30.0
Total volume of peat lost by anthropogenic land use : ~20 km3
Subsidence ≠ CO2 emission
Loss of Volume because of 3 components:1. combustion (in furnaces)2. erosion of ditch banks after peat digging3. drainage of peatlands
Drainage starts 3 processes:1. shrinkage (negligible at longer time scales)2. compaction (consolidation, creep)3. oxidation
Volume loss due to drainage ≠ volume loss due to oxidation
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Peat Mining sites
Dominant process
In area:- 15 % mining- 85 % drainage
In volume:- 34 % mining- 66 % drainage
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Input 3: Bulk density valuesOrganic matter mass per m3 from subsurface samples (n = 664)
Data from S. van Asselen, W.Z. Hoek, UU, Deltares, and TNO
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Input 4: Consolidation vs Oxidation
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Total CO2 respiration
Soil carbon released during the past 1000 years:0.83 Gton (1012 kg) (0.55 – 1.56Gton)
CO2 emitted to atmosphere* by land use in the Netherlands in 1000 year:3.07 Gton (1012 kg) (2.02 – 5.72 Gton)
* 1 kg soil carbon = 3.67 kg atmospheric CO2
The increase of atmospheric CO2 concentration is 0.39 ppmv** Net increase may have been lower due to uptake of CO2 by the worlds oceans and biosphere.
24 mei 2016
The breathing of a coastal plain
CO2 respiration: modern vs. historic
0,0
2,0
4,0
6,0
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1650 1750 1859 1899 1970 2005
Mto
n
Current CO2 respiration due to drainage outranges historic combustion relatesrespiration!
NB values based on Gerding (1995)
COMBUSTION
DRAINAGE
Urban Fieldworkin Kanis, Woerden
Villages on peat
Constructions5 billion Euroso far, ~40miljard Euro till2050(theoreticalmaximum).Deltares 2012
Infrastructure:€ 0,25miljarillipn deuro per jaarextra(0,17 miljard
voor wegen enwater plus 0,08miljard voorriolering).
24 mei 2016
Subsidence 2000-2050
30000.000000
30000.000000
80000.000000
80000.000000
130000.000000
130000.000000
180000.000000
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230000.000000
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Legendahnminstep5.img(m)
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30000.000000
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Legenddh014600dMosaicV2.img(m)
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CLIMATE CHANGESCENARIO
At constant drainagedepth
24 mei 2016
Subsidence Strategies
• Mitigation• Works for human-induced land subsidence• Technical: Diminish pumping, aquifer storage recovery, using lighter
building materials
• Adaptation• Works for natural and
remaining human-induced landsubsidence
• Technical:reintroducingsediment, build higherlevees
• Non-technical: betterspatial planning,governmentalembedding
MeasuresADAPTATION
MITIGATION
National Soil Deformation Database
Double Trouble:subsidence and CO2 respirationdue to 1,000-years of Dutchcoastal peatland cultivationGilles Erkens et al.
