Dr. aljosja hooijer - peatland subsidence sustainability

1 januari 2008
The unrecognized problem: will subsidence flood
drained peatlands in SE Asia, i.e. can drained
agriculture / silviculture on deep peat be
sustainable?
Kuala Lumpur, 8 June 2015
Al Hooijer
for research team & partners

1 januari 2008
• Founded 1927 to help design Netherlands coastal defence, necessary
largely because our peatlands had subsided well below Sea level (!)
What is Deltares (Delta Research)

1 januari 2008
• Founded 1927 to help design Netherlands coastal defence, mecessary
largely because our peatlands had subsidence well below Sea level (!)
• Formerly Delft Hydraulics, GeoDelft and others…
• Now largest specialized water & soil consultancy in the World, with 900+
staff
• Offices in Washington, Singapore, Jakarta etc, often active in areas with
subsidence & flooding problems
• Active at large scale in SE Asia peatlands since 2005, at request of
Governments, Industries and NGOs. Largest projects are for Pulp &
Paper Industry.
What is Deltares

1 januari 2008
25 Mha SE Asian peatlands
• Being deforested and drained at record rates (in time and globally); mostly for
palm oil and pulp (paper) plantations that expand 12% yr-1 2007-2010
• 90% intact by 1990, ~40% now, < < 20% 2020 ?
• Deltares with partners has studied over 10 sites in last 10 years

1 januari 2008
• Intact SE Asia peatlands: accumulated by tropical rainforest since mid-Holocene
• Traditionally used only for selective logging

1 januari 2008
• Being deforested and drained at record rates (in time and globally); mostly for
palm oil and pulp (paper) plantations that expand 12% yr-1 2007-2010

1 januari 2008
Peatland drainage inevitably causes
carbon loss and subsidence
Clay / sand
ΔL
Peat swamp
Stream
channel
Stream
channel
Carbon

1 januari 2008
Waterlevel
Peat dome
Stream
channel
Stream
channel
Carbon

1 januari 2008

1 januari 2008
Smoke & Carbon

1 januari 2008
All thorough long-term studies report that subsidence rate is continuous unless
water level is changed, because subsidence is caused mostly by oxidation
Everglades, USA
Sacramento
Delta, USA
Fenlands, UK
3 m / 70 yrs
5 m / 90 yrs
4 m / 150 yrs
International time series and relation with
water table depth

1 januari 2008
International examples: UK, Fenlands
Ground surface when
pole was built (well
AFTER subsidence
started)
3.5 m / 70 yr

1 januari 2008
Relation temperature and subsidence rate
(Mohr, Van Baren & Van Schuylenborg, 1972)
Organic matter
breakdown by far
highest in tropical
conditions

1 januari 2008
Model by Stephens et al 1984
for USDA still up to date (for
water table depths ~0.6 m).
For tropics, it finds ~5 cm/yr
Compared with ~1.5 cm/yr
In temperate regions

1 januari 2008
IPCC 2013 Carbon Emission Factors reflect this same T dependency (Summary
Table in FAO, 2014)

1 januari 2008
Constant subsidence rate for many decades, until peat is depleted or the
area becomes undrainable (assuming fibric/hemic peat and constant
drainage)
Measured in
SE Asia:
1.5 m subsidence
in first 5 years after
drainage,
then 5 cm/yr
(measured by
a) subsidence poles
b) CO2 gas flux
c) LiDAR landscape
analysis
2.5 m subsidence
in 25 years
> 5 m in 100 years?
(Hooijer et al., 2012)
Field evidence of subsidence in warm climates:
SE Asia, Riau, compared with other regions
Mostly
consolidation
/ compaction
Mostly
oxidation
Hooijer et al. 2012)

1 januari 2008
In summary
Long-term subsidence rate
in agricultural areas in
the SE Asia is 3-6 cm/yr
because:
• Temperature is very high
• Organic content is very high
• Water levels generally kept
low to prevent flooding (huge
areas, low budget, high
rainfall)
Why peat subsidence rates in tropical areas are highest
SE Asia
~5 cm/y
(Stephens et al. 1984)

1 januari 2008
Surface before drainage?
(subsidence pole placed
well after drainage)
The first industrial
oil palm plantations
on peat; developed
early 1960s
Now we see ~3.5
metres of subsidence
within 50 years
International examples: Johor, Malaysia

1 januari 2008
Model projections of subsidence & flooding in SE Asia:
Sarawak
First study area: the Rajang Delta study area in Sarawak (Malaysia), on the island of Borneo.

1 januari 2008
Map of ‘agriculture capability’ for
part of the study area (Dept of
Agriculture Sarawak, 1982).
DARK BLUE area (class O5)
presents deep peat and is
described as “Land comprising
organic soils with such severe
limitations that agriculture is not
feasible. Land in class O5 has serious
limitations such as low fertility, high
water table, flooding, … low bulk
density resulting in poor anchorage …
and subsidence...”
Sarawak

1 januari 2008
Despite widely being
considered unsuitable, the
Sarawak peatlands were
deforested and drained, for oil
palm plantations.
Industrial plantations covered
6% by 2000, 47% by 2014.
The entire area must now be
considered drained and
subsiding.
Sarawak
2000
20142014

1 januari 2008
To model the impact on
subsidence and flooding of
this development, a Digital
Terrain Model (DTM) was
needed. This was created
from IFSAR radar data.
Sarawak
Raw IFSAR data
DTM

1 januari 2008
Sarawak
IFSAR based DTM

1 januari 2008
Sarawak
IFSAR based DTM with land cover

1 januari 2008
Sarawak
The DTM was used to determine areas below drainablity and flood limits:
• FDL: Free Drainage Limit – below this it is increasingly difficult to remove rainfall by gravity
flow; frequency of first waterlogging and then flooding wil increase, agricultural productivity will
drop.
• HWL: High Water Level – below this, the peatland is frequently flooded by river water;
agriculture is severely affected and may be impossible.
• The land may often be abandoned before the peat surface is below HWL.

1 januari 2008
Sarawak
Subsidence was modelled applying a rate of 3.5 cm/yr (conservative)

1 januari 2008
Sarawak
Flood risk was modelled from the DTM and FDL / HWL rules (conservative)

1 januari 2008
Sarawak
Even in a conservative scenario, at least 75% of peatland will be severely flooded within 100
years (up from 30% now).
Impact scenario
Drainage limit
Subsidence rate
year ha % ha % ha %
2009 291736 34.4 116416 13.7 408152 48.1
2034 (after 25 yrs) 396533 46.8 119913 14.1 516446 60.9
2059 (after 50 yrs) 493953 58.3 114065 13.5 608018 71.7
2084 (after 75 yrs) 579510 68.4 105991 12.5 685501 80.9
2109 (after 100 yrs) 653257 77.1 98769 11.7 752026 88.7
2159 (after 150 yrs) 770437 90.9 55605 6.6 826042 97.4
2009 223346 29.9 101247 13.6 324593 43.5
2034 (after 25 yrs) 312705 41.9 112218 15.0 424923 56.9
2059 (after 50 yrs) 402898 53.9 110102 14.7 513000 68.7
2084 (after 75 yrs) 485065 65.0 103031 13.8 588096 78.7
2109 (after 100 yrs) 557074 74.6 96019 12.9 653093 87.5
2159 (after 150 yrs) 671302 89.9 54110 7.2 725412 97.1
2009 72001 18.3 41376 10.5 113377 28.8
2034 (after 25 yrs) 107906 27.4 58125 14.8 166031 42.2
2059 (after 50 yrs) 153627 39.0 67653 17.2 221280 56.2
2084 (after 75 yrs) 203207 51.6 70528 17.9 273735 69.5
2109 (after 100 yrs) 251384 63.8 70098 17.8 321482 81.7
2159 (after 150 yrs) 335711 85.3 41146 10.5 376857 95.7
'conservative' scenario
Plantation on peat area
HWL (cons.)
3.5 cm/yr
FDL (cons.)
3.5 cm/yr
HWL + FDL (cons.)
3.5 cm/yr
Total area
Peat area

1 januari 2008
Sarawak
The speed of flooding increase and production loss depend on some assumtions, that may be
refned, but the TREND and OUTCOME are clear: problems will increase and land will be lost for
agriculture.

1 januari 2008
Sarawak
There is plenty of evidence of this problem, but the link to peat and subsidence problems is ignored.
Flooding in the Matu-Daro district, in the NW part of the study area near the coast, in 2011.

1 januari 2008
Aceh, October 2011
Indonesia: examples of flooding having started

1 januari 2008
Jambi, December 2013

1 januari 2008
Riau (Dumai, December 2014)

1 januari 2008
Investigations in Jambi (between Berbak TN and Batang Hari river)
Examples of flooding already having started

1 januari 2008
Plantations drained 5-10 years ago. Some 2 of subsidence is evident. Deep peat starts 0.5-2 km
from the river. Flooded frequently to 1 m, and every 5 yrs to 2.5 m.
-14
-12
-10
-8
-6
-4
-2
0
2
4
6
0 500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500 5,000
SEPONJEN (WSI): distance along profile from west to east (m)
Elevation[m]
Land Surface [m]
River level during survey, Oct. 2013 [m]
Peat Bottom [m]
Flood 2003 [m]
oil palm plantations (PT. WSI)
3
1
-9
-1
Peat
surface
10 years
ago ?

1 januari 2008
Flooded every 5 yrs to 2.5 m.
Producivity of 6 y.o. oil palm
seems very low (or absent?).

1 januari 2008
In plantations, ‘canals’ now spaced at 15 m and are in fact excavations used for ‘mounding’.
This is a temporary and pointless ‘mitigation’ measure: this land is already lost while
plantations still plant and expand…

Question Answer
All Gedong K. Seponjen
Number of respondents 47 22 25
LAND USE
How much land per farmer? [ha] 1.8 1.1 2.5
Does the farmer own the land? [yes, %] 96% 95% 96%
Are fertilizers used (average all crops)? [%] 93% 88% 92%
What kind of crops is on the land?[%]
Rice 45% 36% 52%
Oil palm 43% 27% 56%
Rubber 30% 27% 32%
Cacao 70% 68% 72%
Tree fruits 21% 23% 20%
Other 6% 9% 4%
How long has rice been grown? [yrs] 10 8 12
How long have cacao, oil palm and rubber been grown? [yrs] 6 5 6
What is perceived as suitable crops for flooded land?
Rice 17% 36% 0%
Oil palm 15% 32% 0%
Rubber 4% 9% 0%
Cacao 0% 0% 0%
Tree fruits 0% 0% 0%
Kangkung ('water crest' type vegetable) 50% 0% 100%
Jeluting (native rubber / timber) 4% 9% 0%
Hardwood timber 2% 5% 0%
FLOODING REGIME
Is your land affected by river flooding every year? [yes, %] 87% 73% 100%
Are there also floods caused primarily by local rainfall? [yes, %] 35% 50% 21%
How many months is the land flooded on average? 3.1 1.3 4.7
What is the usual flood level above the land? [m] 1.1 0.7 1.5
What is the usual flood level above the land? [m] 2.5 1.4 3.4
Are floods now more common than 10 years ago? [yes, %] 57% 48% 65%
Is only the lowest land in each farm flooded every time? [yes, %] 52% 95% 13%
Is all land in each farm flooded every time? [yes, %] 48% 5% 88%
Is flooding reducing crop yields? [yes, %] 96% 91% 100%
What was done to reduce flood loss? [yes, %]
Changing crops 0% 0% 0%
Raise soil surface by creating mounds 24% 50% 0%
Add canals / ditches 7% 14% 0%
Nothing 70% 36% 100%
What has been presented as a solution to the flooding?
More drainage by canals and ditches 43% 91% 0%
Nothing 57% 9% 100%
Is research into these problems welcome on their land? [yes, %] 100% 100% 100%
1 januari 2008
Investigations in Jambi
“Land from all farmers is flooded,
every year”
“The only crop considered suitable by more
than 20% of farmers is Kangkung (!?)”
“Yet they all grow mostly cocao and OP,
which they consider unsuitable”
“Hardly any farmer is considering alternative
crops or other changes, as no knowledge
on what is possible”
“Research into alternatives welcomed by
100% of farmers”

1 januari 2008
Indonesia’s coastline will effectively be altered, similar to Europea in the past but
much faster and at a much larger scale (in publication)
Long-term drainability projections

1 januari 2008
What can be done ?
Raising water levels in plantations helps a bit, but a rise from 0.6 m to 0.4 m
reduces emissions and susidence by less than 20%...

1 januari 2008
 Most conversion of deep peat in the world has failed due to in subsidence and
flooding, resulting in either production / land loss or very high cost (Netherlands)
 Indonesia & Malaysia now only countries attempting to develop agriculture on deep
peat
 At > 10 Mha the subsidence/flooding largest area in the world (Netherlands: 1.5 Mha
subsided; other areas < 1 Mha); in fact possibly more than the rest of the world
combined. Also larger than global coastal area considered threatened by Sea Level
Rise alone
 This process is already well underway, floods are increasing and plantations failing,
but remain unreported
 Focus in discussions on impacts of peatland deforestation / drainage in SE Asia
often on biodiversity loss and carbon emissions. Subsidence and longer-term
sustainability is still overlooked.
 Comprehensive flood assessments and long-term long-term cost-benefit analyses
needed for policy improvements …
 Switch to flood-tolerant production needs to be considered – requires research and
preparation…
Summary and comments for discussion

Dr. aljosja hooijer - peatland subsidence sustainability

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