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

25 Mha SE Asian peatlands

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

1 januari 2008

Peatland drainage inevitably causes

carbon loss and subsidence

Clay / sand

ΔL

Peat swamp

Str

eam

channel

Str

eam

channel

Carbon

1 januari 2008

Peatland drainage inevitably causes

carbon loss and subsidence

Waterlevel

Peat dome Str

eam

channel

Str

eam

channel

Carbon

1 januari 2008

Peatland drainage inevitably causes

carbon loss and subsidence

1 januari 2008

Peatland drainage inevitably causes

carbon loss and subsidence

Smoke & Carbon

1 januari 2008

Peatland drainage inevitably causes

carbon loss and subsidence

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

Relation temperature and subsidence rate

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

Relation temperature and subsidence rate

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...”

Model projections of subsidence & flooding in SE Asia:

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.

Model projections of subsidence & flooding in SE Asia:

Sarawak

2000

2014 2014

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.

Model projections of subsidence & flooding in SE Asia:

Sarawak Raw IFSAR data

DTM

1 januari 2008

Model projections of subsidence & flooding in SE Asia:

Sarawak IFSAR based DTM

1 januari 2008

Model projections of subsidence & flooding in SE Asia:

Sarawak IFSAR based DTM with land cover

1 januari 2008

Model projections of subsidence & flooding in SE Asia:

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

Model projections of subsidence & flooding in SE Asia:

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

1 januari 2008

Model projections of subsidence & flooding in SE Asia:

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

1 januari 2008

Model projections of subsidence & flooding in SE Asia:

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

1 januari 2008

Model projections of subsidence & flooding in SE Asia:

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

1 januari 2008

Model projections of subsidence & flooding in SE Asia:

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

Model projections of subsidence & flooding in SE Asia:

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

Model projections of subsidence & flooding in SE Asia:

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

Indonesia: examples of flooding having started

1 januari 2008

Riau (Dumai, December 2014)

Indonesia: examples of flooding having started

1 januari 2008

Investigations in Jambi (between Berbak TN and Batang Hari river)

Examples of flooding already having started

1 januari 2008

Investigations in Jambi (between Berbak TN and Batang Hari river)

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.

Examples of flooding already having started

-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)

Ele

vatio

n [

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

Investigations in Jambi (between Berbak TN and Batang Hari river)

Flooded every 5 yrs to 2.5 m.

Producivity of 6 y.o. oil palm

seems very low (or absent?).

Examples of flooding already having started

1 januari 2008

Investigations in Jambi (between Berbak TN and Batang Hari river)

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…

Examples of flooding already having started

Question AnswerAll 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”

Examples of flooding already having started

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

1 januari 2008

Questions?