Degradation and Sustainable Management of Peat Soils in

Indonesia

Fahmuddin Agus

Indonesian Soil Research Institute

Jl. Tentara Pelajar, No. 12, Cimanggu, Bogor 16114, Indonesia

f_agus@litbang.pertanian.go.id

Summary: The 14.9 million ha Indonesian peatland is under pressure for economic use on the one hand and for conservation on

the other. Peat degradation is associted with compaction (shrinkage and consolidation) and CO2 emissions caused by aerobic

microbial decomposition (due to drainage) and by peat fire. CO2 emission is the main national and global concerns. However, the

level of uncertainty is very high in estimating the amount of emitted CO2 from peat fire and peat microboal decomposition. There

is a pressing need for the availability of affordable remote sensing technique to support the estimate of the actual peat burn scar

area, rather than the hot spot area, and burn scar depth at high enough (≤5 cm) vertical resolution. For peat microbial

decomposition, the recent 2013 IPCC Supplement for Wetlands segregates emissions based on land cover types. However, peat

properties and environmental condition and water and soil management systems seem more dominant determinants of the

emission, but these have been the knowledge gaps that need to be addressed in future research. Sustainable peat soil management

is defined as the management systems causing minimum environmental effects and providing feasible economic return.

Minimizing the depth of drainage to the level tolerable by crops for optimum production or selecting economic crops that tolerate

shallow water table reduces the management impacts to the environment. Fire control is inevitable in sustainable peat

management. Agronomic management techniques comprising of water table control, amelioration and fertilization are available

for profitable crop production under drained peat systems, leading to a high opportunity cost of peat forest conservation.

Unfortunately, crop production under undrained systems are not as economically competitive. Therefore, a combination of

incentive and regulatory measures as well as implementation of environmentally friendly management systems are needed for the

win-win environmental and economic objectives.

Keywords: Subsidence, burning, drainage, CO2 emission, burn scar

1. Introduction

Indonesia has the largest tropical peatland area of about 14.9 million ha (Mha) [1]. About half of this area is still

covered by forest but the remaining area has been used for agriculture, forest plantation or being idle and covered by

shrub or being bare. The area of shrubland and bare peatlands is estimated as large as 3.8 Mha [2] and these lands are

not only unproductive, but also the source of emissions due to drainage influence.

There are two contrasting direction in today’s use of peatlands. On the one hand, clearing and draining of peat

forest trigger peat decomposition processes which ends up in carbon dioxide (CO2) emission and peat subsidence.

Subsidence also entails the loss of peat hydrological functions [3]. Furthermore, drained peat is also associated with

susceptibility to peat fire which contributes further and often more significantly to subsidence and carbon loss [4].

The concern of environmental problems due to peat fire are not only associated with the high amount of CO2

emissions and subsidence, but also the haze and health problems. On the other hand, drained peat has enabled the

production of various kinds of high economic value crops such as oil palm, vegetables, fruits, rubber and grain crops

[5, 6, 7]. Profitability derived from peatland, at least for the short term accounting, matches that of mineral land [7].

Science are advanced enough on the management techniques of peatland for increasing farm profitability.

Management techniques are also available for reducing the negative environmental effects, but the opportunity costs

seem very high for implementation. Furthermore, there are knowledge gaps in inventorizing the most important

global environmental concern of peat soil uses under drained conditions, i.e. CO2 emissions caused by decomposition

and fire.

This paper discusses the processes associated with peat subsidence and peat fire. To a lesser detail profitability

from the use of peatland will also be explained. Research gaps and the way forward will be elaborated.

2. Land use and land use change as the drivers of degradation

The increasing demand for land resources has lead to a high pressure for the use of peatlands for producing

various kinds of agricultural commodities, as well as for settlement and mining [8]. The conversion and draining of

peat forests to create favorable conditions for aerobic crops change the peatland role from a C sink to C source [3].

However, not all of the converted and drained peat forest are used for production purposes. About 3.8 Mha of the

cleared areas become idle. They are covered by shrub or grasses or being bare [2]. This lands lose both their

environmental and economic functions. The peat shrubs become carbon sources due to drainage influence as opposed

to natural forests which are considered as near carbon neutral [9]. The rate of shrubland subsidence and CO2

emission may even exceed those of agricultural land because, not only that it shrink and decompose, but it’s also a

subscriber to peat fire during the dry period, which in turn add to the amount of CO2 emissions and subsidence [7, 10,

11].

Oil palm plantation is one of the most important and rapidly expanding agricultural uses on peatland. Oil palm

plantation on peatland has been increasing rapidly from 4% in 2000 to 6% in 2005 and to 10% in 2010 relative to

the total Indonesian peatland area [10]. This is attributed to the ease of market accessibility and profitable use of the

land. Peatlands are also used for rubber, vegetables and paddy rice. So far none of the other commodities excel oil

palm plantation with an estimated area of 1.7 Mha on peatland. Abandoning agricultural practices and restoring the

land to natural conditions are often discussed, but this would imply severe socio-economic consequences [12] unless

high value crops can be produced on a mass basis on rewetted environment.

3. Peat Degradation Processes

In the general term, degrading peat is the one undergoing accelerated subsidence due to land clearing and draining.

For the practical purpose, however, land cover with thin biomass density remote sensing images consisting of

peatshrub, bareland and grassland have been delineated using the geographical information system (GIS), and

classified as degraded peatlands [2, 5, 7, 8, 10]. What is considered as the degrading peat from the environmental

angle may be perceived as the productive land and the source of income by the producers because various lucrative

agricultural commodities may be produced on drained peatland. As the peat surface subsides, it loses functions as the

carbon storage [9] and hydrological control which stores water during the rainy season and releases it gradually

during the dry season, and the niche for peat specific fauna and flora [9, 13].

Subsidence is associted with peat compaction, consolidation and CO2 emissions caused by aerobic microbial

decomposition under drained condition and by peat fire. Subsidence normally happens as the peatland is converted

from the natural forest to economic uses involving land clearing, draining, and sometimes, burning. The higher the

rate of subsidence, the shorter the timespan of the use of peatland.

Subsidence depends on the peat type, the rate of decomposition, the density and thickness of peat layers, drainage

depth, climate, land use, and time since the peatland is converted from forest [3, 14, 15]. Total subsidence from these

several causes is indicated by the lowering of the peat surface. There are three main processes contributing to

subsidence, i.e. peat decomposition, peat consolidation and shrinkage, and peat fire.

3.1. Peat Decomposition

Draining of peat causes escalation of CO2 emission by aerobic bacteria [3, 10, 13]. Water saturation and too dry

condition lead to the low CO2 emission [16]. Likewise, neither saturation, nor too dry condition is ideal for most of

high value economic crops, implying a high CO2 emissions under agronomically favorable soil moisture content and

water table depth. Recommended water table depth for oil palm is between 50 and 70 cm [11] although in practice it

may reach 100 cm, especially during the dry period of the year. Within this range of water table depth, CO2

emissions from microbial decomposition increases with the water table depth [17].

Drösler et al. (2014) [9] seggragated drained-peat CO2 emission factors (EF) into different land cover types under

the Tier 1 (Table 1). As such, there are significant EF differences between lands covered by oil palm plantation, long

rotation plantation such as rubber, and short rotation land cover such as Acacia. However, studies in Sumatra,

Indonesia demonstrated no significant different emission rates from different land cover types. An oil palm

plantation, a secondary forest, an Acacia plantation, a rubber plantation, and a bareland as the land cover types in

Riau research sites did not emit different emission rates (Table 2). Rather, they were the sites, which were associated

with different climate and peat properties that lead to the variation of the emission levels [18, 19]. Water table depth

is the dominant determinant of CO2 emission from microbial decomposition [17] suggesting that where and

whenever possible, the drainage depth should be kept minimum. Furthermore, diurnal variation is also high while

most closed chamber measurements of CO2 emission are biased towards daytime measurement during which the

emission is relatively higher [20]. These shows that there are wide gaps of knowledge and lack of data of CO2

emission estimate for supporting to the more convincing Tier 2/Tier 3 EF of peat decomposition. Regionalized

research on CO2 emission covering a wide range of peat properties and climate variation as well as range of crops for

generating CO2 emission versus water table relationship will be needed.

Table 1. CO2 emission factor for Tier 1 (Mg CO2-C (ha yr) -1) for drained tropical organic soils [9]

Land cover class Emission

factor

95% Confidential Interval Number of

research

sites

Drained peat forest or peat shrub 5.3 -0.7 9.5 21

Long rotation plantation 15 10 21 t.t.

Short rotation plantation, such as Acacia 20 16 24 13

Oil palm plantation 11 5.6 17 10

Plantations with <0.3 m drainage 1.5 -2.3 5.4 5

Annual crops, bareland 14 6.6 26 10

Annual crop, paddy 9.4 -0.2 20 6

Grassland 9.6 4.5 17 n.a. n.a. = data not available

Table 2. Mean and Standard deviation (STD) of CO2 flux under different mean water table depth and mean soil temperature.

Land use Code Mean ± STD

CO2 flux

(Mg CO2 ha-1 year-

1)

Mean ± STD

WT (cm)

Mean ± STD

temperature (oC)

References

1 2 4 5 6 7

Oil Palm J-OP-6 38±2 54±22 27.1±1.3 [19]

J-OP-15 34±16 n/a 29.1±2.9 [19]

J-OP-14 45±25 n/a 26.7±1.7 [20]

R-OP-4a 66±25 72±37 30.6±2.7 [18]

Acacia R-Ac-3 59±19 81±24 28.6±1.0 [18] Secondary forest R-SF 61±25 81±25 27.3±2.5 [18] Rubber R-Rb-6 52±17 67±25 28.6±2.8 [18] Bareland R-BL-p 67±24 67±27 29.8±3.1 [18] R-BL-q 56±26 74±23 30±3.2 [18] R-BL-r 66±27 69±29 31±2.2 [18] In column 2, research sites J = Jambi and R = Riau; land uses OP= Oil Palm, Ac = Acacia plantation, SF = Secondary

forest, Rb = Rubber (Rb) and BL = Bareland; the numbers at the end of column 2 indicate plant age, where applicable.

STD = standard deviation; WT = water table depth.

3.2. Peat consolidation and shrinkage

Peat consolidation is a mechanical compression of saturated peat below the water table caused by the drawdown

of water table level that increases the overburden pressure of the overlying peat layer and increases pressure beneath

the water table. Peat shrinkage is the reduction of peat volume above water table. The shringkage rate is very rapid in

the first few years after the drainage begins and then slows down with time [14, 21]. Peat subsidence is often used

as a proxy for estimating peat emission from decomposition, with peat compaction (the sum of peat consolidation

and shrinkage) factorized in the total subsidence [21, 22]. We believe that the compaction/subsidence ratio should be

based on a carbon balance and subsidence monitoring, but most previous studies did not include sufficient direct

measurement of carbon balance, leading to a compromized certainty of emission estimate. Regionalized research on

peat subsidence, fully supported by peat carbon balance monitoring will be the key to improving the certainty of

emission factors.

3.3. Peat fire

Peat fire emission is perceived as one of the biggest sources of CO2 emissions. However, the uncertainty is high,

especially in relation to the activity data. Under the Tier 1 of IPCC (2014) [23], only burnt area is required as the

activity data. These data are normally generated from the hotspots which are based on the moderate resolution

imaging spectroradiometer (MODIS) (with 250, 500 or 1000 m pixel resolution) interpretation. However, not only

that the MODIS resolution is relatively low, but the hotspots are not always associated with peat fire, i.e. the fire that

actually reaches the peat soil. Therefore, assessment of peat fire area remains a source of uncertainty and require a

better support of advance remote sensing technologies.

Under controlled burning, IPCC (2014) [23] calculation of peat fire emission at Tier 1 is as high as 72 Mg C ha-1.

With about 570 Mg C ha-1 contained in 1 m layer of hemic maturity peat [11], such level of emission translates to

average burn scar of about 13 cm deep. In reality, the depths of peat burn scar varies tremendously from a fraction

to tens of cm. Under the Tier 2 and Tier 3 inventories, the area and the depth of peat burn scar must be known. High

vertical resolution maps (at least 5 cm resolution) demonstrating peat elevation prior to and after fire events will

improve the activity data certainty. Apart from the high resolution, the remote sensing technologies should resolve

tree canopy interference, and has to be cost effective so as not to bulge the transaction cost of carbon inventory.

4. Sustainable peat management

As explained in previous sections, in many cases, the management direction of development and conservation of

peatland are contradictory. Therefore, tradeoff in sustainably managing peat soil leading to minimizing the

degradation processes and optimizing the crop production must be implemented. There are at least four important

approaches for this tradeoff:

a. Avoiding deforestation.

In as much as possible, clearing of peat forest must be avoided. Developing of new agricultural areas should

only be concentrated on degraded peatland [10]. The 3.8 Mha of degraded peatland [2] is large enough to

keep the pace of agricultural development. Its conversion for production purpose will not only reduce the

pressure of encroachment to forest, but also leading to no or minimam additional CO2 emissions from the

biomass loss and peat decomposition relative to peat forest conversion [7].

b. Minimizing water table depth.

In general, the deeper the water table, the higher the rate of peat decomposition [17]. This is because of the

thicker (the larger volume) of oxidized peat layer in most time of the year under the deeper water table.

Therefore, water table depth needs to be adjusted as close to the peat soil surface as possible to a level that

does not cause a significant loss of crop productivity. Technology development for economically competitive

paludiculture system, i.e. production system under undrained condition, is needed to create disincentives for

drained agricultural systems.

c. Controlling peat fire.

There are enough country level regulations banning the use of fire in land management. Nevertheless,

peatland is notorious as a fire subscriber during the dry season because of haze hazards on human health [24]

and transportation as well as escalated greenhouse gases emissions. Therefore, enhancement of regulation

enforcement is a must. In addition, improved preparedness of fire control system such as through improved

forest fire brigade and improved community awareness and involvement in preventing forest fires are

essential [25].

d. Regulatory and incentive measures

Agricultural activities such as those for plantation and vegetable production becomes lucrative businesses

entailing high opportunity cost of peatland conservation [7, 26]. For example, the net present value (NPV)

from oil palm plantation (with assumed 25 year crop cycle and a 15% interest rate) ranged from USD 237 to

528 (ha yr)-1 and opportunity costs for conserving peat forest from conversion to oil palm plantation ranged

from USD 3.70 to 8.25 t-1 CO2e (Table 3). For smallholders, their small (<5ha) land area may be the only

resort for livelihood. Unless some kind of incentive is provided, there is little possibility for them to conserve

peat forest if it means losing the opportunity to generate income from peatland. For large plantations, there

are regulations limiting the expansion of agriculture on peatland. New concessions will not be issued for the

use of peatland for agriculture at least during the suspension period that will last until 2017. Considering the

high opportunity of reducing emissions on land that have been entitled to plantations, incentives in terms of

carbon credit and reforming the legal systems to allow land swap from the high to low C stock land should be

explored.

Management techniques for improving soil fertility on the naturally low fertility peat soils and by regulating the

water table are widely available. Besides the addition of macro nutrients N, P, K, Ca and Mg, micro nutrient

fertilization, especially for B, Zn, Cu is essential. Water tabel should be regulated in the range ideal for crop

production and at the same time causing minimal rate of decomposition and fire risk [6, 11].

Table 3. Opportunity costs of conserving peat forest from conversion to oil palm plantation under the nucleus estate and large plantation schemes with the assumption that mean greenhouse gas annual emission under oil palm plantation is 64 t

CO2 (ha yr)-1 and under forest is zero (from [26]) .

Plantation model/ Stakeholder Net present value (at 15% df)

USD (ha yr)-1

Opportunity cost

USD/t CO2e

Nucleus estate (NE) 310 4.84

Plasma farmer (smallholders in

association with plantation) 237 3.70

Nucleus 528 8.25

Large plantation 260 4.05 Assumptions: crude palm oil price was IDR 10,000 kg-1; palm kernel price was IDR 6,500 kg-1. df = discount factor.

5. Conclusions

The pressing need for agricultural expansion has led to the use of inherently infertile and environmentally crucial

land resource of peatland. The current land uses are dominated by high economic value and high market demand

crops that happen to be requiring drainage of this naturally wetland. Peatland is an important carbon and water

storage and the loss of these functions due to drainage has become a national and global concern. However there are

lack of certainty to support the inventory of carbon loss, especially of the activity data of peat fire and the emission

factor of water table depth versus emission relationship. This strongly suggest regionalized research on these aspects.

Technical, incentives and regulatory measures must be enhanced to make the best benefits of the use of peatland. So

far the implementation of regulatory and incentive measures is far more challenging than those of agronomic

technical measures. Furthermore, exploration of economically competitive crops under undrained system

(paludiculture) should also be prioritized.

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