Jan. 12, 2017 @ GEOSS Asia-Pacific Symposium, TokyoGHGｓ emissions from tropical peatlands
through wildfires and land-use change

Takashi Hirano(Hokkaido University, Japan)

Outlines
1. What is peat or tropical peat?
2. Current conditions of tropical peat
(under severe human pressures)
3. GHGs emission from tropical peatlands

What is peat?
 Peat is an accumulation of partially decayed vegetation matteror histosol (a soil consisting primarily of organic materials).
 Peat is distributed in about 4 million km2, which accounts for 23% of world land area.
 Carbon stored as soil organic matter in peat is estimated at 600700 Gt, which accounts for about 25% of world soil carbon(Turetsky et al., 2014).
9 t = 1015 g = 1 Pg
1Gt=10⇒ Huge carbon pool
Fuel

Peat stack in Scotland

Distribution of peat

(GACGC, 2000)
Page et al. 2004

Tropical peat

Cool climate → More than 80% of peat is distributed in highlatitudes in the northern hemisphereTropical peatland in SE Asia
 In SE Asia, pealtlands are widely distributed in the area of about 250,000

km2 and store 68.5 Gt of soil carbon, which accounts for 11-14% of global
peat carbon (Page et al., 2011).
 Although the tropical petalands naturally coexist with swamp forest, thepeatlands have been devastated by logging and land development since the1970’s, and 20% of peat swamp forest has been deforested and mostly
drained during the last decade (Miettinen et al., 2011).
 The risk of large-scale fires increases with disturbance, because such
disturbances typically dry peat and leave much plant debris, which are
flammable (Page et al., 2002), especially in El Niño years.
Peat swamp forest

Distribution of tropical peatlands in SE Asia (Page et al., 2004)
5

Land-use change in tropical peatlands
Originally, swamp forest

Deforestation

LoggingIndustrial plantation
Oil palm
Land clearing High water table High-density C pool

Drainage

DryingPulp woodHighfire risk

Peat fires（C emissions）

Peat oxidation（C emissions）

 Tropical peatland is a global hot spot of C sources in thiscentury （Global Carbon Project)6

Land-use change emissions
Emissions in the 2000s were lower than earlier decades, but highly uncertain
Higher emissions in 2015 are linked to increased fires during dry El Niño conditions in Asia

IndonesianfiresIndonesian
fires

Three different estimation methods have been used, indicated here by different shades of grey
Land-use change also emits CH4 and N2O which are not shown hereSource: Houghton et al 2012; Giglio et al 2013; Le Quéré et al 2016; Global Carbon Budget 2016

Large-scale disturbance: Mega Rice Project (MRP)

A large-scale national project (MRP) was implemented to develop
paddy fields in tropical petlands in Central Kalimantan, Indonesia.
Through the project, large area was deforested and long canal(drainage) was excavated (4500 km).
However, the project was abandoned in 1999 mainly by theEconomic Crisis, leaving a vast devastated petlands.
Drying & plant debris increased the risk of large-scale peat fires.
Lowering of groundwater level enhanced oxidative peat
decomposition.

Area of MRP: 17000 km2

Devastated area

Large canal system

Prolonged dry season due to ENSO

0.0

-101201 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16

GWL-0.5-1.0

UFDFDB-1.5

Solar radiation(MJ m-2 d-1)

Groundwater level(m)600500400300200100001 02 03 04 05 06 07 08 09 10 11 12 13 14 15 162016128Solarradiation
01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16Monthly values from 2001 to 2016

3SST anomaly (°C)

Precipitation, groundwater level (GWL) and solar radiation along with SSTanomaly (Nino 3.4) at Palangkaraya, Central Kalimantan, Indonesia
700 Rain & SST-2

Precipitation(mm month-1)

SST rise (El Niño)⇒ Prolonged dry season⇒ GWL lowering⇒ Large-scale peat fires⇒ Dense smoke⇒ Solar radiation attenuation

Triggers of peat fires
1. By accident (cigarettes etc.)
2. For land clearing (plant debris and re-growth vegetation)
3. Agricultural practice by small farmers, including asserting land
tenure rights
Onset of the rainy season →under control within farmland

Fires for weeding andnatural fertilization
Late dry season

Normalyears

El Niño years
Large fire scars

Prolonged dry season →out of control

Peat burning (flaming and smouldering) Peat is burnt by flaming and smouldering.
 Flaming is burning aboveground with flame.
 Smourldering is burning underground in the conditions of lower

temperature, lower O2 and higher moisture.
 Smourldering is the main process of peat burning.
 Smouldering continues for long time and is difficult to extinguish.
 Through smouldering, some harmful pollutants are emitted (PM, VOCetc.)

Environmental problems due to fires other than C
 Transboundary issue
 Serious economic impacts (traffic problems, business income lossetc.)
 Human health problems: additional deaths > 10000 persons/year dueto PM2.5 and O3 (Marlier et al., 2012)
 It’s very difficult to extinguish peat fires. ‘Focus on fire prevention
rather than fire fighting with a recognition that the haze problems
dose not disappear until the onset of the rainy season (Page &Hooijer, 2016).’

Carbon balance on ecosystem scales Comparison of net ecosystem CO2 exchange (NEE) in three peatswamp forests with different disturbances

Undrained (UF)Annual net CO2 emissions (4 yrs from 2004 to 2008)
NEE (gC m-2 y-1)

600
500

NEE

Flux tower

400

Drained (DF)

300
200
100
0-100

UFDFDBBurnt (DB) Net CO2 emission: DB > DF > UF
 NEE > 0 even in the UF site, partly becauseof the shading by dense smoke
Hirano et al., 2012

Oxidative peat decomposition (chamber method)
Oxidative peat decomposition is controlled by groundwater level.
Rubber plantation on peat

Burnt peatland (DB)-1

8-2
Soil CO2 efflux (g C m d )Soil CO2 efflux (gC m-2 d -1)

64
20-1.0 -0.8 -0.6 -0.4 -0.2 0.0 0.2
Groundwater level (m)108Drainage

6r2 = 0.99

4Low GWL20-2.0

-1.5

-1.0

-0.50.0

GWL (m)Peat oxidation

CO2 emissions

Hirano et al., 2014

Wakhid et al., 2017

Carbon emissions through peat fires (Bottom-up)
Bottom up approach

Lfire = A ⋅ MB ⋅ Cf ⋅ Gef (IPCC, 2013)
Lfire: C emissions, A: Burnt area, MB: Mass of fuel available forcombustion, Cf: Combustion factor, Gef: Emission factor

or Lfire = A ⋅ D ⋅ BD ⋅ CC
D: Burnt depth, BD: Peat bulk density, CC: Peat carbon content
Peat fire in 2006 in C. Kalimantan (Ballhorn et al., 2009) A: Satellite data
 D: Airborne LiDAR BD, CC: Field data

Mean D = 33 cm

Carbon emissions through peat fires (Top-down) Carbon emissions from fires in 2015 (Huijnen et al., 2016)


Atmospheric carbon monoxide (CO), model & data assimilation
Ratio of emission factors (CO2/CO and CH4/CO)
Carbon emissions
 Carbon emissions: 0.289 GtC (CO283%, CO 16%, CH4 1%)
CO CH N O
1.01000 100
 Smaller than that in 1997 (0.87 GtC,COCH
Page et al. (2002, bottom up))NO
 Smaller burnt area: 0.8 Mha vs. 1.7
500.5500
MhaConcentration (ppm)4242n = 24000.001000

2000

3000

CO2 concentration (ppm)

CO2 : CO : CH4 = 1.0 : 0.38 : 0.026(Hamada et al., 2011)(Huijnen et al.,2016)

Carbon emissions through peat fires (GFED)
 Carbon emissions from fires in 2015 (Global Fire Emissions

Database: GFED, http://www.globalfiredata.org/index.html)

 Carbon emissions (until 16 Nov.): 0.48 GtC
 Greater than that (0.289 GtC) of Huijnen et al. (2006)

Summary and conclusions
 Under the human pressures of land-use change and fires,

tropical peatlands, a huge carbon (C) pool, have become
vulnerable.
 On average for decades, annual C emissions from SE Asia’s

peatlands through peat mineralization and burning were
estimated to be equal at about 0.1 GtC yr-1 (Page & Hooijer,2016). At around 0.2 GtC yr-1, this efflux equals the annual Cemissions from Indonesia and Malaysia arising from fossil
fuel burning and cement production.
 Oxidative peat decomposition mainly depends on

groundwater level.
 Uncertainties both in the bottom-up and top-down approaches

are still high for assessing C emission through peat burning.