C308

Change in Rainfall Pattern due to Climate Change and Its Influence to the Tropical Peat Fire Risks〇Eva YAMAMOTO, Takahiro SAYAMA, Kodai YAMAMOTO

Introduction

to climate change, primarily driven by rising

In recent decades, Indonesian tropical peatlands havetemperatures, our research suggests that changes ingained attention due to frequent fires. Found mostly inrainfall patterns are equally important contributors tolowlands, these areas are seen as having economic

the heightened fire risks.

potential. That's why converting tropical peatland

Methodforests into agricultural lands, like oil palms and acacia

In this study, we employed the MRI-CGCM NEX-plantations, was unavoidable. Unfortunately, these

GDDP-CMIP5 datasets (historical, RCP 4.5, and RCPchanges involve draining peat water through canals,

8.5) along with the modified Keetch-Byram Drought

making the peatlands more susceptible to the risk ofIndex (KBDI) as described by Taufik et al. (2015). Our

fires.

aim was to assess the impact of future changes inrainfall patterns and increasing temperatures on firerisks.
To analyze the contribution of each variable to therisk of fire, we assumed a constant temperature withineach scenario—32°C for the historical period, 33.5°C
for future RCP 4.5, and 35°C for future RCP 8.5. As
temperatures rise, the conditions for high fire risk canoccur with a decreased number of consecutive dry days(CDD), specifically 60 days for the historical scenario,

No. major fire events in

10 years (moving window)

10Hist.

RCP4.550 days for RCP 4.5, and 45 days for RCP 8.5 (Figure2). The study utilized these CDD thresholds to assess

5how the frequency of fires changes based on rainfall
patterns, temperature, and their combination.

01950

2000

2050

2100

Figure 1. Area and frequency of fires increases

Our earlier research indicated that the Keetch-Byram
Drought Index (KBDI) accurately reflects fire risks intropical peatlands. By utilizing the NEX-GDDPCMIP5 MRI CGCM datasets in KBDI, we found thatthe frequency and extent of high fire risks are projected
to rise in tropical peatlands in the future (Figure 1).
While many studies attribute the increase in wildfires

Figure 2. Shorter CDD causes fire risk at higher temperature

Figure 3. Impact of change in rainfall pattern and temperature to distribution of fire frequency

Results and Discussions

historical rainfall pattern, fire risks could still happen

In the future, we expect more consecutive dry days

up to 4 times per decade. However, with the RCP 8.5

each year, and this increase will vary more in RCP 8.5

rainfall pattern, the temperature increase could raise thecompared to RCP 4.5.

frequency of fires to 7 times in a decade.

The way dry days are distributed also changes inConclusions

different scenarios, as shown in Figure 3. In theIn summary, our study indicates that, if there is no

historical period, dry days are relatively short, andincrease in daily maximum temperature (equal tooccurrences of days longer than 60 CDD are rare. Somehistorical scenario), we can expect a major fire event

areas have never experienced such long droughts.

roughly once every decade, regardless of theHowever, in future scenarios, these extended dry

concurrent rainfall pattern. However, with the future

periods happen more often — up to 3 times in RCP 4.5

rainfall patterns, particularly RCP 8.5, there are

and 5 times in RCP 8.5.

occurrences of frequent but relatively smaller fire

As temperatures rise in the future, the conditions forevents in particular areas.

high fire risk can happen with fewer consecutive dry

As temperature rises, the rainfall pattern createdays. For example, with a 1.5°C temperature increasesignificant difference in distribution of fire event. The(RCP 4.5), high fire risk would occur with 50 CDD

historical rainfall pattern still show one major fire event

instead of the historical 60 CDD. If we look at thein a decade but the RCP 8.5 rainfall pattern show that

historical rainfall pattern, fire risks might increase up tosome areas will be on fire every other year.

3 times per decade, but with the RCP 4.5 rainfall pattern,References

fire risks could increase up to 4 times. If theTaufik et al. (2015), Modification of a fire droughttemperature increases by 3°C (RCP 8.5), high fire risk

index for tropical wetland ecosystems by including

can occur with 45 consecutive dry days. In thewater table depth, Agr. and Forest Meteo.,203,1-10pp.