Within this post we are going to discuss the feedbacks mechanisms associated with environmental change in the Tropical Peatland of Borneo, Indonesia. Changes in land management practises and climate forcing have both been found to impact Carbon flux from the system and exacerbate the impacts of each other individually.
From the 1970s deforestation and drainage have
expanded on a national scale exerting a persistent environmental change on the
peatland which has threatened the balance of the systems and made them more
susceptible to fire (Page
et al. 2002).
These management practises were originally
associated with indigenous and small immigrant farming communities within the
swamp forests, involving small scale forest clearances. In recent decades these
practises have expanded, with private corporations and government agencies
clearing large expanses of land for lucrative agri-business such as palm-oil
and pulpwood plantations as well as food crops (Page et al. 2002, Murdiyarso et
al. 2010). These activities have enhanced carbon releases to the atmosphere,
but have also increased the vulnerability of the systems to fire, which accelerates
peatland degradation and carbon output (Takashi et al. 2007).
Takashi
et al. (2007) studied a region of Indonesian Borneo called the Central
Kalimantan (Figure 1), over a three year period and sort to understand the
carbon dioxide flux. The site has been subject to drainage and subsequently
depressed groundwater levels. The study found that peat decomposition
associated with the lowering of the water table was the primary cause of large
volumes of Carbon dioxide release.
Figure 1: Central Kalimantan region
highlighted in green within the Indonesian Borneo.
(http://en.wikipedia.org/wiki/File:IndonesiaCentralKalimantan.png)
However, in addition to this an increased
susceptibility to fire has proven important in carbon flux. In 1997 fires that
were used for forest clearances grew out of control due to the drought
conditions brought on by an ENSO (El Nino- Southern Oscillation) event that
year and spread beyond their intended bounds causing widespread destruction
across the region.
The relationship between land management, climate
and subsequent extensive forest fires has been witnessed not only in 1997, but also
2002 (Takashi et al. 2007) and sparks significant interest not only due the
disruptive impacts on the infrastructure and economy of Indonesia, but also the
large and rapid outputs of Carbon Dioxide from the peatland systems into the
atmosphere. Page et al. (2002) used satellite images of a 2.5million hectare
region within the same site as Takashi et al. (2002); Central Kalimantan,
Borneo, to inform wider estimations of carbon output for the whole of
Indonesia.
Within the region it was estimated that 32% of
the land was burned in the 1997 fires and within that 91.5% was peatland. By
applying data from ground measurements for the burn depth into the peat
substrate and vegetation burn it was estimated that 0.19-0.23 gigatonnes of
carbon was released from peat burn and a further 0.05GT from the vegetation
(Page et al. 2002). If these values are then extrapolated to account for the
tropical peatland surface area of Indonesia, the 0.81-0.57 gigatonnes produced,
totalled to the equivalent of 13-40% of the mean annual global emissions of
fossil fuels in 1997(Page et al. 2002).
In conclusion the carbon flux of tropical
peatlands in Borneo has been seriously impacted by land management practises
and the impact of these in conjunction with ENSO drought events. The events
seen in 1997 and over the 3 year study period of Takashi et al. (2007) show
that the systems are currently contributing globally significant volumes of
carbon dioxide to the atmosphere both in the long term and as rapid events. These occurrences of peatland degradation and carbon
output are not unique in the context of tropical peatlands and are of
importance as development continues within these regions of the world and
future predictions of global climate in relation to climate change for see an
increase in the frequency of ENSO events (Timmerman
et al. 1999) and other climate modes. There is the potential for
significant positive feedback loops to engage and further exacerbate climate
change.
Cheers
Matt
References:
Page,S.E., F, Siegert., J, O’Rieley., H-D.V,
Boehm., A, Jaya., S, Limin. 2002. The amount of carbon
released from peat and forest fires in Indonesia
during 1997. Nature, vol. 420, p 61-65.
Murdiyarso, D., K,Hergoualc’h., L.V, Verchot.
2010. Opportunities for reducing greenhouse gas emissions in tropical
peatlands. PNAS, vol. 107, p19655-19660.
Takashi,H., H, Segah., T, Harada., S, Limin., T,
June., R, Hirata., M, Osaki. 2007. Carbon dioxide balance of a tropical peat
swamp forest in Kalimantan, Indonesia. Global Change Biology, vol. 13,
p412-425.
Timmeremann, A., J, Oberhuber., A, Bacher., M ,
Esch., M, Latif., E, Roeckner., 1999. Increased El Nino frequency in climate
model forced by future greenhouse warming. Nature, vol. 398, p694-697.
