This blog post has less to do with oceans and more to do
with the climate. I found it to be an interesting topic after I had some work
experience two summers ago back home in Malaysia. My three-week stint required
me to travel across the sea to Sarawak, one of the two Malaysian states on the
Island of Borneo to work in a palm oil plantation. The palm oil industry is
inevitably of high economic importance to countries like Malaysia and
Indonesia, being the two largest producers of palm oil in the world. While palm
oil production itself has certain controversies of its own, I will attempt to
reason with an important factor in agriculture – the soil.
To put simply, as the agricultural industry in Malaysia
grew, the availability of fertile mineral soil declined. The use of tropical
peatlands, which happens to be quite abundant in states like Sarawak, proved to
be quite successful. However, eyebrows were raised due to concerns about CO2
emissions from the soil, and parallels were being drawn to temperate peat soil.
This prompted the launch of numerous studies to evaluate the amount of
greenhouse gases (GHGs) released from the various types of tropical peat soils.
One of these studies was being conducted at the palm oil plantation that I was sent
to.
I worked and helped out with data collection, literally
lodging gas chambers on top of gas collars in different plots throughout the
plantation every day. These gas chambers were connected to these machines that operated
on electronic gas measurement (EGM) data. Soil moisture and temperature were
also measured using digital devices, along with the pressure and depth of the
groundwater using a piezometer. It was physically tough having to cross over
streams with logs as bridges, praying that I would not fall in and embarrass myself,
or more importantly destroy the machinery that each of us was assigned to carry
around. I also managed to familiarise myself with how easily compressible peat
is, having plunged thigh-deep into the soil on my second day. Feeling the
entire ground shake whenever one of those load-carrying trucks drove by simply
reinforced this characteristic as well.
I only contributed a minute proportion to the entire study; however,
I was made aware that the parallels drawn between tropical and temperate peat
soil are still being called into question. Do tropical and temperate peat soil
have the same properties when in comes to CO2 emissions? Is it
reasonable to make deductions based on what has been investigated on temperate
peat soil?
As we know, peat soil comprises of a lot of partially
decayed organic matter, which inevitably labels peat soil as a carbon sink. The
main argument is that CO2 emissions from tropical peat soil will
differ from that of temperate peat soil simply due to the different types of
organic matter contained in each soil type. Research conducted on tropical peat
soil is not as vast and widespread compared to what has been done on temperate
peat soil, so many think this method of comparison is unjust.
Here are some points put forward to illustrate a possible disparity
in GHG emissions from these two types of soils:
1.
It is stated that the majority of drained
tropical peat soil in Southeast Asia are sapric, which means that the organic
matter in the soil is quite highly decomposed. This could correlate with the
amount of CO2 emissions being relatively lower since not much
further decomposition would occur when the peat is drained.
2.
Soil subsidence plays a role in the release of
CO2. Stephens
(1984) states that the type of peat soil, water table depth and temperature
of the soil affect soil subsidence. These are factors that vary with different
regions and climate conditions.
3.
While moss may be a common contributor to
organic matter in temperate peat soil, tropical peat soil consists of more
woody material from peat forests and swamps. This woody material may not
decompose quite as easily when tropical peat is drained, and hence may not
necessarily emit the predicted, extrapolated value of GHGs.
4.
The amount of release of GHGs are linked to the
depth of the drainage of peat soil. In plantations such as oil palm, the roots
are said to occupy approximately a 50cm depth of the tropical peat soil.
These are the components being evaluated with greater
scrutiny. The reality of it all is surely more complex. For instance, a study
by Furukawa
et al. done in Indonesia state that groundwater levels are inversely
related to CO2 emissions but positively affects CH4
emissions. Does that mean while less CO2 is being released, more CH4
is emitted?
While there is so much to be taken into account before
drawing conclusions, economic and social aspects of a certain country come into
play. Page
et al. (2011) give figures that show how ample tropical peatlands are in
Southeast Asia in terms of area and volume, claiming 56% and 77% of all tropical peat respectively. Many of these
countries would naturally have the desire to continue with fruitful extraction
of these lands; therefore, evaluation of means of sustainable usage should
become more vital.
Here is the link to a paper published by Hooijer et al. in
2010 regarding CO2 emissions from tropical peatlands in Southeast
Asia:
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