Peatlands: A C a r b o n S i n k t h a t h a s S p r u n g a L e a k

Peatlands and bogs may not look like much on the surface, but they play a vital role in the storage of carbon worldwide. Carbon Dioxide (CO2) is a

greenhouse gas that is thought to be the main driver behind global climate change, causing warming and more frequent severe weather events. Carbon is

found in the atmosphere in the form of CO2 but is also locked away in the worlds oceans, plants, and underground (terrestrial). Peatlands specifically store 30% of the worlds terrestrial carbon globally- thats the same amount of carbon as one passenger taking 1,309 BILLION FLIGHTS across the Atlantic Ocean.

In the UK peatland is responsible for storing 5.5 billion tons of carbon. Soil in general is good at storing carbon, but peatland is unique in its composition. It

has a large layer of waterlogged organic matter, made up of decaying plants and animals.

Because of this composition, peatland absorbs

more carbon than it puts into the atmosphere

making it a carbon sink. Peat bogs are the

worlds most efficient carbon store on land.

Britain plays host to roughly 1.5 to 5 million

hectares of peatland. The variation in this

figure is due to differing definitions of peat

bogs depending on depth. These bogs are

found all over the UK- you may have already

visited one without realizing. The peatlands

are typically protected under the European

Union as special areas of conservation (SAC).

Some examples include Carrington Moss in

Greater Manchester, Migneint in Snowdonia,

Wales, and Red Moss of Netherley in

Aberdeenshire. See the map in figure 1 to

locate the peat bog nearest to you.

Organisms in the soil are constantly breaking

down the plant and animal matter in a process

known as decomposition. This is done by a

variety of life forms, from microbes to fungi to

earthworms. One thing these life forms have in common is that their activity is temperature dependent. In warmer temperatures, chemical reactions are

able to happen at a faster rate, which in turn allows for a higher rate of decomposition. You can put it simply as higher temperature leads to higher

activity in soil organisms. Water takes more energy to heat up than bare soil, meaning that the waterlogged peatlands are typically colder than

surrounding areas. The physical composition of peatlands means that they play host to huge amounts of standing water. The immobile nature of this

water means that it is poorly oxygenated. With limited oxygen (O2), decomposing organisms are not able to work as quickly, in the same way humans are

unable to function efficiently at high altitudes where O2 is reduced.

Why is slow decomposition relevant to the carbon storage potential of peatland?

The slow decomposition of plant and animal matter mean that the carbon stays locked up within

the peat rather than being released back into the atmosphere through the respiration of soil

organisms. In this way, the carbon is kept out of our atmosphere and unable to contribute

further to global climate change. Peatlands cover only 3% of the earths surface, and yet store

30% of the carbon- preserving them is in humankinds utmost interest, as their destruction could

lead to massive release of greenhouse gases. Physical destruction comes in many forms.

Commonly the bogs are drained and cleared out for agricultural use. The peat itself is harvested

and burned for fuel.

While physical destruction of peatland releases huge amounts of stored carbon into the

atmosphere, damage can be done without humans having to even touch the bogs. Due to the

increasing CO2 output from human sources, global temperatures are slowly rising. This rise in

temperature is not going unnoticed by the decomposers in peatlands- as things heat up, they are

beginning to become more active. Of course, this activity leads to higher rates of animal and

plant matter break down, meaning that what was once stored underground is released into the

atmosphere, adding to the vast amounts of CO2 already floating around. CO2 exacerbates global

warming. We start to see a cycle emerging- this cycle is called the Climate-Carbon cycle ( flow

chart, page 1).

As carbon dioxide increases in the atmosphere, carbon sinks will become carbon

producers, speeding up the process of global warming (Figure 1). This spells disaster for life as we

know it on earth.Figure 1: UK special areas of conservation (SAC). The grading system shows how valuable and unique each area is in regards to the quality of the natural habitat and what species are present. Grade A is the highest qualification, while grade D signifies that there are areas within the site which do not meet SAC standards.

In 2013 Susan Ward and her colleagues published the results of an

experiment which supported this theory. Small, open-topped,

greenhouse-like structures were built around plots of peatland in

order to simulate warming. They increased the temperatures by

roughly 1 degree Celsius compared to the plots without structures.

The results showed that ecosystem respiration was higher year

round in the artificially warmed areas of peat. This increase was

attributed to higher activity levels of decomposing microbes in the

soil, along with increased plant respiration. (Figure 2)

Peter Cox and colleagues in 2000 asserted that climate change models

did not take into account the sensitivity of soil carbon sinks to warming

events. He took the opportunity to produce new climate models that

showed the combined effects of the Climate- Carbon cycle on global

warming alongside human emissions (Refer to figure 1). The results

painted a grim picture, with temperatures estimated to be roughly 3 degrees higher

by 2100 than in normal climate models. The normal climate models only take into

account the impact of current vegetation on CO2 levels, as plants absorb CO2 in

photosynthesis. They assume the plant communities will be unchanged in the future.

This not only leaves out the effect of CO2 on soil carbon reservoirs, but also neglects

the idea that plant communities will change over time, and how this will impact the

amount of carbon that can be held in soil. Different types of plants sequester

different amounts of carbon, so a major change in a community could have a large

effect. As the earths climate shifts over the coming years, there is little doubt that

such changes will occur in many parts of the world.

Figure 3 Taken from Cox et al. 2000. This graph shows the predicted CO2 emissions in gigatons (Gt) that is expected when the effects of carbon dioxide on soil carbon reservoirs is taken into account. You can see that although the ocean continues to absorb carbon, in the future it is anticipated that the soil

carbon sinks will become producers, essentially cancelling out the mitigating

effect of the ocean on CO2 emissions.

Figure 2: Taken from Ward et al., 2013. This graph shows the amount of CO2 produced by non-warmed (white) and warmed (black) plots of peat, taking into account different plant community composition. Different plants absorb/release different amounts of carbon, so this is important to take into account. Even in the non-growing season, warmed plots give off more CO2 than non-warmed plots.

What can be done? Can anything be done?

First and foremost, the preservation

and restoration of peatland should be

the main priority. 80% of UK peatland is

considered to be in a bad state, due to

drainage or human interference. Peat is

sought after for many different

purposes (Peatrol? right). Destroying

these bogs releases huge amounts of

CO2 in one fell swoop, which could have

big consequences on the progression of

climate change. Restoring damaged

peatland could be achieved by blocking

the sources of water drains or raising

the water table. Hope also lies in

increasing the amount of carbon stored

in other soils, specifically those involved

in agriculture. Soils with high carbon

content tend to play host to microbes

who help the growth of plants by

providing Nitrogen, which is a nutrient

that can limit growth if its not plentiful.

Agriculture is a major force behind CO2 emissions, between the heavy

machinery and constantly turning up

soil (releasing all of that stored carbon). More efficient practices could not only reduce global levels of CO2 but increase crop yields and secure the

continued health of soils which the human race depends on for food. By generally decreasing CO2 emissions worldwide and looking for alternative fuel

sources, warming events could be slowed down and eventually avoided, which will allow the peatland to continue acting as sinks for whatever extra we do

produce.

=

Discussion points

While peatland absorbs large amounts of CO2, it also releases a much more powerful greenhouse gas, Methane. Some scientists claim that the absorption

of CO2 is enough to counteract this- do you agree?

What other purposes do peatland serve from a biological perspective?

What are some common agricultural practices that might impact soils ability to store carbon?

What are examples of other carbon sinks? Will warming affect these as well?