University of Tartu researchers received €3.5 million research grant to study the formation, cycle and effect of laughing gas emitted from peat soils, and its links to climate change.
Laughing gas is one of the most dangerous greenhouse gases produced by microbial life in the soils of agricultural areas and drained peatlands.
Ülo Mander, professor of physical geography and landscape ecology at the University of Tartu, received the advanced grant from the European Research Council to study the cycle of nitrous oxide (N2O), commonly known as the laughing gas, in fens and peatlands.
Laughing gas is linked to global climate change and possible land-use practices that could help curb the production of this greenhouse gas in the future.
When laughing gas reaches the stratosphere, it destroys the ozone layer that protects the Earth from UV radiation. It is estimated to account for 6 percent of the greenhouse gas impact on climate.
This share is increasing due to changes in land use and the effects of the increasing use of fertilizers in agriculture, which has a long-term impact on the planet and humanity. However, very little is known about its formation, cycle and processes of impact.
Ülo Mander and his research team at the Institute of Ecology and Earth Sciences have, for many years, studied the formation and binding of the laughing gas in the fens and drained peatlands of Estonia and the world.
The recently funded five-year research project will look into the cycle of laughing gas in three tropical wetland areas that, based on monitoring data, are N2O emissions hotspots:
- In the northern part of Borneo Island in Malaysia, where was a massive drainage of swamps for oil palm plantations a few decades ago.
- In the Amazon lowlands in Peru, Mander and his colleagues have already investigated both natural palm swamps and self-reforestation on former agricultural land.
- The nitrogen cycle in the Congo Basin, the world's largest area of tropical swamps, where the nitrogen cycle has not yet been studied in detail by scientists.
"There was a massive drainage of wetlands in Borneo a few decades ago to create oil palm plantations. As palm trees grow on peatland, which in turn is fertilized with nitrogen fertilizers, the world's highest laughing gas emissions are currently measured there. In the research area in Peru, we have previously investigated the processes in natural palm swamps and areas of self-forested former agricultural land. It is an area where rapid forest growth helps to offset N2O emissions and gives hope that recovery is possible," Mander explained the choice of sites for the project.
As peatlands cover 3 to 4 percent of the land surface but store a third of all the carbon and nearly a fifth of all the nitrogen on Earth, they are critical ecosystems on the global scale.
In addition to measuring the N2O emissions from peat soils, the researchers are also interested in the role that tree trunks and crowns of peatland forests play in the cycle of the gas.
The measurement devices in Borneo and Peru will be placed above tree crowns to study it. "We want to investigate what is happening in the tropical trees' foliage that is rich in various algae, mosses, lichens and microbes and can capture some of the gases from the air and produce certain greenhouse gases to the atmosphere," Mander said.
Incorporating the obtained data into existing models will also enable the researchers to assess the effects of climate change on the nitrogen cycle, predict emission peaks, propose improvements to the data underlying the International Panel on Climate Change (IPCC) reports, and adjust land-use strategies and future scenarios based on them.
According to Mander, these strategies have so far been based primarily on the climate impacts of human-induced land use, but climate change has also had a significant effect on the cycles in natural ecosystems, which the current study addresses.
Natural ecosystems are now increasingly emitting dangerous greenhouse gases, and fossil fuels no longer the primary cause of this increase
Fossil fuels are no longer the driver of continued climate warming, but changes in land use and the changes in natural ecosystems are. The amount of carbon dioxide (CO2), the most important anthropogenic greenhouse gas, is steadily increasing in the Earth's atmosphere, despite the constraints on burning fossil fuels.
However, limiting the use of fossil fuels is still necessary to improve the environment, but tackling greenhouse gas emissions requires looking at natural and man-made ecosystems.
In recent years, evidence has emerged that natural ecosystems are increasingly emitting dangerous greenhouse gases other than CO2: methane (CH4) and nitrous oxide (N2O), which are 28 and 273 times more powerful greenhouse gases than CO2, respectively.
On the one hand, this suggests that most terrestrial ecosystems are already affected by climate change and have become a source of greenhouse gases. On the other hand, it also implies an increase in the role of non-human-impacted natural areas in the overall climate warming process.
Peatlands store huge amounts of carbon
The best example of such human-impacted ecosystems are peatlands and other wetland ecosystems. Peatlands cover only about 3 to 4 percent of the land, but they story a third of the organic carbon or about three trillion tons, and nearly ten percent of nitrogen.
Natural peatlands are generally weak CO2 sinks because peat growth is slow and carbon accumulation takes thousands of years. Natural peatlands sequester nitrous oxide, but when drained, peat decomposes rapidly, releasing large amounts of CO2 and N2O.
A rough estimate is that around 10 percent of the world's peatlands are being lost to drainage or peat production. This does not take into account the impact of disturbance due to changes in water regime, drainage or increasing droughts, which increases the appearances of disturbed peatlands to nearly 50 percent.
According to in-depth studies, 46 percent of Europe's peatlands are disturbed or degraded and are destined to disappear unless restoration measures are taken.
Recently published research by Estonian scientists on the microorganisms involved in the nitrogen cycle of the world's peatlands shows that almost all of the peatlands studied, including natural peatlands, have suffered from drought at one time or another.
In a dry peatland, the water level drops and the upper peat layer becomes oxygen-rich. This enhances both the decomposition of organic matter and the release of laughing gas. So droughts are likely to be responsible for the draining of the majority of natural peatlands. The remainder of the world's wetland ecosystems are also threatened for the same reasons.
Restoring peatlands and grasslands will take decades
Conservation measures alone are not enough to halt the further loss of peatlands, and restoration is becoming increasingly important. This work is being undertaken on a large scale in Europe, North America and South-East Asia.
Under the European Union's (EU) Framework Programme for Research and Innovation (FP7) 'European Horizon', a number of basic and applied research projects aimed at sustainable peatland restoration have just started.
However, recovery is a very time-consuming process: if we want to restore former mires and fens, it can take decades before the peat-forming vegetation reaches stable growth and starts to produce peat.
A quicker method is to grow swamp crops, which at least stops the decomposition of the peat and can slowly build up new peat.
Restoring peatland forests is another viable option. However, forestry restoration of peatlands, one of the prerequisites of which is the continuation of drainage, does ensure successful tree growth and fast economic returns, and peat formation is essentially halted under these conditions.
In restored peatland forests, where water levels are kept high, long-term peat preservation and re-growth is possible, but the forestry benefits are almost non-existent.
In short, only restoring water levels will help to restore peatlands, both in the northern hemisphere, where most of the world's peatlands are located, and in the southern hemisphere.
In temperate zones, peat bogs may disappear
In recent months, forest managers and restorationists in the EU have vigorously debated traditional afforestation and restoration of mires. It has also halted EU legislative decisions regarding the restoration of ecosystems.
One of the arguments put forward by the forestry industry is the data collected over the past few years, which is based on a short-term balance of CO2 exchanges between the atmosphere and terrestrial ecosystems that was measured using very accurate techniques. These results indicate that forests planted on restored peatlands can also sequester carbon over the short term. However, the data span is insufficient to make an assessment regarding long-term carbon sequestration in these peat soils.
The peat eventually mineralizes and is initially supplanted by an organic-rich mineral soil where the forest can grow well and store carbon for a long time. However, this forest no longer grows on peat, but on mineral soil with a reduced carbon content. With each new cycle, the mineralisation of peat intensifies.
Large peatlands in Western and Central Europe and North America have been deforested over time, and if this trend continues, peatlands across temperate zones could disappear altogether.
In the tropics, the reforestation of fields and plantations replacing former swamp forests may be more successful, because the peat there is formed from trees and the peat formation process is faster.
Peatland restoration in rainforests
The sustainable restoration of wetlands is important not only to regulate carbon and nitrogen balances, but also to maintain biodiversity.
That is why in recent years the researchers were also interested in the rest of the world's peatlands, especially tropical peatlands, which are the main sources (hotspots) of greenhouse gases on Earth.
Within the framework of the EU Twinning action, the project "LiWeFor" (led by Ülo Mander) has been initiated, which, in addition to researchers from the University of Tartu, the University of Helsinki and the Karlsruhe Institute of Technology, also involves researchers from the Peruvian Amazon Research Institute, the Peruvian National University of the Amazon and the Sarawak Tropical Forest Research Institute in Malaysia.
The broader aim of the project is to create a global network of laboratories for peatland forest research, involving not only scientists but also the local community.
In peatlands, as in the majority of terrestrial ecosystems impacted by humans, it is extremely hard to limit greenhouse gas emissions. Changing the hydrological regime to restore peatlands is feasible, albeit at a high price, but mitigating the impacts of intensifying droughts is also incredibly difficult.
A more realistic approach would be to implement an adaptation strategy that would contribute to rebalancing the greenhouse gas balance of terrestrial ecosystems and reducing CO2 emissions, even if this entails accepting peat mineralization, making the afforestation of peatlands an optimal solution.
In the tropics, the potential for peatland restoration is almost unexplored, but in theory it could be successful.
Finally, there is a small glimmer of hope based on speculation: the reforestation of vast tundra regions caused by climate change could accelerate and, on a global scale, replace or supplement disappearing peatlands.
However, there is one factor we cannot overcome: the length of time required for peatlands to recover. The short-term perspective of a few decades to a century must be supplemented by a longer-term strategy.
The grant received from the European Research Council is nearly €3.5 million. The grant is intended for leading top scientists who have achieved outstanding research results over the last ten years.
Editor: Jaan-Juhan Oidermaa, Kristina Kersa