Peat en peatlands

Peat is humified plant material in the soil. It is formed from dead plant remains that have been preserved under wet conditions with little oxygen.

In the Netherlands, we find peat in the peat meadow areas in the Northern and Western Netherlands, in the stream valleys of the sandy soils, and as raised bog in several Natura 2000 areas. In the past, there was more peat. Much of it has disappeared due to excavation and drainage.

When peat soil is drained, it settles and shrinks, and is broken down by microorganisms. This is called 'oxidation'. As a result, the soil level drops.  

Greenhouse gas emissions from peat soils constitute 2 to 3% of the total emissions in the Netherlands.

Due to higher air and soil temperatures and prolonged periods of drought, the peat oxidation process can accelerate. 

Peat soil is composed of humified plant material. This wet, spongy material is formed by dead plants and is preserved because it is saturated with water. There are different types of peat, depending on the location relative to the groundwater, the plant species, and the nutrient richness of the water in the peat. The thickness of the peat varies from a few meters to a few decimeters, and sometimes the peat is covered by a layer of clay. There are also areas where the peat has largely been excavated. 

Peat is dynamic: when it is wetted, it swells; when it dries out, it shrinks. As a result, the ground level can vary up to a decimeter in height throughout the year. If there is too much drainage, the peat oxidizes, and a permanent drop in the ground level occurs. 

Wageningen University & Research creates maps showing where different types of peat occur. We research soil processes, hydrological functioning, and the dynamics of peat soils. 

During the reclamation of peatlands, the groundwater level is lowered. The peat begins to settle, shrink, and is broken down by microorganisms (oxidation). As a result, the soil subsides. The strongest soil subsidence occurred in the 20th century due to more efficient drainage, which was necessary to make peat areas suitable for agriculture. 

The breakdown of peat releases greenhouse gases (carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O)). Water boards now have policies to prevent further lowering of groundwater levels, but the processes of breakdown and soil subsidence continue today. These greenhouse gases contribute to atmospheric warming. Soil subsidence poses a risk of flooding and can cause damage to buildings, roads, cables, and pipes. Water management becomes more complex and expensive. 

To reduce greenhouse gas emissions and counteract soil subsidence, we want to know how these processes work. This requires measurements and models. Wageningen University & Research works on this through various field experiments and model studies. 

If we want to preserve peat and counteract greenhouse gas emissions, we must ensure that the peat does not oxidize further and is therefore not exposed to the air. This can do this by raising the groundwater level in the peat, or by excavating peat layers or covering them with clay layers. These interventions can have a major impact on land use, the landscape, nature, and the availability of fresh water. How do we ensure that water reaches every part of a peat area? Where do we get that water from? 

Raising the groundwater level in peat can, conversely, cause emissions of nitrous oxide and methane. Where and when does this happen, and how high can you raise the groundwater level without these kinds of undesirable side effects? 

A more integrated and area-based approach to peatlands is therefore necessary to properly weigh land-use desires. Peatlands host important natural areas such as raised bogs, stream valleys, wetlands, and marshes. For these areas, methods are being sought to preserve or restore natural values: for example, by (re)wetting areas and allowing the peat to grow again. They can then also serve as carbon storage sites. 

Wageningen University & Research is a partner in research projects working on peat conservation in agricultural and natural areas. With experiments and model studies, Wageningen scientists gather insight into the effects of measures in the peatlands. Model studies indicate what happens when we apply measures on a large scale. 

Peatlands can be a habitat for a wide variety of plant and animal species, and thus a source of biodiversity. In peatlands that were drained and excavated in the past, peat-forming vegetation can be restored. This can also be done in stream valleys. This also helps to retain water. 

Wet peat meadow areas are an important habitat for meadow birds. Populations of meadow birds have been declining for decades. Large-scale wetting of peat meadow areas offers opportunities for developing suitable habitat for meadow birds. Meadow birds do need grassland, so agricultural management must be carefully designed. 

Wageningen University & Research investigates the development of ecosystems in peatlands and possibilities for the restoration of wet natural areas, peat marshes, and stream valleys. In the short term, we look at the effects of land use and restoration measures on ecological processes. In the long term, we look at the effects of climate change on peat ecosystems. 

A large part of the Dutch subsurface consists of peat. Peat landscapes have emerged from an interplay between man and nature. Parts have been excavated for peat extraction or have disappeared due to oxidation. Other peat areas have become submerged because the soil subsided when they were drained. 

In the peat landscapes we still have in the Netherlands, we find traces of past habitation and other uses. For this reason, our raised bog landscapes are also called archaeological treasure troves. However, peat landscapes are also sources of geological information. Information about the origin of the areas and the properties and behavior of different types of peat is stored in the geomorphology and soil types of these landscapes. 

Knowledge about the origin of peat landscapes in the past and their development is necessary to develop and preserve them for the future as natural areas, habitats, and cultural-historical heritage. Which peat-forming ecosystems can we bring back to the Netherlands? 

Wageningen University & Research investigates interactions between peat landscapes and humans over long timescales. We create reconstructions and projections of peat growth in raised bog landscapes and research the landscape history of peat areas. We create maps of landforms and soil types in peat areas and monitor vegetation with drones.

Peat landscapes make up a large part of the Netherlands and form our soft subsurface. To live in these landscapes, we must organize and use them in clever ways. How can we practice agriculture there without the soil subsiding further and without more greenhouse gases being released, while ensuring farmers have a viable income? Plants and trees on farmyards can contribute to biodiversity in peat meadow areas, and farmers can earn additional income from this. Are forms of residential construction possible on the soft subsurface? What will the landscape look like in the future? 

Peat researchers at Wageningen University & Research create visions for the long-term design of peatlands that are resistant to a changing climate. They search for business models and designs that fit the soil-water system in peatlands and for new forms of agriculture and nature that are adapted to them.