The Dutch Petroleum Company (NAM) has been extracting gas from three wells near and on Ameland since 1986. Gas extraction leads to land subsidence and that can affect the appearance of the island and nature. The decline started in 1986 and will not stop immediately after extraction stops and the decline is greatest close to the well where extraction takes place.
The extraction area under Ameland / Source: NAM
Subsidence
The gas in the Amelander gas fields is contained in a sandstone layer at a depth of approximately three kilometers. That layer consists of sand grains pressed together, between which there are microscopic pores in which the gas is located. When gas is extracted, the pressure in the sandstone layer decreases. The pressure of the three kilometers of earth on the sandstone layer compresses it. On the surface of Ameland this can be measured as land subsidence.
Dish
The subsidence in an extraction area is not the same everywhere: the subsidence is saucer-shaped. The deepest point of the dish is in the center. Towards the edges the decrease gradually decreases; one to two millimeters per hundred meters. The Ameland subsidence dish has a diameter of ten kilometers. The deepest point is on east Ameland. Ameland’s decline started in 1987. According to the forecast, the center of the dish on east Ameland will have sunk 38 centimeters by 2050.
To measure
Since the start of extraction in 1986, measurements have been taken on and around Ameland. The subsidence will not stop when the NAM stops extracting, even if the gas has already been removed from the soil of East Ameland. One measures:
- measured the height of the water on the island
- GPS measurements on the mudflats
- continuous GPS recording above the center of the subsidence dish
Soil Subsidence Monitoring Committee on Ameland
The subsidence and its effects have been monitored and investigated by NAM since the start of gas extraction in 1986. An Ameland Land Subsidence Committee has been established
to supervise – and to ensure independence – the research. The committee has an independent chairman (Jaap de Vlas) and a former NAM employee as secretary (Joop Marquenie). The committee includes representatives from the following organizations:
- Municipality of Ameland
- It Fryske gea
- Ministry of Agriculture, Nature and Food Quality/EL&I
- Province of Friesland
- Rijkswaterstaat Northern Netherlands
- NAM
Most vulnerable
The part of Ameland-Oost south of the first rows of dunes is the most vulnerable to land subsidence. The sand nourishments reduce the consequences of land subsidence for the zone north of the dune rows and to the east.
Influence
It is not only natural gas extraction that has an impact on the situation in East Ameland. More human intervention affects the environment of Ameland. At least four human-induced processes are changing the island.
- The closure of the Lauwerzee (influence from 1968)
- The sand nourishments on and near the North Sea beach of Ameland ((influence from 1980)
- Natural gas extraction on and near Ameland (influence from 1986)
- Sea level rise
Salt marsh
The salt marsh edge on the south side of east Ameland has a different problem than the dunes and dune valleys, which are located further north.
- There is balance between accretion and subsidence of the soil
- There is rejuvenation of the vegetation: more species-rich salt marsh vegetation
- Wetting accelerates vegetation change
Dunes
The subsidence causes wetting and salinization of the dune valleys. The vegetation adapts to this. The rewetting has even been beneficial for some species.
Birds
Many birds breed on East Ameland. If land subsidence increases, the risk of flooding will also increase, but this will be reduced by silting up of the salt marsh. If there is a flood during the breeding season, it can destroy hundreds of nests. More research needs to be done to determine whether land subsidence has an effect on bird populations .
Breeding on East Ameland:
- Oystercatchers
- Spoonbills
- Herring Gull
- Storm gull
- Black-headed gull
- Lesser black-backed gull
- Arctic tern
A report on land subsidence on east Ameland is published every five years.
Win longer
In May 2012, NAM came up with a plan to empty the wells near Ameland, two in the North Sea and one under East Ameland, more slowly than the original plan. The NAM wants a permit until 2035 instead of the agreed 2018.
This means that the platforms off the coast of Ameland will remain in place for longer.
The slower extraction gives a different picture of the subsidence:
- the dish shifts slightly north, towards the North Sea. This is beneficial for soil subsidence on the island.
- the deepest dish is smaller than with faster extraction (until 2018)
- the subsidence in the deepest part is deeper than with faster extraction
2018 and 2035
- With extraction up to 2018, the largest decrease is 32 centimeters
- With extraction until 2035, the largest decrease is 38 centimeters.
read more
- Ameland and the love-hate with natural gas
- Derricks on Ameland – Natural gas extraction in the Wadden area
- Sustainable Wadden Islands
- Earthquake – Natural gas extraction in Groningen
- Gas extraction – gas extraction in the Wadden Sea World Heritage Site