Soil subsidence is simulated sea level rise.
Present soil subsidence at Ameland: ~38 cm
IPCC: sea level rise ~44 cm in 2100
Veerman: sea level rise ~100 cm in 2100
Main concerns:
- will natural areas be flooded, i.e. will their area decrease?
- will there be a loss of biodiversity?
Research objectives:
Ecological impact on the coastal area (salt marsh, fresh water dune valleys, dunes) as a result of soil subsidence by gas extraction and climate change (increasing sea level rise, storm frequency, precipitation) are described. The order of magnitude and direction of the coming impact of climate change in the dune and dune valley habitat are compared with changes as a result of soil subsidence in the real world. More information: website Wageningen IMARES.
Results and products:
Soil subsidence in the salt marsh area is largely compensated by sedimentation from almost completely till ca. 50%. Sedimentation increases as flooding frequency increases. Flooding-related vegetation gradient ('zonation') is extremely stable over time. This may partly explain the increase of sedimentation at higher flooding frequency.
Total sedimentation and sea-level rise over whole observation period (mm.y-1):
area 1 6.2 +/- 9.0
area 2 5.1 +/- 6.6
Expected sea-level rise until 2100 (mm.y-1):
IPCC-scenario 4.4 +/- 3.3
Veerman -scenario 8.8 +/- 3.2
Sedimentation rate is probably large enough to keep pace with sea-level rise according to IPCC, but not according to extreme Veerman -scenario.
Conclusions sea-level rise:
- In pioneer zone and lower salt marsh sea-level rise will be largely compensated by sedimentation
- Present sedimentation rate is large enough to keep pace with sea-level rise according to IPCC, but not according to Veerman
- However, sedimentation increases as flooding frequency increases
- Strongest effect of sea level rise expected in wet dune slack, where sedimentation is low.
Conclusions vegetation:
- Flooding-related vegetation gradient in salt marsh ('zonation') is extremely stable over time this may partly explain the increase of sedimentation at higher flooding frequency
- But in dune slack, vegetation shifts along gradient as conditions change with sea-level rise, this may lead to permanant changes
- Both in salt marsh, dune slack and dry dune, succession towards more eutrophic vegetation is the most prominent temporal trend.
Conclusions biodiversity:
- Loss of species number, and conservancy value is mainly related to succession (both in salt marsh and dune slack)
- Succession is not related to soil subsidence, but is an autonomous process, accelerated by nitrogen deposition, lower cattle intensity, collapse of rabbit population
- Sea-level rise is expected to increase dynamics and thereby retard succession. |
