Remove surface soil/sediment: brackish/salt marshes

Overall effectiveness category Unknown effectiveness (limited evidence)
Number of studies: 1
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How is the evidence assessed?

Effectiveness

40%
Certainty

25%
Harms

10%

Calculating overall effectiveness category

Background information and definitions

Surface soil/sediment – and any vegetation on it – could be removed to create a new bare surface for plants to colonize. This new surface may have fewer nutrients and pollutants, have no undesirable seed bank, and have a looser surface. Soil/sediment removal can also make a site wetter, by bringing the surface closer to the water table, increasing the frequency/duration of tidal flooding, or increasing the water depth in an already flooded site. This action may be particularly useful in naturally dynamic habitats that have been artificially stabilized, mimicking disturbances that would create bare soil/sediment.

Caution: Heavy machinery is usually needed for this action. Heavy vehicles can churn and compress wetland soils (Campbell et al. 2002). Stripping topsoil can have counter-intuitive effects, such as increasing ammonium concentrations because nitrifying bacteria, which break down ammonia, are removed with the soil (Dorland 2004). It may remove seeds of desirable species, and can be expensive.

^{Campbell D.A., Cole C.A. & Brooks R.P. (2002) A comparison of created and natural wetlands in Pennsylvania, USA. Wetlands Ecology and Management, 10, 41–49.}

^{Dorland E. (2004) Ecological restoration of wet heaths and matgrass swards: bottlenecks and solutions. PhD Thesis, Utrecht University, The Netherlands.}

Study locations

Key messages

One study evaluated the effects, on vegetation, of removing surface soil/sediment to restore or create brackish/salt marshes. The study was in the Netherlands.

VEGETATION COMMUNITY

Overall richness/diversity (1 study): One study in the Netherlands reported that 23 plant species colonized over two years after stripping topsoil from coastal farmland.

VEGETATION ABUNDANCE

Individual species abundance (1 study): One study in the Netherlands reported the frequency of plant species that colonized over two years after stripping topsoil from coastal farmland.

VEGETATION STRUCTURE

About key messages

Key messages provide a descriptive index to studies we have found that test this intervention.

Studies are not directly comparable or of equal value. When making decisions based on this evidence, you should consider factors such as study size, study design, reported metrics and relevance of the study to your situation, rather than simply counting the number of studies that support a particular interpretation.

Supporting evidence from individual studies

A study in 1997–1999 aiming to create a brackish marsh on coastal farmland in the Netherlands (Bakker et al. 2002) reported that an area from which topsoil was removed was colonized by farmland weeds and some plant species characteristic of brackish marshes. Two years after topsoil removal, 23 plant species were recorded in the study area. The most abundant taxa were mostly farmland weeds/generalists, such as chamomile Matricaria recutita (in 97% of quadrats), sow thistle Sonchus oleraceus (76%) and meadow grass Poa annua (61%). Taxa characteristic of brackish marshes included rushes Juncus spp. (in 97% of quadrats), sea aster Aster tripolium (7%) and alkali bulrush Scirpus maritimus (5%). The study does not define a full list of characteristic species. Methods: In 1997, a 30 cm layer of topsoil was stripped from an area of coastal farmland (Emmapolder). Not all topsoil was completely removed from the site: some was stored in rows on site, and so provided a source of farmland weed seeds. Brackish groundwater naturally seeped towards the ground surface. In 1999, vegetation was surveyed in an unplanted area of the site, next to a pool (100 quadrats, each 0.4 m²).
Study and other actions tested
Referenced paper
Bakker J.P., Esselink P., Dijkema K.S., van Duin W.E. & de Jong D.J. (2002) Restoration of salt marshes in the Netherlands. Hydrobiologia, 478, 29-51.

Please cite as:

Taylor N.G., Grillas P., Smith R.K. & Sutherland W.J. (2021) Marsh and Swamp Conservation: Global Evidence for the Effects of Interventions to Conserve Marsh and Swamp Vegetation. Conservation Evidence Series Synopses. University of Cambridge, Cambridge, UK.

Where has this evidence come from?

List of journals searched by synopsis

All the journals searched for all synopses

This Action forms part of the Action Synopsis:

Marsh and Swamp Conservation

Related Actions

Actions	Effectiveness	Studies	Category
Raise water level to restore/create freshwater marshes from other land uses Action Link	Likely to be beneficial	26	Synopsis Link
Excavate freshwater pools Action Link	Trade-off between benefit and harms	7	Synopsis Link
Disturb soil/sediment surface: freshwater marshes Action Link	Unknown effectiveness (limited evidence)	2	Synopsis Link