Abandon mined land: allow brackish/saline marshes or swamps to recover without active intervention

Overall effectiveness category Unknown effectiveness (limited evidence)
Number of studies: 1
Share Tweet Email

View assessment score

How is the evidence assessed?

Effectiveness

50%
Certainty

26%
Harms

0%

Calculating overall effectiveness category

Background information and definitions

It may be possible that marshes or swamps will recover on their own, without any active intervention, if human activities are stopped. Such passive recovery can be cheaper than active intervention and allow development of a community well adapted to local conditions. However, plant colonization may not occur at all or, if it does, occur slowly or be dominated by invasive species (Zahawi et al. 2014). Successful recovery may be hindered by physical degradation (e.g. a water table that is too low, restricted tidal exchange, compacted sediment), chemical degradation (e.g. acidified soils or presence of heavy metals) or an insufficient supply of propagules.

To be summarized as evidence for this action, studies must have monitored historically mined land that has been abandoned (mining activities completely stopped, with no additional intervention) with the expectation that marshes or swamps could recover (i.e. excluding studies of abandoned upland mines). Therefore, the summarized evidence is best considered as an indication of what kind of vegetation can develop in historically mined areas, and how long it takes to develop, rather than a complete survey of all relevant evidence.

Related actions: Abandon cropland; Abandon plantations.

^{Zahawi R.A., Reid J.L. & Holl K.D. (2014) Hidden costs of passive restoration. Restoration Ecology, 22, 284–287.}

Study locations

Key messages

One study evaluated the effects, on vegetation, of abandoning formerly mined land with the expectation that brackish/saline marshes or swamps would recover spontaneously. The study was in France.

VEGETATION COMMUNITY

Community types (1 study): One replicated study in France simply classified the plant community types that developed on abandoned salt pans. Areas flooded for at least part of the year developed salt marsh plant communities, with the exact community composition depending on the duration of flooding and soil salinity.

VEGETATION ABUNDANCE

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 replicated study in 1990 of 40 abandoned salt pans in northwest France (Bouzillé et al. 2001) reported that they contained a range of plant community types, depending on the duration of flooding and soil salinity. In areas flooded for long periods (>277 days/year on average) and with low soil salinities (<2.5 mS/cm on average), common and/or abundant species included shoreline sedge Carex riparia, yellow flag Iris pseudacorus, branched bur-reed Sparganium erectum and cuckoo flower Cardamine pratensis. In areas flooded for shorter periods (122–132 days/year on average) and with higher soil salinities (3.3–4.3 mS/cm on average), common and/or abundant species included saltmarsh rush Juncus gerardii and bulbous foxtail Alopecurus bulbosus. Some areas were never flooded and developed upland plant communities. Community data were reported as a graphical analysis, frequency classes and cover classes. Methods: In May 1990, plant species and their cover were recorded in three quadrats (one low elevation, one medium, one high) in each of 40 abandoned salt pans (no artificial inputs of salt water for 150 years). Some sites were still affected by adjacent drainage ditches. Some grazing and/or mowing had occurred on the sites since abandonment.
Study and other actions tested
Referenced paper
Bouzillé J.B., Kernéis E., Bonis A. & Touzard B. (2001) Vegetation and ecological gradients in abandoned salt pans in western France. Journal of Vegetation Science, 12, 269-278.

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
Retain/create habitat linkages in areas of energy production or mining Action Link	No evidence found (no assessment)	0	Synopsis Link
Abandon mined land: allow freshwater marshes or swamps to recover without active intervention Action Link	No evidence found (no assessment)	0	Synopsis Link
Abandon mined land: allow brackish/saline marshes or swamps to recover without active intervention Action Link	Unknown effectiveness (limited evidence)	1	Synopsis Link