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