Use covers/barriers to control problematic plants: freshwater marshes

How is the evidence assessed?
  • Effectiveness
  • Certainty
  • Harms

Study locations

Key messages

  • One study evaluated the effects, on vegetation, of using covers or barriers to control problematic plants in freshwater marshes. The study was in Canada.




  • Overall abundance (1 study): One replicated, randomized, paired, controlled, before-and-after study in iris-invaded lakeshore marshes in Canada reported that covering plots with rubber sheeting after cutting back yellow iris Iris pseudacorus prevented most vegetation regrowth in an intermittently flooded marsh, but had no clear effect in a permanently flooded marsh.


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

  1. A replicated, randomized, paired, controlled, before-and-after study in 2014–2015 in two lakeshore marshes cleared of yellow flag iris Iris pseudacorus in British Columbia, Canada (Tarasoff et al. 2016) reported that the effect of covering plots on recolonizing vegetation depended on the water level. Statistical significance was not assessed. Initially, all study plots were completely covered by invasive yellow flag iris. This was clipped to ground level. One year later, in the intermittently flooded marsh, covered plots had approximately 7% vegetation cover (yellow flag iris seedlings and broadleaf cattail Typha latifolia; species cover not quantified). In contrast, open plots had 100% cover of yellow flag iris. Meanwhile, in the permanently flooded marsh, both covered and open plots had approximately 5% vegetation cover (yellow flag iris seedlings and broadleaf cattail; species cover not quantified). Methods: Nine pairs of plots (approximately 1 m2) were established in iris-dominated marshes on the shores of two lakes. In June 2014, yellow flag iris was cut to 0–4 cm above the sediment in all plots. Cuttings were removed. Then, one random plot/pair was covered with an impermeable rubber sheet for 150 days. Vegetation cover was surveyed in July 2015.

    Study and other actions tested
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

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Marsh and Swamp Conservation

This Action forms part of the Action Synopsis:

Marsh and Swamp Conservation
Marsh and Swamp Conservation

Marsh and Swamp Conservation - Published 2021

Marsh and Swamp Synopsis

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