Physically remove problematic plants: brackish/salt marshes

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

Study locations

Key messages

  • One study evaluated the effects, on vegetation, of physically removing problematic plants from brackish/salt marshes. The study was in the USA.




  • Native/non-target abundance (1 study): One replicated, randomized, paired, controlled, before-and-after study in pepperweed invaded marshes in the USA found that physically removing pepperweed from plots sprayed with herbicide increased cover of native plants, over the following two years, compared to spraying with herbicide only.
  • Individual species abundance (1 study): The same study quantified the effect of this action on the cover of individual plant species, other than the target of control (see original paper for data).


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 2005–2007 in three brackish and salt marshes invaded by pepperweed Lepidium latifolium in California, USA (Boyer & Burdick 2010) found that physically removing pepperweed before spraying herbicide increased native plant cover more than spraying alone. Averaged over the two years following intervention, cleared/sprayed plots had greater cover of native plants (year one: 26–124%; year two: 33–195%) than plots that were only sprayed (year one: 10–67%; year two: 19–113%). In contrast, cleared/sprayed plots had lower pepperweed cover (year one: 0–14%; year two: 5–44%) than plots that were only sprayed (year one: 2–60%; year two: 25–88%). Before intervention, plots destined for each treatment had statistically similar cover of native plants (10–33%) and pepperweed (90–100%). For data on the cover of other individual plant species, see original paper. Methods: In April 2005, five sets of 2 x 2 m plots were established each of three pepperweed-invaded marshes. In each set, there was one replicate where pepperweed was removed (including roots to 20 cm depth) before spraying regrowth with herbicide (1.25% glyphosate), and one replicate that was only sprayed with herbicide. Treatments were randomly allocated to plots. Vegetation cover was measured before (April 2005) and quarterly for two years after (April 2007) intervention, in 1-m2 quadrats.

    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

All the journals searched for all synopses

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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