Physically remove problematic plants: brackish/salt marshes

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

Effectiveness

68%
Certainty

31%
Harms

0%

Calculating overall effectiveness category

Background information and definitions

This action considers complete physical removal of problematic plants, i.e. pulling up or digging up entire plants, or scraping living vegetation from the marsh surface. Removal may be targeted to individual organisms, or applied to the whole plant community. The most appropriate removal method will depend on the species to be removed, and the site conditions (e.g. Tobias et al. 2016).

If plants are completely removed, including roots where applicable, immediate regrowth will be prevented (although long-term recolonization from the seed bank or from neighbouring sites is possible). For some species, disposing of the problem plants off-site may help to prevent regrowth, but disposal should be done carefully to avoid causing an invasion elsewhere (Stevens et al. 1997).

For this action, “vegetation” refers to overall or non-target vegetation. Studies that only report responses of target problematic plants have not been summarized.

Related actions: Remove surface soil/sediment, including any plants on it.

^{Stevens K.J., Peterson R.L. & Stephenson G.R. (1997) Vegetative propagation and the tissues involved in lateral spread of Lythrum salicaria. Aquatic Botany, 56, 11–24.}

^{Tobias V.D., Block G. & Laca E.A. (2016) Controlling perennial pepperweed (Lepidium latifolium) in a brackish tidal marsh. Wetlands Ecology and Management, 24, 411–418.}

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.

VEGETATION COMMUNITY

VEGETATION ABUNDANCE

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).

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, 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
Referenced paper
Boyer K.E. & Burdick A.P. (2010) Control of Lepidium latifolium (perennial pepperweed) and recovery of native plants in tidal marshes of the San Francisco Estuary. Wetlands Ecology and Management, 18, 731-743.

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
Use covers/barriers to control problematic plants: brackish/saline swamps Action Link	No evidence found (no assessment)	0	Synopsis Link
Use herbicide to control problematic plants: freshwater marshes Action Link	Trade-off between benefit and harms	17	Synopsis Link
Use herbicide to control problematic plants: brackish/salt marshes Action Link	Trade-off between benefit and harms	7	Synopsis Link