Control problematic plants (specific intervention unclear): freshwater marshes or swamps

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

Effectiveness

60%
Certainty

33%
Harms

0%

Calculating overall effectiveness category

Background information and definitions

This section considers studies that have controlled problematic plants, but which do not clearly report the specific intervention(s) used for control so the study cannot be summarized elsewhere in this chapter.

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

Study locations

Key messages

One study evaluated the effects, on vegetation, of controlling problematic plants in freshwater marshes or swamps using unspecified or unclear methods. The study was in the USA.

VEGETATION COMMUNITY

Overall richness/diversity (1 study): One replicated, site comparison study in the USA found that marshes in which non-native plants were actively controlled had higher overall plant richness and diversity, after three years, than marshes in which non-native plants were not controlled.

VEGETATION ABUNDANCE

Overall abundance (1 study): One replicated, site comparison study in the USA found that marshes in which non-native plants were actively controlled had similar overall vegetation cover, after three years, to marshes in which non-native plants were not controlled.
Individual species abundance (1 study): One studyquantified the effect of this action on the abundance of individual plant species, other than those being controlled. The replicated, site comparison study in the USA found, for example, that spikerush Eleocharis cover was greater in marshes where non-native plants were actively controlled than where they were not controlled.

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, site comparison study in 2011 of 26 freshwater marshes in Oregon, USA (Rowe et al. 2014) found that marshes in which non-native plants were actively controlled had higher overall plant richness and diversity than marshes where non-native plants were not controlled, but similar overall vegetation cover. Controlled marshes contained more plant taxa (13 taxa/30 m²; 87 taxa across 18 marshes) than uncontrolled marshes (9 taxa/30 m²; 42 taxa across eight marshes). The same was true for plant diversity (data reported as a diversity index). Controlled marshes had statistically similar overall vegetation cover to uncontrolled marshes but lower cover of plants not native to Oregon (reported as statistical model results). The study also reported data on cover of individual plant species. For example, native spikerush Eleocharis sp. had greater cover in controlled marshes (13%, vs uncontrolled: 7%), whereas invasive reed canarygrass Phalaris arundinacea had lower cover in controlled marshes (8%, vs uncontrolled: 33%). Methods: In summer 2011, emergent vegetation was surveyed in 26 permanent and ephemeral marshes (0.08–14.7 ha). In each marsh, plant species and cover were recorded in thirty 1-m² quadrats along transects from the shore to shallow water. Non-native plants had been actively controlled in 18 marshes (“intensive management” applied to >50% of the marsh at least twice in the past three years; no further details reported) but not in the other eight marshes (where the only management, if any, involved “minimal” control of the water level).
Study and other actions tested
Referenced paper
Rowe J.C. & Garcia T.S. (2014) Impacts of wetland restoration efforts on an amphibian assemblage in a multi-invader community. Wetlands, 34, 141-153.

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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This Action forms part of the Action Synopsis:

Marsh and Swamp Conservation

Related Actions

Actions	Effectiveness	Category
Use grazing to control problematic plants: brackish/saline swamps Action Link	No evidence found (no assessment)	Synopsis Link
Add salt to control problematic plants: freshwater swamps Action Link	No evidence found (no assessment)	Synopsis Link
Add salt to control problematic plants: freshwater marshes Action Link	No evidence found (no assessment)	Synopsis Link