Use fences or barriers to protect planted brackish/saline wetlands planted with trees/shrubs

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

Effectiveness

60%
Certainty

29%
Harms

0%

Calculating overall effectiveness category

Background information and definitions

Plants introduced to wetlands may be vulnerable to physical damage from grazing, wind, waves or sediment. Barriers could be used to protect planted vegetation from such physical damage. Here, “barriers” is used quite broadly and includes sleeves, tree guards, fences and fine-meshed silt screens placed around planted vegetation, sticky oils or resins painted onto planted vegetation, and offshore walls or breakwaters. Some of these barriers may have incidental effects on temperature, humidity and sunlight intensity (but covers and screens whose main aim is to modify these factors are considered elsewhere). If the general area containing planted vegetation is fenced, rather than individual planted plants, other colonizing vegetation may benefit too.

Study locations

Key messages

One study evaluated the effects, on vegetation, of using fences or barriers to protect brackish/saline wetlands planted with trees/shrubs. The study was in the USA.

VEGETATION COMMUNITY

VEGETATION ABUNDANCE

VEGETATION STRUCTURE

Height (1 study): One replicated, paired, controlled study in exposed coastal sites in the USA found that red mangrove Rhizophora mangle propagules planted within full-length plastic shelters had grown taller than propagules planted without shelter in three of four comparisons, made 22–129 days after planting.

OTHER

Survival (1 study): One replicated, paired, controlled study in exposed coastal sites in the USA reported that full-length plastic shelters increased the survival rate of planted red mangrove Rhizophora mangle propagules over 4–8 months, but that full-length bamboo shelters and below-ground plastic shelters had no clear effect on survival.

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, paired, controlled study in 1997–1998 in four sandy coastal sites in Florida, USA (Salgado Kent & Lin 1999) reported that planted red mangrove Rhizophora mangle propagules within full-length plastic shelters – but not full-length bamboo shelters or below-ground plastic shelters – had higher survival rates than unprotected propagules, and found that seedlings within full-length shelters grew taller than seedlings in the other treatments. After 4–8 months, the survival rate was 76–100% for propagules/seedlings within translucent plastic shelters that extended above and below ground (vs 0–2% within similar shelters made from bamboo; 0% within plastic shelters that extended below ground only; and 0–6% without shelter; statistical significance not assessed). After 22–129 days, seedlings within full-length plastic shelters were significantly taller than unprotected seedlings in three of four comparisons (other comparison no significant difference, because no propagules had developed into seedlings) and significantly taller than seedlings in the other types of shelters in four of four comparisons (see original paper for data). Methods: In August and November 1997, a total of 796 red mangrove propagules were planted, around the high tide level, in four exposed, sandy, coastal sites. There were 13–35 propagules/site/season for each of the four shelter treatments. Shelters differed in material and height (see above) but were all 3.8 cm internal diameter and had a slit running down them to allow water exchange. Propagules (or the seedlings they became) were monitored twice a month for up to eight months after planting.
Study and other actions tested
Referenced paper
Salgado Kent C.P. (1999) A comparison of Riley encased methodology and traditional techniques for planting red mangroves (Rhizophora mangle). Mangroves and Salt Marshes, 3, 215-225.

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?

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This Action forms part of the Action Synopsis:

Marsh and Swamp Conservation

Related Actions

Actions	Effectiveness	Studies	Category
Transplant wetland soil before/after planting trees/shrubs: brackish/saline wetlands Action Link	No evidence found (no assessment)	0	Synopsis Link
Actively manage water level before/after planting non-woody plants: freshwater wetlands Action Link	Unknown effectiveness (limited evidence)	3	Synopsis Link
Bury surface soil/sediment (before planting) Action Link	No evidence found (no assessment)	0	Synopsis Link