Exclude or remove livestock from historically grazed brackish/saline swamps

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

Effectiveness

65%
Certainty

35%
Harms

0%

Calculating overall effectiveness category

Background information and definitions

This action involves completely excluding or completely removing livestock from marshes or swamps that have been negatively impacted by livestock grazing – whether deliberate or accidental. This may be implemented at a large scale (e.g. removing livestock from an entire farm) or at a small scale (e.g. tethering cattle to keep them off sensitive vegetation patches).

Domestic livestock can directly consume vegetation, destroy vegetation by trampling, create bare patches of ground (e.g. repeatedly used tracks), affect water infiltration and flows by compacting soils, affect nutrient balance through excretion of waste products, and import seeds of undesirable plants (Morris & Reich 2013). Removing livestock can allow grazing-sensitive species to recover. The effects might depend on site conditions such as productivity (determined by soil moisture and nutrient levels; Berney et al. 2014).

^{Berney P.J., Wilson G.G., Ryder D.S., Whalley R.D.B., Duggin J. & McCosker R. (2014) Divergent responses to long-term grazing exclusion among three plant communities in a flood pulsing wetland in eastern Australia. Pacific Conservation Biology, 20, 237–251.}

^{Morris K. & Reich P. (2013) Understanding the Relationship Between Livestock Grazing and Wetland Condition. Arthur Rylah Institute for Environmental Research, Technical Report Series No. 252.}

Study locations

Key messages

One study evaluated the effects, on vegetation, of excluding or removing livestock from historically grazed brackish/saline swamps. The study was in South Africa and the focal livestock were cattle.

VEGETATION COMMUNITY

VEGETATION ABUNDANCE

Individual species abundance (1 study): One replicated, paired, controlled study in South Africa reported that more grey mangrove Avicennia marina seedlings appeared in plots fenced to exclude cattle for two years, than in plots left open to cattle.

VEGETATION STRUCTURE

Height (1 study): One replicated, paired, controlled study in South Africa reported that mangrove trees fenced off from cattle were taller, after two years, than trees accessible to cattle.

OTHER

Growth (1 study): One replicated, paired, controlled study in South Africa found that mangrove trees fenced off from cattle grew more over two years – in height, diameter and crown volume –than trees accessible to cattle.

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 2010–2012 in an estuary in South Africa (Hoppe-Speer & Adams 2015) reported that excluding cattle increased the height and growth rate of grey mangrove Avicennia marina. After two years, grey mangroves were 91 cm tall in plots that had been fenced to exclude cattle (vs 77 cm in plots left open to cattle; statistical significance not assessed). Over the two years, trees in exclusion plots grew more than trees in open plots in three of four metrics: plant height (exclusion: 5.4; open: −0.2 cm/year), plant diameter (exclusion: 7.1; open: 2.0 cm/year) and crown volume (exclusion: 0.5; open: 0.1 m³/year). Circumference growth did not significantly differ between treatments (exclusion: 26; open: 15 cm). In the second year, a total of 75 grey mangrove seedlings appeared in exclusion plots (vs 35 in open plots). Methods: In 2010, five pairs of 25-m² plots were established within stunted, shrubby, estuarine mangroves. In each pair, one plot was fenced to exclude cattle whilst the other remained open to cattle (3–11 cows/ha). Grey mangrove trees were measured and seedlings were counted three times after setting up the experiment, in July 2010, 2011 and 2012.
Study and other actions tested
Referenced paper
Hoppe-Speer S.C.L. & Adams J.B. (2015) Cattle browsing impacts on stunted Avicennia marina mangrove trees. Aquatic Botany, 121, 9-15.

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

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Change type of livestock grazing: brackish/salt marshes Action Link	Likely to be beneficial	3	Synopsis Link
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