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What Works in Conservation 2018

 | 
William J. Sutherland
, 
Lynn V. Dicks
, 
Nancy Ockendon
, 
et al.

6. Peatland conservation

6.2. Threat: Agriculture and aquaculture

Texte intégral

6.2.1 Multiple farming systems

Unknown effectiveness (limited evidence)

Retain/create habitat corridors in farmed areas

  • Vegetation structure: One study in Indonesia found that a peat swamp forest corridor contained 5,819 trees/ha: 331 large trees, 1,360 saplings and 4,128 seedlings.

  • Overall plant richness/diversity: The same study recorded 18–29 tree species (depending on size class) in the peat swamp forest corridor.

  • Assessment: unknown effectiveness – limited evidence (effectiveness 45%; certainty 15%; harms 4%). Based on evidence from: tropical peat swamps (one study).

1https://www.conservationevidence.com/​actions/​1730

No evidence found (no assessment)

2We have captured no evidence for the following intervention:

  • Implement ‘mosaic management’ of agriculture.

6.2.2 Wood and pulp plantations

Likely to be beneficial

Cut/remove/thin forest plantations

  • Herb cover: Three replicated studies (two also paired and controlled) in bogs in the UK and fens in Sweden reported that tree removal increased cover of some herbs, including cottongrasses Eriophorum spp. and sedges overall. One of the studies reported no effect on other herb species, including purple moor grass Molinia caerulea.

  • Moss cover: Two replicated studies, in bogs in the UK and a drained rich fen in Sweden, reported that tree removal reduced moss cover after 3–5 years (specifically fen-characteristic mosses or Sphagnum moss). However, one replicated, paired, controlled study in partly rewetted rich fens in Sweden reported that tree removal increased Sphagnum moss cover after eight years.

  • Overall plant richness/diversity: Two replicated, paired, controlled studies in rich fens in Sweden reported that tree removal increased total plant species richness, especially in rewetted plots.

  • Assessment: likely to be beneficial (effectiveness 60%; certainty 50%; harms 10%). Based on evidence from: fens (three studies); bogs (one study).

3https://www.conservationevidence.com/​actions/​1731

Cut/remove/thin forest plantations and rewet peat

  • Plant community composition: Of three replicated studies in fens in Finland and Sweden, two found that removing trees/rewetting did not affect the overall plant community composition. One reported only a small effect. Two site comparison studies, in bogs and fens in Finland, found that removing trees/rewetting changed the community composition: it became less like forested/drained sites.

  • Characteristic plants: Two before-and-after studies (one site comparison, one controlled) in bogs and fens in Finland and Sweden reported that removing trees/rewetting increased the abundance of wetland-characteristic plants.

  • Moss cover: Five studies (four replicated, three site comparisons) in Sweden and Finland examined the effect of removing trees/rewetting on Sphagnum moss cover. Of these, two studies in bogs and fens found that removing trees/rewetting increased Sphagnum cover. One study in forested fens found no effect. Two studies in a bog and a fen found mixed effects amongst sites or species. Four studies (three replicated, two paired) in the UK and Finland examined the effect of removing trees/rewetting on other moss cover. Of these, three found that removing trees/rewetting reduced moss cover, but one study in forested fens found no effect.

  • Herb cover: Seven studies (two replicated, paired, controlled) in bogs and fens in the UK, Finland and Sweden reported that removing trees/rewetting increased cover of at least one group of herbs. This included cottongrasses Eriophorum spp. in four of five studies and other/total sedges in three of three studies. One study reported that tree removal/rewetting reduced cover of cottongrass (where it was rare before intervention) and purple moor grass Molinia caerulea.

  • Vegetation structure: One replicated study in a bog in the UK found that removing trees/rewetting increased ground vegetation height, but another in a fen in Sweden reported no effect on canopy height after eight years. Two replicated, paired, site comparison studies in bogs and fens in Finland reported that thinning trees/rewetting reduced the number of tall trees present for 1–3 years after intervention (but not to the level of natural peatlands).

  • Overall plant richness/diversity: Of four replicated studies in fens in Sweden and Finland, two (also paired and controlled) reported that removing trees/rewetting increased plant species richness. The other two studies found that removing trees/rewetting had no effect on plant species richness or diversity.

  • Assessment: likely to be beneficial (effectiveness 60%; certainty 60%; harms 10%). Based on evidence from: fens (six studies); bogs (two studies); mixed peatlands (three studies).

4https://www.conservationevidence.com/​actions/​1732

6.2.3 Livestock farming and ranching

Likely to be beneficial

Exclude or remove livestock from degraded peatlands

5 Plant community composition: Of two replicated, paired, controlled studies in bogs in the UK, one found that excluding sheep had no effect on the plant community. The other found that excluding sheep only affected the community in drier areas of the bog, favouring plants typically found on dry moorlands.

6 Herb cover: Seven studies (six replicated, paired, controlled) in bogs and fens in the UK, Australia and the USA found that excluding/removing livestock did not affect cover of key herb groups: cottongrasses Eriophorum spp. in five of five studies and true sedges Carex spp. in two of two studies. However, one before-and-after study in a poor fen in Spain reported that rush cover increased after cattle were excluded (along with rewetting). One site comparison study in Chile found that excluding livestock, along with other interventions, increased overall herb cover but one replicated, paired, controlled study in bogs in Australia found that excluding livestock had no effect on herb cover.

7 Moss cover: Five replicated, paired, controlled studies in bogs in the UK and Australia found that excluding livestock typically had no effect on Sphagnum moss cover. Three of the studies in the UK also found no effect on cover of other mosses. One before-and-after study in a poor fen in Spain reported that Sphagnum moss appeared after excluding cattle (along with rewetting).

8 Tree/shrub cover: Five replicated, paired, controlled studies in bogs in the UK and Australia found that excluding livestock typically had no effect on shrub cover (specifically heather Calluna vulgaris or heathland plants). However, one of these studies found that heather cover increased in drier areas. Three studies (two site comparisons) in bogs in the UK, fens in the USA and a peatland in Chile found that excluding/removing livestock increased shrub cover.

9 Vegetation structure: One replicated, paired, controlled study in a bog in the UK found that excluding sheep increased total vegetation, shrub and bryophyte biomass, but had no effect on grass-like plants.

10 Assessment: likely to be beneficial (effectiveness 40%; certainty 50%; harms 12%). Based on evidence from: bogs (seven studies); fens (two studies); unspecified peatlands (one study).

11https://www.conservationevidence.com/​actions/​1734

Unknown effectiveness (limited evidence)

Reduce intensity of livestock grazing

12 Vegetation cover: One replicated, paired, controlled study in bogs in the UK found greater cover of total vegetation, shrubs and sheathed cottongrass Eriophorum vaginatum under lower grazing intensities.

13 Vegetation structure: The same study found that vascular plant biomass was higher under lower grazing intensities.

14 Assessment: unknown effectiveness–limited evidence (effectiveness 60%; certainty 25%; harms 1%). Based on evidence from: bogs (one study).

15https://www.conservationevidence.com/​actions/​1735

No evidence found (no assessment)

16We have captured no evidence for the following interventions:

  • Use barriers to keep livestock off ungrazed peatlands

  • Change type of livestock

  • Change season/timing of livestock grazing.

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