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What Works in Conservation 2018

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

1. Amphibian conservation

1.12 Habitat restoration and creation

Texte intégral

1.12.1 Terrestrial habitat

Beneficial

● Replant vegetation

1Four studies, including one replicated study, in Australia, Spain and the USA found that amphibians colonized replanted forest, reseeded grassland and seeded and transplanted upland habitat. Three of four studies, including two replicated studies, in Australia, Canada, Spain and the USA found that areas planted with trees or grass had similar amphibian abundance or community composition to natural sites and one found similar or lower abundance compared to naturally regenerated forest. One found that wetlands within reseeded grasslands were used less than those in natural grasslands. One before-and-after study in Australia found that numbers of frog species increased following restoration that included planting shrubs and trees. Assessment: beneficial (effectiveness 70%; certainty 63%; harms 3%).

2http://www.conservationevidence.com/​actions/​849

Likely to be beneficial

● Clear vegetation

3Seven studies, including four replicated studies, in Australia, Estonia and the UK found that vegetation clearance, along with other habitat management and in some cases release of amphibians, increased or maintained amphibian populations or increased numbers of frog species. However, great crested newt populations were only maintained for six years, but not in the longer term. Assessment: likely to be beneficial (effectiveness 60%; certainty 54%; harms 10%).

4http://www.conservationevidence.com/​actions/​761

● Create artificial hibernacula or aestivation sites

5Two replicated studies in the UK found that artificial hibernacula were used by two of three amphibian species and along with other terrestrial habitat management maintained populations of great crested newts. Assessment: likely to be beneficial (effectiveness 50%; certainty 44%; harms 0%).

6http://www.conservationevidence.com/​actions/​759

● Create refuges

7Two replicated, controlled studies, one of which was randomized, in the USA and Indonesia found that adding coarse woody debris to forest floors had no effect on the number of amphibian species or overall abundance, but had mixed effects on abundance of individual species. One before-and-after study in Australia found that restoration that included reintroducing coarse woody debris to the forest floor increased frog species. Three studies, including two replicated studies, in New Zealand, the UK and USA found that artificial refugia were used by amphibians and, along with other interventions, maintained newt populations. Assessment: likely to be beneficial (effectiveness 45%; certainty 55%; harms 0%).

8http://www.conservationevidence.com/​actions/​772

● Restore habitat connectivity

9One before-and-after study in Italy found that restoring habitat connectivity by raising a road on a viaduct significantly decreased amphibian deaths. Assessment: likely to be beneficial (effectiveness 75%; certainty 40%; harms 0%).

10http://www.conservationevidence.com/​actions/​840

Unknown effectiveness (limited evidence)

● Change mowing regime

11One before-and-after study in Australia found that restoration that included reduced mowing increased numbers of frog species. Assessment: unknown effectiveness — limited evidence (effectiveness 50%; certainty 30%; harms 0%).

12http://www.conservationevidence.com/​actions/​783

No evidence found (no assessment)

13We have captured no evidence for the following intervention:

14• Create habitat connectivity.

1.12.2 Aquatic habitat

Beneficial

● Create ponds (amphibians in general)

15Twenty-eight studies investigated the colonization of created ponds by amphibians in general, all of which found that amphibians used all or some of the created ponds. Five of nine studies in Australia, Canada, Spain, the UK and USA found that numbers of species were similar or higher in created compared to natural ponds. Nine studies in Europe and the USA found that amphibians established stable populations, used or reproduced in created ponds. Four found that species composition differed, and abundance, juvenile productivity or size in created ponds depended on species. One study found that numbers of species were similar or lower in created ponds. Sixteen studies in Europe and the USA found that created ponds were used or colonized by up to 15 naturally colonizing species, up to 10 species that reproduced or by captive-bred amphibians. Five studies in Europe and the USA found that pond creation, with restoration in three cases, maintained and increased populations or increased species. Assessment: beneficial (effectiveness 80%; certainty 80%; harms 0%).

16http://www.conservationevidence.com/​actions/​869

● Create ponds (frogs)

17Six of nine studies in Australia, Italy, Spain, the UK and USA found that frogs established breeding populations or reproduced in created ponds. One study in Denmark found that frogs colonized created ponds. One study in the Netherlands found that pond creation, along with vegetation clearance, increased frog populations. One study in the USA found that survival increased with age of created ponds. Assessment: beneficial (effectiveness 75%; certainty 70%; harms 0%).

18http://www.conservationevidence.com/​actions/​865

● Create ponds (natterjack toads)

19Five studies in the UK and Denmark found that pond creation, along with other interventions, maintained or increased populations at 75–100% of sites. One study in the UK found that compared to natural ponds, created ponds had lower tadpole mortality from desiccation, but higher mortality from predation by invertebrates. Assessment: beneficial (effectiveness 75%; certainty 70%; harms 10%).

20http://www.conservationevidence.com/​actions/​866

● Create ponds (salamanders including newts)

21Three studies in France, Germany and the USA found that alpine newts, captive-bred smooth newts and translocated spotted salamanders established stable breeding populations in 20–100% of created ponds. Three studies in France, China and the USA found that alpine newts, Chinhai salamanders and translocated spotted salamanders, but not tiger salamanders, reproduced in created ponds. Assessment: beneficial (effectiveness 70%; certainty 65%; harms 0%).

22http://www.conservationevidence.com/​actions/​867

● Create wetlands

23Fifteen studies, including one review and seven replicated studies, in Australia, Kenya and the USA, investigated the effectiveness of creating wetlands for amphibians. Six studies found that created wetlands had similar amphibian abundance, numbers of species or communities as natural wetlands or in one case adjacent forest. Two of those studies found that created wetlands had fewer amphibians, amphibian species and different communities compared to natural wetlands. One global review and two other studies combined created and restored wetlands and found that amphibian abundance and numbers of species were similar or higher compared to natural wetlands. Five of the studies found that up to 15 amphibian species used created wetlands. One study found that captive-bred frogs did not establish in a created wetland. Assessment: beneficial (effectiveness 75%; certainty 70%; harms 0%).

24http://www.conservationevidence.com/​actions/​880

● Deepen, de-silt or re-profile ponds

25Four studies, including one replicated, controlled study, in France, Denmark and the UK found that pond deepening and enlarging or re-profiling resulted in establishment or increased populations of amphibians. Four before-and-after studies in Denmark and the UK found that pond deepening, along with other interventions, maintained newt or increased toad populations. Assessment: beneficial (effectiveness 71%; certainty 65%; harms 0%).

26http://www.conservationevidence.com/​actions/​817

● Restore wetlands

27Seventeen studies, including one review and 11 replicated studies, in Canada, Taiwan and the USA, investigated the effectiveness of wetland restoration for amphibians. Seven of ten studies found that amphibian abundance, numbers of species and species composition were similar in restored and natural wetlands. Two found that abundance or numbers of species were lower and species composition different to natural wetlands. One found mixed results. One global review found that in 89% of cases, restored and created wetlands had similar or higher amphibian abundance or numbers of species to natural wetlands. Seven of nine studies found that wetland restoration increased numbers of amphibian species, with breeding populations establishing in some cases, and maintained or increased abundance of individual species. Three found that amphibian abundance or numbers of species did not increase with restoration. Three of the studies found that restored wetlands were colonized by up to eight amphibian species. Assessment: beneficial (effectiveness 80%; certainty 73%; harms 0%).

28http://www.conservationevidence.com/​actions/​879

Likely to be beneficial

● Create ponds (great crested newts)

29Three studies in Germany and the UK found that great crested newts established breeding populations in created ponds. One systematic review in the UK found that there was no conclusive evidence that mitigation, which often included pond creation, resulted in self-sustaining populations. Four studies in the UK found that great crested newts colonized up to 88% of, or reproduced in 38% of created ponds. Assessment: likely to be beneficial (effectiveness 60%; certainty 61%; harms 0%).

30http://www.conservationevidence.com/​actions/​863

● Create ponds (green toads)

31Two studies in Denmark found that pond creation, along with other interventions, significantly increased green toad populations. One study in Sweden found that green toads used or reproduced in 41–59% of created ponds. Assessment: likely to be beneficial (effectiveness 73%; certainty 59%; harms 0%).

32http://www.conservationevidence.com/​actions/​864

● Create ponds (toads)

33Five studies in Germany, Switzerland, the UK and USA found that toads established breeding populations or reproduced in 16–100% of created ponds. Two studies in Denmark and Switzerland found that wild but not captive-bred toads colonized 29–100% of created ponds. One study in Denmark found that creating ponds, along with other interventions, increased toad populations. Assessments: likely to be beneficial (effectiveness 70%; certainty 60%; harms 0%).

34http://www.conservationevidence.com/​actions/​868

● Remove specific aquatic plants

35One before-and-after study in the UK found that habitat and species management that included controlling swamp stonecrop, increased a population of natterjack toads. One replicated, controlled study in the USA found that more Oregon spotted frogs laid eggs in areas where invasive reed canarygrass was mown. Assessment for ‘Control invasive plants’ from ‘Threat: Invasive alien and other problematic species’: likely to be beneficial (effectiveness 60%; certainty 47%; harms 0%).

36http://www.conservationevidence.com/​actions/​815

● Restore ponds

37Fifteen studies investigated the effectiveness of pond restoration for amphibians. Three studies, including one replicated, controlled, before-and-after study in Denmark, the UK and USA found that pond restoration did not increase or had mixed effects on population numbers and hatching success. One replicated, before-and-after study in the UK found that restoration increased pond use. One replicated study in Sweden found that only 10% of restored ponds were used for breeding. Three before-and-after studies, including one replicated, controlled study, in Denmark and Italy found that restored and created ponds were colonized by up to seven species. Eight of nine studies, including one systematic review, in Denmark, Estonia, Italy and the UK found that pond restoration, along with other habitat management, maintained or increased populations, or increased pond occupancy, ponds with breeding success or numbers of amphibian species. One found that numbers of species did not increase and one found that great crested newt populations did not establish. Assessment: likely to be beneficial (effectiveness 60%; certainty 63%; harms 0%).

38http://www.conservationevidence.com/​actions/​878

Unknown effectiveness (limited evidence)

● Remove tree canopy to reduce pond shading

39One before-and-after study in the USA found that canopy removal did not increase hatching success of spotted salamanders. One before-and-after study in Denmark found that following pond restoration that included canopy removal, translocated toads established breeding populations. Assessment: unknown effectiveness—limited evidence (effectiveness 30%; certainty 25%; harms 0%).

40http://www.conservationevidence.com/​actions/​758

No evidence found (no assessment)

41We have captured no evidence for the following interventions:

  • Add nutrients to new ponds as larvae food source
  • Add specific plants to aquatic habitats
  • Add woody debris to ponds
  • Create refuge areas in aquatic habitats.

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