Action

Create or restore wetlands

How is the evidence assessed?
  • Effectiveness
    not assessed
  • Certainty
    not assessed
  • Harms
    not assessed

Study locations

Key messages

  • Seven studies evaluated the effects of creating or restoring wetlands on reptile populations. Six studies were in the USA and one was in Kenya.

COMMUNITY RESPONSE (3 STUDIES)

  • Richness/diversity (3 studies): One before-and-after, site comparison study in the USA found that reptile species richness and diversity tended to be lower in a restored wetland compared to an undisturbed wetland. One replicated, site comparison study in the USA found that created, restored, enhanced and natural wetlands had similar combined reptile and amphibian species richness. One site comparison study in the USA found that created wetlands and adjacent natural forest had similar reptile species richness and diversity.

POPULATION RESPONSE (2 STUDIES)

  • Reproductive success (2 studies): One site comparison study in the USA found that a created wetland was used by snapping turtles for egg laying. One before-and-after, site comparison study in the USA found that in a restored wetland, 16 snake, six lizard and eight turtle species successfully reproduced.

BEHAVIOUR (4 STUDIES)

  • Use (4 studies): One site comparison study and three before-and-after studies (including one replicated study) in the USA and Kenya found that created or restored wetlands were used by black rat snakes and snapping turtles, turtles, lizards, green grass snakes and terrapins, six or 18 reptile species.

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

  1. A site comparison study in 1995–1996 of two forested wetlands in Maryland, USA (Perry et al. 1996) found that some reptiles colonised a created forested wetland. Black rat snakes Elaphe obsoleta were seen basking and several snapping turtles Chelydra serpentina laid eggs in a created forested wetland. A single five-lined skink Eumeces fasciatus was trapped in the adjacent natural wetland but none were trapped in the created wetland. As mitigation for loss of wetland, a 9 ha wetland was constructed in 1994, of which 5.5 ha was forested wetland. Reptiles were captured in pitfall and funnel traps along drift-fencing within the created and adjacent natural forested wetland. Trapping was conducted several times in 1995–1996.

    Study and other actions tested
  2. A before-and-after study in 1996–1997 of a created wetland in Nairobi, Kenya (Nyakang’o & vanBruggen 1999) found that reptiles used the wetland. Turtles, lizards, green grass snakes and terrapins were recorded in the wetland. In 1996, a 0.5 ha wetland was constructed using a combination of a sub-surface horizontal flow system planted with Typha, followed by a series of three pond systems planted with a variety of species including local reeds and ornamental plants. Ponds were shallow near the shore with deep sections in the centre (1.5 m).

    Study and other actions tested
  3. A before-and-after, site comparison study in 1995–1996 of a degraded forested wetland in South Carolina, USA (Bowers et al. 2000) found that restoration increased numbers of reptile species over the first four years. Twenty-four snake species, nine lizard species, nine turtle species and American alligator Alligator mississippiensis were captured in the restoration area. Successful reproduction was documented for 16 snake, six lizard and eight turtle species. It was assumed that there were no reptiles prior to restoration. However, species diversity (in one of three years) and overall richness was lower in the restored compared to natural site (results presented as indices). Planting regimes, burning or herbicide application had little effect on species assemblage. Restoration included tree planting in 1993–1995 (549–1,078 trees/ha). In some areas herbicide application and prescribed burns were undertaken to control scrub. Approximately 25% of the restoration area was left as unmanaged strips for comparison. Reptiles were monitored over 21 months in planted and unplanted areas and in adjacent natural wetland area using coverboards, minnow traps, turtle traps and hand captures.

    Study and other actions tested
  4. A before-and-after study in 1992–1994 in a wetland in Florida, USA (Kent & Langston 2000) found that six reptile species used the wetland within the first two years. The reptiles were first observed six months after the wetland was created and in total six reptile species usually associated with wetlands were recorded. Overall species richness continued to increase throughout the study. A 32 ha wetland was created in July 1992. Reptiles were monitored quarterly from July 1992 to August 1994. Counts were undertaken on transect and perimeter walks.

    Study and other actions tested
  5. A replicated, site comparison study in 1999–2000 of 17 wetlands in South Dakota, USA (Juni & Berry 2001) found that combined reptile and amphibian species richness was similar between created, restored, enhanced and natural wetlands. There were a similar number of species in created, restored, enhanced and natural wetlands (1–3 species/wetland). A total of 11 reptile and amphibian species were recorded. Four created, four restored, four enhanced and five natural wetlands were sampled. Wetland creation involved either impounding a small stream or excavating a basin. Restoration included plugging drainage ditches or breaking sub-surface drainage tiles. Enhancement included manipulating water levels to increase wetland size or changing vegetation structure. Wetland creation, restoration and enhancement were carried out within the previous 10 years. Monitoring was undertaken using drift-fences with pitfall traps, fish nets and visual surveys around wetland perimeters in spring and autumn in 1999–2000.

    Study and other actions tested
  6. A site comparison study in 1995–1996 of a created wetland and adjacent forest in Maryland, USA (Toure & Middendorf 2002) found that created wetlands had similar reptile richness and diversity to the adjacent natural forest. Reptile richness or diversity were similar between created wetlands (richness: 2–6 species; Simpson’s diversity index: 0.2–0.8) and natural forest (richness: 4; diversity: 0.7). Two of 12 total species were recorded in both created wetland and natural forest. Eight of 12 species were recorded in created wetland but not natural forest and two of 12 species were recorded in natural forest but not created wetland. The 52 ha wetland was constructed in four terraces and was surrounded by regenerating forest. Monitoring was undertaken in March–September 1995–1996 using transects, call counts, drift-fencing with pitfall and funnel traps. The adjacent forest was used as a reference site.

    Study and other actions tested
  7. A replicated, before-and-after study in 2000–2004 of three constructed wetlands in southern Illinois, USA (Palis 2007) found that reptiles colonized, and continued to colonize, wetlands over four years of monitoring. A total of 18 species were recorded including seven turtle species (38–66 individuals/wetland), nine snake species (101–129) and two lizard species (0–2). Five additional reptile species were recorded in the second year after wetland creation, two in the third year and four in the fourth year, suggesting ongoing colonization. Wetlands were created on a former vegetable farm in 1999–2000 by enclosing water behind earth dams at the end of valleys. Hardwood tree seedlings were also planted. Wetlands were surveyed in April–June in 2001–2004. Monitoring was undertaken using drift-fencing (four fences/wetland and three fences/adjacent habitat) with funnel traps (4 traps/fence), artificial coverboards (0.7 m2), visual encounter surveys and baited hoop net traps (one trap/wetland).

    Study and other actions tested
Please cite as:

Sainsbury K.A., Morgan W.H., Watson M., Rotem G., Bouskila A., Smith R.K. & Sutherland W.J. (2021) Reptile Conservation: Global Evidence for the Effects of Interventions for reptiles. Conservation Evidence Series Synopsis. University of Cambridge, Cambridge, UK.

Where has this evidence come from?

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Reptile Conservation

This Action forms part of the Action Synopsis:

Reptile Conservation
Reptile Conservation

Reptile Conservation - Published 2021

Reptile synopsis

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What Works in Conservation

What Works in Conservation provides expert assessments of the effectiveness of actions, based on summarised evidence, in synopses. Subjects covered so far include amphibians, birds, mammals, forests, peatland and control of freshwater invasive species. More are in progress.

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