Action

Leave standing/deadwood snags in forests

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

Study locations

Key messages

  • Two studies evaluated the effects of leaving standing/deadwood snags in forests on reptile populations. Both studies were in the USA.

COMMUNITY RESPONSE (2 STUDIES)

  • Richness/diversity (2 studies): One of two replicated, randomized, controlled studies in the USA found that adding snags and woody debris had mixed effects on reptile diversity and species richness when compared to not manipulating debris or removing debris. The other study found that increasing standing coarse woody debris had no effect on reptile diversity and species richness.

POPULATION RESPONSE (2 STUDIES)

  • Abundance (2 studies): One of two replicated, randomized, controlled studies in the USA found that adding snags and woody debris had mixed effects on reptile abundance when compared to not manipulating debris or removing debris. The other study found that increasing standing coarse woody debris had no effect on reptile abundance.

BEHAVIOUR (0 STUDIES)

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 replicated, randomized, controlled study in 1998–2005 of pine stands in South Carolina, USA (Owens et al. 2008, same experimental set-up as Davis et al. 2010) found that the creation or removal of snags (standing dead trees) had no effect on reptile abundance, species richness and diversity compared to not manipulating debris in forests. In two trials, reptile abundance, species richness and diversity was similar between plots with snags added (abundance: 0.2–0.3 individuals/plot, richness: 5–6 species, diversity: 10–13 Shannon-Weiner index), or all snags and coarse woody debris removed (0.3–0.5, 6–7, 13–17), compared to not manipulating debris (0.3–0.4, 7, 13–17). In the second trial, reptile abundance, richness and diversity were lower when standing snags were added (0.3 individuals/plot, 5 species, 10 Shannon-Weiner index, respectively) compared to when all woody debris was removed (0.5, 7, 17). Snake abundance was higher with woody debris removal compared to snag addition (debris removal: 0.2 individuals/plot; snags added: 0.1), but lizard abundance was not (debris removal: 0.3 individuals/plot; snags added: 0.2). Treatments were randomly assigned to 9 ha plots within three forest blocks in 1996–2001: standing snag addition (10 fold increase), all woody debris removal, downed woody debris addition (five-fold increase), and no manipulation and in 2002–2005: downed woody debris addition, woody debris removal, standing snag addition, and no manipulation. Reptiles were sampled using drift fences with pitfall traps in 1998–2005.

    Study and other actions tested
  2. A replicated, randomized, controlled study in 1996–2008 in a loblolly pine Pinus taeda forest in South Carolina, USA (Davis et al. 2010, same experimental set-up as Owens et al. 2008) found that increasing standing coarse woody debris had no effect on reptile abundance, species richness or diversity. Abundance, species richness and diversity were similar between plots with increased standing woody debris (abundance: 0.18 individuals/m fencing, richness: 0.10 species/m fencing, diversity: 0.03 Shannon-Wiener Index) and plots with no manipulation of debris (0.15, 0.11, 0.03). Nine-ha plots within three pine stands (approximately 45 years old) were randomly assigned the following management: standing woody debris increased 10 fold by girdling then injecting with herbicide (initiated 2001, to 35 m3/ha woody debris in 2007) or no manipulation of woody debris (initiated 1996, 13 m3/ha woody debris). All plots were prescribed burned in 2004. Reptiles were sampled for 14 days/plot in each of seven seasons (January 2007–August 2008) using drift fences with pitfall traps.

    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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