Close roads during seasonal amphibian migration

Overall effectiveness category Likely to be beneficial
Number of studies: 2
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How is the evidence assessed?

Effectiveness

85%
Certainty

50%
Harms

0%

Calculating overall effectiveness category

Background information and definitions

Road traffic can have significant effects on amphibian populations, particularly where their annual migration routes between overwintering and breeding sites cross roads. In some areas, roads can be closed to protect important migration routes.

One study showed that reducing traffic on minor roads by creating a highway prevented fragmentation of populations of palmate newts Lissotriton helveticus but not midwife toads Alytes obstetricans (Garcia-Gonzaleza et al. 2012).

Garcia-Gonzaleza C., Campoa D., Polaa I.G. & Garcia-Vazqueza E. (2012) Rural road networks as barriers to gene flow for amphibians: Species-dependent mitigation by traffic calming. Landscape and Urban Planning, 104, 171–180.

Study locations

Key messages

Two studies (including one replicated study) in Germany found that large numbers of amphibians were protected from death during breeding migrations at road closure sites and at road closure sites with assisted crossings and barrier fences.

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 before-and-after study in 1983 of a road in Oberbergischer Kreis, Germany (Karthaus 1985) found that closing the road allowed common toads Bufo bufo to successfully cross. While the road was open none of the young amphibians reached the other side. However, one hour after closure about 100,000 toads were found crossing along a 400 m section of the road. The road was closed for eight days until the migration of amphibians was over in spring.
Study and other actions tested
Referenced paper
Karthaus G. (1985) Protective measures for migrating amphibians from danger from road traffic - observations and experiences. Natur und Landschaft: Zeitschrift fur Naturschutz und Landschaftspflege, 60, 242-247.
A replicated study in 1986 of 114 sites including at least 11 road closure sites, 60 amphibian barrier fences and 23 hand-collected human-assisted crossings in Nordrhein-Westphalia, Germany (Feldmann & Geiger 1989) found that 131,061 amphibians were protected from death on roads during breeding migrations. Between one and 116,515 individuals of 14 species were recorded at the road closure sites, assisted crossings and barrier fences at the 114 sites. Nine sites had a combination of two of the interventions and for 20 sites it was unknown which of the interventions were used.
Study and other actions tested
Referenced paper
Feldmann R. & Geiger A. (1989) Protection for amphibians on roads in Nordrhein-Westphalia. Amphibians and Roads: Proceedings of the Toad Tunnel Conference, Rendsburg, Federal Republic of Germany, 51-57.

Please cite as:

Smith, R.K., Meredith, H. & Sutherland, W.J. (2020) Amphibian Conservation. Pages 9-64 in: W.J. Sutherland, L.V. Dicks, S.O. Petrovan & R.K. Smith (eds) What Works in Conservation 2020. Open Book Publishers, Cambridge, UK.

Where has this evidence come from?

List of journals searched by synopsis

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This Action forms part of the Action Synopsis:

Amphibian Conservation

Related Actions

Actions	Effectiveness	Studies	Category
Use signage to warn motorists Action Link	Unknown effectiveness (limited evidence)	1	Synopsis Link
Close roads during seasonal amphibian migration Action Link	Likely to be beneficial	2	Synopsis Link
Modify gully pots and kerbs Action Link	Likely to be beneficial	1	Synopsis Link