Action: Clear vegetation
- Six 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 animals, increased numbers of frog species, or increased, stabilized or maintained populations of natterjack toads. One before-and-after study in the UK found that vegetation clearance, along with other habitat management, maintained a population of great crested newts for the first six years, but not in the longer term.
- One before-and-after study in England found that vegetation clearance, resulted in increased occupancy by natterjack toads.
Vegetation can be removed to prevent natural succession where specific habitat types are desired, or where invasive species are out-competing native species for example.
Studies that used fire or removed vegetation in forest are discussed in ‘Threat: Natural system modifications – Use prescribed burning’, ‘Use herbicides to control mid-storey or ground vegetation’ and ‘Mechanically remove mid-storey or ground vegetation’.
Studies that investigated the effect of removing aquatic plants are discussed in ‘Habitat restoration and creation – Remove specific aquatic plants’, ‘Threat: Invasive alien and other problematic species – Control invasive plants’ and as one of a combiniation of restoration management actions in ‘Habitat restoration and creation – Restore wetland’ and ‘Restore ponds’.
Supporting evidence from individual studies
A before-and-after study in 1972–1991 of heathland in Hampshire, UK (Banks, Beebee & Denton 1993) found that vegetation clearance resulted in increased occupancy by natterjack toads Bufo calamita (see also Buckley & Beebee 2004). At least six toads, including four juveniles, took up residence and established home ranges at the site within a year of vegetation clearance. However, within two years rank vegetation covered 90% of the ground and no toads remained in the area. Scrub was cleared from 40 ha by cutting and uprooting and bracken was treated with herbicide over 12 ha. Toads were monitored once every 10 days in March and August each year.
A replicated, before-and-after study in 1972–1995 of 10 dune and heathland sites in England, UK (Denton et al. 1997) found that extensive vegetation clearance, along with other terrestrial and aquatic habitat management, increased or maintained natterjack toad Bufo calamita populations. Abundance and range increased at four of the 10 sites. Success at another four sites was not yet clear, although toads persisted. At two sites, where vegetation clearance was less complete, populations continued to decline. At six sites where scrub removal was needed but not possible, populations remained low or were maintained by artificial methods (e.g. common toad removal). Clearance of invasive scrub and woodland and rotovation to clear patches of ground was undertaken. Low-density sheep or cattle grazing (<1 animal/3 ha) was also established at some sites (all/part year) to control succession. New ponds were created at most sites. Small numbers of ponds were treated with limestone. Translocations were made to some restored habitats. Ponds were monitored by counting spawn strings and estimating toadlet production.
A replicated, before-and-after study in 1972–1999 at two sites in England, UK (Buckley & Beebee 2004) found that vegetation clearance, along with pond creation and restoration and release of captive-reared toadlets increased natterjack toad Bufo calamita populations over 20 years. The continuation of a study in 1972–1991 (Banks, Beebee & Denton 1993) until 1999 indicated that there was a doubling of the population. Spawn string counts (female population) increased from 15 in 1972 to 32 in 1999, with a maximum number of 48 in 1989. At a second site, spawn string counts increased from 1 in 1973 to 8 in 1999, with a maximum number of 29 in 1997. Ponds were created and restored by excavation, scrub and bracken was cleared and captive-reared toadlets raised from spawn and released. Toads were monitored annually.
A before-and-after study in 1994–2004 of a coastal meadow on an islet in Estonia (Lepik 2004) found that vegetation clearance, along with other terrestrial and aquatic habitat restoration, resulted in a stable population of natterjack toads Bufo calamita. A total of 17 natterjacks were counted in 1992 and seven in 2004, with numbers in the range 1–17/year. It is considered by the author that without management the natterjack population might have declined further or become extinct. Common toad Bufo bufo counts were eight in 1992 and four in 2004 and ranged from 3–40/year. Restoration involved reed and scrub removal, mowing (cuttings removed) and implementation of sheep grazing. Toads were counted along a 1 km transect.
A replicated, before-and-after study in 2001–2004 of three coastal meadows in Estonia (Rannap 2004) found that vegetation clearance, along with other terrestrial and aquatic habitat restoration increased numbers of natterjack toads Bufo calamita on one island and halted the decline on the other two islands. In 2001–2004, habitats were restored on three coastal meadows where the species still occurred. Restoration included reed and scrub removal, mowing (cuttings removed) and implementation of grazing where it had ceased. Sixty-six breeding ponds and natural depressions were cleaned, deepened and restored.
A before-and-after study in 2005 of a mitigation site in England, UK (Lewis, Griffiths & Barrios 2007) found that vegetation clearance, along with other terrestrial and aquatic habitat management, maintained a great crested newt Triturus cristatus population (see also (ewis 2012). The population was classified as ‘large’ (peak count: 167) six years after habitat management. Management included tree felling, clearance of both terrestrial and aquatic vegetation and the re-profiling of ponds. Artificial hibernacula and refugia were also created in 1999. Monitoring was undertaken in March–May 2005 using egg searches, torch surveys and bottle trapping.
A before-and-after study in 1997–2004 of a golf course with degraded woodland and grassland in Sydney, Australia (Burgin & Wotherspoon 2009) found that restoration that included removing non-native weeds resulted in an increase in frog species over two years. Frogs increased from seven to 10 species in the first year and then remained stable for the following six years. A total of 18 species of frogs were predicted in the area and so 56% were present following restoration. The golf course was developed in 1993 and restoration undertaken in 1997–2001. Non-native weeds were removed, endemic shrubs and trees were planted and coarse woody debris was reintroduced to the woodland floor. The mowing regime was changed to develop grasslands and a narrow band of herb vegetation retained around ponds as a buffer zone. Pond perimeters were walked to record frog calls in 1996–2004.
A replicated, site comparison study in 1985–2006 of 20 sites in the UK (McGrath & Lorenzen 2010) found that natterjack toad Bufo calamita populations increased with species-specific habitat management that included vegetation clearance, in some cases with translocations. In contrast, long-term trends showed population declines at unmanaged sites. Individual types of habitat management (aquatic, terrestrial or common toad Bufo bufo management) did not significantly affect trends, but length of management did. Five of the 20 sites showed positive population trends, five showed negative trends and 10 trends were not significantly different from zero. Data on populations (egg string counts) and management activities over 11–21 years were obtained from the Natterjack Toad Site Register. Habitat management for toads was undertaken at seven sites. Management varied between sites, but included vegetation clearance, pond creation, adding lime to acidic ponds, maintaining water levels and implementing grazing schemes. Translocations were also undertaken at seven of the 20 sites using wild-sourced (including head-starting) or captive-bred toads.
A continuation of a study (Lewis, Griffiths & Barrios 2007) in 2006–2010 of a mitigation site in England, UK (Lewis 2012) found that although vegetation clearance, along with other terrestrial and aquatic habitat management, initially maintained a great crested newt Triturus cristatus population, numbers then declined. The number of newts recorded declined from 167 in 2005, six years after management, to just 10 in 2010. Management included tree felling, clearance of both terrestrial and aquatic vegetation and the re-profiling of ponds. Artificial hibernacula and refugia were also created in 1999. Monitoring was undertaken in March–May using egg searches, torch surveys and bottle trapping.
- Banks B., Beebee T.J.C. & Denton J.S. (1993) Long-term management of a natterjack toad (Bufo calamita) population in southern Britain. Amphibia-Reptilia, 14, 155-168
- Denton J.S., Hitchings S.P., Beebee T.J.C. & Gent A. (1997) A recovery program for the natterjack toad (Bufo calamita) in Britain. Conservation Biology, 11, 1329-1338
- Buckley J. & Beebee T.J.C. (2004) Monitoring the conservation status of an endangered amphibian: the natterjack toad Bufo calamita in Britain. Animal Conservation, 7, 221-228
- Lepik I. (2004) Coastal meadow management on Kumari Islet, Matsalu Nature Reserve. Pages 86-89 in: Coastal meadow management - best practice guidelines. Tallinn.
- Rannap R. (2004) Boreal Baltic coastal meadow management for Bufo calamita. Pages 26-33 in: Coastal meadow management - best practice guidelines. Tallinn.
- Lewis B., Griffiths R.A. & Barrios Y. (2007) Field assessment of great crested newt Triturus cristatus mitigation projects in England. Natural England report. Natural England Research Report NERR001.
- Burgin S. & Wotherspoon D. (2009) The potential for golf courses to support restoration of biodiversity for biobanking offsets. Urban Ecosystems, 12, 145-155
- McGrath A.L. & Lorenzen K. (2010) Management history and climate as key factors driving natterjack toad population trends in Britain. Animal Conservation, 13, 483–494
- Lewis B. (2012) An evaluation of mitigation actions for great crested newts at development sites. PhD thesis. The Durrell Institute of Conservation and Ecology, University of Kent.