Action: Provide buffer strips alongside water courses (rivers and streams)
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- Three studies (including one replicated site comparison) from the Netherlands and the UK reported that the provision of riparian buffer strips had a positive influence on plant, invertebrate and bird diversity or abundance, and supported vegetation associated with habitats preferred by water voles.
- Two replicated site comparison studies from France and Ireland found that the provision of riparian buffer strips on farms did not result in an increase in the number of plant species when compared to farms without buffer strips.
- One replicated site comparison study found ground beetle diversity was higher in grazed riparian zones and narrow fenced strips than in wide riparian buffer strips. However the ground beetle assemblages in wide riparian buffer strips were more distinct from the adjacent pasture field assemblages than either the grazed riparian zones or narrow fenced strips.
Supporting evidence from individual studies
A site comparison study in 1995 and 1997 of two areas under the Habitat Scheme Water Fringe Option in Wiltshire and Kent, UK (Critchley et al. 1999) found that the scheme, which includes establishment of riparian buffer strips (10-30 m wide), resulted in river bank vegetation associated with habitats preferred by water voles Arvicola terrestris (in terms of plant species and vegetation heights). Wetland, grassland or ruderal plant species dominated river bank vegetation in the three rivers studied in Wiltshire (40% wetland, 27% grassland and 6% ruderal species) and comprised over half the species along the one river studied in Kent (21% wetland, 20% grassland and 15% ruderal species). The three sites sampled in Wiltshire in 1997 had a relatively high frequency of vegetation up to 60 cm tall, which has been shown to be important for water voles. In Kent, two of the three sites also tended to have a higher frequency of taller vegetation. The species composition of bankside vegetation was sampled within 20 m long representative sections at 27 sites in the two areas in 1995. At six sites surveyed in 1997, plant species were allocated to different height classes and the number of species in each class summed for each of five 4 m sub-sections.
A replicated paired sites comparison in 1999 of grassland habitats on 30 farms in Counties Laois and Offaly, Ireland (Feehan et al. 2002) (same study as Feehan et al. 2005) found that fenced watercourse margins on Rural Environment Protection Scheme farms did not have higher numbers of plant species than unfenced watercourse margins on non-Rural Environment Protection Scheme farms. For watercourse margins (eight paired replicates) more plant species were found in unfenced than fenced margins (52 and 56 species on unfenced margins on Rural Environment Protection Scheme and non-Rural Environment Protection Scheme farms respectively, 50 and 48 species on fenced margins on Rural Environment Protection Scheme and non-Rural Environment Protection Scheme farms respectively). Watercourse margins were fenced to exclude grazing livestock. Plants were surveyed on one watercourse margin on each farm.
A replicated paired sites comparison study in 2000 in counties Laois and Offaly, Ireland (Feehan et al. 2005) (same study as Feehan et al. 2002) found that fenced watercourse margins on Rural Environment Protection Scheme farms did not have higher numbers of plant species than unfenced watercourse margins on non-Rural Environment Protection Scheme farms (14.7 and 16.1 plant species/margin respectively). Fifteen farms with Rural Environment Protection Scheme agreements at least four years old were paired with 15 similar farms without agreements. On each farm, a randomly selected watercourse margin was surveyed for plants: all plant species were recorded in two 5 x 3 m quadrats, and percentage cover estimated in a 1 x 3 m quadrat within each margin. Eleven of the farm pairs enabled a fenced/unfenced comparison.
A replicated site comparison study in 2005 and 2006 in Seine-et-Marne, France (Chateil et al. 2007) found that the number of plant species was higher on farms that did not have buffer strips (mostly along rivers to prevent water pollution), relative to farms that did include these measures. The numbers of plant species in this comparison are not given, and the number of farms with and without these buffer strips not specified. Twenty-six fields from 17 farms were sampled three times in 2005 (April, June, September). Sixty-four fields from 31 farms (including all those surveyed in 2005) were sampled twice in 2006 (April and July). Plants were recorded in ten permanent, regularly spaced, 1 m2 (0.5 x 2 m) quadrats along the permanent margins of each field.
A replicated site comparison study from 1999 to 2004 in the Netherlands (Manhoudt et al. 2007) found that ditch bank plant diversity was significantly higher on farms with ecologically-managed ditches with ≥ 3 m-wide field margin buffer strips (36-65 plant species/400 m2) compared to conventionally managed farms without buffer margins or ecological management (26-34 plant species/400 m2). The number of plant species on ecologically-managed ditch banks with buffer strips was also higher than ditch banks without buffer strips or ecological management on organic farms (32-52 plant species/400 m2). Ecologically managed strips were cut once in September and the cuttings removed to reduce nutrient input. Cutting date varied on conventional and organic farms, but cuttings were never removed. Four ecologically managed farms, 18 conventional and 20 organic arable farms were studied. On ecologically managed farms, plant species surveys of 100 m of ditch bank spread over the whole farm were undertaken once a year from 1999 to 2004. On organic (in 2001) and conventional (2003) farms, plant species presence was recorded on 10 x 25 m of ditch bank along a transect (May-June).
A single-site study from 2004 to 2006 in Leicestershire, UK (Stoate et al. 2007) found that a sequence of seven constructed pools and a riparian buffer strip provided habitat for plant, invertebrate and bird diversity including previously absent species. Pools supported 30 aquatic plant species (macrophytes) including two locally scarce species (9-18 species/pool). Six Nationally Scarce and four locally uncommon water beetles (Coleoptera) were found in the pools (total 84 invertebrate species, 24-52 species/pool). Five species of grasshopper and cricket (Orthoptera) previously absent from the site were recorded, in addition to twelve hoverfly (Syrphidae) species of which two were scarce or new county records. More whitethroat Sylvia communis, reed bunting Emberiza schoeniclus and moorhen Gallinula chloropus territories were found following establishment of the wetland (4, 3 and 1 territories with pools/buffer strip vs 1, 1 and 0 prior to pools/buffer strip). The buffer strip was also used by lapwing Vanellus vanellus, yellowhammer Emberiza citrinella (breeding species), common snipe Gallinago gallinago and jack snipe Lymnocryptes minimus (overwintering species). The field drain fed wetland was constructed in 1998. The pool sequence was a maximum of 20 m wide, within a riparian buffer strip approximately 70 m wide by 100 m long. Aquatic plants were listed and aquatic macroinvertebrates sampled (3 minutes/pool, June 2004-2005) in six of seven pools. Grasshoppers and crickets (June 2005-2006) were sampled and a ten-visit territory mapping bird survey (May-June 2006) undertaken within the buffer strip; birds had also been surveyed in 1992.
A replicated, site comparison study from 2004 to 2006 in Scotland (Cole et al. 2008) found that there were more plant species in riparian zones (grazed and ungrazed strips) compared to the adjacent intensively managed pasture fields. Ground beetle (Carabidae) diversity was greater in grazed riparian zones and in narrow ungrazed strips than in wide buffer strips or adjacent fields. However, ground beetle assemblages in wide buffer strips were more distinct from adjacent field assemblages than those in narrow strips or grazed riparian zones. There were no significant differences between the numbers of ground beetles or plant species in narrow or wide ungrazed buffer strips. Three types of riparian zone on seven farms were studied: open sites (no fence between the field and the watercourse, grazed by livestock), narrow strips (strips less than 2 m-wide fenced off around watercourse, ungrazed), and wide buffer strips (strips more than 4 m-wide fenced off around watercourse, ungrazed). Two transects were sampled at 22 locations, one adjacent to the watercourse, the other 4–6 m into the field from the fenceline (dividing the riparian zone from the field), or for unfenced, open sites 4–6 m from the watercourse transect. For wide buffer strip sites an additional transect was sampled, halfway between the fenceline and the watercourse transect. Ground beetles were sampled along transects during two 4-week periods (June and July) using pitfall traps (75 mm diameter). Vegetation composition was sampled using a quadrat (1 x 1 m) survey.
- Critchley C.N.R., Hodkinson D.J. & McKenzie S.E. (1999) Potential benefits to water voles Arvicola terrestris of waterside buffer strips in an agri-environment scheme. Aspects of Applied Biology, 54, 179-184
- Feehan J., Gillmor D.A. & Culleton N.E. (2002) The impact of the Rural Environment Protection Scheme (REPS) on plant and insect diversity. Tearmann, 2, 15-28
- Feehan J., Gillmor D. & Culleton N. (2005) Effects of an agri-environment scheme on farmland biodiversity in Ireland. Agriculture, Ecosystems & Environment, 107, 275-286
- Chateil C., Abadie J.C., Gachet S., Machon N. & Porcher E. (2007) Can agri-environmental measures benefit plant biodiversity? An experimental test of the effects of agri-environmental measures on weed diversity. Vingtième conférence du columa journées internationales sur la lutte contre les mauvaises herbes, Dijon, 356.
- Manhoudt A.G.E., Visser A.J. & de Snoo G.R. (2007) Management regimes and farming practices enhancing plant species richness on ditch banks. Agriculture, Ecosystems & Environment, 119, 353-358
- Stoate C., Whitfield M., Williams P., Szczur J. & Driver K. (2007) Multifunctional benefits of an agri-environment scheme option: riparian buffer strip pools within 'Arable Reversion'. Aspects of Applied Biology, 81, 221-226
- Cole L.J., Morton R. & Harrison W. (2008) The influence of riparian buffer strips on carabid beetle (Coleoptera, Carabidae) assemblage structure and diversity in intensively managed grassland fields. Biodiversity and Conservation, 17, 2233-2245