Objective: create habitat heterogeneity and/or restore hydrology
Definitions
● Intertidal zone = area between high and low tide.
● Reprofiling = changing the topography or landscape heterogeneity.
1. Description
Reprofiling intertidal habitats involves moving around the soil or sediment to create variation in the structure of a salt marsh or tidal flat. This includes excavating depressions or pools, creating mounds or ridges, or altering the slope. Moving and re-shaping sediment is a way of restoring the natural hydrology and topographic variation, to restore wetland function to support key species by creating a mosaic of sub-habitats and microhabitats. Depressions can provide shelter for colonising plants, while pools and islands can be used by birds for foraging, roosting and breeding. Variation in abiotic conditions (e.g. elevation and sediment grain size) drives variation in the species present, such as invertebrates and, consequently, birds (Cai et al ., 2023).
2. Evidence for effects on biodiversity
Birds: Evidence from inland wetlands has shown that creating wet features, like ponds and pools, to restore the original habitat can increase bird abundance (Provost, 1948; Hoffman, 1970; Holton & Allcorn, 2006; Squires & Allcorn, 2006), although some species may prefer to use older ponds rather than newly created ponds (Provost, 1948). On a coastal wetland in south-eastern USA, Great Egrets Ardea alba used man-made ponds but, overall, they tended to use natural wetlands more (Fidorra et al. , 2015). A study in Italy found that created intertidal ponds were the most heavily used feature by birds, followed by dykes and mounds with vegetation (Scarton & Montanari, 2015). Invertebrates: Benthic invertebrates both use and create microtopographic structures (Erftemeijer, 2023). They are sometimes referred to as ‘ecosystem engineers’ because of how they modify the substrate (e.g. by burrowing) (Jones et al. , 1994). A varied microtopography means there is variation in organic material, sediment and water across a site and thus more habitat options for different species (Desjardins et al. , 2012). Vegetation : Studies that have tested the effects of adding sediment to alter the elevation of a site, or to counteract subsidence, find that vegetation abundance increases to be higher than that in degraded sites (DeLaune et al. , 1990; Pezeshki et al. , 1992; Ford et al. , 1999; Schrift et al. , 2008; Stagg & Mendelssohn, 2012). A gentle slope provides a gradient that can aid the natural development of a salt marsh by generating areas that experience different amounts of flooding (Pitre & Anthamatten, 1981; Langis et al. , 1991; Pétillon et al. , 2010). A site in Belgium – from which buildings and fill material were removed and the remaining sediment reprofiled into an intertidal slope – developed salt marsh vegetation within one year but colonisation
72
Made with FlippingBook - professional solution for displaying marketing and sales documents online