Aquatic macroinvertebrate biodiversity associated with artificial agricultural drainage ditches

Abstract

Agricultural drainage ditches are ubiquitous features in lowland agricultural landscapes, built primarily to facilitate land drainage, irrigate agricultural crops and alleviate flood risk. Most drainage ditches are considered artificial waterbodies and are not typically included in routine monitoring programmes, and as a result the faunal and floral communities they support are poorly quantified. This paper characterises the aquatic macroinvertebrate diversity (alpha, beta and gamma) of agricultural drainage ditches managed by an internal drainage board in Lincolnshire, UK. The drainage ditches support very diverse macroinvertebrate communities at both the site (alpha diversity) and landscape scale (gamma diversity) with the main arterial drainage ditches supporting greater numbers of taxa when compared to smaller side ditches. Examination of the between site community heterogeneity (beta diversity) indicated that differences among ditches were high spatially and temporally. The results illustrate that both main arterial and side ditches make a unique contribution to aquatic biodiversity of the agricultural landscape. Given the need to maintain drainage ditches to support agriculture and flood defence measures, we advocate the application of principles from 'reconciliation ecology' to inform the future management and conservation of drainage ditches.

Turning old foes into new allies – harnessing drainage canals for biodiversity conservation in desiccated novel ecosystems

“…Although grassland canals proved to be more species rich for most taxa than agricultural ones, both types deserve our attention, as grassland ones exceed adjacent semi-natural grassland richness and agricultural canals represent the only conservation value in hostile agricultural landscapes. Large canals may be expected to have higher conservation value than small ones (Hill et al, 2016), but we found little evidence for this, as butterfly, true bug, spider and bird richness were not affected by canal size. Although plant species richness on the gamma level was higher in large canals, the abundance of invasive species was also higher in them, meaning that they are stronger conduits of plant invasion than small canals.…”

“…Drainage canals are ubiquitous components of managed lowland landscapes worldwide (Shaw et al, 2015; Hill et al, 2016). Although drainage is among the primary causes of the loss of the original biodiversity, there is growing evidence that canals can act as refuges for a variety of native species in desiccated and transformed landscapes (Chester & Robson, 2013; Golubovic et al, 2017; Torma et al, 2018), reinforcing the importance of moist microenvironments in the face of local and global environmental changes (Keppel et al, 2011; Mclaughlin et al, 2017).…”

“…Drainage and subsequent land cultivation has been a major threat to global wetland ecosystems for centuries (Herzon & Helenius, 2008; Blann et al, 2009; Davidson, 2016). In Europe, most lowland fens have been drained (Langheinrich et al, 2004; Hill et al, 2016); approximately 25% of the arable land of the United States is artificially drained (Herzon & Helenius, 2008), and immense wetlands have recently been drained in tropical Southeast Asia to gain land for agriculture (Aldhous, 2004). Canals, the main tools of drainage, are usually retained after the draining process and are regularly managed to sustain low and stable water balance in the cultivated landscape.…”

“…Canals, the main tools of drainage, are usually retained after the draining process and are regularly managed to sustain low and stable water balance in the cultivated landscape. Drainage canals are thus ubiquitous in heavily modified lowland agricultural landscapes worldwide (Shaw et al, 2015; Hill et al, 2016) and can form dense networks of interconnected artificial waterways. For instance, over 100,000 km of canals criss-cross the farmlands of the United Kingdom (Hill et al, 2016), and the total length of canals exceeds 300,000 km in the Netherlands (Blomqvist et al, 2003).…”

The use of palaeoecological and contemporary macroinvertebrate community data to characterize riverine reference conditions

“…For each of the 32 samples (12 contemporary samples recorded across three seasons, nine historical samples, and 11 palaeoecological), gamma and alpha diversity of the macroinvertebrate community (GTC) were determined. Gamma diversity is defined here as the total diversity within a predefined region based on available samples and alpha diversity as that within an individual sample (Hill, Chadd, Morris, Swaine, & Wood, ). Statistical differences in GTC alpha diversity among contemporary, historical (1972—Pearson & Jones, , and 1930—Whitehead, ), and palaeoecological samples were examined via a Kruskal–Wallis test using the function Kruskal.test .…”