The Beauty and Ecosystem functions of Small Shallow Waters

Abstract

Growing agricultural land use and use of agrochemicals have led to pressure on ecosystems and are among the causes for the decline in biodiversity. In agriculturally dominated landscapes, ditches provide interesting opportunities for enhancing biodiversity and mitigating detrimental effects of agricultural practises. This review aimed to qualitatively explore the value of ditches for 1) biodiversity and 2) mitigating agricultural pollution. A systematic search was performed using the Pubmed, Web of Science and SpringerLink databases for primary papers published in the last 25 years and conducted in the EU. 98 eligible papers were identified, and a thematic saturation approach was chosen for this review. Ditches were found to have the capacity to enhance biodiversity by cumulatively harbouring many species, including rare and endangered ones. That said, homogenisation and loss of functional diversity were identified risks. Maintaining heterogeneity and creating microhabitats though management is important for maintaining ecological value. On top of this, ditches were also found to have valuable nutrient and pesticide retention capacity. This capacity is driven by denitrification, plant uptake, microbial degradation, sorption to soil, and trapping sediment. Vegetation and buffer zones were found contribute to trapping sediment, increase retention time and sorption surface thus enhancing retention efficiency. Additionally, availability of organic matter was also found to increase sorption of hydrophobic pesticides and affect microbial functionality. Designing ditches with low slopes, vegetation in ditch beds and buffer zones can help achieve the dual purpose of enhancing biodiversity and mitigating agricultural pollution. Maintenance strategies of ditches were shown to be able to both positively and negatively affect biodiversity. Mainly breaking dominance of nitrophytes and creating heterogeneity in microhabitats were beneficial. With careful planning, maintenance strategies can be designed to maximise both outcomes. Variables such a soil climatic factors, soil properties and ditch design need to be understood to allow for adequate interpretation of these values and correctly designing strategies.