A Review of Current Scientific Perspectives on the Effects of Dredging in Freshwater Environmental Restoration

Abstract

Mechanical dredging has been used to desilt and remove excessive vegetation in aquatic environments, with the aim of restoring water quality and local physical characteristics. However, the biotic and abiotic impacts of this process are still poorly understood. Therefore, we conducted a scientometric review and produced a synthesis of the main impacts and benefits of mechanical dredging on aquatic ecosystems. From 2,314 unique articles identified in the database searches, 46 met the eligibility criteria for evaluating the effects of dredging for restoration in freshwater environments on aquatic communities. The number of studies has increased over time, with studies carried out mainly in the USA, Poland, China and the Netherlands. Studies in fields and lotic environments were the most common. During dredging, most studies showed an increase in nutrient concentration and a reduction in dissolved oxygen and diversity. Only two studies evaluated the effect of dredging on greenhouse gasses and seven studies on population metrics. The planktonic communities were the least studied. In general, during the dredging process there is a deleterious change in water parameters and a reduction in biodiversity. The benefits of dredging are observed later, with an increase in biodiversity and dissolved oxygen concentration and a reduction in the concentration of nutrients and chemical pollutants. Therefore, alternatives for remedying the impacts during the dredging process should be considered when drawing up the management project.