Regulate water levels
Overall effectiveness category Awaiting assessment
Number of studies: 1
Background information and definitions
Dams or ‘impoundments’ directly influence reptile populations, especially turtles, by fragmenting habitat and causing nest mortality through flooding via artificial stream regulations (e.g. artificially raising water levels in summer for boat navigation purposes; Bodie 2001). Undamming rivers and restoring ecological flow are both management interventions used to increase river health and change water levels (Bednarek 2001).
Bednarek A.T. (2001) Undamming rivers: a review of the ecological impacts of dam removal. Environmental Management, 27, 803–814.
Bodie J.R. (2001) Stream and riparian management for freshwater turtles. Journal of Environmental Management, 62, 443–455.
Supporting evidence from individual studies
A controlled, before-and-after study in 1997–2013 in two marshes with canals in Camargue, France (Ficheux et al. 2014) found that autumn–spring flooding along with autumn–winter grazing increased European pond turtle Emys orbicularis abundance. European pond turtle abundance was greater with autumn–spring marsh flooding and moderate-stocking density autumn–winter grazing (192–436 individuals), compared to winter–spring marsh flooding and high-stocking density spring–summer grazing (107–182 individuals) or year-round flooding and low-stocking density grazing (182–227 individuals). In a nearby site with moderate year-round flooding and grazing, European pond turtle abundance was stable over the same time period (29–153 individuals, data taken from graphs). Turtles were live-trapped in April–August 1997–2013 (7,059 total captures of 963 individuals) in two sites (100–250 ha, 1.5 km apart). In 1997–2001, both sites were flooded and grazed year-round at low-moderate stocking density. In one site, in 2002–2006, water levels were modified to create a dry period in summer–autumn, with natural flooding in winter–spring and grazing was changed to high density stocking in spring–summer (see original paper for details). In the same site, in 2007–2013, the flooding period was extended so that autumn–spring were flooded and only summer was dry, and moderate density grazing took place in autumn–winter.Study and other actions tested