1. The most common mechanism of biological invasions is an increase in competition, which usually results in the loss of biodiversity. The invasion of Bromus erectus (Syn. Bromopsis erecta) in calcareous grasslands of western and central Europe is well-documented. However, it is largely unknown to what extent this development affects biodiversity. 2. In this study, we analysed the effects of B. erectus invasion on vascular plant and leafhopper assemblages of calcareous grasslands. At each of the 15 randomly selected sites, we compared one plot with stands of Bromus (presence) and one without (absence) (paired sampling design). 3. The invasion of B. erectus affected vegetation structure as well as vascular plant and leafhopper assemblages. Despite similar abiotic site characteristics, Bromus plots had a higher turf height, vegetation density and litter cover. Additionally, we recorded a much lower species richness in Bromus plots than in absence plots in all analysed groups of vascular plants. A similar pattern was found for leafhoppers. Absence plots exhibited a higher species richness of habitat and diet specialists than Bromus plots. The overall abundance of all leafhopper species was highest in presence plots, whereas that of diet specialists peaked in absence plots. 4. We conclude that the ongoing invasion of B. erectus will lead to a strong structural homogenisation with negative effects on plant and insect diversity. One possible management tool might be a goal-driven rough grazing with sheep – especially in spring when B. erectus is much more palatable than in summer and autumn.
During offshore wind farms construction, abundance in harbour porpoise (Phocoena phocoena) is known to be negatively affected. From 2011 to 2013, extensive passive acoustic monitoring was conducted during research projects accompanying the construction of two wind farms in the German North Sea. Using C-PODs, we studied the effect ranges of pile driving disturbance on acoustic porpoise detections to test how these may change with different wind speeds. We found that disturbance radii highly depended on the prevailing wind speed during construction with further reaching effects at lower wind speed. Disturbance effects reached to 16 km at wind speed of 2m/s and to 10km at wind speed of 5m/s. With increasing wind speed, more air bubbles in the upper water layer may lead to greater mitigation of piling noise, thereby reducing disturbance radii for porpoises. Alternatively, increasing wind may increase high frequency noise due to sediment movement in the water, which could decrease the signal to noise ratio of piling noise leading to a decrease in porpoises' behavioural reactions. Our results indicate that wind speed and possibly background noise are important factors when assessing disturbance effects of anthropogenic noise on marine mammals.
The world’s growing demand for sustainable and environmentally friendly energy has led a growing number of countries to explore the options for the installation of offshore wind farms. In particular, noise emissions during the construction phase, when, in many cases, steel foundations are driven into the seafloor, are expected to cause temporal avoidance of the area by marine mammals and even have the potential to inflict physical damage to their sensory system (Madsen et al. 2006).
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