RATIONALE. Measures to reduce disturbances
Disturbances caused by transport infrastructure and its associated traffic have impacts on biodiversity. Artificial lighting, noise, and chemical pollution reduce habitat suitability, increase barrier effect, and can even increase wildlife mortality (Sordello et al., 2019; 2022). These effects reach distances far beyond their source, affecting adjacent habitats and even protected areas (Jechow et al., 2020; Mu et al., 2021; Sordello et al., 2022).
Light pollution has been demonstrated to create impacts on ecosystems, affecting flora and fauna, both diurnal and nocturnal species (Knop et al., 2017; Falcón et al., 2020; Touzot et al., 2021; Sanders et al., 2021; Meng et al., 2022; Sordello et al., 2022). Moreover, the use of extensive artificial lighting to increase road safety is not always justified as some studies have found little or no evidence of any such relationship (CEDR, 2009; Steinbach et al., 2015; Marchant et al., 2020).
Within transport infrastructure the presence of light, either from vehicles or from the infrastructure itself, reinforces habitat fragmentation (Barré et al., 2020; Sordello et al., 2022). Several species from different groups have shown a general avoidance of light in the infrastructure (Degen et al., 2016; van Grunsven et al., 2017), including avoidance of underpasses which are provided with lighting (Bliss-Ketchum, et al., 2016; Barré et al.,2020; Bhardwaj et al., 2020b).
The need to establish ‘dark corridors’ as an ecological network for nocturnal wildlife has been proposed as a measure to enhance ecological connectivity (Challéat et al., 2021). The timing and location of lighting within these networks must be carefully considered in order to be truly effective.
Traffic noise has also been demonstrated to affect many biological functions, like communication or reproduction, in a wide variety of species (Sordello et al., 2019, and references therein). Usually, noise mitigation measures are implemented to protect people from disturbance, since noise has negative effects on human health (EC, 2002). International transport organisations, such as CEDR, PIARC and UIC, have developed different solutions in this framework (CEDR, 2012; PIARC, 2013; 2019; UIC, 2021). These solutions can be extended to natural protected areas or any other area important for ecological connectivity, such as ecological corridors.
Traffic and maintenance of transport infrastructure produce numerous chemical substances that pollute surrounding habitats. Reduction of carbon emissions by cars is a main focus, but there are other initiatives necessary to reduce or avoid the spread of pollutants, for example by treating water runoff from roads (CEDR, 2016).
Chemicals used in the maintenance of vegetation in verges and medians is another source of pollution. Projects like TRISTRAM (UIC, 2021) provide alternative sustainable methods for vegetation control. While this project’s focus is on railways, its findings and recommendations are relevant for to and can be extended to other transport modes.
Some of these disturbances can also be mitigated by managing traffic. Measures like temporary road closures, usually implemented to reduce roadkill in specific seasons, also eliminate other disturbances. Similarly, lower vehicle speeds reduce the animal vehicle collision (AVC) risk as well as producing less noise. Therefore, measures aimed at modifying driver behaviour, such as road narrowing or alerting drivers, for example with optical pavements, can contribute to reducing both impacts (Hussain et al., 2021).
The edge effects and pollution that transport infrastructure cause on biodiversity can spread far from the infrastructure (see Chapter 1 – Ecological effects of infrastructure). These include different disturbances such as light or noise, but also the spread of Invasive Alien Species (IAS) or effects on hydrological systems. The magnitude of these impacts, how they can affect the surrounding ecosystems, and how to avoid or mitigate them need to be considered from the early stages in the transport infrastructure life cycle (see Chapter 2 – Policy, strategy and planning and Chapter 3 – The mitigation hierarchy).
Mitigation measures to reduce disturbances from infrastructure to surrounding habitats can provide benefits to biodiversity and contribute to the enhancement of the transport infrastructure’s resilience to climate change. A thorough evaluation can help to achieve solutions that provide benefits to both ecosystem and infrastructure. Some examples are:
- Embankments to mitigate noise could provide new habitats for endangered flora species, provided they are designed to avoid wildlife mortality risk.
- Retention ponds to manage runoff water and avoid the spread of chemical pollutants can provide habitats for several species (see Section 5.7.2 – Ponds and other blue areas).
- Alternative methods to the use of chemical substances in the management of green areas, such as grazing, can also contribute to the control of Invasive Alien Species (IAS) (see Section 5.8.2 – Invasive Alien Species (IAS). Control measures).
- Traffic management measures, such as reducing traffic volume or speed, can also reduce the risk of accidents involving wildlife.
Measures to reduce specific disturbances; i.e. light, noise and pollution, are described in the following sections.