The impact of linear infrastructure on biodiversity and the effectiveness of mitigation strategies
The development of linear infrastructure such as oil and gas pipelines, roads, and transmission lines has an impact on biological diversity and ecosystem function. Species or ecological communities (i.e., “bioindicators”) are chosen to assess project impacts and quantify the success of restoration, in part, in order to demonstrate compliance with government regulations. The mitigation hierarchy is the leading framework for reducing impact. Its purpose is to avoid, minimize, restore, and offset impacts to biodiversity. We surveyed over 140 published articles on pipelines and transmission lines to answer three primary questions. 1) Which taxa are most commonly used as bioindicators? 2) What are the most recognized direct and indirect impacts of linear infrastructure on biodiversity? 3) What are the most common and/or most successful methods for mitigating impacts? We focused on pipelines and transmission lines because their impact on biodiversity has been synthesized less frequently than roads and because roads are dissimilar to other linear infrastructure.
Studies focused on transmission lines nearly exclusively describe impacts to birds, whereas studies on pipelines include more diverse organisms, such as plants and large mammals. However, we found no or few publications on several groups of taxa that could provide valuable information about ecosystem structure or function, such as microbes, herpetofauna, mosses, lichens, and insects. This is likely because government regulations do not require information on these taxa and so industries are not supporting their study. Another limitation of the research is that baseline data often were not collected before linear infrastructure was constructed, so many of the direct and indirect impacts could not be identified. Post construction, the most commonly cited direct impact caused by the infrastructure we reviewed is bird injury/mortality caused by transmission lines. The direct loss of species or habitat during construction of transmission lines or the indirect effects of habitat fragmentation and the creation of corridors post-construction is largely unaddressed. Whereas the effectiveness of mitigation efforts, such as building aboveground pipelines high enough for large mammals to pass beneath or placing markers on transmission lines to prevent bird collisions, is reported in some publications, few include suggested improvements to mitigation practices. Research is needed that will identify the impact of linear infrastructure on ecosystem function and take a holistic approach to identifying effects on biodiversity. Appropriate baseline studies will enable practical recommendations for effective mitigation.