Identifying the deleterious ecological effects of developments, such as roads, mining, and urban expansion, is essential for informing decisions surrounding these developments and identifying appropriate forms of mitigation. Impact evaluations tend to reduce complex impacts of human activity to simple, user-friendly metrics to streamline integration of economic and environmental concerns in decision making. They are usually limited in scope to impacts on a predetermined subset of environmental values. Impact evaluations are also limited by the knowledge and tools available for identifying impacts, the skills, interests, and motivations of the people conducting, approving, and auditing evaluations, and political dynamics.
As a consequence of these limitations, there are many types of ecological impacts that slip ‘under the radar’ of conventional impact evaluations and undermine the potential for successful impact mitigation (including offsets). These ‘enigmatic’ impacts can be cumulative, offsite, cryptic, or secondary. They include those that are small but act cumulatively; those outside of the area directly considered in the evaluation; those not detectable with the methods, paradigms, or spatiotemporal scales used to detect them; those facilitated, but not directly caused, by development; and synergistic impact interactions.
In this review, Keren Raiter and colleagues propose a framework for conceptualising enigmatic impacts and discuss ways to address them. Potential solutions include improved strategic and cumulative assessments, no-development and restricted access zones, addressing historical impacts, improving professional and ethical practice and decision-making processes, and adopting environmental insurance schemes. Ultimately, it is reasonable to expect a fair accounting process whereby the beneficiaries of development are responsible for the full environmental costs of those developments, including costs that are currently borne by the broader society and future generations.
Raiter KG, HP Possingham, SM Prober and RJ Hobbs (2014). Under the radar: mitigating enigmatic ecological impacts. Trends in Ecology & Evolution 29: 635-644. http://www.sciencedirect.com/science/article/pii/S0169534714001980