Theory and practice: Defining indirect effects for science and management

Indirect ecological effects-in which interactions of two species are modified by another species or abiotic factor-are generally considered equal to or greater in magnitude than direct effects. The ecological literature describing indirect effects suffers from redundancy and confusion regarding terminology and quantification, limiting its utility to regulators working to estimate indirect relative to direct effects in assessing environmental risks of development. To evaluate consideration for indirect ecological effects in regulatory practice, we reviewed 24 National Environmental Policy Act (NEPA) documents for proposed US mining projects to compare the treatment of indirect effects in the regulatory versus ecological literature. A clear dichotomy between regulatory and academic definitions of indirect effects suggests that NEPA documents overlook scientifically defined ecological impacts of development. Consequently, for scientific inquiry to be useful to regulators and for regulation of development to comprehensively assess risks, multidisciplinary efforts are urgently needed to bridge the gap between ecological science and environmental management.