1. Governments around the world rely on environmental impact assessment to understand the environmental risks of proposed developments. 2. To examine the basis for these appraisals, we examine the output of environmental impact assessment processes in jurisdictions within seven countries, focusing on scope (spatial and temporal), mitigation actions, and whether impacts were identified as ‘significant’. 3. We find that the number of impacts characterized as significant is generally low. While this finding may indicate that environmental impact assessment is successful at promoting environmentally sustainable development, it may also indicate that the methods used to assess impact are biased against findings of significance. To explore the methods used, we investigate the environmental impact assessment process leading to significance determination. 4. We find that environmental Impact assessment reports could be more transparent with regards to the spatial scale they use to assess impacts to wildlife. We also find that few reports on mining projects consider temporal scales that are precautionary with regards to the effects of mines on water resources. Across our sample of reports, we find that few environmental impact assessments meaningfully consider the different ways that cumulative impacts can interact. 5. Across countries, we find that proposed mitigation measures are often characterized as effective without transparent justification, and sometimes are described in ways that render the mitigation measure proposal ambiguous. 6. Across the reports in our sample, professional judgement is overwhelmingly the determinant of impact significance, with little transparency around the reasoning process involved or input by stakeholders. 7. We argue that the credibility and accuracy of the environmental impact assessment process could be improved by adopting more rigorous assessment methodologies and empowering regulators to enforce their use.

Data was collected from Environmental Impact Statements