What is the primary tool used in Leopold's circular to assess environmental impacts?

The primary tool used in Leopold's circular to assess environmental impacts is a matrix. This approach involves outlining the potential environmental impacts of a proposed project in a systematic way, typically representing various factors and their interactions. The matrix allows for a clear visual representation of impacts, making it easier to assess and compare different environmental factors and their potential consequences.

Using a matrix helps decision-makers analyze multiple variables simultaneously and understand the relationships between them, facilitating comprehensive environmental assessment. This structured method supports systematic evaluation and can help in identifying significant adverse effects as well as mitigating measures, which is essential in the context of environmental impact assessments. The other options, while useful in their own right, do not provide the same level of structured analytical support that a matrix does in this specific context.