What is one of the data loss effects resulting from a change in custom field type?

Changing a custom field type in Salesforce can indeed lead to potential data loss effects, and one significant impact is on assignment and escalation rules that use those fields. When a custom field's type is modified, the data it holds may no longer be compatible with the functionality of those rules. For instance, if a field that's used in an assignment or escalation rule changes from a picklist to a text field, the logic of those rules may become invalid because they rely on the specific data type and its associated operations.

This often requires administrators to review and potentially modify the rules to ensure they continue to work as intended with the new field type. Thus, it highlights the importance of careful consideration and testing before making such changes to custom fields.

The other options imply that there are more drastic data loss events, such as the deletion of reports, dashboards, or list views, which are not directly affected by simply changing the type of a custom field. It’s important to note that while reports and dashboards can be impacted by changes in the underlying data, they are not deleted outright just because of a field type modification, making the effect on assignment and escalation rules the most accurate choice in this context.