On this page, environmental lawsuit means "a lawsuit where the well-being of an environmental asset or the well-being of a set of environmental assets is in dispute". Also on this page, lawsuit with environmental relevance means "a lawsuit where a non-environmental entity or a set of non-environmental entities is in dispute, but whose outcome has relevance for an environmental asset or for a set of environmental assets".
Because the distinction between the two types of lawsuit is not clearly defined, it is beneficial to keep the two lists together on one page, but separated according to that distinction.
References
List of environmental lawsuits Wikipedia(Text) CC BY-SA