What is the fine-grained topic of the following text: The 2,600-acre project in Hennepin, Illinois, backed by the Wetlands Initiative and a motley of other major environmental groups, aims to show that restoring wetlands would be a cost-effective, and potentially lucrative, way to filter harmful nitrogen and phosphorus and remove carbon dioxide from the atmosphere. Only return the topic.
Restoring wetlands for carbon dioxide removal and water filtration