Georges River Land Trust (GRLT) invites the public to  a guided walk on Riverview Hayfields Preserve, starting at the Finnish Church in South Thomaston at 3 p.m. on Thursday, April 20. Dave Marceau, a licensed soil and wetland scientist with civil engineering firm Gartley & Dorsky, will lead the walk, describing the varieties of wetlands, their role in the environment, and how humans influence their functions. The walk is part of Georges River Land Trust’s Walks and Talks, a free educational series aimed at encouraging the public to explore its 17 preserves. People should bring “rubber boots and questions”; for more information or directions, call GRLT at 594-5166.