River damming is expected to proliferate across Tropical American Rivers in the forthcoming decades with expected declines in ecosystem health to costly invasive species. Historical data and modern aquatic plant surveys of one of the largest and oldest tropical dam projects (the > 100 years old Panama Canal) reveal that modern plant communities in areas adjacent to terrestrial Natural Protected Areas (tNPAs) retain a pre-damming community structure that is apparently more resistant to invasive species. Establishing tNPAs adjacent to impounded rivers could be a cost-effective nature-based solution for tropical reservoir management.