Final answer:
Dam removals on the Kennebec and Penobscot rivers aim to restore natural fish migrations, facilitating the return of anadromous species like salmon, to improve biodiversity and river health.
Step-by-step explanation:
The primary motivation for recent dam removals in the Kennebec and Penobscot rivers in Maine is to restore passage for migrating fish species, which is fundamental to promoting biodiversity and ecological balance. The aging dams are being considered for removal due to a paradigm shift in understanding the ecological importance of free-flowing rivers.
This process has facilitated the return of anadromous fish species, a group that includes fishes such as salmon that migrate from the sea to freshwater to spawn. With the removal of these barriers, these species can more easily access upstream habitats, crucial for their life cycles, and in turn, provide benefits such as nutrient transport and increased fish diversity which improve overall water quality and ecosystem health.