Final answer:
Bio-geo interactions along riverbanks, fostered by native grasses and trees, lead to less erosion and improved river health by stabilizing banks and providing nutrients for aquatic life.
Step-by-step explanation:
When a river is bordered by native grasses and trees, the interaction that reduces erosion and improves the river's condition is a bio-geo interaction. The positive effects of this interaction include enhanced health of the river's ecosystem. This is because the root systems of the vegetation stabilize the riverbanks, reducing soil erosion, and contribute organic materials which support diverse aquatic life.
The presence of native vegetation along the banks of a river creates a buffer zone that reduces the impact of erosive forces, thereby maintaining the river's channel integrity and improving water clarity. Leaves and other organic materials falling into the water provide nutrients that fuel the food web, sustaining a diverse biotic community. Overall, these bio-geo interactions play a crucial role in maintaining the health and ecological balance of riverine systems.