In Norway, environmental constraints applying to hydropower may become stricter to safeguard local ecosystems. At the same time, Norwegian hydropower flexibility has a vital role in facilitating the transition to a higher proportion of renewables within the North European power system. This study quantifies the aggregated impact of environmental constraints on the Norwegian power system and its interactions with its neighbours. Simulations are performed using the FanSi model developed by SINTEF, based on scenarios of the Northern European power system up to 2050. Requirements for augmented protection of the local environment affect hydropower operation and, hence, the power system, altering price patterns and the use of transmission between price areas. The abundance of cheap renewable energy can mitigate the price impacts of new environmental constraints, but losses in flexibility can be difficult to recover completely within the existing hydropower infrastructure. While prioritizing only hydropower plants with vulnerable surrounding ecosystems for adding new environmental targets helps limit their constraining effect on the whole power system, it also leads to a disparity between individual plants. Stricter environmental constraints on parts of the hydropower fleet actually benefit the unaffected part. A discussion on the cost-benefit redistribution is provided.