What is the best long-term solution to maintain polar bear populations?

Maintaining the genetic diversity is long term solution which help to maintain polar bear population.

Explanation:

Polar bear from Norwegian way bears are genetically unique. These bears are only who survive in the world. they have lack genetic diversity so it is possible to they stay healthy and somehow survive in worst condition.

The climate and condition of Norwegian is way better so it is necessary to relocate the other polar bear. The other important thing is to ensure about their food. Polar bear mainly eat seal but due to the melting of ice they are unable to get proper food.  

we would need to see the picture to answer it

affects the water bodies: excessive use of fertilizers causes eutrophication. the fertilizers which are used on plants affect the quality of land on which it is used, further causing erosion of soil. the fertilizers used on plants contain harmful chemical fumes which affect the environment.