The white bears can only live in cold environments. So they can reproduce easier because they only live in this environment. While the brown bears can live in all environments but its not as easy for them to live in the snow.
The white bears have reproduced more and the brown bears are still living just not as easy as the white bears.
The brown bears are starting to live a little easier because the brown bears eat plants and some plants are starting to show and its getting a little warmer so the white bears are struggling a little more now.
The white bears are really struggling because the climate is starting to change to warm and the brown bears are starting to reproduce more easy because they live better in this weather and there is more plants now so they have more food.
All the snow has melted and the few white bears left are dying out and the brown bears live a lot easier in this new environment.
All of the white bears have died out because they cant survive in the warm environment and the brown bears can. Therefore, there are more brown bears moving to this area and reproducing a lot more because they have water with fish in it and plants around the land.