The Scandinavian Peninsula, home to Northern European countries such as Sweden, Norway, and Finland, covers more than a quarter of Europe’s total area, yet its population is only around 30 million. These countries, with most of their territory consisting of mountains and lakes and a stable social structure prioritizing peace and welfare, are relatively insulated from environmental pollution. However, signs of ecological abnormalities began to appear in the forests and lakes from the 1950s. Once lush forests gradually disappeared, and fish in rivers and lakes began to vanish. This environmental degradation was caused by acid rain resulting from air pollutants emitted by neighboring countries.