Deforestation or logging should be your answer
Green house gases and pollution
Saint Petersburg has a population of 5 million.
Moscow has a population of 11 million.
Minsk (the capital of Belarus) has a population of 2 million
Kiev (the capital of Ukraine ) has a population of 3 million
So the biggest city of those is Moscow. - a lot bigger than others
Strait of Magellan. Hope this helps