Complex sentence: Many European deciduous trees were planted in the 1970s and 1980s and have since matured on roadsides and on private properties, invasive species remain as one of the suburbs major environmental problems.
Split into simpler sentences: Many European deciduous trees were planted in the 1970s and 1980s and have since matured on roadsides and on private properties. Invasive species remain as one of the suburbs major environmental problems.