What major issue contributes to high rodent populations in urban and suburban areas?

Poor sanitation is the primary factor that contributes to high rodent populations in urban and suburban areas. When garbage is not regularly collected or stored improperly, it provides a readily available food source for rodents. Over time, these conditions can lead to an increase in rodent breeding and survival rates, as they find not only food but also water sources and shelter in neglected areas.

Proper sanitation practices, such as keeping trash in sealed containers, cleaning up food debris, and maintaining a clean environment, can significantly reduce the chances of attracting and sustaining rodent populations. While factors like abundant nesting materials can be relevant, they are secondary to sanitation issues which directly affect food availability and habitat suitability for rodents. Lack of traps and high temperatures are not primary drivers of rodent population issues in the context of urban and suburban environments.