In recent years, more and more migrant workers have moved into big cities and they have been making great contributions to the development of cities. New buildings need them, roads can't be repaired without them, and the planting and protecting of trees and flowers depend on them. Indeed, they play an important role in the construction of cities in China today.
　　However, they have brought about some problems. The biggest one is the increase of the city population. The once crowded cities have now become more crowded. And their arrival may cause a serious crisis in housing, water and other resources. In addition, they have taken so many jobs that the labor market in cities has become even weaker. What's more, some of the farmland is left uncultivated as a result of the farmers' emigration.
　　In my opinion, migrant workers' contributions outweigh the inconveniences they bring us. On the whole, they have become an important part of our socialist builders. Nevertheless, the government should work out new policies to control the emigration of farmers on the one hand and to protect migrant workers' rights and interests on the other hand.