The effects of gang violence are many. They can destroy neighborhoods and communities. They increase the crime rate, increase the load on the legal system, makes people afraid to go out night, and cause the deaths of innocent victims.
The biggest reason youth join gangs is the breakdown of family structure. Everyone needs acceptance & rules to live by. If they don't get them at home, they will get them other places, usually gangs. The same applies to adults that join gangs (motorcycle, etc.). They are looking for acceptance. Once a person joins a gang, their complete loyalty is demanded by the gang, even over their family. Everything the gang tells them to do, they have to do, even stealing from their family. Gangs rule by fear & intimidation. They accomplish this by committing crimes within their turf, or boundary, as set by various gangs. Many times the worst crimes are committed by younger members of the gang, & for 2 reasons. First, they want to show the gang their loyalty & second, they get in less trouble with the law if they get caught. The main effects are the amount & degree of crime committed by members that over burden law enforcement, jails, & courts. Another is the breakdown of the community because of the fear. & intimidation. Gang areas usually have a run down, graffiti appearance, another effect. Prior to my retirement as a Deputy Sheriff II in Ca, I was over the gang task force for our agency. I was in major crimes & a case that took most of my time prior to retirement was an attempted murder, torture, mayhem, etc. case where a person was hogtied, shot, stabbed, & tortured with a pointed hammer, by members of the Misfits Outlaw Motorcycle Gang. This was over a marijuana issue. Lake Co, Ca. is the county with the most marijuana in the nation, last year over 600,000 plants were eradicated. The Mexican Cartels (gangs) control the marijuana, meth. heroin, & cocaine markets on the west coast & most of the US. They use other gangs (crisp, bloods, surenos, nortenos, & motorcycle gangs such as the hells angels, vagos, mongols, etc, to distribute & sell their products. I hope this helps answers your question.