Park ranger
The duties of the modern park ranger are as varied and diverse as the parks where they serve and in recent years have become more highly specialized. Regardless of the regular duties of any one discipline, the goal of all rangers remains to protect the park resources for future generations and to protect park visitors. This goal is accomplished by the professionalism and sometimes overlapping of the different divisions. For example, an interpretive ranger may perform a law enforcement role by explaining special park regulations to visitors and encouraging them to be proper stewards of natural and cultural history. Law enforcement rangers and other park employees may contribute to the mission of the interpretive ranger by providing information to park visitors about park resources and facilities. The spirit of teamwork in accomplishing the mission of protecting the parks and people is underscored by the fact that in many cases, for the U.S. National Park Rangers in particular, all park rangers share a common uniform regardless of work assignment.The Adopt A Ranger Foundation has calculated that worldwide about 150,000 rangers are needed for the protected areas in developing and transitions countries. There is no data on how many rangers are employed at the moment, but probably less than half the protected areas in developing and transition countries have any rangers at all and those that have them are at least 50% short. This means that there would be a worldwide ranger deficit of 105,000 rangers in the developing and transition countries.
New York City Parks Enforcement Patrol
Begun in 1996 the NYC Parks Enforcement Patrol Mounted Auxiliary Unit is a volunteer unit within the department. This unit is made up of private citizens who volunteer their time by working with officers of the Parks Enforcement Patrol. 
Auxiliary officers patrol in full uniform and on horseback in various NYC parks, and "ensure the preservation of the natural and living resources in the city's parks, as well as the safety of those utilizing the parks, by maintaining a clearly visible presence. They monitor areas that are not accessible by vehicle; they deter, identify and report illegal or unsafe activities that require Parks Enforcement Patrol or police attention; and they advise the public on park rules and regulations."
As an IRS 501C Corporation, the Auxiliary solicits funding to purchase horses, tack and provide training for both the Volunteers and the Professional Officers. Since inception it has provided several hundred thousand dollars towards the operation of the Mounted Unit, including the Capital Construction of a new barn. Former Parks Commissioner Adrian Benepe was quoted as saying "there is some doubt that the Parks Department could afford to run a mounted unit without the Mounted Auxiliary."
Auxiliary officers do not have powers beyond a citizen and cannot make arrests. For this reason a typical patrol will include a PPEP Officer and an Auxiliary Officer. By combining the two, the manpower of the Parks Enforcement Patrol is significantly increased at no cost to the City. Should the team come upon a situation requiring enforcement, the PEP Officer can deal with it while the Auxiliary Officer covers the Officer's back and radios the situation to Parks Central and if needed will ask for additional help.