Authorities are installing two dozen surveillance cameras in the Massapequa Preserve — a popular 432-acre park where a homicide victim’s body was found in March and a spate of indecent exposure incidents unnerved visitors.

Nassau acting Police Commissioner Patrick Ryder announced the new surveillance system Wednesday at the department’s intelligence center in Massapequa Park. He said the idea came from local lawmakers whose constituents expressed concern for their safety in the park, following the flashing incidents and the body discovery.

“The idea is to let the bad guy know that we’re watching,” said Ryder, who added that the park is “safe.”

The heavily wooded county preserve, named for the late lawmaker Peter J. Schmitt, runs through Massapequa and attracts joggers, hikers and dog walkers as well as bicyclists. There are lakes for fishing, gardens, and nature walks and it connects to Bethpage State Park.

Richard Schary, co-founder and president of the 17-year-old group, Friends of Massapequa Preserve Inc., estimated the park gets some 200,000 visitors annually from the local area, but also from Suffolk County and New York City.

“It’s really popular,” Schary said. “It’s back to nature. And very few ticks.”

The park cameras join a network of surveillance cameras and license plate readers installed in public spaces across Long Island as a preventive measure to stop crime and assist in police investigations. It’s a system that Ryder, who used to run the department unit that oversees use of surveillance cameras, has long pushed for in Nassau.

After friends Nisa Mickens, 15 and Kayla Cuevas, 16, were killed last September in Brentwood by suspected MS-13 gang members, Suffolk police announced they were installing a network of license plate readers in the area as a deterrent.

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Cops have also installed surveillance cameras on the Long Beach Boardwalk and license plate readers in Freeport and Hempstead villages.

On March 23, a man walking his dog discovered the body of Julio Cesar Gonzales-Espantzay, 19, of Valley Stream, in the preserve, near Seaview and Ocean avenues, police said.

Gonzales-Espantzay had several lacerations and blunt-force trauma to his upper body and head, and police said his body may have been in the preserve for as long as three weeks, police said. No arrests have been made in the case.

Last October, police investigated five reports of public lewdness involving men exposing themselves on jogging trails in the preserve, prompting police spokesman Det. Lt. Richard LeBrun to warn potential visitors.

Legis. James Kennedy (R-Massapequa) and Rose Walker (R-Hicksville), whose districts include the preserve, said after the body was found that they heard from residents and contacted the police department about putting in cameras.

“There was concern because of a couple of things that happened in the preserve, the body and the streaker,” Kennedy said. “There was concern about going in at certain times of the day.”

Walker added: “We want our residents to feel comfortable, to feel that they are safe.”

The cameras were funded through $50,000 in Community Revitalization Program money from the county legislature, officials said. Each camera costs about $2,000.

Ryder identified two cameras — visible to the public — that have already been installed near entrances to the preserve on Linden Street and Clark Boulevard, but said covert cameras will be dispersed throughout the park.

Ryder acknowledged the preserve cameras aren’t monitored 24/7, citing staffing costs.

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“Nobody gets arrested from the camera, meaning nobody’s jumping out of the cameras and putting cuffs on you, but it’s capturing data,” Ryder said. “It’s preventive. And if there was a crime, we can then use it to help solve that crime.”

But, he added: “If something happens, they can go to the tape. It’s just data that’s being captured; if we need it, it’s there.”

LeBrun said precinct cops and problem-oriented policing, or POP cops, patrol the preserve. In 2015, there were two arrests in the preserve and last year there were six arrests, four for marijuana possession, one for public lewdness and one for disorderly conduct. There have been no arrests so far this year.

Mike Alperin, a social media advertiser from North Massapequa who was walking his Australian cattle dog, Cinder, in the preserve Wednesday said the cameras are a good idea, but he wanted to see a greater police presence.

“I come with the dog because I won’t come by myself,” said Alperin, 29. “I don’t ever see cops here — ever . . . . You pay enough taxes for them to have the mounted officers; put some in here.”

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Richard Schary’s wife, Lisa, co-founder of Friends of Massapequa Preserve, said the park is especially busy in the summer, including with visits from organized groups such as Audubon societies who come to see the herons and egrets that live there. Also, Boy Scout groups frequently do community service projects there, such as repairing footbridges and painting over graffiti, she said.

“One crazy incident doesn’t scare most of the people away,” said Lisa Schary. “We have 600 members who keep their eyes open and report any incidents. People think of the preserve as their own backyard . . . it’s swarmed with baby carriages. People enjoy being there after they get off the train and meet their friends there. It’s one of the safest and most beautiful places to go on Long Island.”