Oahu residents will foot most of the city’s multimillion-dollar security tab to host the upcoming World Conservation Congress, a major international event next month in Waikiki, which may attract President Barack Obama as opening speaker.

“The estimate right now is that the WCC will cost the city $3 million to $4 million in support of the state,” said Melvin Kaku, director of the city Department of Emergency Management. The overtime bill alone for the Honolulu Police Department is expected to reach $455,000.

Coming to Hawaii Sept. 1-10, the premier conference of the International Union for Conservation of Nature is the state’s highest-profile international meeting since the 2011 Asia-Pacific Economic Cooperation forum. In fact, the event is often dubbed the “APEC of Conservation.”

Kaku said this is the first time the WCC will be holding a conference in the United States, and Honolulu is honored to have been selected.

“Hawaii is considered the extinction capital of the world, and when you also consider the issues of climate change, sea-level rise and resiliency, Oahu appears to be a ‘perfect fit’ to hold this year’s WCC,” he said.

Still, public security costs are just as high or maybe even higher than APEC, which came with twice the attendance and economic benefit and 10 times the media. Some 8,000 visitors, including 5,000 attendees and 200 journalists are expected to attend the WCC, generating an economic impact of $62 million. In comparison, APEC brought roughly 15,000 visitors, including 2,000 journalists and heads of state from 21 member nations. That event, which was hosted by President Obama, was estimated to have pumped $120 million into Hawaii’s economy.

Security for APEC cost the city $8.5 million. However, Kaku said, the federal government reimbursed the city $4.5 million through a National Special Security Event Grant Program award. This time the city has access to only $475,000 in Urban Areas Security Initiative federal grant funds to offset overtime costs incurred supporting the state event, he said.

“This is the only federal money available as the event does not rise to the level of a National Special Security Event, as that would require the presence of President Obama and two other heads of state of equal stature,” he said.

Kaku said state lawmakers also set aside $4 million in planning for the WCC during the 2014 legislative session. However, he said that the state has not committed to transfer any of those funds to the city. State officials could not be reached for comment on Friday.

So far, most of WCC’s support has come from city and state funds rather than private sponsorships. This legislative session, Gov. David Ige asked for another $4 million in special fund money from the state Department of Land and Natural Resources. HTA gave $1.5 million, which included $690,000 of in-kind fee waivers at the Hawai‘i Convention Center.

Even with that infusion, the effort is running $500,000 to $1 million short of its commitment to IUCN to pay $11.4 million of WCC’s $13.2 million cost, said Randall Tanaka, executive director of Hawaii’s WCC National Host Committee.

Colin Moore, director of the the University of Hawaii’s Public Policy Center, said it’s concerning that more of WCC’s expense was not picked up by the private businesses that will benefit.

“Often politicians and public officials are far more enthusiastic about hosting these blue-chip conferences than the public. It’s the sort of thing that mayors and governors like to be associated with because it raises their profile. But it’s not the bread-and-butter issues that the public cares about,” Moore said. “It’s also hard to quantify the investment when our tourism is already pretty robust.”

Honolulu resident Edwyna Speigel said it’s “asinine” for the city and state to pay such high fees to bring more tourists to Hawaii when the state is already overrun with them.

“I am annoyed and dismayed at the dismal quality of life that results from overcrowding by tourists,” said Speigel, who has lived in Hawaii on and off since 1966.

“It seems like all this money could have gone to something better,” Speigel said. “At least APEC seemed more important than this one.”

Barry Wallace, executive vice president for hospitality services for Outrigger Enterprises Group, said the family-owned chain looks forward to hosting participants for WCC, but so far its impact on business is undetermined.

“This event is not as well communicated as APEC — that one everyone talked about for a year before they came. This one is much more low key. It hasn’t gotten the incredible attention that APEC got,” Wallace said.

Said UH’s Moore: “There are a lot of good reasons to host this conference, such as contributing to a worthy cause and helping Honolulu raise its profile. But it’s troubling that these investments are usually justified by saying that we’ll reap economic benefits when that’s not always the case.

“We need to push politicians to say, ‘We’re going to support it because it’s worth it for other reasons.’”

That’s Tanaka’s point. APEC was about showcasing Hawaii as a meetings destination and promoting tourism, he said, but WCC is about creating an opportunity for Hawaii to play a key role in conservation strategy. As many as 76 of WCC’s 1,500 sessions are focused on Hawaii, he said.

European scientists already are working with Hawaii scientists to eradicate mosquitoes, Tanaka said. Climate change, water resources and invasive species like the coconut rhinoceros beetle and the coqui frog also will be popular topics. “We have a chance to make a huge difference,” Tanaka said.