The committee, chaired by National leader Simon Bridges, was set up to empower MPs to scrutinise the Government's response to Covid-19 in the absence of Parliament.
Gluckman said the past few weeks had left "indelible marks" on our society.
"The Government has done much that is very good under serious pressure but this may have been the easiest part," Gluckman said.
Many Kiwis will have had their certain futures ripped away from them and will mean an increase in fear, anxiety and frustrations emerge, he said.
Gluckman said there would be a lot who are newly vulnerable, for example a 55-year-old travel agent now out of work and without a future, who would join New Zealand's large number who were already disadvantaged.
New Zealand needed to make sure we have "more inclusive discourse" about how we rebuild our future.
Gluckman, who now heads think-tank Koi Tū: The Centre for Informed Futures, said we were not yet at the peak of the distress from the lockdown - that will come in the next few weeks.
Based on other disasters, about 10 per cent of the population would develop depression and there would be some who are suicidal, he said.
Marijuana was now the main way people are managing stress in South Auckland, Gluckman said he'd been told.
The primary need now was to support the social services providing help and solutions to our communities and the focus had to be on how to mitigate the effects of the crisis.
Gluckman said Maori were disappointed and excluded by not being included in the room of decision makers, and giving them a seat at the table would be useful.
Despite not being included, they'd done well with iwi providing food distribution and checkpoints, he said.
There would also be a "massive increase" in young people wanting to go to university and there'll be a big increase in demand from overseas students as New Zealand is seen as safe.
Now was not the time to be shrinking our universities, he said.
The Government also needed to release more data to give people more certainty in uncertain times.
"The more that we can give certainty to the people, the better."
Chris Farrelly, Auckland City Mission
The Covid-19 crisis has created opportunities to fix two problems - homelessness and food insecurity, said Chris Farrelly of the Auckland City Mission.
New Zealand has an "unacceptable" level of homelessness due to the housing crisis but Covid-19 meant there was an unexpected supply of accommodation.
Telling people to isolate at home didn't work for people who didn't have a home.
"Simple as that," he said.
About 1000 motels had been made available around the country for the homeless, in Auckland alone 415 rooms were used to house 490 people.
The challenge was to bring in a new tranche of wraparound services, like addiction and mental health expertise, to give people support while they were in temporary accommodation.
The cost to New Zealand was many, many times higher to have people on the street than it was to house them and give them support.
About 10 per cent of New Zealanders experience food hardship and Farrelly said that could rise to 20 per cent.
During the crisis, people who'd never had to ask for assistance were now having to put their hand out.
Farrelly said a team sat behind him and took calls all day from people needing food and assistance.
New Zealand produces enough food to feed 20 million people but we needed to work out how we can feed our 5 million first.
Food was a fundamental human right, he said.
We need to work out how to make sure the food we have goes "to the right people at the right time".
Food insecurity was caused by incomes not meeting household expenses and the recommendations from the Welfare Expert Advisory Group should be looked at.
They included ensuring a living wage and improving benefits.
Farrelly thanked Paula Bennett for funding the first Housing First pilot and the current Government for continuing it.
Dr Ang Jury, National Collective of Independent Women's Refuges
We won't know the impact of the lockdown on domestic violence rates for some time, said Dr Ang Jury of the National Collective of Independent Women's Refuges.
The collective has 40 refuges around the country.
"We've seen absolutely no changes yet because of course it's very early on," Jury said.
"We're just guessing at the moment."
Jury has been in contact with colleagues in the United States and the United Kingdom which are lifting lockdown provisions and are seeing increased levels of those seeking help.
Women's Refuges were preparing for the hidden harm, she said.
To help avoid this "we need to be looking out for each other".
We're good at seeing, hearing and worrying about things but we're not so good at doing something about it, Jury said.
She urged anyone with any concerns at all to get in touch with them or the police.
"We would far rather be called to a nothing than to be called to a serious injury or a death."
The Government has already given $40,000 per refuge as it became apparent very quickly the initial $20,000 per refuge wouldn't be enough to house many women and children in motels, she said.
Jury said they were grateful for the quick work by the Ministry of Social Development.
The Covid-19 crisis meant there was a sudden bringing together of agencies to have broad conversations. Jury said that should continue.
There'd also recently been good progress for Women's Refuges and she hoped those productive conversations stayed on track and weren't derailed by Covid-19.
Jacqui Graham, The Wise Group
The Covid-19 crisis had changed how social services, the Government, ministers and District Health Boards worked together, said Jacqui Graham of mental health service The Wise Group.
There's now a high trust model which meant they could get things done very quickly without barriers.
"We don't want to go back to how it was before Covid."
The recommendations from the Inquiry into Mental Health and Addiction needed to be actioned, Graham said. It was a good blueprint but it needed to be used.
"[We need] more action and more funding towards what works."
New Zealand also needed to move forward with the evidence and empathy, which had been the focus during the lockdown.
We need to move away from slow bureaucracy.
Graham said about 60 days of the year - three months - were used up by government agencies auditing them.
They were different bodies auditing the same thing - sometimes it was even the same person.
But this had been paused during the Covid-19 crisis which had been useful.
"We need to just get on with it."
There had also been a bias towards face-to-face therapy but there were other options, like E-Therapy, Graham said.
They'd also been able to buy phones and data so people could access essential services, which Graham called "a game changer".
Andrew Coster, Commissioner of Police
As restrictions lift and people locked down with their abusers are able to contact services, there's likely to be an increase in reports, said Police chief Andrew Coster.
After school holidays, for example, police see an increase in reports of child abuse.
"Sadly I fear we will see that in this situation," said Coster.
During the lockdown police have had to limit their presence in people's homes and were working closely with partners like MSD and the Hey Bro helpline.
In light of how quickly the crisis unfolded without any planning, Coster said he was encouraged about how different agencies had worked together.
"Nothing quite like a common focus in a crisis to get people joined up."
Police had worked with communities which implemented their own roadblocks to make sure they were legal.
They'd discouraged community checkpoints, but represented communities that were fearful.
As communities came to understand the threat was diminishing, the community checkpoints were easing.
National Party leader Simon Bridges said those checkpoints were illegal and claimed police had turned a blind eye and condoned the checkpoints by adding their presence.
Coster completely rejected this. He said they'd not turned a blind eye and had come alongside the community checkpoints to work with them to ensure they were legal.
He said they were communities that were very fearful and felt vulnerable and police were using their power with discretion by having a small police presence at the checkpoints.
If they tried to shut the checkpoints down there could have been protests which would require a larger police presence.
Coster said he felt their approach had been the right call.
But the checkpoints should be stopped at alert level 2.
Coster said he'd not had any influence from ministers or Government about the checkpoints.
The only minister he'd spoken with was Police Minister Stuart Nash and that was to brief him on police operations.
Police were entitled under the Health Act and the Civil Defence Management Act to use their powers under alert level 3.
Coster was asked about self-isolation monitoring but said he'd have to come back to the committee with detail about visits and breaches.
Earlier, Coster said the focus of police during the lockdown had been on public safety and public order, with patrols making sure there are no congregations and travel checkpoints.
Coster said the "measured approach" by police towards breaches saw the public respond well to the unprecedented restriction on freedoms and civil liberties.
And the breaches represented just 0.1 per cent of the population.
Coster said he hadn't received any concerns or feedback about lack of clarity on police powers since the second Section 70 health notice was issued.
He didn't believe it was a current issue or that harm had come from an early lack of clarity on police powers when asked whether their legal advice would be released.
Bridges asked about what legal advice they'd had from Crown Law about the statute they were operating under during the lockdown.
Coster, who also confirmed to Bridges he had a law degree, said Crown Law advice was not the law but an interpretation of the law.
It wasn't a matter for the police to seek advice on whether the s70 notice was legal but they do get advice on how to implement it, Coster said.
WHERE TO GET HELP:
If you are worried about your or someone else's mental health, the best place to get help is your GP or local mental health provider. However, if you or someone else is in danger or endangering others, call police immediately on 111.