Gazans face the task of replacing "60-plus years of development lost" during the 15-month war between Israel and Hamas, UNDP Administrator Achim Steiner says.

Following the start of the ceasefire on January 19, attention has turned to helping people rebuild their lives in Gaza.

According to UN estimates, there are about 42 million tons of rubble strewn across the Gaza Strip after over two-thirds of the infrastructure was destroyed in Israeli airstrikes and ground incursions.

The war also caused the deaths of 46,000 people in Gaza, according to the Hamas-run Health Ministry. The number is expected to rise as more bodies are identified.

The UN also says the process of rebuilding society there is likely to take decades, with costs running as high as $80 billion (€76 billion).

Rubble in Gaza 'extremely toxic environment'

Steiner heads the United Nations Development Program (UNDP). It is one of the UN agencies supporting Palestinians, focusing on infrastructure in the occupied Palestinian territory.

"We put an estimate of 60 plus years of development lost. 67% of the infrastructure is either damaged or destroyed," he told DW in an interview at the World Economic Forum in Davos, Switzerland.

"We are dealing with a situation where most Gazans will return to either a heavily damaged building they cannot move into or simply a pile of rubble. That rubble is still dangerous. Not only are there potentially bodies that have never been evacuated, there is also unexploded ordnance, landmines. It's an extremely toxic environment," he said.

'Not only physical infrastructure'

Along with moving essential food and medical supplies into Gaza as quickly as possible, he says initial efforts must be focused on rapid recovery of critical infrastructure, such as solar-powered water treatment plants.

After that, the task of clearing rubble and rebuilding homes, schools and hospitals can begin.

Along with physical assistance, Steiner says people will need significant support for mental health and help finding relatives.

"If you look at the trauma that people have lived through, it is not only the physical infrastructure that has suffered enormous damage. People have lost tens of thousands of relatives," he said.

"There is a level of trauma that — we also know from past instances like this — will obviously affect people for years to come.

"Many children may be orphans right now. They have been taken care of by strangers who took them into their tent."

Recovery work 'enormous uphill struggle'

For any reconstruction to begin, the ceasefire between Israel and Hamas must hold.

"There is still a great deal of nervousness," Steiner pointed out. "Will the ceasefire hold, will the steps 2 and 3 really evolve?"

The second stage of the ceasefire includes a permanent end to fighting, the return of remaining hostages in exchange for Palestinian detainees in Israeli prisons and the withdrawal of Israeli troops from Gaza. The third stage concerns rebuilding Gaza.

If the ceasefire does hold, Steiner says there are significant pledges from the international community to support the initial humanitarian work.

But efforts to rebuild Gaza will require longer term pledges from UN member states and the private sector.

"The billions of dollars that will need to be mobilized for even early recovery work and then in the longer term for reconstruction will be in the tens of billions," said Steiner.

"The international community will be called upon to step forward. The private sector can also invest… in that recovery and reconstruction work. It is an enormous uphill struggle to mobilize the resources for this huge early recovery and reconstruction work over the next years."

Israel must be a negotiator in 'good faith'

Steiner sees a key role for the United States and Europe in financing and supporting the reconstruction of Gaza, arguing that they have a political interest in peace in Gaza.

He is also hoping for significant support from countries in the Middle East, although Lebanon and Syria are currently facing their own rebuilding efforts.

Steiner also sees it as crucial that Israel maintain dialogue. "I think Israel, as in any conflict, has to be a good faith negotiating partner," he said.

The war between Israel and Hamas began after the militant group, classified as a terrorist organization by multiple countries, launched a terrorist attack into southern Israel on October 7, 2023.

That attack led to more than 1,200 deaths and the kidnapping of nearly 250 people. Ninety-one of those hostages remain unaccounted for.

The interview was conducted by DW Editor-in-Chief Manuela Kasper-Claridge.

Edited by: Rob Mudge