Five years in, the war in Syria is costing about $4.5 billion a month (4.0 billion euros) in lost production and services alone, according to a report entitled "The Cost of Conflict for Children".

It was released by World Vision International, a Christian charity focused on children, and the consultancy Frontier Economics.

Since the war's beginning in 2011, the economic loss has been $275 billion. If the war continues until 2020, it will have cost a staggering $1.3 trillion, the report says.

"The $275 billion this war has already cost the Syrian economy is lost money. It will never be recovered, never be spent to provide education, health care, safe environments, livelihoods or a future for children," said Conny Lenneberg, regional leader for World Vision's Middle East programs.

Frontier Economics looked at Syria's economic productivity before the war started, and calculated the value of production of goods and services (gross domestic product, or GDP) that would have been produced in Syria had life continued as normally, and the war never started. It compared that with estimates of Syria's greatly reduced GDP under its present circumstances.

Syrian children, Bab al-Salama near Aleppo in February 2016

Further losses

"Even if the conflict ends this year, the cost of the conflict will grow to between $448 billion and $689 billion" in terms of lost economic output, the report says. That's a much larger figure than $275 billion, because even after peace returns, it will take years for Syria's ruined infrastructure to be rebuilt and productivity restored.

"This is 140 times the amount currently requested by UN agencies and partners to meet humanitarian needs inside Syria and almost 100 times the amount to meet Syrian refugee needs across the region," the report continues, noting that this is an optimistic scenario which assumes economic growth will allow Syria to recover its shortfall in GDP per capita "within 10 to 15 years."

The estimates took into account the economic costs and losses accrued by Lebanon, Jordan and Turkey as well as Syria itself – countries where millions of Syrians have fled as refugees from the destruction, bombing and slaughter in their home country.

Among Syria's neighbors, Lebanon has been hit especially hard by the Syrian conflict. Real GDP per capita is nearly 23 per cent lower than it would have been in the absence of the Syrian conflict, according to Frontier Economics.

Syrian refugees in the Bekaa Valley in Lebanon. Many are from Homs and have been in Lebanon for over two years

The cost to children

World Vision paints a grim picture of the future for Syria's children, in view of the war's long-term consequences: "At least 8.2 million children inside Syria and across the region are now experiencing displacement, interrupted schooling, broken health systems, food insecurity and limited protection from serious harm and abuse. Without the means for these children to receive support, rebuild their lives and gain essential skills, conditions are being created that will transmit poverty across generations, fuel social instability and undermine prospects for recovery."

Families are under acute financial pressure, with 90 percent of refugees in Lebanon and Jordan considered poor. Barred until recently from formal employment, parents are sending their children to work or entering them into marriage at a young age just to help the family survive, making children less likely to return to school. Only 48 percent of refugee children from Syria are able to access education opportunities.

"Direct and indirect impacts on education services resulted in the equivalent of 24.5 million years of lost schooling by the end of 2015," the report says. "With one in every four schools damaged, destroyed or used to shelter displaced people, about 5.7 million children inside Syria are in need of education assistance. There were 400,000 more children out of school in 2015 than 2014."

Syrian children play in the rebel-held neighborhood of Tishreen in Damascus, Feb. 27, 2016

Support the refugees, end the war

World Vision called on Turkey, Jordan and Lebanon to keep their borders open to refugees, provide schooling for children and opportunities to legally work for adult refugees. At the same time, the charity called on international donor countries in Europe, the US and elsewhere to support Syria's neighboring countries - especially Lebanon and Jordan - financially, organizationally and technically in their efforts to host displaced Syrians and Iraqis.

World Vision also called on the many parties involved in the Syrian conflict to end it. Unfortunately, that may turn out to be a forlorn hope for the present. World Vision Germany spokesman and peace researcher Ekkehard Forberg told DW that "both sides" - the group of countries supporting Syria's secular government under Bashir al Assad, and the group of countries attempting to overthrow his government by military force channeled through various armed proxy groups, most of them extremist Sunni Islamist jihadist paramilitaries - "continue to pursue their maximalist aims and to believe or hope they can achieve these through military means."

Syrians in the ruins of Homs

Conflict research shows that once a war has got going, it continues until all the parties to a conflict realize they cannot achieve their aims through military means. Before they've reached that point of exhaustion, they will not be serious about peace negotiations, Forberg said, adding: "The supporters of Assad's government and of the rebels include wealthy and powerful countries that can easily afford to continue to pump weapons and munitions into the conflict, which they are doing. So it continues."

Asked whether the government of Germany is playing a constructive role in pressuring the various parties pumping weapons into the conflict to cease doing so, Forberg said he didn't know. However, he said that peace negotiations should be restarted with as few preconditions as possible. Demanding that Assad step down first, for example, was a non-starter, and any party demanding this as a precondition for peace talks "probably isn't serious about wanting peace," he said.

"This new research is another way of demonstrating the urgency with which the international community must mobilize its collective diplomatic influence to end this conflict once and for all," said Fran Charles, World Vision's Syria crisis response advocacy director, referring to the World Vision and Frontier Economics study. "It will take decades for Syria to recover. We need peace now so we can start planning for the enormous task of the reconstruction and long-term investment Syria will need to get back on its feet."