Four million Syrians will be in need of urgent food aid, UN agencies have warned, as crop and livestock production has been devastated by the civil war.

The most vulnerable include the internally displaced, small-scale farmers, herders, casual traders, the urban poor, pregnant mothers, the disabled and chronically sick.

If the present conflict continues, the food security prospects for 2014 could be worse than they are now, said a joint report from the World Food Programme and Food and Agriculture Organisation. "With so many adverse factors now stacked against the crop and livestock sectors, and assuming that the present crisis remains unresolved, domestic production over the next twelve months will be severely compromised," the report said.

The world's worst humanitarian disaster has left 93,000 people dead, displaced 4.25 million people internally and forced more than 1.6 million to leave the country to seek refuge in Jordan, Lebanon and Turkey. The number of people in need is expected to rise to 10 million, nearly half of the population, by the end of the year.

According to the Syria Humanitarian Assistance Response Plan in June, 6.8 million people were in need of humanitarian help. It estimated the number of people in need of urgent and sustained food help at 4 million for the rest of the year. Even before the crisis, the nutrition situation was already alarming, with 9.3% of children suffering from wasting and 23% of them stunted. Besides a worsening in quality of diet, child health concerns are also due to reduced vaccination coverage from 95% in 2009 to 80% in 2012. Coverage is expected to decrease as the crisis persists.

Agriculture has played an important part in Syria's economy, contributing some 18% to GDP and involving 17% of its labour force. Before the crisis, 10 million Syrians lived in rural areas, 80% of whom made a living from agriculture. The war, however, has had a devastating impact on agriculture. Food production has been hampered by high costs and reduced availability of inputs, damage to agricultural machinery and storage facilities, the threat of violence and the flight from the land by farmers. Some crops may not be harvested.

Irrigation canals and cotton mills, among other infrastructure, have also suffered damage. Wheat flour milling factories and bakeries are either no longer operating or are operating at low capacity. In addition, sanctions have exacerbated the situation, leading to shortages of agricultural inputs, crop-protection materials, diesel, and spare parts.

Accordingly, wheat production for this year is estimated at 2.4m tonnes, 40% lower than the average for the 10 years before 2010-11 and 15% less than the poor 2011-12 crop, although barley production is up. Livestock has been badly affected by the current conflict and by international sanctions with sheep and cattle numbers down by about 35% and 25% respectively.

There are practically no routine drugs or vaccines for animals and no vets to administer them.

"Due to higher prices, more Syrian livestock are being sold in Jordan, Lebanon, Turkey and Iraq. With the virtual loss veterinary services within Syria, livestock diseases are being transmitted to neighbouring countries, thereby posing a potentially serious regional animal-health problem," said the report.

Before the crisis, Syria was a significant exporter of agricultural produce, including cotton, fruit and vegetables, sheep and cattle. But exports have dried up leading to losses of about $500,000 a year.