The environment has been caught in the crossfire between Israel and Lebanon. So far, 15,000 tonnes of fuel oil has leaked into the Mediterranean Sea from Lebanon's bombed Jiyyeh power plant, 30 kilometres south of Beirut.

With more than 100 kilometres of the Lebanese coastline, and 10 to 20 kilometres of Syria's coast now affected, biologists are scrambling to try to assess how much damage the Lebanese spill could do, and how best to contain it.

“Every oil spill is different,” says Robin Crump, a marine biologist who was involved in the clean-up operations after a 1996 spill off the coast of Wales. “Everything depends on the type of oil, the temperature of the water and the air, the intertidal regions.”

Satellite images show that most of the fuel oil leaked by the Jiyyeh plant has been pushed to the Lebanese shore by southwesterly winds; the lack of wave action in the Mediterranean has meant the slick has not been broken up.

A satellite image shows the extent of an oil slick, spilled from a bombed power plant in Lebanon. Credit: DLR

Although thick oil such as Jiyyeh's is less immediately toxic to wildlife, it can cause problems in the long term. It can pick up sand and sediment from beaches and the mix can then be carried offshore and sink, spreading the oil over a wider area. Warm temperatures can also bake it into a biologically inert crust, like tarmac, that protects the fresher oil underneath from breakdown by bacteria.

Although the Lebanese government has received international aid in the form of floating barriers and barrels of detergent to help combat the slick, clean-up has not yet begun. Part of the problem is that no emergency experts from outside the country have been granted security clearance to conduct an impact assessment. And even if experts are given access, the conflict will make it hard to recruit locals to help clean the beaches, observers say.

An untreated spill can cause lasting harm, says Jacqueline Michel, president of Research Planning, an environmental-management firm based in Columbia, South Carolina. During the first Gulf War in the early 1990s, oilfields were sabotaged and some 1.5 million tonnes of crude oil spilled into the Persian Gulf. Most of it ended up on the Saudi Arabian coastline, and only around 10% was ever recovered. Today, Michel says, “the intertidal communities have shown little or no recovery”.

In Lebanon, the failure to mount a swift clean-up operation could most harm the region's threatened leatherback, loggerhead and green turtles. Bluefin tuna may also be at risk depending on where the oil goes, adds Luisa Colasimone of the United Nations Environment Programme. The eastern Mediterranean is home to a large spawning ground for the tuna.

Environmental damage can occur even after a hasty clean-up, says Charles Peterson, a marine ecologist at the University of North Carolina, Chapel Hill. He and his colleagues have studied the long-term effects of an oil slick spilled when the Exxon Valdez tanker ran aground in Alaska's Prince William Sound in 1989. In 2003 they reported that the recovery of whale, otter and duck populations at the site of the spill has been slower than expected owing to indirect effects of oil contamination (C. H. Peterson et al. Science 302, 2082–2086; 2003). And a spill along the eastern coast of Panama caused extensive damage to the region's mangroves, despite efforts to minimize the impact of the slick.

On the other hand, some areas affected by spills bounce back relatively quickly. The 1996 spill off Wales is a case in point. “Ten years on, the system has recovered,” Crump says.