Not all the Somali "pirates" are gangsters: some are locals who've watched their loved ones sicken and die after European toxic waste was dropped on their shores and decided to do something about it.

Yes: nuclear waste. As soon as the government was gone, mysterious European ships started appearing off the coast of Somalia, dumping vast barrels into the ocean. The coastal population began to sicken. At first they suffered strange rashes, nausea and malformed babies. Then, after the 2005 tsunami, hundreds of the dumped and leaking barrels washed up on shore. People began to suffer from radiation sickness, and more than 300 died.

Ahmedou Ould-Abdallah, the UN envoy to Somalia, tells me: "Somebody is dumping nuclear material here. There is also lead, and heavy metals such as cadmium and mercury – you name it." Much of it can be traced back to European hospitals and factories, who seem to be passing it on to the Italian mafia to "dispose" of cheaply. When I asked Mr Ould-Abdallah what European governments were doing about it, he said with a sigh: "Nothing. There has been no clean-up, no compensation, and no prevention."

At the same time, other European ships have been looting Somalia's seas of their greatest resource: seafood. We have destroyed our own fish stocks by overexploitation – and now we have moved on to theirs. More than $300m-worth of tuna, shrimp, and lobster are being stolen every year by illegal trawlers. The local fishermen are now starving. Mohammed Hussein, a fisherman in the town of Marka 100km south of Mogadishu, told Reuters: "If nothing is done, there soon won't be much fish left in our coastal waters."

This is the context in which the "pirates" have emerged. Somalian fishermen took speedboats to try to dissuade the dumpers and trawlers, or at least levy a "tax" on them. They call themselves the Volunteer Coastguard of Somalia – and ordinary Somalis agree. The independent Somalian news site WardheerNews found 70 per cent "strongly supported the piracy as a form of national defence".

No, this doesn't make hostage-taking justifiable, and yes, some are clearly just gangsters – especially those who have held up World Food Programme supplies. But in a telephone interview, one of the pirate leaders, Sugule Ali: "We don't consider ourselves sea bandits. We consider sea bandits [to be] those who illegally fish and dump in our seas."