Like many communities in southern Nigeria, the people of Okpare rely on the waters of the creeks that surround them for fishing and farming to survive.Pollution is a constant threat in the Niger Delta but locals say it is not just thieves stealing crude oil from pipelines that criss-cross the region who threaten their livelihoods.Military operations against illegal "bush refineries" and militants who target oil and gas infrastructure are also adding to the damage."Aquatic life in our rivers has been destroyed and our farms have been ravaged by fire as a result of the burning of stolen crude oil by the army," said Okpare resident Gabriel Ekoh.Oil is the mainstay of Nigeria's economy, accounting for some 70% of overall government revenue and nearly 90% of export earnings.The West African giant, which is home to more than 180 million people, currently churns out some 1.8 million barrels per day. But oil has been a curse for the people of the Niger Delta since it was found in commercial quantities in the 1950s. Despite the billions of dollars it has generated, few locals have shared in the wealth and the region remains desperately poor. Instead, theft from pipelines, or "bunkering" as it is called locally, has become commonplace. Water not fit to drink Nigeria's government in 2015 estimated that the equivalent of at least 250 000 barrels of crude were being stolen every day, feeding a thriving black market for illicitly refined fuel.The deputy commander of the military's Operation Delta Safe, Brigadier-General Kelvin Aligbe, last month gave an indication of the scale of the problem.Since 2016, troops had destroyed 1 437 illegal refineries, 795 wooden cargo boats, 3 872 metal surface tanks, 1 019 plastic tanks, 13 129 drums and 13 343 jerry cans, he said.Across Nigeria's southern coastal states, the effects of oil pollution area not hard to see.Little grows in the blackened soil and few fish swim under the glistening slicks on the surface of the creeks; the surrounding mangroves have died and water is not fit to drink.Researchers say exposure to oil spills increases the risk of infant mortality while the UN has said a much-delayed clean-up of the region could take decades to complete.Soldiers tipping barrels of illegally refined fuel into the creeks or burning down bush refineries does not help, say locals and environmentalists.Sheriff Mulade, from the Centre for Peace and Environmental Justice in the Delta state capital, Warri, said illegal refineries were being destroyed every day outside the city."As long as illegal refineries continue, security agents will continue to destroy them by spilling their contents into the river," he added.The situation has created a dilemma for Nigeria's military, which is over-stretched by multiple security threats across the country.Last November, an Operation Delta Safe commander, Colonel AB Mohammed, said they were overwhelmed by the sheer number of illicit oil installations."We do not have the resources to bring the illegal crude and release them to the Nigerian Security and Civil Defence Corps or police," he told reporters."Again, we are afraid of compromise, which kills the morale of the military, and it is one of the reasons we burn out the illegal crude." 'Unbridled pollution' In Port Harcourt, Nigeria's oil hub, black soot has been falling from the sky for more than a year, prompting growing concern about the quality of the city's air.Levels of PM2.5s, the finer particulate matter from fumes and smoke that harm human health, regularly match or even exceed more well-known polluted cities such as New Delhi or Beijing.Readings typically spike in the early morning. Locals blame the smoke from illegal refineries in the creeks, which operate at night to avoid detection.Mulade applauded the military for its efforts but said there was widespread concern about the "way and manner they are handling the discarding of the crude oil and its products"."The emissions are very dangerous and the lifespan of residents of these areas has been cut short because of this," he added.Nnimmo Bassey,a former head of Friends of the Earth International, said military tactics against the oil thieves were exacerbating the problem."These acts add to the environmental degradation of the region at a time when all efforts should be aimed at cleaning up six decades of unbridled pollution," he said."The response of the security forces should not add to the problem."* Sign up to News24's top Africa news in your inbox: SUBSCRIBE TO THE HELLO AFRICA NEWSLETTERFOLLOW News24 Africa on Twitter and Facebook.