"When you visit these communities, the first thing you notice is the stench of crude oil," says Makmid Kamara, a business and human rights campaigner at Amnesty International. The environmental clean up of the Niger Delta, the biggest oil-producing region in Africa, is long overdue, Kamara told DW.

Shell operates around 50 oil fields and 5,000 km of pipelines in the region. According to the company's own figures, it is responsible for 1,693 oil spills since 2007. The researchers from Amnesty International and the Centre for Environment, Human Rights and Development (CEHRD), however, believe that actual figures are even higher.

In some areas, the environmental pollution has been taking place for decades, robbing the communities of their land and their livelihood. With this report, the rights groups hope to ensure that Shell as the region's biggest oil company takes responsibility and restores the land to a state where it is arable again. "Because that is all that the people ask for," says Kamara. "They want to have their land back to farm and feed their communities and have money to send their children to school."

The investigations by the rights group at four oil spill sites identified as highly polluted by the United Nations Environmental Program in 2011 showed that the contamination persists to this day, despite Shell's claims to have cleaned it up. The rights groups said that they found layers of oil on both the soil and the water in several locations. At one of the sites, Shell's Bomu Well 11, the oil spill happened 45 years ago and Shell claims to have cleaned it up twice.

Nigerian law is very clear on the matter, says Kamara. "When a spill occurs, the responsible company has to clean that spill within 24 hours". Yet according to the report, the problem lies in the implementation of that law. The Nigerian watchdog, the National Oil Spill Detection and Response Agency (NOSDRA) is under-resourced and has in several cases certified areas as clean that are still visibly polluted. Moreover, says the report, areas which are cleaned up, have only been cleaned superficially. "This is just a cover up," one contractor hired by Shell, reportedly told the researchers. "If you just dig down a few meters you find oil."

According to Amnesty International, Shell disagrees with their findings. On the company's website, Shell cited sabotage and oil theft as a significant cause of oil spills. It claims it has been able to improve pipeline security by entering into a cooperation agreement with local communities. In January 2015, Shell agreed to pay 55 million British pounds ($83.5 million) to local fishing communities after a three year long legal battle.