For decades, energy giants like Shell have extracted oil from Nigeria's Niger Delta.

It has earned the companies and the Nigerian government billions of dollars, but locals have long complained of massive environmental damage.

You can't grow crops. You know you can't drink the water. You know you can't fish cuz the fish are dying or they're dead.

Shell announced in January, it is pulling out of the Niger Delta, selling off its Nigerian subsidiary and its mining licenses and infrastructure to a consortium of five mainly local firms.

Shell says it's part of a plan to transition away from fossil fuels.

Civil society groups say Shell must do more to clean up the environment before it leaves.

A recent report by the Dutch organization the Center for Research on Multinational Corporations or SOMO warned the divestment plan is a ticking time bomb.

We are very concerned about the legacy of pollution being left behind by Shell, but not only Shell, but even other oil companies that have divested their assets from the Niger Delta.

We believe that it's very important for the federal government to look into these issues because the oil is not going to flow forever.

Oil companies like Shell have often blamed theft and sabotage for oil spills which is disputed by environmental groups.