Ecocriticism is a field of inquiry that first developed in the 1970s. It refers to the study of literature, and the arts generally, from an environmental perspective.
There are two waves of Ecocriticism. The first wave mainly concerned itself with local conservation. The second wave concerns itself with globalization, and looks at how environmental concerns impact poor communities and communities of color (e.g., environmental racism).
Helon Habila's "Oil on Water" is part of the second wave of Ecocriticism. It looks at the ways in which the environmental destruction of the Niger Delta, due to greed for petrodollars, has warped human relationships.
Two men, Rufus and Zaq, journey upriver, observing the destruction that oil companies reap on the ecosystem along the delta: "dead birds draped over tree branches, their outstretched wings black and slick with oil; dead fishes bobbed white-bellied between tree roots".
Initially, villagers are excited to receive a contract with the oil companies (the novel probably mirrors Nigeria's relationship with Royal Dutch Shell), but the result of such an alliance is not prosperity; instead it results in the loss of their homes. Once water becomes contaminated, fields become non-arable, causing villages to be abandoned. Survivors of this environmental crisis are given jobs at the oil company -- a means of keeping them quiet and ensuring loyalty -- while others turn to crime for profit.
Ecocriticism, particularly the second wave, looks at the connections that human beings have to their environment and how those connections, even at seemingly minor levels, are necessary in maintaining a sustainable environment. Habila's novel is a work with an Ecocritical context because it examines these connections, and shows what happens when ecosystems no longer function.