Counting the cost of the Niger Delta's largest oil spills: Satellite remote sensing reveals extensive environmental damage with ＞1 million people in the impact zone

摘要

The Niger Delta has a long history of oil and gas exploration and production, but this has come with a heavy environmental cost arising from oil spills and other pollution events. Two oil spills in Ogoniland in 2008/9 were by far the largest in terms of both duration (149 days combined) and magnitude (82,939,1701 combined), but little is understood about the extent of impact of these events because traditional field-based surveys are virtually impossible in this region. In this study, the normalised difference vegetation index, a technique used for measuring plant health, was applied to multi-temporal satellite images to delineate an extensive area of 393 km2 that has experienced vegetation mortality resulting from the oil pollution. These effects persist to present and are exacerbated by continuing subsequent spill events. Independently collected field samples confirmed the high concentrations of hydrocarbon pollutants in the impact area. The extensive tidal river network and mangrove swamps have facilitated the spread of oil, with the delta becoming a sink for the oil that is dispersed but not removed. Over 1 million people live within the area contaminated by oil and have potentially been exposed to pollution through direct and indirect pathways over a prolonged period. The population in the impact area is particularly vulnerable to chronic illness due to its young age structure and pre-existing very low life expectancy. Hence, there is an urgent need to mitigate the impacts of the pollution on environmental and human health. The novelty of this work is that satellite remote sensing allows the impacts of pollution to be monitored across large areas in a geographically remote and challenging environment. The outputs from this study could be used to guide the future spatial targeting of the limited remediation resources that are available, to achieve positive outcomes.