# Remote Monitoring of the Impact of Oil Spills on Vegetation in the Niger Delta, Nigeria
## 2 Materials and Methods  
### Study Area  
The Niger Delta region (Nigeria) comprises nine oil-producing states--sometimes called the political Niger Delta--hosting approximately 1500 communities and various oil and gas companies ([PERSON] et al., 2010). Traditionally, the Niger Delta comprises the three states of Rivers, Bayelsa and Delta States. These three states account for approximately 70% of Nigeria's oil spillage incidences ([PERSON] et al., 2010). The study area is located within longitudes 4\({}^{\circ}\)55\({}^{\prime}\) E and 7\({}^{\circ}\)39\({}^{\prime}\) E and latitudes 4\({}^{\circ}\)7\({}^{\prime}\) N and 6\({}^{\circ}\)33\({}^{\prime}\) N (Figure 1a). All three states are oil and agricultural-producing states. The climate in the Niger Delta region has been classified as a wet equatorial climate characterised by persistent cloud cover and few sunshine hours, which produces damp weather conditions for most parts of the year [36]. The annual rainfall ranges from 1500 to 2000 mm in the northwestern portions of the Niger Delta [37]. The average monthly temperature for the warmest months (from February to April) ranges from 28 to 33 \({}^{\circ}\)C, whilst the average monthly temperature for the coolest months (from June to September) ranges from 21 to 23 \({}^{\circ}\)C [38]. The Nigerian coastal geology is sedimentary, dominated by the geology of the arcuate Niger Delta [39]. The large amount of sediment carried by the river system over the centuries has resulted in a vast, relatively flat basin [40]. The river Niger forms a complex network of channels that drain into the Gulf of Guinea, characterised by rain-fed deltaic vegetation. The area is formed of fluvial and marine sediments built up over the past 50 million years since the upper Cretaceous period [32]. The natural delta of the Niger River is a vast sedimentary basin with deltaic deposits, which are comprised mainly of medium to coarse unconsolidated sands, silt, clay, shale, and peat [38]. The three lithostatic units in the Niger Delta were developed from the Akata Formation, Agbada Formation, and Benin Formation [41].  
However, the vegetation in the Niger Delta region was grouped into three primary types of cover for this study: (1) mangroves, which cover the coastal region of the delta, along with brackish lagoon and river systems, and freshwater swamp forest; (2) dense vegetation, which comprises rainforest; (3) sparse vegetation consisting of derived savannah grassland. The dominant mangroves are Red Mangroves (_Rhizophora_ spp.), which comprise more than 90% of the vegetation in the mangrove zone [42]. Common species belonging to the dense vegetation category are Oil Palm (_Elaeis guineensis_) and mango trees (_Mangifera indica_), whereas the sparse vegetation category is dominated by Elephant grass (_Pennisetum purpureum_), Spear grass (_Panicum maximum_), and Awolowowo grass (_Chromolaena odorata_). The sparse vegetation could be found in the seaward ecological zone, the outer edge of the  
Figure 1: (**a**) Map of the study area (**b**) in relation to Nigeria and (**c**) in relation to West Africa, and field picture of dense vegetation (**d**), sparse vegetation (**e**), and mangrove vegetation (**f**).  
-magnrove ecosystem away from the oceans [43]. Field photographs of the three main types of vegetation found in the study area are shown in Figure 1d-f.