# Remote Monitoring of the Impact of Oil Spills on Vegetation in the Niger Delta, Nigeria
## 3 Results and Discussion
### The Response of Vegetation Health to the Volume of Oil Spills for Individual Locations  
Table 4 presents a comparison of \(\Delta\)NDVI for each pair of CSs and SSs for different oil spill volumes. Overall, this shows that oil spills, irrespective of volume, have less significant impacts on the health condition of dense vegetation than other vegetation types, with only one site (D1 at spill volume 280 bbl) experiencing significant differences in \(\Delta\)NDVI values compared to its corresponding CS. The sparse vegetation has more impacted locations, with five out of eight spill locations exhibiting very significant differences in \(\Delta\)NDVI compared to their SS, which indicates negative impacts on the vegetation health condition following exposure to oil spills. This is followed by the mangrove vegetation, with three out of six CS locations having a significant difference in their vegetation health condition compared to their SS counterparts. The results also show that the significant difference in \(\Delta\)NDVI between SS and their CS is not directly positively correlated to the spill volume. For instance, the only significant difference for dense vegetation is observed for a spill volume of 280 bbl (\(p\)-value \(<0.05\)), which is the smallest spill volume for such sample sites. A similar scenario is also observed for the mangrove vegetation for a spill volume of 1554 bbl, which has larger statistically significant differences in \(\Delta\)NDVI than for a spill volume of 2500 bbl. One potential reason for this could be gas flaring from nearby refineries [67; 71], which increases the temperature and affects the soil quality around SSs located closer to refineries. The impact of oil spills on vegetation is beyond the spill volume, though it is an important factor, as reported by [32]. However, [PERSON] et al. [67] reported that impacted area size, spill oil volume, residual oil volume on-site, impacted area environment, and response, recovery, and clean-up timing are major determinants of oil spill influence on the Niger Delta's vegetation.  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \begin{tabular}{c} **Sample** \\ **Points** \\ \end{tabular} & \begin{tabular}{c} **Spill Volume** \\ **(bbl)** \\ \end{tabular} & \begin{tabular}{c} **Sample** \\ **Points** \\ \end{tabular} & \begin{tabular}{c} **Spill Volume** \\ **(bbl)** \\ \end{tabular} & \begin{tabular}{c} **Sample** \\ **Points** \\ \end{tabular} & \
\begin{tabular}{c} **Spill Volume** \\ **(bbl)** \\ \end{tabular} &
\begin{tabular}{c} **\(p\)-Value** \\ **(bbl)** \\ \end{tabular} \\ \hline \multicolumn{3}{c}{**Dense Vegetation**} & \multicolumn{3}{c}{**Sparse Vegetation**} & \multicolumn{3}{c}{**Mangrove Vegetation**} \\ \hline D1 & 280 & * & S1 & 228 & * & M1 & 264 & * \\ D2 & 346 & ns & S2 & 235 & ns & M2 & 800 & ns \\ D3 & 367 & ns & S3 & 260 & ** & M3 & 1020 & ns \\ D4 & 367 & ns & S4 & 440.3 & ns & M4 & 1510 & ns \\ D5 & 429 & ns & S5 & 529.5 & ns & M5 & 1554 & ** \\ D6 & 1000 & ns & S6 & 802.5 & ** & M6 & 2500 & * \\ D7 & 1430 & ns & S7 & 1000 & * & & \\ D8 & 1500 & ns & S8 & 1500 & ** & & \\ \hline \hline \end{tabular}
\end{table}
Table 4: Paired \(t\)-test analysis of \(\Delta\)NDVI values after a spill between each spill site (SS) and control site (CS) at different volumes for dense, sparse, and mangrove vegetation.