Suchergebnisse

Abstract
Vegetation cover over Nigeria has been on the decrease recently, hence the need for adequate monitoring using geo-information technology. This study examined the spatio-temporal variation of vegetation cover over Nigeria for thirty years with a view to developing a strategy for enhancing environmental sustainability. In order to predict the spatial extent of vegetation cover in 2030, the study utilised satellite images from between 1981 and 2010 using the Normalised Difference Vegetation Index (NDVI) coupled with cellular automata and Markov chain techniques in ArcGIS 10.3. The results showed that dense vegetal areas decreased in area from 358,534.2 km2 in 1981 to 207,812 km2 in 2010, while non-vegetal areas increased from 312,640.8 km2 in 1981 to 474,436.4 km2 in 2010 with a predicted increase to 501,504.9 km2 by 2030, i.e. an increase of about 27,068.4 km2 between 2010 and 2030. The study concluded that geoinformation techniques are effective in monitoring long-term intra- and inter-annual variability of vegetation and also useful in developing sustainable strategies for combating ecological hazards.

AbstractProlonged instability and insufficiency of rainfall resulting in drought, extreme weather events, and food insecurity are climate change‐related challenges bedeviling humanity. This study assessed drought conditions and rainfall trends in southwestern Nigeria, using the 1984–2014 rainfall dataset from the Nigerian Meteorological Agency (NIMET). The coefficient of variation (CV), long‐term standardized precipitation index (SPI), serial correlation test, Mann–Kendall trend analysis, Sens's slope estimation, and Pettit test were carried out using various R programming packages. Long‐term mean annual rainfall ranged between 1224.7 and 1537.1 mm. The highest variation (17.3%) was observed for Abeokuta and Ikeja. SPI analysis revealed Ibadan and Oshogbo as the driest and wettest stations, respectively. There was no serial autocorrelation in the dataset. The Mann–Kendall trend showed an upward rainfall trend for Abeokuta, Ibadan, and Ikeja and a downward trend for Akure and Oshogbo. Sen's slope annual rates of change in mm for Abeokuta, Akure, Ibadan, Ikeja, and Oshogbo are 6.69, −2.36, 2.07, 7.82, and 1.42 respectively. The Pettit test revealed change points that are not statistically significant. The drought assessment largely showed a cyclical SPI pattern with greater years of dryness. Given the increasing impact of climate change, future studies are needed to simulate the local drivers of drought severity and frequency and the changing rainfall pattern in rapidly urbanizing cities. There is also the need to incorporate climate‐related adaptive strategies in existing water management policies.