MANGROVE HEALTH AND COVER ASSESSMENT: A REMOTE SENSING APPROACH

Abstract

Mangrove vegetation are known for their unique ability to thrive in brackish environment. In addition, they provide a number of basic and fundamental services to mankind, the world over. They are however undergoing a lot of pressure owing to urbanisation and population increase. Recent/up-to-date follow-up studies, for the purpose of mangrove vegetation management through efficient mangrove monitoring, especially in the Niger Delta of Nigeria, are limited in literature. Against this backdrop therefore, this study examined mangrove vegetation health and coverage change in a portion of the Niger, through the period of 2001/2002 to 2015/2016. This was carried out using the enhanced change detection method and the Normalized Difference Vegetation Index (NDVI), within the Geographic Information System (GIS) environment. Landsat images, for the period under study, were used to ascertain the aforementioned. The study area was reclassed into: (1) healthy vegetation (2) weak vegetation and (3) no vegetation based on the NDVI values of < 0.3, 0.1 – 0.3 and > 0.3 respectively. In 2001/2003, the “no vegetation cover”, “weak vegetation” and healthy vegetation comprised 11.4%, 14.64%, 73.89% of the study area respectively. In 2015/2016, the aforementioned classes comprised 24.71%, 28.70%, 46.59% respectively. The “no vegetation cover” and “weak vegetation” classes increased at the rate 8.24%/year and 6.86%/year respectively. The “healthy vegetation” class however reduced at the rate of 2.64%/year, marking a marginal improvement., In view of the already established degradation trend, it is being recommended that mangrove conservation sites and environmentally friendly policies and alternatives be adopted.