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Watershed is an ecosystem area bordered by topographic pattern and serves as serves as a collector, storage and distributor of water, sediments, pollutants and nutrients in the river system and throughout by a single outlet. The high of population growth led to greater land use change. This research aimed to identify land cover classes and land cover change in Besitang watershed between 1990, 2005 and 2015. This research used Landsat 5 imagery in 1990 and 2005, and Landsat 8 imagery in 2015 with supervised classification using method maximum likelihood classifier. The result showed that there were 12 classes of land cover in the Besitang watershed, they were primary forest, secondary forest, mangrove forest, scrub, rubber plantations, oil palm plantations, dry land agriculture, bare land, settlement, fishpond and water body. The largest area of land cover area is primary forest covering an area of 38,542.43 hectares (39.94%) in 1990, 34,279.16 hectares (35.52%) in 2005, and 34,620.41 hectares (35.88%) in 2015. The largest area of land cover change between 1990 until 2005 is mangrove forest to fishpond with covering an area of 2,364.21 hectares change. While the largest area of land cover change between 2005 until 2015 is mangrove forest to oil palm plantation with covering an area of 1,016.82 hectares changes.

Vegetation existence contributes to environmental quality in urban areas. The increase in population and development of cities has led to land conversion with lesser vegetated areas. Information on land cover change is needed, especially for urban regional planning with green open space consideration. The research aims to analyze urban vegetation cover and its changes in two sub-districts of Medan between the years 1999 and 2019. Normalized difference vegetation index (NDVI) and change analysis were conducted in the research. The diversity of plants within these areas was observed. The results showed changes in vegetation cover areas in the mentioned years. In 1999, most areas were under a highly dense vegetation class, while in 2019, they were under a lowdensity vegetation class. This finding indicates a decrease in vegetation cover as a result of increasing built-up areas. Within the vegetation cover, it was found many tree species and agricultural plants. Those vegetations existed in some areas: city parks, house yards, gardens, agricultural fields, etc. A special emphasis should be placed on riverside areas with less vegetation in order to provide a higher level of protection, particularly in the event of a flood. To increase the vegetated areas and maintain the environmental quality, optimizing the land by replanting in the area with no or less vegetation should be done.

The mangrove ecosystem in Forest Managemen Unit - VII (FMU) Sumatera Utara is a natural forest. FMU has not managed and utilizes mangrove forests optimally. It can open up opportunities for illegal loggers and trigger damage to these natural ecosystems. This condition requires prevention and mitigation so that severe damage to mangrove forests does not occur. This study aims to determine the relationship between vegetation index and mangrove density in the field and map the mangrove density distribution based on the image vegetation index value. The density distribution mapping was carried out by compiling a vegetation density estimator model NDVI, GNDVI, and TVI as independent variables. Correlation test and regression analysis between the vegetation index value (NDVI, GNDVI, and TVI) to the number of trees per unit area. The distribution model for the density of mangrove stands was chosen based on the coefficient of determination (R2). The study resulted from NDVI selected as the vegetation index used to map the distribution of mangrove density with a Pearson correlation coefficient (R) of 0.738. The selected model is Y = 2.48e2.8667x, which is an exponential equation with a coefficient of determination (R2) of 61.3%. Based on this model, the distribution of mangrove density has the lowest density reaching 400, and the highest density is 2,200 trees per hectare

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