No abstract

In recent years, land use (LU) and landscape structure in ecoregions around the world have been faced with enormous pressures, from rapid population growth to urban sprawl. A preliminary account of changes in land cover (LC) and landscape structure in the ecoregions of Ghana is missing from the academic and research literature. The study therefore provides a preliminary assessment of the changing LU and landscape structure in the ecoregions of Ghana, identifying the causes and assessing their impact on land-based resources, and on urban and agricultural development. LU/LC maps produced from 30 m resolution Landsat TM5 in 1990 and ETM+ + + in 2000 were classified into dominant land cover types (LCTs) and used to survey the changing landscape of Ghana. LC-change map preparation was done with change detection extension "Veränderung" (v3) in an ArcGIS 10.1 environment. At the class level, Patch Analyst version 5.1 was used to calculate land use (LU) statistics and to provide landscape metrics for LU maps extracted from the satellite imagery. The results showed that commonly observed LCCs in the ecoregions of Ghana include conversion of natural forest land to various forms of cultivated lands, settlements, and open land, particularly in closed and open forest and savannah woodland. The dominant LU types in the ecoregions of Ghana are arable lands, which increased by 6168.98 km 2 2 2 . Forest and plantation LCTs decreased in area and were replaced by agricultural land, forest garden, and open land. Afforestation rarely occurred except in the rainforests. The mean patch size (MPS), a measure of fragmentation, was generally reduced consistently from 1990 to 2000 in all the ecoregions. Similar results that indicated increased fragmentation were an increased number of patches (NumP) and the Shannon diversity index (SDI). Habitat shape complexity inferred from mean shape index (MSI) decreased in all ecore-gions except for rainforest and wet evergreen. The SDI and Shannon evenness index (SEI) showed that habitat diversity was highest in the coastal savannah and the deciduous forest ecoregions. The main drivers of changes in the LUs and landscape structure are demand for land and land-based natural resources to support competing livelihoods and developmental activities in the different ecoregions.

The wet evergreen forest ecological zone of Ghana is undergoing notable structural changes, although most maps erroneously depict the area to be an intact forest. Several hectares of plantation agriculture such as rubber, oil palm, and cocoa are replacing the natural vegetation and habitats, thereby threatening indigenous biodiversity. This study aimed to assess the effects of tree monocrop proliferation on landscape transitions between 1986 and 2020 in the Wassa East District of Ghana. The ISODATA clustering technique was used to produce land cover category maps from Landsat images of 1986, 2002, and 2020. A post-classification change detection technique resulted in transition matrices which were used for the computation of land cover transition intensities over 34 years. The results showed that the landscape was dominated by forests in 1986. Still, the forest continuously declined by 34% (1% annually) in 2020 while all other land cover types increased in both periods with cocoa covering 23% oil palm covering 14%, and rubber covering 2% of the land area. These conversions in the land area are important, especially since the closed forests usually transition to monocrops through the intermediate process: food crop farming. This information is essential for decision making on land development and biodiversity conservation.