Determining the response of vegetation to urbanization and land use/land cover changes using NDVI and NDBI differencing techniques.. [DOI: 10.21203/rs.3.rs-3050037/v1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

Urban ecosystem is a self-organising system of unusual complexity, made up of different interacting social, economic, institutional and ecological subsystems. The response of vegetation to urbanization and accompanying land use and land cover changes in urban areas depends on the form of urbanization and climatic region. Many scholars believe that vegetation is destroyed or at least stunted by urbanization while others are of the opinion that urbanization enhances urban vegetation. This study assessed the relationship between urban expansion and tree density in Sokoto metropolis over a 32-year period using NDVI and NDBI differencing techniques. Results show that the net vegetation gain was 927.8ha while the built-up area expanded by 2918.1ha. Urbanization and urban expansion may have detrimental effects on urban vegetation but with controlled planning, it will have little or no negative impacts. The results show that management and policy measures can be taken in cities in order to mitigate the negative impacts of urbanization on urban vegetation. These findings are relevant in the planning and management of urban forests.

Response of benthic invertebrate assemblages to seasonal and habitat condition in the Wewe River, Ashanti region (Ghana)

Aquatic macro-invertebrates play a vital role in the food chain of river ecosystem at several trophic guilds and consumer levels, and are used as biomonitoring tools for aquatic ecosystem health. However, hydrologic conditions of these ecosystems have been severely altered because of the increase in urban development and agricultural expansion. This study examined benthic invertebrate response to processes that structure their community in the Wewe River, segmented into intact, medium, and severe condition zones. We sampled in 100 stations in a period of 4 months in the wet (June–September, 2019) and 3 months in the dry (January–March, 2020) seasons. Geometric series, rarefaction, and Hill numbers models were used to quantify invertebrate assemblages, while ordination technique, canonical correspondence analysis, was used to evaluate the influence of predictive factors on their assemblages. A total of 2,075 individuals belonging to 20 family taxa were registered. There was no significant difference in benthic assemblages between the dry and wet seasons. Predictive factors accounted for 47.04 and 50.84% variances, respectively. Taxa distribution patterns differed significantly only in the severely disturbed zone during the wet season. Neptidae, Libellulidae, and Chironomidae were the most abundant taxa, indicating their broad range habitat preference and their ability to adapt to seasonal changes. Asellidae and Perlidae were the least detected, suggesting their sensitivity to elevated levels of some water quality parameters. The findings highlight the threats to the benthic community and overall functional state of the Wewe River, with the need to consider the proposed conservation interventions indicated in this study.

Assessing How Land-Cover Change Associated with Urbanisation Affects Ecological Sustainability in the Greater Accra Metropolitan Area, Ghana

Intensive land-cover changes (LCC) driven by unplanned urbanisation continue to threaten the sustainability of ecological assets in many cities in Africa. Evaluating the nature and processes of these changes is key to understanding the extent to which ecological instability may be affecting sustainability futures. This study employed integrated remote sensing, GIS, land accounting techniques and utilisation of high-resolution Quickbird and Worldview 2 images to analyse actual (2008–2017) and future (2017–2030) LCC and explored implications for ecological sustainability in the Greater Accra Metropolitan Area, Ghana. After mapping and classifying actual LCC, multi-layer perception (MLP) neural network and Markov chain were employed to predict future LCC for the year 2030. The results indicate that the built-up area increased substantially from 27% in 2008 to 46% in 2017 and is expected to rise to 73% by 2030. In contrast, open-space (10%), forestlands (5%) and grassland/farmlands (49%) decreased progressively (2008–2030). In effect, these land-cover types experienced area turnover ˃100% during the actual and predicted period, indicating high vulnerability of natural land cover to urban growth, ecological degradation and resource depletion. These findings highlight significant implications of LCC for ecological sustainability in the study area. A proactive land-cover/use management plan is necessary to ensure sustainable urban development and ecological land conservation.