Assessment of Vegetation Cover Dynamics and Nature-based Conservation Strategies in Response to Climate Variability and Change in Old Oyo National Park, Nigeria

Abstract

Human-induced climate change has led to significant impacts on ecosystems globally, particularly in African savannas, where the frequency and intensity of extreme events have increased. Escalating ecological threats in protected areas due to climate change, encroachment from invasive species, habitat fragmentation, and poaching, results in habitat degradation and biodiversity loss, underscoring the urgent need to preserve this critical ecosystem. However, literature on vegetation dynamics in the savanna ecosystem of Old Oyo National Park (OONP) lacks comprehensive long-term studies that integrate climate change effects using temperature and rainfall variability. Moreover, limited research focuses on the practical adoption of nature-based solutions for conserving vegetation in OONP, which hinders informed decision-making and adaptive management strategies. This study, therefore, examined the interplay between climate variability, vegetation dynamics, and the utilization of nature-based solutions (NbS) for conservation within OONP by: (i) examining changes in vegetation cover from 1999 to 2020; (ii) evaluating the effects of temperature and rainfall variability on the vegetation (NDVI) of the study area; and (iii) investigating the adoption of nature-based solutions in managing and conserving vegetation cover in the park. Landsat satellite images from 1999 to 2020 were used to analyze changes in vegetation cover, using supervised image classification. Climate data from TAMSAT and Climate Engine, from 1990 to 2022, were used to examine climate-NDVI dynamics, while interviews and participatory mapping with park officials were used to assess perceived climate change impacts and the adoption of nature-based solutions for vegetation conservation within the park. The findings revealed that the mixed open savanna, comprising of mosaic grassland, shrubland and woodland, dominated the park, with a net increase of ~54 Km2, with a ~69.7% decrease in bare land, a net loss in water bodies by ~18.6%, and considerable growth of forest outliers and woodlands by ~59.8%. Variability in rainfall (CoV = 7.95%) and a significant upward trend in temperature (S = 345, p <0.0001) were observed. Pearson correlation revealed no statistical significance in temperature-NDVI (r=0.295, p>0.05) and rainfall-NDVI (r=0.072, p>0.05) relationships. However, higher vegetation indices positively correlated with areas receiving more rainfall for the years 1990 (r=0.221, p< 0.01), and 2000 (r=0.168, p<0.05), and negatively correlated with temperature for the years 1990 (r=- 0.253, p<0.01), 2000 (r=-0.167, p<0.05), 2010 (r=-0.271, p<0.01) and 2021 (-0.423, p<0.01). Fire management practices, afforestation, avoided grazing and conservation education were identified conservation practices that contributed to the overall vegetation conservation efforts. However, the findings suggest that the proliferation of invasive Chromolaena odorata may have contributed to forest encroachment, potentially threatening native vegetation. The study concludes that while overall positive vegetation stability in OONP may have been aided by the identified NbS, the threat of invasive Chromolaena odorata indicates that the observed stability may not equate to ecological balance or benefits. Targeted water management strategies, effective invasive species management practices, preservation and restoration of native plant species, strengthening conservation education programs, and increasing government investment in conservation infrastructure are essential to support sustainable conservation efforts within OONP. Further studies should evaluate existing conservation practices and explore the potential impacts of climate change on vegetation cover within OONP to inform adaptive management strategies and enhance the park's resilience.