Bioscience Evidence 2024, Vol.14, No.2, 69-80 http://bioscipublisher.com/index.php/be 75 6 Challenges and Threats to Savanna Ecosystems 6.1 Climate change Climate change poses significant threats to the energy flow and trophic dynamics in African savanna ecosystems. Predicted impacts include shifts in vegetation types and changes in the distribution of species, which can alter the entire food web. For instance, climate-driven vegetation changes are expected to increase tree cover in savannas, potentially leading to woody encroachment into grasslands. This shift can disrupt the balance between herbivores and their food sources, affecting the entire trophic structure (Martens et al., 2022). Additionally, the increase in carbon in aboveground biomass due to elevated CO2 levels could further exacerbate these changes, leading to a decline in grassland areas and a subsequent impact on herbivores that depend on these grasses. The predictability of these changes is complicated by the interaction of climate with other factors such as fire and human activities, making it essential to develop flexible adaptation strategies (Martens et al., 2020). 6.2 Habitat fragmentation and land use change Habitat fragmentation and land use change, driven by agriculture, urbanization, and infrastructure development, are major threats to savanna ecosystems. Agricultural expansion, in particular, has been shown to reduce plant biodiversity and carbon storage, leading to ecosystem degradation (Balima et al., 2020). In the miombo woodlands of northern Mozambique, small-scale agricultural expansion has resulted in a non-linear relationship with biodiversity, where moderate levels of land use change initially increase species richness but extreme levels lead to significant declines. This fragmentation not only affects plant communities but also has profound impacts on mammal species, leading to homogenization of mammal communities and increased dissimilarity among tree communities (Tripathi et al., 2021). The combined pressures of land use change and climate change further threaten the integrity of protected areas, which are crucial for conserving biodiversity (Martens et al., 2022). 6.3 Invasive species The introduction and spread of non-native species pose significant challenges to the trophic dynamics of savanna ecosystems. Invasive species can outcompete native species for resources, leading to shifts in species composition and disruptions in trophic interactions. For example, the introduction of non-native plant species can alter the availability of food for herbivores, which in turn affects predator populations. This cascading effect can lead to a decline in native biodiversity and changes in ecosystem functioning (Irob et al., 2022). In the Brazilian Cerrado, a savanna-like ecosystem, anthropogenic disturbances such as cattle grazing and the introduction of non-native species have been shown to reduce taxonomic and phylogenetic diversity, further highlighting the vulnerability of these ecosystems to invasive species (Coelho et al., 2020). Effective management strategies are needed to control the spread of invasive species and mitigate their impacts on native trophic interactions. 7 Conservation and Management Strategies 7.1 Ecosystem restoration and management Restoring energy flow and trophic balance in African savanna ecosystems requires a multifaceted approach that integrates both ecological and socio-economic strategies. Long-term ecological monitoring, as demonstrated in the Amboseli landscape, is crucial for understanding the spatial and temporal changes in species composition, structure, and function of rangeland ecosystems. This monitoring helps in identifying the declining role of natural agencies and the increasing impact of human activities, thereby guiding effective restoration efforts (Western and Mose, 2021; Western et al., 2021). The rewilding of key species, such as the African savannah elephant, has shown to promote landscape openness and modify fauna habitats, which are essential for maintaining a balanced trophic structure (Gordon et al., 2023). Protected areas and wildlife corridors play a significant role in conserving biodiversity and maintaining ecological processes. Studies have shown that protected areas, such as the Tswalu Kalahari Reserve and Manyeleti Nature Reserve, are effective in preserving essential trace elements across different trophic levels, which is vital for the health and sustainability of wildlife populations (Webster et al., 2021). Moreover, the establishment of wildlife corridors can facilitate the movement of species, thereby enhancing genetic diversity and resilience against environmental changes. The Amboseli Conservation Program highlights the importance of space, landscape heterogeneity, and social networks in sustaining large herbivore populations, which are critical for ecosystem stability (Western and Mose, 2021).
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