The research by Mark Ritchie of Syracuse University on climate change in the Serengeti ecosystem reveals several significant consequences expected from global environmental changes:
1. Global Change Factors Affecting Serengeti:
Stats
CO2 levels have increased by 70% (from 220 ppm in 1910 to 375 ppm in 2000).Current rates of increase suggest concentrations approaching 475–500 ppm by 2050, indicating a substantial rise in atmospheric CO2 levels.
- Carbon Dioxide (CO2): CO2 levels are predicted to rise dramatically, increasing photosynthesis and water-use efficiency in plants, though it could lead to nutrient depletion, affecting herbivores and cascading through the food web.
- Rainfall and Temperature: Decreases in wet-season rainfall and increased temperature are expected to reduce plant productivity, but nutrient concentration in plants may increase. Reduced rainfall will negatively affect herbivore populations and vegetation cover, favoring grasses over trees.
2. Plant and Ecosystem Responses:
Stats;
Elevated CO2 is predicted to increase plant productivity by up to 33% in grasslands, but this comes with a trade-off of reduced nutrient concentration.A 1-2°C increase in temperature combined with a 20% reduction in rainfall could reduce overall plant productivity by as much as 40%.These combined changes (CO2, temperature, and rainfall) are expected to result in nearly 20% less primary productivity in the Serengeti.
Discussion;
- Plant Productivity: Elevated CO2 may increase plant productivity by 30%, but decreased rainfall could reduce it by 40%. Combined, these factors may lower primary productivity by around 20%. Water-use efficiency is expected to improve, but decreased rainfall will likely shrink woodland areas.
- Species Composition: Drier conditions will favor water-efficient grass species, reducing the dominance of woody plants. Extreme rainfall events that support diversity may become rarer, leading to reduced biodiversity.
3. Impact on the Food Web:
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Annual rainfall in the Serengeti has decreased since the 1960s, with projections suggesting continued declines in wet-season rainfall.Global climate models predict a 2–5% increase in annual rainfall in East Africa by 2050, but historical trends in the Serengeti show a significant decline in wet-season rainfall since the 1960s, creating uncertainty.Extreme rainfall events, which support plant diversity, may become increasingly rare, leading to potential declines in biodiversity.
- Herbivores: Smaller herbivores may benefit from higher plant nutrient content, while larger herbivores may decline due to reduced biomass. Elephants could become even more dependent on woody plants.
- Carnivores: Reduced herbivore biomass could negatively affect predators, although smaller herbivores may increase prey availability for medium-sized carnivores like cheetahs and wild dogs.
- Decomposers: Reduced plant productivity and improved water-use efficiency may shift the ecosystem toward detritus-based dynamics, reducing fire occurrences and affecting nutrient cycling.
4. Human-Wildlife Interactions:
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WUE is expected to increase by nearly 30% in response to elevated CO2, mitigating some of the productivity losses due to reduced rainfall.
- Livestock and Agriculture: Climate change could lead to more nutritious but less abundant forage for livestock, limiting the areas livestock can graze due to fewer water sources. This could intensify human-wildlife conflicts as both compete for limited resources.
- Food Security: Reduced rainfall and longer droughts may make livestock less reliable as “banks” for food security, pushing humans to switch to more drought-resistant crops or increasing the pressure to harvest wildlife.
- Disease Risks: Drier conditions may reduce malaria risks but increase the transmission of diseases like rabies and tuberculosis, as humans, livestock, and wildlife are forced to share water sources more frequently.
5. Predictions and Uncertainty:
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Shifts in rainfall and nutrient content may reduce herbivore diversity, particularly among larger species like buffalo, eland, and elephants.Coughenour and Chen’s simulations suggest that a 20% reduction in rainfall could lead to a decline in plant nutrient concentration, directly affecting herbivore populations.Smaller herbivores may benefit from the higher nutrient concentration, while larger herbivores may face declines due to reduced forage availability.
- Complex Interactions: Global changes in CO2, temperature, and rainfall are likely to interact in complex ways, with rainfall predicted to have the most significant impact on plant production. Predictions suggest worsened food security for humans and increased pressures on conservation areas.
- Human Vulnerability: Longer droughts and limited resources will increase human vulnerability to climate variations, intensify disease transmission, and make the Serengeti ecosystem more fragile.
Another Study titled Cross-boundary human impacts compromise the Serengeti-Mara ecosystem, underscores the need for further studies to better understand the intricate relationships between climate change, ecosystems, and human activities, particularly in sensitive environments like the Serengeti.
This study focuses on the impact of human activities on the Serengeti-Mara ecosystem and provides critical statistics that help make a convincing case for the effects of human encroachment:
Key Findings:
- Human Population Growth:
- The human population around the Serengeti-Mara ecosystem increased by 2.4% annually from 1999 to 2012.
- Crop agriculture expanded from 37% of the region in 1984 to 54% in 2018, indicating a rapid conversion of land surrounding the protected area (PA).
- Livestock Expansion:
- The cattle population grew by 0.9% annually from 2002 to 2012, with the highest increase (4.2% annually) near Lake Victoria.
- Sheep and goat populations in the region grew by 3.8% annually, further intensifying grazing pressure on the land.
- Impact on Wildlife:
- Wildlife biomass inside the first 15 km of the Masai Mara National Reserve (MMNR) decreased by 75% in the wet season and by 50% in the dry season from the 1970s to the 2000s, due to human-induced “spatial compression.”
- Wildebeest utilization of the ecosystem’s borders decreased by more than 10% in areas where livestock incursions occurred frequently.
- Vegetation and Fires:
- The total burned area in the Serengeti-Mara ecosystem decreased from 52% to 29% between 2001 and 2016, corresponding to a 40% reduction in fires over 16 years. This is linked to reduced vegetation biomass from overgrazing by livestock.
- The maximum vegetation greenness (maxNDVI) decreased by 8% over the same period, highlighting the reduction in vegetation health and ecosystem productivity.
- Soil Carbon and Ecosystem Function:
- Soil organic carbon (SOC) sequestration decreased, with only 28.3% of plots sequestering more than 1 mg of carbon per hectare from 2009 to 2017, compared to 58.6% from 2001 to 2008.
- Grazing intensity increased by 1.08% per year, leading to shifts in ecosystem function, including reduced resilience and carbon storage.
Summary of “Spotted Hyenas Adapt to Climate Change in Famed Tanzanian Park”
In another Study on Spotted Hyenas, below were the findings.
- Context: Spotted hyenas in Tanzania’s Serengeti National Park are adapting to changing rainfall patterns, which have shifted the timing of prey migrations.
- Key Observation: Over the past decade, migratory herds such as wildebeest have been arriving later than before, which impacts the hyenas’ access to their usual prey.
- Hyenas’ Adaptation: Despite these changes, researchers found no significant alteration in the amount of time lactating hyenas spend with their cubs. This indicates that hyenas are effectively adapting by finding food further from their dens without negatively affecting their time with offspring.
- Social Learning: Hyenas rely on social learning within their clans to locate prey, which allows them to maintain their usual foraging behavior even with migratory delays.
- Climate Change Impact: The ongoing shifts in rainfall patterns, due to climate change, are altering migration dynamics, and future scenarios predict even more dramatic changes. In extreme cases, herbivore migration might cease altogether.
- Broader Concerns: While hyenas show adaptability in the Serengeti, in other fragmented habitats, they may not be as resilient due to human activities and habitat loss.
This study highlights the spotted hyena’s behavioral flexibility in response to environmental challenges caused by climate change, though concerns remain about their ability to adapt in more heavily impacted areas.
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Another study found that climate change, particularly reduced vegetation quality, has a more significant impact on impala stress levels in the Serengeti than human disturbances. Impala showed elevated faecal glucocorticoid metabolite (FGM) concentrations when vegetation was poor, indicating higher stress. Rainfall improved forage quality, reducing stress. Human activities, such as settlement density and proximity to park borders, also increased stress, but not as strongly as the availability of nutritious vegetation. The findings suggest that maintaining forage quality through habitat protection and addressing climate change effects is critical for conserving impala and other herbivores in the region.
Consequences:
- Human activity outside the protected areas compresses wildlife into the core areas, leading to overgrazing, reduced fire frequency, and declining vegetation health. This spatial compression compromises the ecological function of the entire ecosystem, resulting in diminished soil carbon sequestration and altered ecosystem processes.
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A study conducted over eight years in Tanzania’s Serengeti National Park has revealed that competition for food drives the migration and grazing patterns of zebras, wildebeest, and gazelles. Zebras, needing large amounts of vegetation, migrate faster to graze ahead of the larger wildebeest population, which numbers 1.3 million. The zebras remove taller plants, allowing gazelles to access flowering plants and later new vegetation. The research, led by Michael Anderson and published in Science, shows a balance of competitive and cooperative forces among these species and offers insights into managing migratory herbivore populations amid ecosystem degradation and climate change.
Implications:
- These findings highlight the urgent need for better land management strategies at the edges of protected areas to preserve biodiversity and maintain ecosystem functions. Without intervention, human pressures will continue to degrade the Serengeti-Mara ecosystem, reducing its resilience to climate change and threatening both wildlife and human livelihoods.
The statistics provide clear evidence of how human encroachment is affecting one of the world’s most iconic ecosystems, making a strong case for policy changes to manage human activities in surrounding areas.