Global ocean oscillations and climate change affect weather patterns in the Serengeti

The impacts of global climate change are now widely recognized, but the regional impacts -- especially in the Southern Hemisphere -- are less well understood. In the Southern Hemisphere and particularly in East Africa, climate change is primarily manifested through fluctuations in wind and sea surface temperatures that cause irregular cooling and warming periods, specifically, the global El Niño-Southern Oscillation (ENSO) in the Pacific Ocean and the regional Indian Niño in the Indian Ocean. These phenomena influence rainfall and temperature, making their patterns and interactions crucial to understanding the regional impacts of climate change.

In the new study, researchers used a variety of models to uncover long-term trends, cycles and seasonality in rainfall, temperature and vegetation for the Greater Mara-Serengeti ecosystem, and influences from ENSO and the Indian Niño. The team found that the area experienced recurrent severe droughts and erratic wet conditions and recorded a rise in temperatures of 4.8 to 5.8 degrees Celsius over six decades. Wet and dry season rainfall amounts have fluctuated in varying cycles, but year-to-year, average rainfall has remained similar and occurred in regular seasons. However, rainfall was above average in both dry and wet seasons from 2010-2020, likely influenced by global warming and the Indian Niño.

The researchers conclude that understanding regional climate trends and how they are influenced by large-scale oceanic and atmospheric oscillations is crucial for predicting future climate conditions and mitigating their impact on people and animals. For example, droughts increase the risk of starvation for wildlife, shrink wetlands and intensify human-wildlife conflicts, while heavy rainfall can lead to habitat destruction. The insights from this work can be used to develop strategies to reduce the impacts of climate change in the region and to inform environmental planning and conservation efforts.

The authors add: "The Mara-Serengeti ecosystem, like many African savannas, has seen a 5.3-degree Celsius rise in minimum temperatures since 1960, concurrent with the warming Indian Ocean, leading to habitat desiccation and severe threats to wildlife populations. Frequent severe to extreme droughts and rare instances of very wet to extremely wet years in the Mara-Serengeti ecosystem also significantly threaten wildlife populations."