Mathematical Modelling of Coupled Climate–Population Dynamics Systems: Climate Change, Bifurcations, Extinctions

Climate change has led to many extinctions in the Earth’s history. Environments change over time, pushing some species out of their comfort zone while creating new opportunities for other species; thousands of animal and plant species went extinct. The situation is dangerous now, and other extinctions may happen because of climate change. Climate warming is expected to lead to one-third of animal and plant species extinction by 2100 if proper measures are not implemented to control global warming.

Rising global temperatures due to greenhouse gases are likely to cause the extinction of different plant and animal species. Marine heat waves will create a harsh environment for the survival of aquatic animals and plants. Climate change continues to threaten global biodiversity because temperatures could increase mortality rates and result in population extinction. We mainly focus on phytoplankton, essential organisms living in the ocean’s upper layer (photic zone) and producing the majority of atmospheric oxygen. Temperature affects their growth rate and also their oxygen production. On the other hand, the abundance of phytoplankton also affects climate; phytoplankton can change the Earth’s surface albedo and disturb the energy balance. In this thesis, we use several coupled climate–phytoplankton models of various complexity; we study them (both analytically and numerically) in terms of climate change. By revealing the bifurcation structure of the systems, our results help to reveal critical thresholds in the systems’ dynamics and hence to understand how the mass extinctions may have happened in the past.