Discuss the extent to which human societies have destabilised ecological systems [9 marks]

Indicative Content	Guidance
Key concepts and terminology: Steady state and dynamic equilibria → balance between inputs/outputs in ecosystems Stability/resilience/tipping-points → capacity of ecosystems to absorb disturbances and the thresholds beyond which they may irreversibly change Diversity → variety of species within an ecosystem contributes to its stability/adaptability Storage sizes → amounts of nutrients/energy/biomass in an ecosystem can affect its stability → importance of having substantial reserves of resources within ecosystems Productivity → rate of biological production in ecosystems → high productivity in supports ecosystem resilience Negative/positive feedback / knock-on effects → changes in one component can affect other components in an ecosystem Ecosystem complexity → intricacy of relationships/interactions within ecosystems Human impacts → overexploitation, pollution, habitat degradation, unsustainable development, carbon emissions, conservation, legislation, sustainable agriculture, renewable energy → all affect ecosystem stability/resilience in different ways	You will always have to answer two 9 mark questions from Section B in your IB ESS SL Paper 2 exam This is a 'level of response' answer. The examiner will award you a combined mark out of 9 for knowledge, application, analysis and evaluation ‘Discuss’ (for 9 marks) requires: Knowledge of concepts, principles and models Application to the context using relevant and focused examples Analysis showing logical and coherent chains of reasoning of a range of issues Evaluation showing critical thinking linked to the context Depth is more important than breadth It is sensible to discuss two or three main points but to apply, analyse and evaluate them fully For top-level evaluation, informed judgement is required This can be demonstrated in a conclusion that synthesises and weighs up the arguments to form a supported answer to the question
Model Answer
Human societies have undeniably played a substantial role in destabilising ecological systems, with serious consequences for the environment and biodiversity. To assess the extent of this destabilisation, it is important to consider a range of concepts and factors that contribute to ecological stability and resilience [K]. These include diversity, storage size, productivity, and the presence of negative and positive feedback loops within ecosystems [K]. Several human activities have weakened the stability of ecological systems. Overfishing, for example, has significantly reduced the storage size of targeted fish populations, decreasing their stability [Ap]. Carbon dioxide emissions and their contribution to global warming have led to changes in climate patterns, disrupting the primary productivity of various ecosystems [Ap]. As high primary productivity is generally found to support ecosystem resilience, human-induced climate change is weakening ecosystems, making them unstable and potentially moving them towards tipping points. Tipping points represent critical thresholds within ecosystems and when these thresholds are crossed, ecosystems may undergo irreversible changes [An]. Eutrophication, often driven by agricultural runoff, interferes with negative feedback loops in freshwater systems, creating imbalances [Ap]. A tipping point may be reached when nutrient levels increase past a certain level, pushing the freshwater system into a new equilibrium with much lower productivity and species diversity [An]. However, it's important to acknowledge that not all human activities have a detrimental impact on ecosystem stability [E]. Many countries engage in legislation and conservation efforts that aim to protect the complexity of relationships within ecosystems, increasing stability [K]. Sustainable agricultural techniques that focus on soil conservation can help to maintain high productivity levels, supporting ecosystem resilience [Ap]. Additionally, renewable and alternative energy sources, such as wind and solar power, offer a more sustainable approach to energy production, reducing the negative environmental impacts by transitioning away from the significant carbon footprint associated with fossil fuel consumption [Ap]. When considering the overall extent of human-induced ecosystem destabilisation, this is highly complex and multi-factor issue. The role of humans in this process is diverse, with both negative and positive impacts, although the magnitude of negative human influence on ecological systems has grown significantly due to population growth and almost overwhelmingly outweighs the positive influences [E]. Urgent and wide-scale efforts are now necessary to adopt a proactive role in re-stabilising these systems, as failing to do so could have irreversible consequences for our planet [E].
Commentary
This answer is an example - yours may be different The answer discusses both negative and positive human impacts on ecosystem stability, and finishes with a supported final judgement The impacts of these human activities are evaluated in their respective paragraphs, as well as in the concluding paragraph The response is annotated to show where the skills of knowledge (K), application (Ap), analysis (An) and evaluation (E) have been demonstrated

Energy & Equilibria (SL IB Environmental Systems & Societies (ESS))

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