Population, resources and pollution model: positive and negative feedback.…

The idea

The Population, Resources and Pollution (PRP) model maps interactions between demographics and the environment. Positive feedback amplifies changes: population growth drives resource extraction, increasing pollution and degrading resources. Negative feedback dampens effects: severe pollution increases mortality, reducing population and resource pressure. Malthus posits that geometric population growth outstrips arithmetic food supply, causing famine. Neo-Malthusians apply this to all finite resources, predicting systemic collapse. Conversely, Boserup argues population pressure drives agricultural innovation, while Simon views human ingenuity as the ultimate resource, ensuring technological solutions will always overcome resource depletion.

What earns the marks

• Explain the PRP model by detailing how population size, resource acquisition, and pollution generation are interconnected.
• Distinguish between positive feedback (e.g., agricultural expansion causing soil degradation, requiring more land clearance) and negative feedback (e.g., resource scarcity reducing birth rates).
• Contrast Malthusian 'limits to growth' perspectives with the optimistic, technocentric views of Boserup and Simon.
• Evaluate the relevance of neo-Malthusian models, such as the Club of Rome's Limits to Growth, in the context of modern global resource consumption.

Common mistakes and how to put them right

• Confusing positive and negative feedback.

  Put it right: Positive feedback amplifies a change in the PRP model, whereas negative feedback restores balance or dampens the change.

• Treating Malthusian and neo-Malthusian theories as identical.

  Put it right: Malthus focused primarily on food supply, whereas neo-Malthusians consider a broader range of environmental limits and resources.

• Misattributing theories; stating Boserup believed in inevitable population collapse, when she actually argued that population growth stimulates agricultural innovation.

Exam tips

• Use specific historical or contemporary examples, such as the Green Revolution, to evaluate Boserup's theory of induced innovation.
• When discussing the PRP model, clearly draw out the feedback loops using step-by-step logical chains to show how one variable affects another.
• Compare and contrast the theories directly in essay questions rather than discussing them in isolation, highlighting their differing views on human carrying capacity.