Outline how feedback loops are involved in alternate stable states and the tipping points between them.

In 2016, the Earth’s atmospheric levels of carbon dioxide reached 400 ppm. Suggest the potential impacts of high levels of greenhouse gases on human societies in different locations.

Discuss the consequences of changing global per capita meat consumption on the conservation of ecosystems and biodiversity.

negative feedback loops occur when the output of a process inhibits or reverses the same process;
…thus inhibiting change/deviation / maintaining a system in equilibrium/one stable state;
positive feedback loops occur when the output of a process accelerates that same process;
…thus amplifying changes/deviations / driving system away from its equilibrium/stable state;
excessive change/deviation may drive system beyond its tipping point;
…when it will adopt a new equilibrium/alternate stable state.

Credit any of the above MPs if they are clearly shown by means of an annotated diagram or named example.

Impacts may include:
increased mean global temperature causing increased use of A/Cs (especially in developed countries);
greater frequency/intensity of extreme weather events causing damage to infrastructure (especially in cities);
long-term changes in climate/weather patterns requiring cultural changes/adaptation in societies;
ocean acidification killing plankton/reducing fisheries (especially significant for coastal populations);
melting permafrost increasing productivity/arable land/water availability (for tundra populations);
decreased water availability/desertification leading to migration/relocation (especially for tropical populations);
biome shifts reducing/enhancing crop productivity (especially significant in crop-growing areas);
biodiversity loss reducing aesthetic value of ecosystems (significant for tourism-dependent societies);
disruption of ecosystem services causing increased flooding (particularly in high rainfall locations);
rise in sea level causing coastal erosion (especially significant to areas dependent on coastal tourism);
coastal inundation causing salinization of underground aquifers/soils (especially for coastal populations);
wider spread of tropical diseases (especially significant for previously sub-tropical areas).

Award [4 max] if there is no reference to different locations (as in brackets above).
Do not credit effects of high levels of greenhouse gases that are not linked to some impact on human societies, at least implicitly as in examples above.

Answers may demonstrate:

• understanding concepts & terminology of terrestrial and aquatic food production systems; diet and food choices; ecological efficiency; food chains/pyramids; habitat destruction; pollution; hunting; greenhouse gases; climate change; community based conservation; commercial farming; livestock waste; eutrophication; buffer zones; sustainability; human population growth and carrying capacity; ecological footprints; EVSs;
• breadth in addressing and linking changes in meat consumption with cultural values, EVSs, food choices, climate change, ecological footprint, habitat degradation/loss, pollution, threats to biodiversity, conservation
  efforts;
• examples of impacts of different food production systems on range of ecosystems and biodiversity;
• balanced analysis of the extent to which increase and decrease in meat consumption (in different societies) impacts ecosystems and biodiversity and the extent to which these consequences can be limited/mitigated/justified;
• a conclusion that is consistent with, and supported by analysis and examples given eg Increased meat consumption clearly has many negative impacts on the conservation of ecosystems and biodiversity because of the associated habitat loss and degradation through pollution and climate change, although these impacts can be significantly mitigated, particularly for populations where food choices are limited, through more sustainable farming practices.

Refer to paper 2 markbands, available under the "your tests" tab > supplemental materials.

The general grasp of feedback mechanisms and tipping points was strong. This was the highest scoring part (a) question in Section B.

There were a few common faults in addressing this question – firstly, just giving too few examples of impacts of greenhouse gases. Secondly, candidates often failed to link these impacts to human societies as required. And, thirdly, the confusion of ozone depletion and global warming was once more manifest.

Disadvantages of meat consumption were often identified at some length but their specific impact on ecosystems & biodiversity were not always made clear. Furthermore, responses often lacked the necessary element of counterargument to achieve any balanced analysis or evaluation.