Distinguish between negative and positive feedback using examples from environmental systems.

The rate of world population growth is expected to slow so that by 2050 it will have stabilized at 10 billion. Explain three development policies that would enable the population to stabilize.

A vegetarian diet is often described as “better for the environment”. Discuss this statement using your knowledge of ecosystems and environmental value systems.

Award [1 max] for definition and [1 max] for example of each. NB: Credit may be given for definition where the key concept is explicitly identified within the example. Please add a comment on the work if you give credit in this manner.

Negative feedback:
Definition:
Feedback that tends to damp down/neutralize/counteract/self-regulate any deviation from an equilibrium/promote stability; [1 max]
examples:
eg increased global temperatures cause more evaporation/cloud cover that reduces input of solar radiation thus decreasing temperatures;
eg increase in predator population increases consumption of prey reducing food available for predators thus decreasing predator population; [1 max]

Positive feedback:
Definition:
Feedback that amplifies/increases change / leads to exponential deviation away from an equilibrium; [1 max]
examples:
eg increased global temperatures cause melting/shrinking of ice sheets reducing albedo/reflected energy thus further increasing global temperatures;
eg melting permafrost releases methane that increases global warming/temperatures thus further increasing the melting of permafrost; [1 max]

NB: Valid examples must link a change in a named factor to the subsequent reversal/acceleration of change in that same factor.
Do not accept non-environmental system examples such as blood temperature or thermostat regulation.

[4 max]

Award [1 max] for each of three valid policies; and [1 max] for a valid explanation of each policy named

development policy:
Increased education/empowerment for women; [1 max] 
explanation:
evidence shows that the longer females stay in school, the lower their fertility rate;
women have more choice and are able to make informed decisions about having children; [1 max] 

development policy:
Increased education about contraception/birth control/family planning; [1 max] 
explanation:
as people learn more about the ranges of contraception then more likely to choose to use them and reduce fertility rate;
as people learn about child spacing and the benefits to mother/child health of smaller families the fertility rate will reduce; [1 max] 

development policy:
Increased access to free/cheap contraception; [1 max] 
explanation:
greater availability/access to contraception (particularly in rural areas) gives greater choice to reduce fertility; [1 max] 

development policy:
Improved sanitation / access to clean water; [1 max] 
explanation:
improving sanitation / access to clean water decreases avoidable childhood deaths (due to gastrointestinal problems) from contaminated water, which then leads to decreased CBR; [1 max] 

development policy:
Increased healthcare; [1 max] 
explanation:
vaccination programmes reducing child deaths/more doctors/nurses/clinics so illness and disease can be treated early to reduce infant mortality leads to reducing CDR which then leads to decreased CBR;
eg Access to smoke-free cooking in homes so reducing deaths which then leads to decreased CBR;
eg Improved nutrition for children by educated mothers so reducing deaths which then leads to decreased CBR;
eg Mothers can read instructions on medication so reducing child deaths which then leads to decreased CBR; [1 max] 

development policy:
Government fertility/anti-natal policies eg one child policy in China / tax on more children; [1 max] 
explanation:
China has successfully reduced its CBR through implementation of a one child per family policy; [1 max] 

development policy:
Empowerment of landless and marginal people; [1 max] 
explanation:
evidence has shown that giving landless and marginal people more power and choice in their lives successfully reduces fertility in these populations; [1 max] 

development policy:
Improved cooperation / transfer of technology / transfer of funds, between MEDCs and LEDCs / Sustainable development; [1 max] 
explanation:
improved economy provides funds for education and workforce opportunities away from agriculture, moving away from agrarian society and less need for children to support family; [1 max] 

Accept other reasonable responses of equivalent validity, relevance and significance.

[6 max]

Arguments supporting claim:
Ecological/ecosystems: vegetarian means eating at the first trophic level/producers/plants;
second law of thermodynamics explains that energy is lost at each transfer as heat;
so reducing the length of food chains, reduces energy loss/maximizes efficiency (of energy transfer);
less land area/water is needed when only first trophic level is consumed / lower ecological footprint / when animals are consumed more land/water is needed (for same quantity of food) / higher ecological footprint;
less land being used for agriculture means less loss of biodiversity/environmental degradation;
meat production results in large amounts of greenhouse gases being released/global warming;
ecocentrics may support vegetarianism as it may reduce exploitation of resources/may attribute greater intrinsic value to animals;
ecocentrics support self-sufficiency which is more easily supported in an urbanized environment through growing vegetables rather than managing livestock;

Counterarguments:
Ecological/ecosystems: some livestock eat on pastures where human food crops cannot grow, so can be environmentally sound eg goats and sheep;
vegetarianism may be worse in some locations if supply requires long-distance transport/high food miles;
some animals eat the leftovers/peelings of human food production eg pigs and chickens reducing waste;
open water fish farming and wild fish harvesting can be practised sustainably providing better quality protein/without increasing land use;
technocentrics believe that humans are ingenious and could resolve impacts of meat production through technology;
eg genetically modified cattle/cattle feed to produce fewer greenhouse gases / laboratory-grown meat / harvesting of insect protein;
cornucopians would believe that whatever resources (meat or vegetable) are available are valid for human exploitation;

Award [1 max] for an explicit and valid conclusion.
Alternative points of equivalent validity, significance and relevance to those given, should be credited.
Award [5 max] for responses that do not address both ecological principles and value systems, or only address one side of the argument.
Otherwise, award [7 max] for marking points above, and [1 max] for a clear conclusion.

[8 max]

Generally the candidates showed that the concepts of positive and negative feedback have been understood. Most made a reasonable to very good attempt at using examples to illustrate the feedbacks. Only a few candidates gave non-ecological examples. Weak answers showed glimpses of understanding and too vague was the annotation often used. Some candidates did confuse the two types of feedback.

Naming three development policies was not a problem for the majority of candidates. The stronger candidates gave detailed explanations of how these policies lead to population stabilization over time. Weaker candidates sometimes gave explanations but without the link back to the population stabilization.

The candidates struggled with the discussion aspect of the question. Most candidates took a stand for or against being vegetarian. However keeping to the question asked proved more difficult to do. Many candidates diverted to farming practices and how those impact the environment. Most of these environmental issues apply whether crops or livestock are being raised, so not addressing the question. Only the strongest candidates managed to balance the answer to mention the positives/negative of being a vegetarian and being a meat-eater. Simplistic conclusions about vegetarians or meat-eating being healthier for a person were common.