Outline four ways in which the differences between sand and clay soils may affect primary productivity.

A non-governmental organization has been contracted to investigate the impacts of a landfill site on the surrounding terrestrial ecosystem.

Suggest how the investigation should be designed to ensure reliability and validity.

The impacts of acid rain on terrestrial ecosystems may include acidified soils, leaching of nutrients, release of toxins and damage to vegetation. The impacts of global warming on these systems may include desertification, flooding, loss of species and shifting of biomes.

For terrestrial ecosystems, discuss the difficulty of managing the impacts of acid rain compared to that of managing the impacts of global warming.

[1 max] if the soils are compared but not linked to productivity.

Link to productivity is expected, but credit should be given if it is not mentioned against each point but is unambiguously evident from introduction/context. Also credit where the candidate mentions “sand is better because … “ but with no explicit mention of clay or vice versa.

[4 max]

there should be a large number of sampling locations;
to ensure consistency and comparability of results the same sampling techniques should be used in all sampling sites / sampling should be done by appropriate and scientifically rigorous methods appropriate for each parameter required to evaluate;
sampling could be based on a transect with sampling points at varying distances away from landfill site / or should include comparable sites not influenced by landfill;
sampling should be repeated in different seasons / over an extended time period;
direct methods should be employed to identify presence of toxins/pollutants;
e.g. chemical analysis for pollutants in soil, water and biotic components of system;
indirect methods should be employed analysing ecosystem/communities as a whole;
eg biotic indices evaluating species diversity/abundance / their tolerance/sensitivity /presence of indicator species;
The NGO could partner with a government organisation to use its resources and bolster validity / the NGO should show up unannounced to ensure the landfill does not hide evidence/practices;
Independent experts should be appointed to gather the data. 

Responses focusing on EIA may still be credited wherever they directly relate to question as asked.

[6 max]

Please note: although "quality of expression" marking is no longer used in exams, this question from a past syllabus may still be useful for student practice.

Managing impacts [3 max].
acid rain impacts can be managed through prevention ie alternative energy/scrubbers/catalytic converters;
…or through remedial action ie liming/fertilisers/replanting;
global warming impacts can be managed through prevention ie alternative energy/carbon taxing/energy efficient technology;
…or through mitigation ie flood defences/irrigation/afforestation/carbon storage;
both can be managed through education / changing lifestyles to reduce use of Fossil Fuels;

Relative difficulty [7 max].
impacts of acid rain are more regional/localised and so easier to address;
SOx and NOx (causing acid rain) can be removed from emissions but greenhouse gases/CO₂ (causing global warming) cannot;
…so prevention of acid rain impacts would not depend on the unpopular banning/reducing fossil fuel use, whereas prevention of global warming does;
global warming is subject to positive feedback cycles so once it kicks in there is no telling the tipping point;
anthropogenic acid rain impacts are caused only by the use of fossil fuels, whereas global warming has many other causes (eg deforestation/farming of cattle/rice);
Acid rain may cross some international boundaries but global warming crosses all boundaries making international agreements even more difficult to obtain;
...although sometimes global agreements are more easy to obtain than agreements between a limited number of conflicting nations;
there is greater contention over the causes of global warming making agreements more difficult;
it is generally easier to reverse the root problem of acid rain (acidity) than global warming (mean global temperature);
...however in some cases actual damage from acid rain (e.g. forest defoliation) already caused is nearly impossible to reverse;
...and much damage from global warming is as yet hypothetical/predicted;
it is often possible to trace regions responsible for impacts of acid rain, but more difficult to attach responsibility for global warming impacts. 

Award [7 max] for marking points above.
Award a further [1 max] for an explicit and valid conclusion that is justified by points raised.

Note to examiners: An isolated statement eg “Global warming is difficult to manage” or an unjustified opinion eg “I think acid rain is easiest to manage” should not be considered as a valid conclusion. The conclusion must be supported/ justified by points raised.

eg the overall scale and complexity of causes make global warming impacts more difficult to manage;
more people are aware of global warming / Kyoto protocol & UNFCCC exert more political pressure whereas acid rain may be overlooked. 

Alternative points of equivalent validity, significance and relevance to those given, should be credited.

[8 max]

Expression of ideas [2 max]

The candidates clearly understood the differences between clay and sand soils. Stronger candidates outlined four distinct ways the soils differed and linked these clearly to productivity. However, there were also good answers that only mentioned productivity at the start or the end of the answer. As long as the link to productivity unambiguously evident from the context then marks were awarded.

Many candidates answered this question using an EIA. So they described how an EIA is carried out. This was not appropriate for answering the question asked. The information given is asking for the impacts to be investigated so a method for collecting data about the environment around the landfill is required. This question looks at how biotic and abiotic data are collected. Credit was given for candidates who recognized having an EIA would provide data as a baseline for comparison. Some candidates gave very strong answers for this question, detailing how data can be collected reliably in the field.

Most candidates gained 2 or 3 marks for the management of the impacts of acid rain and/or global warming. The discussion on the comparison of the relative difficulty of management was not as strong. The conclusion mark was attained by many candidates as they recognized the complexity/inter-relationships of the impacts. Weaker candidates tended to write descriptive answers that seldom allowed a mark to be awarded.