Outline the role of the atmospheric system in the distribution of biomes.

Explain how human impacts on the atmosphere may influence the productivity of terrestrial biomes.

To what extent is the need for conservation more significant in tropical biomes?

atmospheric/tri-cellular circulation (including Hadley, Ferrel & polar cells) creates patterns of climate that determine dominant vegetation types;
low pressure due to intense heating/high insolation at the equator causes / rising moist air in the tropics creates high precipitation giving rise to rainforests;
moving polewards (at high altitude), air cools, becomes denser and sinks forming a high-pressure zone / descending/dry air (20–30° latitude/tropics) creates water-limiting/arid conditions giving rise to deserts;
some of the air continues towards the poles to equalize temperature difference / atmosphere transfers heat from (sub-)tropics to mid-latitudes giving rise to temperate biomes;
descending/dry air (high latitude/polar regions) creates water-limiting conditions in tundra;
water vapour (from mid-latitudes/temperate regions) is transferred to high latitudes giving rise to heavy precipitation/snow in boreal forest;
water vapour is transferred from ocean surfaces overland generating freshwater aquatic systems;
prevailing winds/jet streams (blowing from high to low pressure) bring precipitation to a region, e.g. temperate rainforest in mountainous region/riverine/water-margin systems;
rain shadow effect of high mountains causes dry winds in the leeward side, resulting in arid or semi-arid biomes (e.g. Tibetan Plateau, Mongolian Gobi desert and steppes);
atmosphere may be responsible for shifting biomes due to global warming/climate change;

release of ozone-depleting substances reduces stratospheric ozone increasing UV on Earth...;
UV can damage plants/photosynthesis reducing primary productivity;
release of NO_x/SO_x from fossil fuels can generate acid precipitation...;
acid rain can damage plants/leaves reducing primary productivity;
acid rain can cause leaching of nutrients from soils reducing plant growth/productivity;
acid rain can release toxic cations/minerals in soil that reduce plant growth/productivity; emission of greenhouse gases can lead to an increase in global temperatures/global warming...;
increased temperatures may lead to higher rates of photosynthesis/increased productivity;
higher temperatures may damage certain plant species reducing productivity;
higher temperatures may cause greater evaporation/water scarcity that reduces plant growth/productivity;
higher temperatures may melt permafrost increasing primary productivity in tundra / ice retreat, e.g. in Greenland, can lead to expansion of tundra ecosystem;
emissions from fossil fuel combustion causing photochemical smog which reduces photosynthesis;
any reduction in primary productivity will lead to reduction in secondary productivity/productivity of consumers;

Note: Credit may be given for any further potential impacts of atmospheric pollution on productivity of terrestrial biomes.

Refer to paper 2 markbands, available under “your tests”  tab > supplemental materials.

The following guide for using the markbands suggests certain features that may be offered in responses. The five headings coincide with the criteria given in each of the markbands (although “ESS terminology” has been conflated with “Understanding concepts”). This guide simply provides some possible inclusions and should not be seen as requisite or comprehensive. It outlines the kind of elements to look for when deciding on the appropriate markband and the specific mark within that band.

Answers may include:

• understanding concepts and terminology of biodiversity; conservation strategies; tropical biomes; rainforests; swamps; coral reefs; hotspots; LEDCs & MEDCs; international v national conservation bodies; environmental value systems; productivity; carbon sinks; global warming; unsustainable exploitation; resources of tropical ecosystems; medicines; indigenous cultures; endangered species; Red List, etc.;
• breadth in addressing and linking threats to biodiversity with different societies, ecosystems, conservation strategies; the global dependence upon and significance of tropical biomes compared with others; implications of economic development in tropical regions with challenges of conservation; different EVS perspectives on reasons for conservation, etc.;
• examples of tropical biomes/ecosystems; their local societies; conservation efforts; reasons/needs for conservation, etc.;
• balanced analysis evaluating the extent to which conservation efforts are of particular importance for tropical biomes along with relevant limitations and counterarguments, etc.;
• a conclusion that is consistent with, and supported by, analysis and examples given e.g. “although the loss of any species may be considered of equal significance from an ecocentric point of view, the high productivity and biodiversity that characterize tropical biomes, along with the limited facility of local societies, which are often less developed, make tropical biomes a priority for international conservation efforts”;

While many had some idea of the tri-cellular model of atmospheric circulation they were often unable to link this closely with the distribution of biomes.

It was this question that revealed the perennial confusion over climatic pollution issues with many candidates identifying UV radiation as the cause of global warming and greenhouse gases as the cause of ozone depletion and many similar mistaken associations.

This question generated many very good responses identifying the many values of tropical biomes and the associated issues of their conservation. Only the better responses, however, considered some counterarguments in favour of other biomes.