Support materials only that illustrate some possible contexts for exploring Science as a Human Endeavour concepts in relation to Science Understanding content.
Biological soil crusts are formed by living organisms such as cyanobacteria, lichen or algae and their byproducts, creating a crust of soil particles bound together by organic materials. Biological soil crusts are found globally in arid and semiarid environments, and are common in Australia. They play an important role in soil fertility and protect the soil surface from erosion and evaporation. The cyanobacteria in soil crusts are photosynthetic and research indicates that they are important for fixing and storing soil carbon; they also secrete compounds that increase the bio-availability of phosphorus and nitrogen (ACSES038). However crusts are easily disrupted by domestic livestock grazing, leading to nutrient leaching and a significant rundown in the productivity of the pasture, especially in Australian environments where hooved animals have been introduced relatively recently. Some ecologists believe that a switch to harvesting kangaroo rather than sheep or cattle would have a significant impact on rangeland productivity and ecosystem health, but kangaroo meat is not currently as highly valued by consumers (ACSES040).
Artificial ecosystems (closed to materials import and export) have been developed to aid research in ecosystem function and to assess their potential as life support systems in space stations or for space colonisation. One of the most significant experiments of this type was Biosphere 2, constructed in Arizona in the late 1980s. The Biosphere dome is a large terrarium in which water and nutrients are recycled, with solar radiation entering via the vast glass surfaces of the dome. The first ‘mission’ involved eight people being sealed inside the closed system for two years. The system was designed to enable biogeochemical cycling of matter and particularly provided insight into carbon and oxygen cycling in carbon dioxide rich environments (ACSES041). The $200 million experiment has been criticised for contamination of the system when an ill crew member was removed and reinstated, bringing in some new materials, but other members of the science community consider its contribution to closed system ecological studies to be invaluable (ACSES037).
The majority of primary production in marine environments occurs via phytoplankton floating near the surface of the ocean. The zone in which sufficient sunlight is available for photosynthesis to occur is called the photic zone and almost 90% of marine organisms live in this zone. Water turbidity has a significant effect on the depth of the photic zone; pollution of marine ecosystems via erosion from mining, forestry, farming or coastal dredging can cause high turbidity that impedes photosynthesis (ACSES043). However recent studies have shown that phytoplankton populations appear to be rising in a number of locations across the globe as they absorb more carbon dioxide from the atmosphere. Some scientists predict an increase in the primary productivity of the oceans of between 0.7% and 8.1% as atmospheric carbon dioxide increases, but this predicted increase is likely to vary significantly with location, and may be offset by large predicted losses in productivity around the polar regions due to ice cap contraction (ACSES042).