Topic 5 Land

At the end of this subtopic 5.1 you should understand:

• Soils provide the foundation of terrestrial ecosystems as a medium for plant growth (a seed bank, a store of water, and almost all essential plant nutrients). Carbon is an exception; it is obtained by plants from the atmosphere. (5.1.9)

• Soils contribute to biodiversity by providing a habitat and a niche for many species. (5.1.10)

• Soils have an important role in the recycling of elements as a part of biogeochemical cycles. (5.1.11)

• Soil is a dynamic system within the larger ecosystem that has its own inputs, outputs, storages, and flows. (5.1.1)

• Soil system inputs include those from dead organic matter and inorganic minerals. (5.1.4)

• Soil system outputs include losses of dead organic matter due to decomposition, losses of mineral components, and loss of energy due to heat loss. (5.1.5)

• Transfers occur across soil horizons, into and out of soils. (5.1.6)

• Transformations within soils can change the components or the whole soil system. (5.1.7)

• Systems flow diagrams show flows into, out of, and within the soil ecosystem. (5.1.8)

• Soils can act as carbon sinks, stores or sources, depending on the relative rates of input of dead organic matter and decomposition. (5.1.14)

• Soil is made up of inorganic and organic components, water, and air. (5.1.2)

• Soils develop a stable, layered structure known as a profile made up of several horizons, produced by interactions within the system over long periods of time. (5.1.3)

• Soil texture defines the physical make-up of the mineral soil. It depends on the relative proportions of sand, silt, clay, and humus. (5.1.12)

• Soil texture affects primary productivity through the differing influences of sand, silt, clay, and dead organic matter, including humus. (5.1.13)

At the end of this subtopic 5.2 you should understand:

• Land is a finite resource, and the human population continues to increase and require feeding. (5.2.1)

• World agriculture produces enough food to feed eight billion people, but the food is not equitably distributed and much is wasted or lost in distribution. (5.2.3) 

• Food security is the physical and economic availability of food, allowing all individuals to get the balanced diet they need for an active and healthy life. (5.2.12) 

• Marginalised groups are more vulnerable if their needs are not taken into account in land-use decisions. (5.2.2)

• Humans are omnivorous, and diets include fungi, plants, meat and fish. Diets lower in trophic levels are more sustainable. (5.2.10)

• The Green Revolution (also known as the Third Agricultural Revolution in the 1950s and 1960s) used breeding of high-yielding crop plants – combined with increased and improved irrigation systems, synthetic fertiliser and application of pesticides ––to increase food security. It has been criticised for its sociocultural, economic and environmental consequences. (5.2.7)

• Current global strategies to achieve sustainable food supply include reducing demand and food waste, reducing greenhouse gas emissions from food production and increasing productivity without increasing the area of land used for agriculture. (5.2.11) 

• Agricultural systems across the world vary considerably due to the different nature of the soils and climates. (5.2.4)

• Agricultural systems are varied, with different factors influencing the farmers’ choices. These differences and factors have implications for economic, social and environmental sustainability. (5.2.5)

• Nomadic pastoralism and slash-and-burn agriculture are traditional techniques that have sustained low-density populations in some regions of the world. (5.2.6)

• Synthetic fertilisers are needed in many intensive systems to maintain high commercial productivity at the expense of sustainability. In sustainable agriculture, there are other methods for improving soil fertility. (5.2.8) 

• A variety of techniques can be used to conserve soil, with widespread environmental, economic and sociocultural benefits. (5.2.9)