Topic 4: Water and aquatic food production systems and societies

5.1: Introduction to water systems
Significant ideas: The hydrological cycle is a system of water flows and storages that may be disrupted by human activity. The ocean circulatory system (ocean conveyor belt) influences the climate and global distribution of water (matter and energy).
Knowledge and understanding: Solar radiation drives the hydrological cycle. Fresh water makes up only a small fraction (approximately 2.6% by volume) of the Earth’s water storages. Storages in the hydrological cycle include organisms, soil and various water bodies, including oceans, groundwater (aquifers), lakes, rivers, atmosphere, glaciers and ice caps. Flows in the hydrological cycle include evapotranspiration, sublimation, evaporation, condensation, advection (wind-blown movement), precipitation, melting, freezing, flooding, surface runoff, infiltration, percolation, and stream-flow or currents. Human activities such as agriculture, deforestation and urbanization have a significant impact on surface runoff and infiltration. Ocean circulation systems are driven by differences in temperature and salinity. The resulting difference in water density drives the ocean conveyor belt, which distributes heat around the world, and thus affects climate. Applications and skills: Discuss human impact on the hydrological cycle. Construct and analyse a hydrological cycle diagram.	Guidance: The effect of urbanization on water flows and potential of flash floods should be covered. International-mindedness: Many hydrological cycles are shared by various nations. This can lead to international disputes. Theory of knowledge: The hydrological cycle is represented as a systems model—to what extent can systems diagrams effectively model reality, given that they are only based on limited observable features? Connections: ESS: Climate change—causes and impacts (7.2); terrestrial food production systems and food choices (5.2); aquatic food production systems (4.3); resource use in society (8.2); sustainability (1.4) Diploma Programme: Social and cultural anthropology; geography (options A and D)

4.2: Access to fresh water
Significant ideas: The supplies of freshwater resources are inequitably available and unevenly distributed, which can lead to conflict and concerns over water security. Freshwater resources can be sustainably managed using a variety of different approaches.
Knowledge and understanding: Access to an adequate freshwater supply varies widely. Climate change may disrupt rainfall patterns and further affect this access. As populations, irrigation and industrialization increase, the demand for fresh water increases. Freshwater supplies may become limited through contamination and unsustainable abstraction. Water supplies can be enhanced through reservoirs, redistribution, desalination, artificial recharge of aquifers and rainwater harvesting schemes. Water conservation (including grey-water recycling) can help to reduce demand but often requires a change in attitude by the water consumers. The scarcity of water resources can lead to conflict between human populations, particularly where sources are shared. Applications and skills: Evaluate the strategies that can be used to meet an increasing demand for fresh water. Discuss, with reference to a case study, how shared freshwater resources have given rise to international conflict.	Guidance: Consider examples of unequal distribution and inequitable supply. International-mindedness: Unequal access to fresh water can cause conflict between countries that have an abundance of fresh water and those that do not. Theory of knowledge: Aid agencies often use emotive advertisements around the water security issue—to what extent can emotion be used to manipulate knowledge and actions? Connections: ESS: Climate change—causes and impacts (7.2); terrestrial food production systems and food choices (5.2) and aquatic food production systems (4.3); resource use in society (8.2) and sustainability (1.4) Diploma Programme: Social and cultural anthropology; geography (topic 3; options A, B and F); economics

4.3: Aquatic food production systems
Significant ideas: Aquatic systems provide a source of food production. Unsustainable use of aquatic ecosystems can lead to environmental degradation and collapse of wild fisheries. Aquaculture provides potential for increased food production.
Knowledge and understanding: Demand for aquatic food resources continues to increase as human population grows and diet changes. Photosynthesis by phytoplankton supports a highly diverse range of food webs. Aquatic (freshwater and marine) flora and fauna are harvested by humans. The highest rates of productivity are found near coastlines or in shallow seas, where upwellings and nutrient enrichment of surface waters occurs. Harvesting some species, such as seals and whales, can be controversial. Ethical issues arise over biorights, rights of indigenous cultures and international conservation legislation. Developments in fishing equipment and changes to fishing methods have led to dwindling fish stocks and damage to habitats. Unsustainable exploitation of aquatic systems can be mitigated at a variety of levels (international, national, local and individual) through policy, legislation and changes in consumer behaviour. Aquaculture has grown to provide additional food resources and support economic development and is expected to continue to rise. Issues around aquaculture include: loss of habitats, pollution (with feed, antifouling agents, antibiotics and other medicines added to fish pens), spread of diseases and escaped species (some involving genetically modified organisms). Applications and skills: Discuss, with reference to a case study, the controversial harvesting of a named species. Evaluate strategies that can be used to avoid Explain the potential value of aquaculture for providing food for future generations. Discuss a case study that demonstrates the impact of aquaculture.	Guidance: Wild fisheries are also known as “capture fisheries”. Aquaculture is the farming of aquatic organisms in both coastal and inland areas that involves intervention in the rearing process to enhance production. Examine different points of view regarding harvesting of a controversial species; for example, the historical Inuit tradition of whaling versus modern international conventions. When looking at the increase in demand for food resources, consideration should be given to changes in attitude towards “health foods” and food fashions. Consider how two contrasting fisheries have been managed and relate to the concept of sustainability; for example, cod fisheries in Newfoundland and Iceland. Issues that should be covered include: improvements to boats, fishing gear (trawler bags), and detection of fisheries and boats via satellites. Management aspects should include: use of quotas, designation of marine protected areas (exclusion zones), and restriction on types and size of fishing gear (including mesh size of nets). Students should understand maximum sustainable yield (MSY) as applied to fish stocks. International-mindedness: Successful management of marine and some freshwater fisheries requires partnership between different nations. Theory of knowledge: The Inuit people have an historical tradition of whaling—to what extent does our culture determine or shape our ethical judgments? Connections: ESS: Biodiversity and conservation (topic 3); terrestrial food production systems and food choices (5.2); human population carrying capacity (8.4); resource use in society (8.2); sustainability (1.4) Diploma Programme: Geography (option B); economics

4.4: Water pollution
Significant idea: Water pollution, both to groundwater and surface water, is a major global problem, the effects of which influence human and other biological systems.
Knowledge and understanding: There are a variety of freshwater and marine pollution sources. Types of aquatic pollutants include floating debris, organic material, inorganic plant nutrients (nitrates and phosphates), toxic metals, synthetic compounds, suspended solids, hot water, oil, radioactive pollution, pathogens, light, noise and biological pollutants (invasive species). A wide range of parameters can be used to directly test the quality of aquatic systems, including pH, temperature, suspended solids (turbidity), metals, nitrates and phosphates. Biodegradation of organic material utilizes oxygen, which can lead to anoxic conditions and subsequent anaerobic decomposition, which in turn leads to formation of methane, hydrogen sulfide and ammonia (toxic gases). Biochemical oxygen demand (BOD) is a measure of the amount of dissolved oxygen required to break down the organic material in a given volume of water through aerobic biological activity. BOD is used to indirectly measure the amount of organic matter within a sample. Some species can be indicative of polluted waters and can be used as indicator species. A biotic index indirectly measures pollution by assaying the impact on species within the community according to their tolerance, diversity and relative abundance. Eutrophication can occur when lakes, estuaries and coastal waters receive inputs of nutrients (nitrates and phosphates), which results in an excess growth of plants and phytoplankton. Dead zones in both oceans and fresh water can occur when there is not enough oxygen to support marine life. Application of figure 3 to water pollution management strategies includes: reducing human activities that produce pollutants (for example, alternatives to current fertilizers and detergents) reducing release of pollution into the environment (for example, treatment of waste water to remove nitrates and phosphates) removing pollutants from the environment and restoring ecosystems (for example, removal of mud from eutrophic lakes and reintroduction of plant and fish species). Applications and skills: Analyse water pollution data. Explain the process and impacts of eutrophication. Evaluate the uses of indicator species and biotic indices in measuring aquatic pollution. Evaluate pollution management strategies with respect to water pollution.	Guidance: Sources of freshwater pollution should include runoff, sewage, industrial discharge and solid domestic waste. Sources of marine pollution should include rivers, pipelines, atmosphere and activities at sea (operational and accidental discharges). The role of positive and negative feedback in the process of eutrophication should be covered. Coastal eutrophication can lead to red tide blooms. With respect to measuring aquatic pollution, a polluted and an unpolluted site (for example, upstream and downstream of a point source) should be compared. International-mindedness: Countries with limited access to clean water often have higher incidences of water-borne illnesses. Theory of knowledge: A wide range of parameters are used to test the quality of water and judgments are made about causes and effects of water quality—how can we effectively identify cause–effect relationships, given that we can only ever observe correlation? Connections: ESS: Terrestrial food production systems and food choices (5.2); climate change—causes and impacts (7.2); sustainability (1.4); resource use in society (8.2); biodiversity and conservation (topic 3); solid domestic waste (8.3) Diploma Programme: Social and cultural anthropology; chemistry (topic 9; options B and D)