Unit 4 - Water, aquatic food production systems, and societies

Water pollution

The contamination of streams, rivers, lakes, oceans, or groundwater with substances produced through human activities.

Water quality

The degree of purity of water, determined by measuring substances in the water, such as phosphate and nitrate.

Direct measures of water pollution

Measuring the levels of:

- Phosphate

- Nitrate

- Salt

- Ammonia

Biochemical oxygen demand (BOD)

Amount of oxygen required by aerobic organisms to decompose a given load of organic waste; a measure of water pollution.

Indirect measures of water pollution

- Species present/absent

- PH

- DO

Indicator species

Their presence can be indicative of the level of pollusion. E.g. if salmo and mayfly are present the water quality is good and can be used for domestic supply.

Trent Biotic Index

A measurement of levels of pollution in aquatic ecosystems, based on indicator species which tend to disappear from a river as the level of pollution increases.

Eutrophication

Excessive richness of nutrients in a water body which causes a dense growth of plant life and death of animal life from lack of oxygen. Can be both anthropogenic from fertilizers and natural from decaying matter.

Negative effects of eutrophication

- Other species than algae in the eutrophic water body may die out due to lack of sunlight.

- The water becomes undrinkable and species dependent on the water might get sick or even die. There are studies done that show a correlation between drinking eutrophic water and getting stomach cancer for humans.

- Farmers can get economic losses due to being forced to stop using the fertilizers that created the eutrophication.

Management strategies for eutrophication

- Reducing the human activities that produce pollutants, e.g. using alternative fertilizers.

- Reducing release of pollution into the environment. E.g. treatment of waste water to remove the nitrates and phosphates.

- Removing the pollutant from the environment and restoring ecosystems. E.g. removing mud and reintroducing plant and fish species.

Dead zones

Areas in oceans and fresh water where there is an extremely low oxygen concentration and very little life.

Red tides

A discoloration of seawater caused by a bloom of the toxic red algae (dinoflagellates).

The impacts of waste on the marine environment

Over 80% of marine pollution is cause by land-based activities. This includes dumping very concentrated waste directly into the water. E.g. industrial waste, sewage sludge, and radioactive waste.

60+ L of oil end up in the oceans each year in the US.

Oil pollution

Oil spills happen from time to time. Those are disasters, but it is possible to clean up most of the damage. However, certain species might digest the oil or they might be too far gone already.

Radioactive waste pollution

Radioactive waste is another pollutant that is dumped into the ocean. Between 1958-1992 the USSR and Russia dumped 18 unwanted nuclear reactions containing nuclear fuel into the Arctic Ocean.

Plastic pollution

This is a huge type of water pollution. There are even trash islands floating around in the ocean. 100 million tonnes of plastic waste was found in the central Pacific in 2006.

The hydrological cycle

- The cycle of water, the movement of water and its transformation between the gaseous, liquid, and solid forms.

- Solar radiation drives the cycle.

- Important terms here: evaporation, transpiration, evapotranspiration, precipitation, sublimation, groundwater, run-off, melting.

Sublimation

A change directly from solid to gaseous state without becoming liquid, from ice to vapour.

Evapotranspiration

The evaporation of water from soil plus the transpiration of water from plants.

Advection

The horizontal transfer of energy or matter, usually by the wind.

Percolation

The downward movement of water through soil and rock due to gravity.

Evaporation

The change of water from liquid to gas.

Transpiration

Evaporation of water from the leaves of a plant.

Infiltration

The process by which water on the ground surface enters the soil.

Condensation

The change of water from gas to liquid.

Freezing

The change of water from liquid to solid.

Stream-flow/currents

The movement of water in channels, like streams and rivers.

Flooding

The covering of normally dry land by water. It occurs because the water body is unable to contain the amount of water added to it, e.g. due to heavy rainfalls.

Global water stores

- Only about 2.5% of Earth's water storages are fresh water.

- 97.4% is oceans.

- Storages include: various water bodies (oceans, lakes, rivers, groundwater, glaciers), organisms, soil water, and the atmosphere.

Flows in the hydrological cycle

- Evapotranspiration.

- Sublimation.

- Evaporation.

- Condensation.

- Advection.

- Precipitation.

- Melting.

- Freezing.

- Flooding.

- Surface run-off.

- Infiltration.

- Percolation.

- Stream flow/currents.

Turnover time

The time taken for water to completely replace itself in a part of the system. Polar ice caps take 10 000 years, while biological water only needs a few hours. Large lakes require 17 years.

The impact of agriculture on water systems

- Freshwater is extracted from various water bodies in order to be used for irrigation in farming.

- In Texas, irrigation has lowered water levels by 50 m.

- Certain crops require more water than others, e.g. rice paddies.

- Irrigation can reduce the Earth's irrigation by as much as 10%.

- Hail storms and tornadoes are more common on irrigated areas than non-irrigated ones.

The impact of deforestation on water systems

- After deforestation, flood levels in rivers increase because there aren't as many trees left to absorb the water and keep the levels under control.

- Removing trees also leads to more light, higher temperatures, increased wind speed, and more moisture at ground level. This means that organic matter is decomposed faster, that raindrop impact decreases, and that overland run-off increases.

- Water recycling slows down due to the decrease in evapotranspiration.

- Grazers can favour the deforested areas because there are more buds for them to eat. Their trampling compact the soil and increase its density. This leads to decreasing infiltration of water, and so increased overland flow, which in turn increases soil erosion.

Ocean circulation systems

- Oceans cover about 70% of the Earth's surface.

- They are very important to humans, especially as they regulate climatic conditions.

- They are driven by differences in temperature and salinity that affect water density. The resulting difference in water density drives the ocean conveyer belt which distributes heat around the world and affects climate.

- Warm ocean currents move water away from the equater to the poles, and cold ocean currents move water away from the cold regions towards the equator.

Oceanic salinity

- Oceanic water varies in salinity, the average being about 35 ppt.

- Concentrations of salt are higher in warm seas because of the increased evaporation rates of the water.

- In tropical seas, salinity decreases rapidly with depth.

- Run-off from rivers has little effect on reducing salinity. However, very large rivers like the Amazon in South America can result in less or no salt in over a kilometer out to sea.

- The freezing and thawing of ice affects salinity. Thawing decreases it, while freezing increases it temporarily.

- The mineral ions in seawater, chloride and sodium, combine and form salt.

Ocean temperature

- Temperatures vary a lot on the surface of the ocean, but barely at all at depth.

- In tropical and subtropical areas, sea surface temperatures exceding 25C are caused by insolation. From about 300-1000m, temps decline steeply to about 8-10C. Below 1000m, the temps are about 2C.

Water density

- Density in the ocean varies due to water temperature and salinity levels.

- As temperature increases, water becomes less dense.

- As salinity increases, water becomes more dense.

- As pressure increases, water becomes more dense.

- Cold, salty water is more dense than warm, less salty water.

- When large water masses with different desnities meet, the denser water slips under the less dense one. This is one reason for deep ocean circulation patterns.

The Great Ocean Conveyer Belt

- A global thermohaline circulation, driven by the formation and sinking of deep water.

- It's responsible for the large flow of upper ocean water, as well as the transfer of energy by wind, ocean currents, and deep-sea currents.

- The amount of heat given up is about 33% of the energy we receive from the sun.

Specific heat capacity

- The amount of energy required to raise the temperature of a body.

- Water needs more energy than land, which is why the sea is cooler than land during the day, but warmer than land at night.

- Places close to the sea are cool by day, but mild by day. This effect is reduced with increased distance from the sea.

Access to fresh water

- Humans use fresh water for all kinds of things, but the supply is scarce and the demand is high.

- There are over a billion people who don't have access to clean drinking water.

- The availability of fresh water is likely to become more stressed in the future. E.g. due to climate change and rising temps.

- The scarcity of water resources can lead to conflict between human populations, especially on places where the water sources are shared.

Unsustainable demands of water resources

- As population, irrigation, and industralization increase, the demand for fresh water increases.

- In LEDCs, the expanding populations require more water.

- In MEDCs, people require more water for FWPs (washing cars, gardening, etc).

- In LEDCs, 82% of fresh water is used for farming, while in MEDCs it's only 30%.

- There is a risk that fresh water supplies may become limited through contamination and unsustainable extraction.

- Water supplies can be enchanced through reservoirs, redistribution, desalination, artificial recharge of aquifers, and rainwater harvesting-schemes.

- Water conservation, e.g. grey-water recycling, can help to reduce demand, but often requires a change in attitude by the water users.

Sustainably managing water resources

- Individuals and local communities, as well as national governments need to make efforts to make this happen.

- E.g. individuals can take shorter showers and turn off the tap when washing dishes.

- Education campaigns can increase local awareness of issues and encourage water conservation.

- Retain water in reservoirs for use in dry seasons.

- Redistribute water from wetter areas to drier areas.

- Desalinate sea water (expensive).

- Water conservation, e.g. recycle grey-water.

- Making new buildings more water-efficient (e.g. recycling rainwater).

- In agriculture, one could focus on drought-resistant crops and use organic fertilizers and pesticides as they don't contaminate the water as much. One can also invest in efficient sprinklers and irrigation.

Water harvesting

- Making use of available water before it drains away or is evaporated. One can do this by:

- Extraction from rivers and lakes.

- Trapping behind dams and banks.

- Pumping from aquifers.

- Desalinating saltwater to produce fresh water.

- These can be achieved with either high tech or low tech.

Case study: Water and conflict in the Nile Basin

- The River Nile runs through 11 countries in Africa with a total population of 450 million, which all depend on the river for their food and water security.

- The population is expected to double in 25 years, which will put immense pressure on the river for water for agriculture, industry, and domestic uses.

- Egypt and Sudan have built mega-dams to exploit the water for irrigation.

- There have been decade long negotions between the 11 countries regarding each country's water use. In 2010, 6 countries signed some kind of agreement but it was rejected by both Egypt and Sudan.

- However, the use of the Nile is more balanced today because they managed to figure something out.

- The Nile is threatened by various environmental problems, like climate change, salinization, pollution, land degradation, reduced river flow, and increased chances of drought and flooding.

World fisheries

- World fisheries and aquaculture produced almost 150 million tonnes of fish in 2010 valued at over $215 billion.

- Over 125 million tonnes were for food. 2/3 of the consumption was in Asia.

- China is the most responsible for the increase in aquaculture.

Fish stocks

- Production of the world's marine fisheries increased from 16.8 million tonnes in 1950 to a peak of 86.4 million tonnes in 1996, and then stabilized at about 80 million tonnes.

- In 2010 it was 77.4 million tonnes.

Global overfishing

- Modern fishing ships can sail further out on the seas and remain there for days and weeks. They can therefore fish less touched areas, which is not good.

- In LEDCs dynamite and cyanide fishing is still common, which isn't great because those methods kill reefs.

- In 2010 a peak in overfishing was reached, namely 32%.

- A solution to this is to improve the technology. E.g. to hinder huge nets from catching all kinds of stuff, one can have sensors that will only target a specific type of fish.

- More than 50% of the fish consumed in Europe is imported because Europe itself is so extremely overfished.

Case study: The closure of Grand Banks off Newfoundland

- Once a fish stack is overfished to the point of collapse, it's very hard for it to fully recover.

- The Grand Banks off Newfoundland were once the world's richest fishery.

- In 1992, the area had to be closed to allow the stocks to recover.

- It was expected that it would only be closed for three years, but it remains closed today as well because fish species haven't recovered, especially cod.

- Cod has a hard time to regain its numbers because langoustine, something that had previously been its prey, has now increased in numbers due to the cod's absence and then the grown up langoustines eat the baby cods - reversing the pattern.

Managing fisheries

- The number of fishermen and boats have to be reduced.

- Technology has to be improved.

- A 2008 report showed that $50 billion dollars per year is lost in poor management, inefficiency, and overfishing in world fisheries.

- Increased awareness in certain parts of the world regarding the problems of the fish industries has led to consumers demanding sustainable fish. This led to the creation of the MSC label which is put on all packages of fish that come from sustainable fisheries.

Strategies for the European fishing industry

- Use small meshed nets.

- Protect young fishes and encourage breeding.

- Discourage the black fish market.

- Have restrictions on the total allowed catches.

- Match supply to demand.

- Protect sensitive stocks.

- Have tradable fishing permits (like the CO2 thing).

- Restrict number of fishing vessels allowed on the sea.

- Apply penalties to overfishing and other illegal actions.

History of and facts about fish farming (aquaculture)

- Fish farming was first introduced when over-fishing of wild Atlantic salmon in the north Atlantic and Baltic seas caused their populations to crash.

- Aquaculture involves raising fish commercially, usually for food.

- In contrast, a fish hatchery releases juvenile fish into the wild for recreational

fishing or to supplement a species' natural numbers.

- The most important fish species raised by fish farms are salmon, carp, tilapia, catfish, and cod.

- Salmon make up 85% of the total sale of Norwegian fish farming, but most global aquaculture production now uses non-carnivorous fish species, such as tilapia and catfish.

- Technological costs are high, and include using drugs, such as antibiotics, to keep fish healthy, and steroids to improve growth. Breeding programmes are also expensive.

- An issue is the loss of natural habitats. In some cases, aquaculture may occur in sea lochs. In other cases, it occurs in fish pens off the coastline. In both cases, natural ecosystems are transformed into commercial operations, in which human activities interfere with natural processes, such as migration, predator-prey relationships, removal of competing species and vegetation, and so on.

- Environmental effects can be damaging, especially with salmon farming.

- Other environmental costs include the sea lice and disease that spread from farmed fish into wild stocks, and pollution (created by uneaten food, faeces, and chemicals) contaminating surrounding waters.

- Accidental escape of genetically modified fish can affect local wild fish gene pools when the escaped fish interbreed with wild populations. This reduces the wild fish genetic diversity, and potentially introduces non-natural genetic variation. In some parts of the world, escapes from farmed salmon threaten native wild fish, as it may be an alien species.

- Despite the disadvantages, the positive environmental benefits of not removing fish from wild stocks, but growing them in farms, are great. Wild populations are allowed to breed and maintain stocks, while the farmed variety provides food.

Global aquaculture facts

- Between 1980 and 2010, world food fish production by aquaculture grew by 8.8% per year.

- World aquaculture production in 2010 was about 60 million tonnes and worth US$125 billion.

- Aquaculture production is vulnerable to adverse impacts of disease and environmental conditions.

- Disease outbreaks in recent years have affected farmed Atlantic salmon in Chile, oysters in Europe, and marine shrimp farming in several countries in Asia, South America, and Africa.

- The global distribution of aquaculture remains imbalanced. In 2010, the top 10 producing countries accounted for 87.6% by quantity and 81.9% by value of the world's farmed food fish.

- LEDCs, mostly in sub-Saharan Africa and in Asia, remain minor in terms of their share of world aquaculture production.

Case study: Rice-fish farming in Thailand

- Cultivating rice and fish together has been a tradition for over 2000 years in South East Asia.

- This polyculture system (paddy rice field stocked with fish) was gradually abandoned due to population pressure and decreasing stocks of wild fish.

- The fall in fish stocks was due to the toxic effects of the pesticides and herbicides used in high-yield rice monoculture.

- However, this farming method experienced a revival in the early 1990s, as concerns over the widespread use of pesticides emerged.

- Implementation is relatively inexpensive and low risk. The system requires farmers to dig small ponds or trenches in low-lying areas of rice, which become refuges for fish during rice planting and harvesting, or when water is scarce. The excavated soil is used to raise banks around the field to grow other crops on (e.g. vegetables and fruit trees). Once the paddy fields are flooded, young fish (fingerlings) are introduced to the trenches: carp, tilapia, catfish, or other species. After 3 weeks, when the rice is well established, the fish are let into the rice fields. They obtain their food from the fields, but carnivorous species can be fed if necessary.

- The fish contribute to a decrease of disease and pest incidence in the rice, and rice yields are higher. Because rice productivity increases, farmers do not need to use fertilizers (the fish produce faeces and excreta which naturally fertilize the soil).

- Rice-fish culture may increase rice yields by up to 10%, and increase income by 50-100% over rice alone, while providing farmers with an important source of protein.

- The process counters the decrease in available wild fish in many countries. The most common and widespread fish species used in rice-fish farming are the common carp (Cyprinus carpio) and the Nile tilapia (Oreochromis niloticus). Both feed on the vegetation and plankton available and do not attack.

- Once the newly planted rice is established, fish are released into the flooded fields from holding pens.

- This food production system is an example of intensive subsistence farming. The cost of feeding the fish is low but demands on labour are high. Technology is low.

- Other inputs include water for irrigation, and the cost of the breeding stock. The outputs are high per hectare but low per farmer, but overall efficiency is high, and yields of rice improve significantly with this system compared to monoculture rice agriculture.

- Environmental impacts are low, but include change in the nutrient balance, and the introduction of alien species, which may have impacts for local biodiversity - both plant and animal.

- There are several cultural issues regarding the system: other sources of animal protein may be preferred (e.g. poultry, beef, and pork), and the commonly cultured fish species (e.g. tilapia and carp) are not highly valued by people who have access to marine species and wild species.

- Fish predators such as snakes can lower the fish yield. The system may only be appropriate if there is a reliable water supply, a source of young fish, and fields located close to the family house so they can be monitored.

Whaling - contrasting views

- Harvesting some species (such as seals, sharks, and whales) is controversial.

- There are ethical issues regarding biorights - the rights of an endangered species, a unique species, or landscape to remain unmolested.

- The rights of indigenous culture and international conservation legislation also should be considered.

- In the late 1930s, more than 50 000 whales were killed annually.

- The International Whaling Commission (IWC) was set up to decide on hunting quotas based on the findings of its Scientific Committee. In 1982, the IWC voted to establish a ban on commercial whaling, which took effect in 1986.

- Japan now wants to lift the ban on stocks that have recovered. However, anti-whaling countries and environmental groups believe that whale species remain vulnerable and that whaling is both immoral and unsustainable.

- According to the IWC, indigenous subsistence whaling occurs in Greenland (fin,

bowhead, humpback, and minke whales), in Siberia, (gray and bowhead whales),

St Vincent and The Grenadines (Bequia, humpback whales) and North America (bowhead whales; Washington State, gray whales).

- There are other threats to whales apart from whaling. These include collision with ships, chemical pollution, habitat degradation, noise pollution, and by-catch (the unintentional capture of whales in fish nets).

- To protect whales, the Southern Ocean around Antarctica was declared a whale sanctuary in 1994.

Inuit and whaling

- North American whaling is carried out by small numbers of the Inuit population. The only species hunted is the bowhead whale. Whaling is a central part of Inuit culture and provides a vital source of protein in their diet.

- The 10 000 Inuit in Alaska were allowed to kill a total of up to 336 bowhead whales between 2013 and 2018, with no more than 67 whales in any one year. This represents about half of the meat in the Inuit diet.

- Scientific research suggests that the bowhead whales are not an endangered species, and their hunt is sustainable. But conservationists take a very different view and state that whales have biorights and should not be killed, especially in a way that causes them great pain and suffering.

- In Greenland, Inuit whalers catch around 175 whales per year, making them the third largest hunt in the world after Japan and Norway, which annually averaged around 730 and 590 whales, respectively from 1998 to 2007.

Case study: Japan and whaling

- Japan was, for many years, the greater hunter of whales. It reluctantly stopped commercial hunting in 1986. However, it continued to hunt whales for 'scientific research' to establish the size and dynamics of whale populations.

- Japan clashed repeatedly with Australia and other western countries, which strongly oppose whaling on conservation grounds.

- Australia took a case to the UN's International Court of Justice (ICJ) and argued that Japan's scientific research whaling programme was simply commercial whaling in disguise. Japan argued that the suit brought by Australia was an attempt to impose its cultural norms, and furthermore, that minke whales and a number of other species are plentiful and that its whaling activities are sustainable.

- In 2014 the ICJ ruled that the Japanese government must halt its whaling programme in the Antarctic. The ICJ believed that the programme was not for scientific research as claimed by Tokyo. It claimed Japan had caught some 3600 minke whales since its current programme began in 2005, but the scientific output was limited.

- Japan agreed to abide by the ruling but added it 'regrets and is deeply disappointed by the decision'.