School biology notes: Food security - needs, solutions, farming methods & issues

food security world population growth chart graph food security world energy use needs growth chart graph exa is 1018 !

Food security and agriculture

population growth, food production and farming sustainability issues, applications of biotechnology, pest control, hydroponics

 Doc Brown's school biology revision notes: GCSE biology, IGCSE  biology, O level biology,  ~US grades 8, 9 and 10 school science courses or equivalent for ~14-16 year old students of biology

 This page will help you answer questions such as ...  How is food security defined?   How can we increase food production?  How can be devise sustainable agriculture?   Can GM crops help? Why are GM crops controversial? Are there alternatives to GM crops? What are the problems in increasing food production?

Sub-index for this page

(1) Thoughts on the world's population, need for increased food production and security

(2) What threatens food security? What threatens increasing necessary food production?

(3) Ways of tackling food production to avoid food insecurity

See also Genetic engineering: uses - making insulin, medical applications, GM crops

(1) Thoughts on the world's population and the production of food

What is 'food security'?

Food and the world's population, which is now around 7 billion people (~7 x 109 individuals!).

Lets start with some statistics - two graphs of population and energy use - pretty similar, surprise!

exa is 1018

The graphs shows the acceleration of the world's population and their corresponding energy use.

Not surprisingly, I would imagine a graph of food demand would be similar to provide the whole population of the world, ideally, with food security.

This begs the question 'how do we maintain a constant food supply in a sustainable way and protect the environment in the process?'.

Although I have no data myself on the world's total food production, there are some graphs on ...

https://ourworldindata.org/yields-and-land-use-in-agriculture ...

which clearly show a similar pattern in rising agricultural production attempting to meet our needs.

BUT how long can this be sustained?, and there are millions (billions?) of undernourished people suffering from starvation and disease, primarily from lack of local food production for one reason or another e.g. climate conditions, war, overuse of soil using non-sustainable agricultural practice.

To minimise the effects of lack of food, everyone should have access to safe nutritious food - sufficient as well as providing a balanced diet - this concept is known as 'food security'.

Food security can be simply defined as ...

"The state of having reliable access to a sufficient quantity of safe, affordable and nutritious food".

The World Food Summit definitions for:

(i) Food security exists when all people, at all times, have physical, social and economic access to sufficient, safe and nutritious food which meets their dietary needs and food preferences for an active and healthy life. Household food security is the application of this concept to the family level, with individuals within households as the focus of concern.

(ii) Food insecurity exists when people do not have adequate physical, social or economic access to food as defined above.

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(2) What threatens food security?

What threatens increasing necessary food production?

The problems facing us in tackling food insecurity and increasing food production

The UN estimates from ~2020

 (i) there could be nearly 1 billion people suffering from food insecurity i.e. undernourished with their health at risk,

(ii) and food production needs to be increased by 60% by 2050 to meet the increase in population number estimated to be 10 billion by then.

In the sections below, in no particular order of priority, I've discussed various issues concerning the difficulties that will, and are, being encountered in trying to feed everyone on the planet adequately.

A lack of sustainability is a major factor for the world's food production

Can we increase food production rates without endangering the needs of future generations?


(a) The world's population keeps on increasing with high birth rates, particularly increasing in developing countries, which are also often the poorest and least able to provide food security for all of their populations.

It will not easy for the current agricultural systems to keep pace with the rate of increase in the world population.

As people get more affluent their diet changes to a wider variety of foods, usually involving more expensive items like meat and fish.

The production of meat is via a food chain that involves a lot of energy usage and loss of biomass.

Per unit area of land, you can produce more food from crops than grazing animals.

It should also be noted that animals and fish on farms are often fed supplementary food based on crops, adding to the inefficiency of animal food production.


(b) Farming is affected by insect pests, weeds, fungi and pathogens like bacteria and viruses, and growing monoculture crops on the same land is reducing biodiversity.

Any new infestation of pests (including locusts) and pathogens will reduce crop yields.

The plants gene pool may not cope with a new disease and the lack of 'genetic resistance' means many plants will become diseased and damaged sufficiently to reduce crop yields of saleable edible food.

This requires the application of expensive insecticides, herbicides and fungicides or using GM products to maintain high crop yields, but then its difficult to avoid environmental damage.

New pests and pathogens are always emerging to affect farming - reducing crop yields.

Many crops are 'monocultures', just one species of plant, this considerably reduces biodiversity and the use of pesticides (insecticides and herbicides) has considerably reduced the numbers of pollinating insect, either through poisoning or lack of food - nectar.


(c) Agriculture is greatly affected by environmental conditions e.g. the local weather, particularly drought conditions from lack of rain leading to reduced yields and total crop failure - global warming won't help!

This often happens in hot dry countries where the greatest state of food insecurity exists.

The food security targets may well become more difficult to achieve with climate change.

Any change in the climate can affect growth patterns of crops, with both positive (perhaps increased yields in a warmer/wetter climate) and negative consequences (famine as a result of drought and good soil blown away).

See Greenhouse effect, global warming, climate change from fossil fuel burning


(d) Poor quality soil lacking in nutrients or water means crops will fail, even if they are GM.

The quality of soil initially depends on the local geology, but the weather and climate change will have their effects e.g. heavy rain can wash fertile soil away.

Any form of soil pollution will affect the growth of crops reducing fertility of the soil and reducing yields.

Soil contamination is caused by the presence of various human-made chemicals. It is often caused by industrial activity e.g. factories or mining, agricultural chemicals or improper disposal of waste. The most common chemicals involved in pollution are hydrocarbons, solvents, pesticides, lead, and other heavy metals.


(e) The richer developed countries able to buy and import selected food products from poorer countries.

But the purchase of exports from poorer countries means there is less food available to feed the indigenous population - 'cash crops' for export brings in much needed revenue but leads to food scarcity for the poorest people - who are often the ones growing the crops!

At the same time, as people become wealthier in developing countries, demands for a wider variety of foods in their diet will increase e.g. more expensive fish and meat and this increases food production pressure and doesn't help food security for many other less wealthy people.

The people of poorer countries are not able to afford the cost of importing agricultural products.

See section (h) on biomass because cattle is an inefficient way of 'growing' food.


(f) The poorest countries with the greatest food needs are also the least able to afford the initially high costs of farming.

You need expensive fertilisers, machinery and fuel, livestock, seeds (GM and non-GM) plus pest control systems to sustain any significant agricultural production.

This makes it difficult for poorer less developed countries to produce enough food to feed their own populations.

It also means that if its costly to produce food, the price at the market place increases - the poorer you are less food you can buy and perhaps of less quality too.

Many richer countries give aid to poorer countries, and long may it be so, but politics and globalisation economics don't always help!


(g) Poorer underdeveloped countries, particularly in Africa, but not exclusively, suffer from the effects of political unrest including civil war and terrorist group activity.

Economic interests, including mining and water, are fought over.

Any lack of political stability in a country makes it difficult to retain the constant agricultural production of much needed food for the people.

In times of civil unrest, and even worse in a civil war, important infrastructures breakdown e.g. lack or organisation and transport for distributing food and medical supplies.


(h) Biomass and food chain considerations

As you move up a food chain you lose energy and biomass at every stage.

See Food chains, food webs, trophic levels and biomass   gcse biology revision notes.

Therefore, for a given area of land, you can produce more crops for food than rearing animals on the same land - which often need extra food from crops or other animals!

Crops, primary producers using photosynthesis, are more efficient producers of food than livestock.

Many farm animals and fish are partly reared on grain (e.g. corn, oats) that could have been used for food - and to make matters even less efficient, part of reared livestock and fish diets are supplemented with protein food derived from other animals.


(i) Crops are being grown to partly replace fossil by converting plant material into biofuels.

The idea is to replace non-renewable fossil fuels from oil and gas with renewable plant based fuels - like bioethanol, made by fermenting processed sugar cane and other carbohydrate rich crops.

Unfortunately this uses land that could be otherwise used for growing food crops for 'human consumption' - not for fuelling road vehicles!


(a) to (i) are very much about growing crops of edible grain or vegetables and raising cattle for milk or meat, but fish is a very important source of food (protein, essential oils and vitamins).


(j) Unfortunately in many parts of the world fish stocks are declining due to over fishing.

We can be talking about lakes, seas or oceans, and if you take out too many fish too quickly, there is not sufficient time for enough fish to reproduce and grow into adult fish.

Overfishing, especially of young fish prior to reproducing, means food chains are disrupted and we run the risk of species of fish disappearing from lakes, seas, and areas of the oceans.

There are plenty stretches of water on the planet were fish stocks have decreased to very low non-sustainable levels.


(k) Climate Change - causing significant environmental changes

  • Know and understand that levels of carbon dioxide and methane in the atmosphere are increasing and contribute to ‘global warming’. These two gases are known as 'greenhouse gases' because they reabsorb infrared radiation radiated from the Earth's surface, which of course is heated directly by solar radiation, so the atmosphere acts as an insulation layer like the glass panes of a greenhouse.

    • Know and understand that an increase in the Earth’s temperature of only a few degrees Celsius and is likely to cause 'climate change':

      • Climate change may cause big changes in the Earth’s climate, there is more thermal energy in the Earth's weather system, this may cause eg more violent hurricanes, areas of drought, in other words, quite significant climate changes with different effects in different parts of the world.

        • e.g. in Africa, the Sahara desert is increasing in area, reducing land for farming, reducing food production capacity in either growing crops or razing cattle.

        • There is some evidence that natural disasters like storms and flooding are increasing due to global warming.

      • Climate change may cause a rise in sea level from thermal expansion and melting land ice leading to flooding of low lying coastal areas - maybe areas of food production like rice.

      • Climate change may reduce biodiversity, e.g. temperature changes may affect a particular species which may lead to the drastic decline of a plant or animal species in a particular area.

      • Climate change may cause changes in migration patterns, eg in birds.

      • Climate change may result in changes in the distribution of species e.g. change in temperature or pH of the seas and oceans can have a profound effect on local populations of marine organisms (plants or animals which maybe sources of food).

        • If an area becomes warmer in the northern hemisphere, then particular animals may migrate north to find a cooler region to which they are accustomed.

        • If more carbon dioxide dissolves in the oceans, they become slightly more acidic and maybe too acidic (pH falls) for certain species to survive.

        • Similarly, a warmer ocean maybe to warm for species to survive eg coral and its complex colonies of plants and animals is very susceptible to pH and temperature changes in the ocean.

  • Know and understand that carbon dioxide can be sequestered in oceans, lakes and ponds and this is an important factor in removing carbon dioxide from the atmosphere.

    • Carbon dioxide is slightly soluble in water and so is readily absorbed by any water.


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(3) Ways of tackling food production to avoid food insecurity

I realise the preceding section sounded all very negative, but there are ways to help the situation with good practice in land and sea management and protect the environment for the future.

We must be POSITIVE in our outlook and we are an intelligent animal that can solve these problems!

Methods of how to appropriately increase efficiency in food production

BUT there are still issues to be addressed!

We need sustainable methods of food production to provide enough to feed the world's growing population.

Sustainable food production means producing enough food to give everyone food security without consumption outstripping supply AND without damaging the environment and its ecosystems.

This includes using, as far as possible, renewable resources of food, materials and energy.

We need a variety of methods to increase food production and avoid food insecurity because situations differ around the world.


Plants are the producers at the start of any food chain.

Producers (mainly plants) take in the elements they need from their environment.

Molecular compounds like water (roots), carbon dioxide (leaves) and mineral ions e.g. nitrate for nitrogen, phosphate for phosphorus and small quantities of metals like magnesium, iron, potassium and zinc (absorbed by roots).

If plants don't get enough of theses nutrients their growth is inhibited giving lower crop yields.

There can be lack of nutrients in soil due the previous uptake of them by the previous crop or the soil is poor in nutrients in the first place.

Farmers can replace the missing nutrients used by the previous crop or enrich poor soils by applying artificial fertilisers - but this can adversely affect the environment.

Overuse of fertilisers and pesticides can lead to pollution problems - see biodiversity notes.

By boosting soil nutrition, growth is increased and the subsequent yield increased.

Note: Yield can be defined as the quantity of food produced by a specified area of land (the growing time might be specified too).

Increased crop yields means increased food production, whether the yield is measured as a grain crop directly for food or the plant crop is fed to help raise herds of animals.


See also Photosynthesis, importance explained, limiting factors affecting rate, leaf adaptations


(a) GM crops can help, but it is only one approach to increasing food production:

I've describe some ideas in more detail on my GM crop developments page, applications so far include:

Genetically engineered crops designed to:

(i) be pest resistant - insects/fungi/pathogens,

(ii) survive in drought conditions,

(iii) unaffected by herbicides used to protect the crop from weeds.

These are all potentially beneficial applications of genetically engineered crops.

Crops can also be GM designed to combat certain nutrient deficiencies e.g. increasing the content of a chemical in 'Golden Rice' that helps make Vitamin A in the body.

Again this is good science, the concept of food security includes nutritional quality.

However, there are still issue of concern and situations where GM might not help e.g.

Poor quality soil lacking in nutrients or water means crops will fail, even if they are GM.

Hunger exists where people cannot afford to buy food, even if it is available, therefore you need political and economic strategies to tackle poverty and improve/make fairer the economy and maybe import food too.

There is a danger that the agricultural production of a country might be too dominated by multinational companies that manufacture the GM seeds and are only interested in maximising profits for the few (rich) at the expense of the many (poor).

GM crops are not the complete answer and neither should they always the 'first choice' in the future.

However, traditional methods of selective breeding for crops (and animals too!) can still produce varieties of crops and livestock which give improved yields.

Other genetic methods for increasing crop yields

Scientific research of plant genes gives us detailed genomes of different plant species.

From this genome knowledge you can selectively cross-breed plants which have advantageous genes

e.g. that give plants more resistant to weather conditions (dry, wet, hot, cold) and other abiotic factors - make crops more efficient in water use, cope with dry periods,

and make them more resistant to biotic factors such as pests e.g. insects and diseases which damage crops.


(b) Poor soil is improved by application of fertilisers - overuse causes environmental problems.

Fertilisers contain important nutrients for plants to grow e.g. nitrates for nitrogen, phosphates for phosphorus, ions of magnesium and sulfate (for sulfur) and compounds of trace elements like copper, zinc and boron.

The idea of using fertilisers is twofold:

(i) bring into use poor quality soil deficient n nutrients,

(ii) replace nutrients used up by the previous crops,

(iii) grow crops with increased yield,

(iv) although (i) to (iii) apply to any fertiliser, naturally produced organic fertilisers produce a much better quality of soil.

BUT overuse of synthetic inorganic fertilisers has created eutrophication problems in lakes and rivers and they are not cheap, particularly in the context of a poorer country.

Eutrophication is when an excess of nutrients like nitrates and phosphates causes algal blooms, so water is covered in a thick mass of green slimy algae that reduces oxygen levels in water and kills most aquatic life beneath it.

Organic fertilisers based on plant and animal waste are more beneficial for soil quality

See The manufacture & use of fertilisers and NPK fertilisers-environmental problems

Infertile soils too acidic for growing crops or raising cattle (pH <7), can be treated with alkaline lime to increase the pH of the soil to a more neutral value (~pH 7).


(c) An assortment of agrichemical and pharmaceutical products to increase yields

You can control disease and insect damage without using GM crops by the use of herbicides and pesticides.

Pesticides are chemical compounds designed to be toxic to any living thing that attacks crops and reducing damage to crops and increase yields by utilising pest control methods.

'Pests' include microorganisms-pathogens including bacteria and fungi, a variety of insects and mammals like rats.

The pest control is usually sprayed onto crops to kill the 'pest', but they are often toxic to humans and other animals that are not considered as pests e.g. bees, ladybirds and birds of prey are affected - anything higher in a food chain is affected if their food supply is damaged.

The minimum 'safe level' of pesticide is applied to minimise contamination of toxic chemicals accumulating in the local ecosystem food chains.

Insecticides kill insects, fungicides kill fungi, herbicides kill weeds.

All of these increase crop yields and are extensively used for intensive farming methods, but not without unwanted consequences.

Again, as with fertilisers, they are not to be overused and unfortunately organisms like insects and bacteria can undergo mutations and develop 'strains' resistant to e.g. a particular fungicide or insecticide product.

This is happening all the time, so new costly products have to be developed all the time.

As well as treating plant crops with anti-pest agents, you can vaccinate livestock against certain diseases.

Antibiotics can be given to animals to protect against bacterial pathogens - but this means antibiotics have entered the food chain, so we may consume them - not good for our immune system?

Plant growth hormones are applied to crops to encourage growth and increase crop yields.

You can also control when crops ripen and harvesting - as far as I know, these methods are not controversial.

See Hormone control of plant growth and uses of plant hormones  gcse biology notes

Growth hormones are also used in cattle rearing as well as feeding the animals supplementary high protein foods.

Animals may be deliberately confined in huge cattle sheds to minimise movement, so less energy is wasted and more used for growth - so hormones, protein food and confinement all increase the energy transfer to the cattle.

BUT, the ethics of these methods is being questioned and there are biological consequences too.

The spread of a disease is rapid because of the close confinement of the animals.

Cattle have been bread to produce greater yields of beef meat or greater volumes of milk, but such animals and not as genetically healthy as their predecessors e.g. lameness in milk cows.

Is it fair to not allow the animals to move naturally freely beyond their 'cages'?

The unethical nature of some animal transportation and slaughtering.

Cattle can also be given hormones to increase milk and meat yields - but this also means these hormones are entering the food chain to reach us and out into the environment via faeces!


(d) You can use biological methods to control pests.

You can deploy other organisms to reduce pest numbers which can act as predators or parasites.

e.g. cane toads were introduced into Australia to eat beetles causing crop damage.

These biological methods can be more sustainable than chemical pesticides, so less harmful to the environment.

They do not involve toxic chemicals that can poison harmless organisms and accumulate in food chains and passed on from one trophic level to the next.

This means less pollution, less risk to people and other wildlife!

BUT, there is often a 'but' e.g. the cane toads are now a 'pest' because they poison native animals that eat them.

Quote from Wikipedia: "The long-term effects of toads on the Australian environment are difficult to determine, however some effects include the depletion of native species that die eating cane toads; the poisoning of pets and humans; depletion of native fauna preyed on by cane toads; and reduced prey populations for native insectivores." - not good!!!

Introducing one organism to control another can lead to unintended consequences.

You can control aphids (greenfly and black fly) by employing a predatory insect - can be very effective in the confines of a large greenhouse.

e.g. ladybirds will eat greenfly,

Parasitic wasps can be introduced to control aphid populations that feed on fruit crops - the wasps lay their eggs inside the aphids, which die when the larval wasps hatch out.

The wasp parasites act as a vector' when introduced to control pests e.g. another example is flies laying their eggs on slugs to kill them.

Bacteria can be used to deliberately infect caterpillars with diseases.

BUT, there are always risks in adding another organism to an existing ecosystem, you can never be sure of 'unintended' long term effects!

Some of these biological methods of pest control are used in large scale greenhouses and hydroponics units - these are good methods of 'factory farming' plants - see sections (h) and (i).


(e) To avoid overfishing and keep fish stocks at sustainable levels

We must only take out numbers of fish that still allow breeding at a rate to keep a constant sustainable population.

A sort of 'rate of breeding = rate of fishing' = sustainability situation!

You can do this in several ways:

(i) Placing limits on the numbers of fish extracted from the lake or fishing ground.

(ii) Fishing nets can have various mesh sizes depending on the species being fished.

This controls the size of fish caught and helps reduce the number of accidently 'unwanted' and resulting 'discarded' fish.

A bigger mesh will allow smaller fish to 'escape' and grow into breeding adults, hence helping to maintain fish stocks.

(iii) Fish can be 'factory farmed' in cages where they cannot escape (aquafarms).

In fish farms, the cages are placed in more sheltered estuaries or bays to minimise the effect of rough water and their natural food is often supplemented with other fish-based protein products. There is a quite a lot of criticism of ALL factory farming methods (see section (f) below) and the following comments ....

Nearly half of all fish consumed worldwide each year are raised in aquafarms. Farmed fish spend their entire lives in cramped, sometimes dirty enclosures, and many suffer from parasitic infections, diseases, and debilitating injuries - which means chemicals and antibiotics are used to help the fish survive.

Food is added to the enclosed nets to feed the fish, who then produce large amounts of waste. The waste can leak out causing eutrophication and death of wild species - the waste contains pathogens. Fish farms are breeding grounds for parasites, again these can escape and threaten wild species.

Predators like seals and sea lions are attracted this food resource, but can get trapped in the nets and die.

The farmed fish can escape and compete with indigenous species of fish.

Fish tank farms only contain one species and are therefore low on biodiversity - they are kept free of any plants or predators, the parasites and microorganisms are usually killed.

For more see section on reduction of biodiversity

The Food and Agriculture Organization of the United Nations reports that the aquaculture industry is growing three times faster than land-based animal agriculture, and aquafarms will surely become even more prevalent as our natural fisheries become exhausted.


(f) Livestock management

(i) You can limit the of farm animals and keep them in a temperature controlled environment to reduce their movement and reducing the transfer of energy from livestock to the environment.

This increases efficiency because the animals use less energy moving around and controlling their body temperature and so more energy is released in growth for the same feed input.

This seems to me to be a form of factory farming.

(ii) Calves and chickens can be factory farmed by raising them in small confined indoor pens - but many people find this style of farming unacceptable.

The animals like 'battery hens or chickens' (for eggs or meat) are cramped allowing the rapid spread of any disease - requiring animals reared in this way to be treated with antibiotics - again these become part of our food chain.

The animals must be fed with protein based feed, reducing the efficiency of this form of protein production.

People have every right to question the ethics of factory farming and point out the cruel unnatural and uncomfortable conditions under which these animals are made to live.


(g) Mycoprotein - another application of biotechnology using fungi

Modern biotechnology techniques can be used to culture and make large quantities of useful microorganisms to produce food.

This done in huge vats (stainless steel tank fermenters) under very controlled conditions e.g pH, temperature, type of microorganism and nutrient substrates.

Mycoprotein is the ingredient common to all Quorn™ 'artificial meat-free' protein products.

It is a high protein meat substitute for meals acceptable in the diet of vegetarians.

It is high in protein, high in fibre, low in saturated fat and contains no cholesterol, and therefore quite a nutritious component of any diet.

mycoprotein fermenter design labelled explaining diagram biotechnology gcse biology igcse microorganism fungus Fusarium reaction conditionsMycoprotein is made in fermenters (large vats) similar to those found in a brewery - typical design of mycoprotein fermenter is shown in right-hand labelled diagram.

It's made by continuously adding oxygen, nitrogen (from ammonia/nitrate), carbohydrate (e.g. glucose syrup) and essential minerals to a fungus called Fusarium venenatum, which is grown in aerobic conditions.

Nutrients, minerals, fungus and sterile air are fed into the fermenter. The fungus needs oxygen for aerobic respiration. The amino acids and protein are synthesised from glucose syrup and ammonia.

The pH (~6) and temperature (~40oC) are carefully monitored and controlled. A cooling water jacket is needed to remove excess heat - thermostat control.

The stirring paddles ensure the suspended fungus, glucose syrup, ammonia, minerals, oxygen and heat are all continuously evenly distributed throughout the fermenter vat.

The fungus rapidly grows producing the protein which is 'harvested', purified and converted into a safe edible mycoprotein food product.

The Fusarium fungus can double in mass in as little as 5 hours - compare this with how long it takes for grain or cattle to grow.

It is estimated the carbon footprint of mycoprotein is 4x less than that of producing chicken.

Mycoprotein is almost tasteless so a range of textures and flavourings can be added to make it palatable for the human diet.


(h) Growing plants in glasshouses  (see also section (i) on hydroponics)

principles of operating a greenhouse in horticulture sunlight heater carbon dioxide source artificial lighting water supply humidifier

The growing conditions in a green can be rigorously controlled for maximum growth.

glasshouse of Mulgrave Estate Gardens, North YorkshireA greenhouse used is to artificially create the best environment for growing plants and increase photosynthesis efficiency.

Ventilation - need to keep the air fresh and ensure the carbon dioxide level doesn't fall below that in the air outside. You can artificially increase CO2 available to plants to increase rate of photosynthesis.

Glass (or transparent plastic) panels - allows the transmission of visible light for photosynthesis and infrared radiation to be absorbed and raise the temperature.

Plants need a constant supply of water, the soil or compost may get to dry for optimum plant growth and the higher temperatures in a greenhouse increase the rate of transpiration.

An electric heater can raise the temperature on colder days, preferably from renewable source.

Artificial lighting enables photosynthesis to be continuous 24/7 and independent of the weather, BUT you need periods of darkness (use a timer) to allow the plant to transport and store glucose as starch.

Growing crops in greenhouses can significantly increase the crop yield for a given area.

Large scale greenhouses and hydroponics units are good methods of 'factory farming' plants and biological methods of pest control are quite successful, see section (d).

See also Photosynthesis, importance explained, limiting factors affecting rate, leaf adaptations 

and specifically How to successfully operate a commercial  greenhouse!


(i) Hydroponics - growing plants without soil in a greenhouse/glass house


Many of the factors discussed in (h) about a greenhouse obviously apply here too.

The growing conditions in hydroponics can be rigorously controlled.

Instead of using soil, plants are grown with their roots 'dangling' into a nutrient solution.

The water contains the best balance of dissolved mineral ions and can be individually formulated for a particular plant.

The plants must be supported in some way - e.g. a frame with holes, through the plants grow.

The growth medium doesn't have to be water, it can be course particles of mineral or fibres e.g. gravel, rock wool or brown fibres from coconuts and watered with the nutrient solution.

The plants are grown in a large greenhouse to protect the crops from the weather.

Even the floor can be painted white to reflect more light onto the plants!

Two features to maximise light absorption by the plants:

The glass panels used have a low iron content to ensure maximum transmission of visible light.

The metal frames supporting the glass panels are made as thin as possible to maximise the 'window' area.

Hydroponics is an excellent example of applying modern technology to agriculture-horticulture

Computer systems can electronically control the conditions to optimise plant growth.

Temperature can be continuously monitored and controlled using a thermostat system.

Nutrient concentrations can be monitored and adjusted when necessary and unused minerals can be recycled and the concentrations adjusted for maximum growth.

There is also no polluting run-off into the surrounding land or waterways.

Light intensity is monitored and special lighting systems are used to increase the length of 'daylight', but can also be timed to switch off for shorter periods to allow plants to transport glucose around the plant.

The external weather conditions can be monitored and vents and blinds can be adjusted to control the internal conditions of the glasshouse/greenhouse.

Advantages of hydroponic horticulture to maximise growth and maximise yields

Its easier to control pests and diseases.

Nutrient levels can be accurately controlled e.g. the concentrations in the hydroponic water.

Hydroponics can be used where plants cannot be grown in soil - either there is no soil or it is so infertile and devoid of nutrients for plants to grow.

It can be used if the climate is unsuitable e.g. areas of very low rainfall - but you still need a water supply.

Examples of the use of hydroponic plant culture

Large scale glasshouses (big greenhouses!) are used to cultivate tomatoes and lettuce and other salad crops on big commercial scale.

Disadvantages of hydroponics

Large quantities of artificial fertilisers must be used.

The capital cost to set up a 'hydroponic farm' is high.

If a disease enters the system (e.g. big glasshouse) it can spread quickly from plant to plant causing major damage to crops.


Overall, large scale greenhouses and hydroponics units are good methods of 'factory farming' plants and biological methods of pest control are quite successful, see section (d).


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Some learning objectives for this page

  • Know and understand that at each stage in a food chain, less material and less energy are contained in the biomass of the organisms.

    • Realise that this means that the efficiency of food production can be improved by reducing the number of stages in food chains.

    • As you move up a food chain, at every stage you lose biomass and therefore energy, so the greater the number of stages in food chain from producer to final consumer, the food production becomes less and less efficient.

    • Because of the fewer stages in the food chain, it is more efficient to produce food by growing crops than raising herds of animals if you compare the efficiencies of equal areas of land.

    • However a healthy diet should be varied diet, so meat or meat substitutes are important, but it is possible to grow cereal crops with a higher protein content.

    • Also, not all land is suitable for growing crops and poor quality land in upland areas of wild moorland may be more suitable for sheep for mutton and deer for venison.

  • Know and understand that he efficiency of food production can also be improved by restricting energy loss from food animals by limiting their movement and by controlling the temperature of their surroundings.

    • Intensive farming, where animals are constrained in large 'sheds' with limited movement and kept in a warmer environment, does improve efficiency of meat production making it cheaper for the farmer to produce food by reducing production costs.

    • This makes cheaper food for us via our local shops and supermarkets and supermarkets have a powerful influence on the cost of food but are increasingly being pressured to source from farmers who adhere to strict standards of animal husbandry - but this is not the case in all countries.

    • Less energy is wasted as body heat and animals grow fatter on less food, and animal feed is becoming increasingly costly, but, at what cost to the quality of existence of these factory farmed animals?

    • There are also disadvantages to intensive farming eg the over-crowded conditions are ideal for the spread of disease eg avian flu in chickens, foot-and-mouth-disease in cows. To combat these diseases by treating the animals with antibiotics increases production costs and introduces these same antibiotics into the food chain, so potentially weakening our own immune system if we become infected.

    • But, these 'factory farming' methods means the lives of the quality of life of these animals is much reduced compared to living out in open fields with plenty of space to move about freely, fresh air and sunlight, hence consumer demand for organic meat from animals not intensively farmed.

  • Know and understand that fish stocks in the oceans are declining.

    • Know that it is important to maintain fish stocks at a level where breeding continues or certain species may disappear altogether in some areas.

    • Fish stocks of popular varieties are becoming alarmingly low in many regions of our seas and oceans due to over-fishing, which itself derives from the food demands of increasing population.

      • Its ironic that a lot of fish is used as 'unnatural' feed for the contained intensive farming of other species such as trout and salmon in fish farms.

    • Know and understand that net size and fishing quotas play an important role in conservation of fish stocks.

      • Fishing quotas are all about controlling the number of fish caught and the size of the fishes allowed to be caught e.g. fishing boat catches are carefully monitored and recorded and fishing nets inspected to check that the mesh spacing in the nets is not too small so that too many small immature fish (who can breed later) are not caught and hopefully unwanted species of fish or other marine creatures (eg crustaceans like crabs, lobsters, crayfish) can escape!

      • Understand that this is an example of sustainable food production, so that the numerical catch rate can match the numerical growth rate of the fish species we like to eat.

        • In fact in some areas, some fish species are so low in numbers, the catch rate is being highly restricted or banned all together to give the fish stock in the seas to get back to a sustainable level.

      • Such methods are needed because food chains are being disrupted and species may die out from particular oceanic regions from intensive fishing from huge trawlers and factory ships.

  • Know and understand that the fungus Fusarium is useful for producing mycoprotein, a protein-rich food suitable for vegetarians and is a meat substitute eg like the commercial product 'Quorn' (though it does need tasting up a bit!).

    • Know that the fungus is grown on glucose syrup (supplies energy for the process as well as the carbon, hydrogen and oxygen for the protein molecules), in aerobic conditions (air containing oxygen needed), with a source of nitrogen eg ammonia or ammonia compounds (nitrogen is the other important element in amino acids and proteins).

    • Fungi grow rapidly in moist warm conditions so production rates are quite efficient and it doesn't require as much land - though do need sufficient land to the maize from which the glucose syrup is made. When the raw materials have been consumed by the Fusarium fungi the biomass is harvested and purified to be used in various food products.

    • The glucose syrup is made from breaking down maize starch with the appropriate enzyme containing microorganism, though in the mycoprotein production it is important that only the correct microorganism is present to ensure the right biochemistry happens and other microorganisms start multiplying. Therefore all ingredients must be heated and sterilised to kill all microorganisms and the air filtered to remove airborne microorganisms, before the mycoprotein forming fungi are introduced into the fermenter - which itself must be first sterilised with very hot steam.

    • In poor third world countries mycoprotein might be a good efficient substitute for inefficient meat production from animals grazing on large areas of relatively barren infertile land, but is the source of nitrogen from ammonia cheap? I don't think so?

  • Know and understand that humans often upset the balance of different populations in natural ecosystems, or change the environment so that some species find it difficult to survive.

  • Know and understand that with so many people in the world, there is a serious danger of causing permanent damage not just to the local environments but also to the global environment unless our overall effect is managed carefully.

  • Know and understand that humans rely on ecosystems for food, water and shelter.

  • You should be able to use your skills, knowledge and understanding to:

    • analyse and interpret scientific data concerning environmental issues,

      • In examination questions you may be given data to work on,

    • evaluate methods used to collect environmental data and consider their validity and reliability as evidence for environmental change,

      • There is a considerable amount of climate data being collected around the world every day and many weather records go back tens and even hundreds of years.

      • Thermometers provide temperature data of the air and oceans, water collectors for rainfall, snowfall records, glacier size and their rates of melting, satellites can map rain clouds, storm patterns, glacier areas etc.

      • So, we are not short on data, and the consensus is that the Earth is warming, and by 1-2oC over that past 100-150 years. It doesn't sound much, but a 1oC rise does represent a huge amount of extra energy in our global weather system!

      • It is important that the data record is as long and accurate as possible. Computer modelling of the climate and trying to make predictions is not easy because there are so many variables and many not very predictable.

    • evaluate the methods being used to feed and provide water to an increasing human population, both in terms of short term and long term effects,

    • evaluate the use of biogas generators,

      • You should have considered a number of biogas generator designs ranging from third-world generators supplying a single family to commercial generators,

      • you should understand how the output from a biogas generator might be affected by climatic conditions,

    • evaluate the positive and negative effects of managing food production and distribution, and be able to recognise that practical solutions for human needs may require compromise between competing priorities,

      • You should consider:

        • the differences in efficiency between producing food from animals and plants,

        • the pros and cons of factory farming of animals,

        • the implications of ‘food miles’ - some food imports have come from thousands of miles away from the source of food production.

          • There are several issues which makes this an undesirable situation It adds extra costs to the consumer.

            • The transport costs increase the price of the food.

            • There is environmental damage from burning more fossil fuels - carbon dioxide -global warming - climate change.

            • These food imports often originate from third world countries where this is pressure to increase the national income from selling cash crops to foreign countries, BUT, many of the people in these exporting countries do not access to good food supplies - its the richer important countries who often benefit the most.

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