Food Security

Efficiency Equation and Worked Example

• The efficiency of energy transfer between trophic levels can be calculated to show exactly how much food is lost.

A farmer grows $4500\text{ kg}$ of grain. This grain is entirely consumed by a herd of cows, which build up $315\text{ kg}$ of biomass. Calculate the efficiency of biomass transfer.

Step 1: Identify the biomass at each level.

• Lower trophic level (grain) = $4500\text{ kg}$
• Higher trophic level (cows) = $315\text{ kg}$

Step 2: Substitute the values into the equation.

• $\text{Efficiency} = \left( \frac{315}{4500} \right) \times 100$

Step 3: Calculate the final percentage.

• $\text{Efficiency} = 0.07 \times 100 = 7\%$

Intensive Farming and Fish Farming

• To keep up with growing demands, modern agriculture has transformed into a highly controlled, industrialised process.
• Intensive farming (or factory farming) maximises food production efficiency by restricting animal movement (saving energy otherwise used for muscle contraction) and keeping animals in heated pens (saving energy used for thermoregulation).
• Animals are also given high-protein feed to accelerate growth and convert a higher proportion of their diet directly into meat.
• Fish farming helps reduce the severe pressure on wild fish stocks and is made efficient by controlling water oxygen levels, using protective nets to stop predation, and feeding fish high-protein pellets.
• Biologically, fish are ectotherms (cold-blooded), meaning they use far less energy maintaining a constant body temperature compared to endotherms (warm-blooded mammals like cows), making them highly efficient to farm.
• However, intensive farming faces severe criticism regarding animal welfare and the rapid spread of disease within crowded enclosures.

Pests, Pathogens, and Environmental Change

• A single microscopic fungus or a swarm of insects can devastate an entire nation's food supply in a matter of weeks.
• Global trade and modern transport allow new pests (like locusts and caterpillars) and pathogens (bacteria, viruses, and fungi) to spread rapidly to new geographical areas.
• Modern farming often relies on monoculture, which involves growing a single crop species over a vast area; this severely reduces biodiversity and means a single newly introduced pathogen (like potato blight) can cause total crop failure.
• Furthermore, human-induced environmental change is causing global temperatures to rise and weather patterns to become unpredictable.
• This leads to an increased frequency of extreme weather, such as droughts and flooding, which physically destroy crops and lead to famine.
• Climate change also alters the distribution of pests and pathogens, allowing them to migrate into new regions where local crops have no natural genetic resistance.

Sustainability and Biofuels

• We are increasingly turning to crops not just to feed ourselves, but to power our vehicles and generate electricity.
• A biofuel is a renewable energy source derived from recently living biological materials, which can replace fossil fuels.
• Bioethanol is produced when carbohydrate-rich crops (like sugar cane or maize) are fermented by yeast in anaerobic conditions.

• Biogas is produced via the anaerobic respiration of plant or animal waste in a generator, creating a mixture of roughly 70% methane and 30% carbon dioxide.
• Crops like elephant grass provide a high yield of biomass specifically for these fuels.
• While biofuels promote sustainability, they create a severe "food vs. fuel" conflict.
• Growing crops for fuel takes up valuable agricultural land, reducing the space available to grow food, which restricts the food supply, drives up global prices, and directly worsens food security.

The Cost of Agricultural Inputs

• Farming is a business, and producing high yields requires a massive financial investment before a single seed even sprouts.
• Modern agriculture relies heavily on agricultural inputs, which include expensive high-yield or genetically modified seeds, mechanisation (buying and fuelling tractors and harvesters), and agrochemicals.
• These chemicals include inorganic fertilisers (used to replace vital soil nutrients like Nitrogen, Phosphorus, and Potassium) and pesticides to kill insects.
• These high costs can make farming economically unviable, particularly in LEDCs (Less Economically Developed Countries).
• If farmers cannot afford these necessary inputs, crop yields drop significantly, threatening both local and national food security and forcing many to abandon farming entirely.