Human Population and Food Resources

What you'll learn

This topic examines the relationship between growing human populations and the Earth's capacity to produce food. You'll explore population dynamics, carrying capacity, food production systems, and sustainable approaches to feeding the world's population whilst minimising environmental damage.

Key terms and definitions

Carrying capacity — the maximum population size that an environment can support indefinitely with available resources, food, water, and habitat.

Birth rate — the number of live births per 1,000 people in a population per year.

Death rate — the number of deaths per 1,000 people in a population per year.

Population pyramid — a graphical representation showing the age and sex distribution of a population, used to predict future population trends.

Food security — when all people, at all times, have physical and economic access to sufficient, safe and nutritious food to meet their dietary needs.

Subsistence farming — agricultural production where farmers grow crops and rear animals primarily to feed their own families, with little or no surplus for sale.

Commercial farming — large-scale agricultural production aimed at selling produce for profit, often using intensive methods and technology.

Green Revolution — the development and spread of high-yielding crop varieties, pesticides, fertilisers and irrigation techniques that dramatically increased food production from the 1960s onwards.

Core concepts

Population growth and its impacts

Human population has grown exponentially, from 1 billion in 1800 to over 8 billion today. This growth is uneven across the globe.

Factors affecting population growth:

• Birth rates decline with economic development, improved education (especially for women), and access to contraception
• Death rates fall due to improved healthcare, sanitation, nutrition and disease control
• Natural increase = birth rate minus death rate
• Migration affects population distribution but not global totals

Population distribution patterns:

Most Economically Developed Countries (MEDCs) show:

• Low birth rates (10-15 per 1,000)
• Low death rates (8-12 per 1,000)
• Ageing populations with declining or stable numbers
• Population pyramids with narrow bases and wider tops

Most Less Economically Developed Countries (LEDCs) show:

• Declining but still higher birth rates (20-40 per 1,000)
• Falling death rates (6-15 per 1,000)
• Young, rapidly growing populations
• Population pyramids with wide bases and narrow tops

Environmental impacts of population growth:

• Increased demand for agricultural land leads to deforestation and habitat loss
• Greater water extraction for irrigation and domestic use
• Higher energy consumption and associated pollution
• Increased waste production and management challenges
• Loss of biodiversity through habitat conversion
• Soil degradation from intensive farming

Carrying capacity and resource limitations

The Earth's carrying capacity for humans remains uncertain and contested. Unlike animal populations that crash when exceeding carrying capacity, humans modify environments and develop technologies to increase food production.

Factors determining carrying capacity:

• Available agricultural land and soil quality
• Water availability and distribution
• Climate and weather patterns
• Technology and farming methods
• Energy resources for food production and distribution
• Socio-economic systems and food distribution networks

Limiting factors for food production:

• Land availability — agricultural land is finite; urban expansion and desertification reduce productive area
• Water scarcity — agriculture uses 70% of freshwater withdrawals globally; many regions face water stress
• Climate change — alters growing seasons, increases extreme weather events, shifts agricultural zones
• Soil degradation — erosion, nutrient depletion and salinisation reduce productivity
• Energy costs — modern agriculture depends heavily on fossil fuels for machinery, transport and agrochemical production

Food production systems

Subsistence farming

Common in many LEDCs, particularly in Africa, Asia and parts of the Caribbean.

Characteristics:

• Small plots (often less than 2 hectares)
• Family labour with simple tools
• Low inputs of fertilisers and pesticides
• Mixed cropping for food security
• Livestock integration for manure and protein

Advantages:

• Low environmental impact
• Preserves traditional knowledge
• No dependence on external inputs
• Maintains crop genetic diversity

Disadvantages:

• Low yields and productivity
• Vulnerable to crop failure
• Limited income generation
• Labour-intensive

Commercial farming

Dominant in MEDCs and increasingly in LEDCs through agribusiness.

Intensive arable farming:

• High inputs of fertilisers, pesticides and water
• Mechanisation throughout production cycle
• Monocultures of high-yielding varieties
• Large field sizes (10-100+ hectares)
• Examples: wheat production in UK, maize in USA

Intensive livestock farming:

• High stocking densities
• Controlled environments (battery cages, feedlots)
• Concentrated feeds and growth promoters
• Example: poultry production in Caribbean nations importing feed

Plantation agriculture:

• Large estates producing single cash crops
• Found in tropical/subtropical regions
• High external inputs and machinery
• Examples: banana plantations in Caribbean, tea estates in India

Environmental impacts of modern agriculture

Impacts of intensive farming:

• Eutrophication — nutrient runoff (nitrogen and phosphorus from fertilisers) causes algal blooms in waterways, depleting oxygen and killing aquatic life
• Pesticide pollution — chemicals accumulate in food chains (bioaccumulation), kill beneficial insects, contaminate water supplies
• Soil erosion — removal of hedgerows and vegetation cover; heavy machinery compacts soil; monocultures leave soil exposed
• Loss of biodiversity — habitat destruction, hedgerow removal, pesticide use reduces species diversity
• Greenhouse gas emissions — methane from livestock (especially cattle), nitrous oxide from fertilisers, carbon dioxide from machinery
• Water depletion — irrigation lowers water tables, particularly in semi-arid regions

Specific regional concerns:

In the Caribbean:

• Soil erosion on hillside banana plantations
• Pesticide runoff affecting coral reefs
• Water scarcity during dry seasons affecting irrigation

In the UK:

• Eutrophication in rivers and coastal areas from agricultural runoff
• Declining pollinator populations linked to pesticide use
• Loss of traditional meadows and hedgerows

Sustainable food production

The Green Revolution achievements and limitations:

Achievements:

• Increased cereal production dramatically (1960s-1990s)
• High-Yielding Varieties (HYVs) of rice and wheat
• Prevented widespread famines, particularly in Asia
• Improved food security in many LEDCs

Limitations:

• Required expensive inputs (fertilisers, pesticides, irrigation)
• Benefited wealthier farmers disproportionately
• Reduced crop genetic diversity
• Environmental damage from agrochemicals
• Not suitable for all climates and regions

Sustainable farming approaches:

Organic farming:

• No synthetic pesticides or fertilisers
• Crop rotation to maintain soil fertility
• Natural pest control (predators, companion planting)
• Animal welfare standards for livestock
• Growing market in MEDCs but lower yields (20-30% less typically)

Integrated Pest Management (IPM):

• Uses pesticides only when necessary
• Biological control (natural predators)
• Crop rotation and resistant varieties
• Monitoring pest populations
• Reduces chemical use by 50-70%

Soil conservation techniques:

• Contour ploughing on slopes to reduce erosion
• Terracing in mountainous regions
• Cover crops to protect soil between main crops
• Reduced tillage/no-till farming
• Windbreaks and shelter belts

Water conservation:

• Drip irrigation delivers water directly to roots (90% efficiency vs 60% for sprinklers)
• Rainwater harvesting and storage
• Drought-resistant crop varieties
• Mulching to reduce evaporation

Agroforestry:

• Combines trees with crops or livestock
• Trees provide shade, prevent erosion, fix nitrogen
• Multiple products (fruit, timber, crops)
• Common in tropical regions including Caribbean

Alternative protein sources and food technologies

Reducing meat consumption benefits:

• Livestock farming produces 14.5% of global greenhouse gas emissions
• Beef production requires 15,000 litres of water per kg
• Land used for animal feed could grow crops for direct human consumption
• Converting plant protein to meat is inefficient (10:1 ratio for cattle)

Alternative approaches:

• Plant-based protein sources (legumes, soy products)
• Insect farming — high protein, low environmental impact, common in parts of Asia and Africa
• Aquaculture (fish farming) — fastest-growing food sector but concerns over pollution and disease
• Lab-grown meat — emerging technology, high energy costs currently
• Genetically modified crops — pest-resistant varieties reduce pesticide use, but controversial

Food distribution and waste

Food security challenges:

Food insecurity affects over 800 million people despite global surplus production. The issue is distribution, not absolute shortage.

Causes of food insecurity:

• Poverty and lack of purchasing power
• Political instability and conflict disrupting production
• Poor infrastructure limiting distribution
• Climate shocks (droughts, floods)
• Price volatility on global markets
• Post-harvest losses (up to 40% in some LEDCs due to poor storage)

Food waste:

• MEDCs waste 30-40% of food, mostly at retail and consumer levels
• LEDCs lose 30-40% through poor harvesting, storage and transport
• Reducing waste could feed additional 1 billion people
• Wasted food represents wasted water, energy and land resources

Worked examples

Example 1: Calculating population change

Question: A country has a birth rate of 28 per 1,000 and a death rate of 9 per 1,000. The population is currently 15 million. Calculate the natural population increase in one year. [3 marks]

Solution:

• Natural increase rate = birth rate - death rate
• Natural increase = 28 - 9 = 19 per 1,000 [1 mark]
• Annual increase = (19/1,000) × 15,000,000 [1 mark]
• = 285,000 people [1 mark]

Example 2: Comparing farming systems

Question: Compare subsistence farming and commercial farming in terms of their environmental impacts. [6 marks]

Model answer:

Subsistence farming generally has lower environmental impacts because it uses minimal chemical inputs such as synthetic fertilisers and pesticides, reducing pollution of waterways [1 mark]. Fields are typically small with diverse crops, maintaining biodiversity and reducing soil erosion [1 mark]. However, it may contribute to deforestation if land is cleared for expansion [1 mark].

Commercial farming has greater environmental impacts due to high inputs of agrochemicals causing eutrophication and pesticide pollution [1 mark]. Large monocultures reduce biodiversity and can lead to soil erosion, especially if hedgerows are removed [1 mark]. However, commercial farms may use more efficient irrigation and precision agriculture to reduce resource waste [1 mark].

Example 3: Sustainable agriculture strategy

Question: Explain how Integrated Pest Management (IPM) contributes to sustainable food production. [4 marks]

Model answer:

IPM reduces reliance on chemical pesticides by using biological control methods such as introducing natural predators of pests [1 mark]. This minimises pesticide pollution in waterways and soil, reducing environmental damage [1 mark]. Farmers monitor pest populations and only apply chemicals when economically necessary, reducing costs and chemical resistance [1 mark]. Crop rotation and pest-resistant varieties are used as preventative measures, maintaining long-term soil health and productivity [1 mark].

Common mistakes and how to avoid them

• Confusing birth/death rates with actual population numbers — rates are per 1,000 people, not total numbers. Always convert when calculating actual increases.

• Assuming food shortage is always due to lack of production — many food security issues stem from poverty, distribution problems and waste, not insufficient global production. Address economic and social factors in answers.

• Overlooking the environmental costs of the Green Revolution — don't just list benefits. High-Yielding Varieties require substantial inputs of water, fertilisers and pesticides, causing environmental damage.

• Writing vague statements about sustainability — be specific. Instead of "organic farming is better for the environment," explain precisely how it reduces chemical pollution or maintains biodiversity.

• Failing to provide regional context when asked — questions may specifically ask about Caribbean or other regions. Use appropriate examples like banana plantations in the Caribbean or wheat farming in the UK.

• Mixing up extensive and intensive farming — intensive = high inputs per unit area; extensive = low inputs over large areas. Many students reverse these definitions.

Exam technique for "Human Population and Food Resources"

• Command words matter: "Describe" requires characteristics or features; "Explain" needs reasons or mechanisms with linking words like "because," "therefore," "this causes." "Compare" demands similarities AND differences.

• Use data effectively: When graphs or tables are provided, quote specific figures to support your answer. For 3-4 mark questions, aim for 2-3 developed points rather than many superficial ones.

• Structure extended answers: For 6+ mark questions, consider organising by environmental, economic and social impacts, or by LEDC vs MEDC contexts. This ensures comprehensive coverage.

• Link concepts: Strong answers connect population growth → increased food demand → intensification → environmental impacts → need for sustainable approaches. Show these relationships explicitly.

Quick revision summary

Human population growth drives increased food demand, pressuring Earth's carrying capacity. Subsistence farming has low environmental impact but limited productivity, while commercial intensive farming achieves high yields but causes eutrophication, pesticide pollution, soil degradation and biodiversity loss. The Green Revolution increased production through HYVs and agrochemicals but created environmental problems. Sustainable approaches include organic farming, IPM, soil conservation, water-efficient irrigation and agroforestry. Food insecurity results from distribution inequality and waste, not absolute shortage, affecting 800+ million people despite global surplus production.