Population and the Environment

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What is population distribution?

The pattern of where people live

What is population density?

The population of an area divided by the size of the area

Why has population grown rapidly since the 19th century?

Improvements in medicine and food production increased life expectancy and reduced infant mortality rates. During this period, the populations of developing countries remained stable- infant and maternal mortality rates were high, and famine was common.

Why has most population growth been driven by developing countries?

Life expectancy has increased and death rates have decreased significantly

Why has the distribution of populations changed?

Urban populations are increasing faster than rural ones, so populations are becoming less evenly distributed with higher densities in cities

How does climate type affect population?

Few people live in arid areas, but many live in temperate areas. Temperate areas usually have larger populations and higher population densities as it’s easier to produce food

How does climate change affect population distribution?

In coastal areas where sea levels are rising, people are moving inland and some people living on small islands are having to abandon their islands. Climate change is causing levels of nutrition to fall in some developing countries

How does soil fertility affect population?

Determines the amount and type of food that can be produced in a region and has played a role in determining where human settlements have developed, and the size of populations. Fertile soil supported large scale agriculture, but soil erosion can cause people to migrate as agriculture becomes difficult

How does resource distribution affect population?

Availability of fresh water and other natural resources, lack of safe water can lead to food insecurity and health problems. Places with naturally occurring food and fuel are able to support fairly large populations

How did the Neolithic Revolution affect population size and distribution?

Around 12,000 years ago people developed agriculture, and lifestyles changed from hunting and gathering to farming in permanent settlements- population increased in these areas as food supply became reliable

How did the Industrial Revolution affect population size and distribution?

From around 1760-1850, there was a rapid rise in the use of machinery in developed countries. This coincided with major population growth- population growth doubled between 1750 and 1850 in Britain. Death rates fell because of increased food production and more money meant people had better diets. People moved to cities for work as farming became less labour intensive, leading to concentrated populations.

Why has food production increased globally over the last 50 years?

The area of land for producing food has increased and technological advances such as rotary combines, pesticides and modern irrigation have made it possible to produce more food from less land

Why do East Asia and North America produce a lot of food?

Climates and investments that are good for farming

Why do Central America and Africa produce small amounts of food?

A lack of resources and funding for farm equipment, large areas of land that are unsuitable for farming as they are either mountainous or have poor quality soil, unsuitable climates due to lack of rainfall and high temperatures

Why do more developed areas like North America and Europe consume a lot?

They can afford to import a large variety of foods, have a culture of consumerism and many people have high disposable incomes so can afford more food

Why do less developed areas like Africa and parts of South America and Asia consume less food?

They can’t afford as much

Why do the types of food consumed vary between countries at different levels of development?

Some foods cost more to produce than others so makes up a larger proportion of the diet in more developed countries- the average amount of meat consumed per person per year in developed countries from 2013-2015 was 67.5kg, whereas in developing countries it was 26.6kg

How are farms open systems?

• some inputs to farmland are natural, such as solar energy and rainwater, and some are introduced by humans such as seeds and fertilisers

• Energy and matter are transferred to and stored in the soil, crops and/or animals on the farm

• The main output is the food produced, although there are other outputs such as runoff

What is agricultural productivity?

A measure of the amount of food produced in an area- ratio of agricultural outputs to inputs

How is agricultural productivity affected by commercial farming?

Commercial farming is the production of crops and livestock to make a profit, and has high agricultural productivity. It’s often more common in developed countries than developing countries.

How is agricultural productivity affected by capital-intensive farming?

Capital-intensive farming has a high input of capital and a low input of labour for the area of land. It often involves using fertilisers, pesticides and labour-saving machinery

How is agricultural productivity affected by labour-intensive farming?

Labour-intensive farming doesn’t involve as much capital but it uses a lot of labour.

How is agricultural productivity affected by extensive farming?

Extensive farming has low capital and labour input for the area of land so produces less food than intensive farming. Extensive farming has less environmental impact and provides better animal welfare than intensive farming.

How is agricultural productivity affected by nomadic farming?

Farmers move from place to place to grow crops or graze animals on different land.

How is agricultural productivity affected by climate?

The climate affects how successfully plants can grow in an area and the animals that can survive there. Some crops are adapted to particular conditions, but some climates make farming more difficult

How is agricultural productivity affected by soil?

Some areas are unsuitable for farming because there is not enough soil, or the soil is of poor quality. Different types of soils are suited to different types of farming- some soils are too shallow or not fertile enough to grow crops so are used for grazing.

Describe the Arctic

• covers the Arctic Ocean, much of which has a surface layer of ice

• Areas around the Arctic Ocean such as northern Canada, Greenland and northern Russia have a polar climate

• In winter, temperatures are often below -40 degrees

• In summer, temperatures range from about -10 to +10 degrees

• Precipitation is generally less than 100mm per year

Describe Antarctica

• colder than the Arctic- winter temperatures can fall below -80 degrees

• The interior of Antarcticas is very dry and gets less than 50mm of precipitation each year. Precipitation is higher in coastal areas

Which two environments are produced by polar climates?

Ice caps, which are layers of ice permanently covering an area, and tundra, which has permanently frozen ground called permafrost

How do low temperatures and precipitation affect transitional lifestyles in the Arctic?

• agricultural productivity is low, so lifestyles are based on subsistence

• Arable farming isn’t possible so Arctic diets are often meat-based

• Many species eaten by people in the Arctic leave in the winter so some people also have to migrate seasonally so they’re closer to a food source

• People adapt to the temperatures, e.g. Inuit people build stone houses into hillsides which are insulated by coverings of turf and snow

How does climate affect development in polar regions?

• low temperatures and frozen ground make it hard for people to work or construct buildings

• Seasonal work exists, for example tourism, oil and gas reserves, usually in the summer

• The melting of sea ice in the summer opens up shipping routes that make trade easier and commercial fishing can take place

What is the difference between hot and temperate deserts?

Hot deserts occur around 30 degrees north and south of the equator and maximum temperatures are above 40 degrees. Temperate deserts occur at higher latitudes and are cooler but still as arid.

Rain is rare and unreliable and temperature ranges can be huge.

How does climate affect lifestyles in arid regions?

• agriculture is impossible in most areas because rain only falls infrequently, usually in the form of heavy conventional rainstorms which cause flash floods and soil erosion

• Water can be drawn from oases to irrigate crops and crops such as cereals can be grown in the shade of taller plants, so these methods allow people to settle around oases

• Nomadic people can keep grazing livestock despite the sparse vegetation

What are some more modern solutions to the challenges of arid climates?

• groundwater for irrigation can be accessed with motorised pumps. Modern irrigation techniques include drip irrigation, where water slowly drips onto crops to minimise evaporation

• Major cities can develop if there is enough money to invest in obtaining water, for example Las Vegas, which relies on water from Lake Mead, a reservoir created by a dam on the Colorado River, for 90% of its water supply

How can climate change decrease agricultural productivity?

Reduced rainfall can damage harvests and limit food available to livestock

How can agricultural productivity increase due to climate change?

Increased temperature and rainfall may increase productivity in North America and Europe by encouraging crop growth

How can there be changes in the types of crops grown due to climate change?

Crops that prefer warmer conditions could be grown further north, and crops that prefer cooler conditions could produce lower yields in their current locations

How can agricultural pests and diseases increase in some areas due to climate change?

They can migrate due to increased or decreased temperatures, for example the range of the European Corn Borer is shifting northwards due to increased temperatures

What is soil?

All of the material between the ground surface and bedrock

How are soils formed?

A combination of minerals from weathered bedrock and organic matter from vegetation

How is soil formation linked with climate?

Climate determines the rate of weathering of the bedrock, the type of vegetation that grows there, and how quickly this vegetation decomposes

What are zonal soils?

Mature soils that have developed from the interaction between climate, vegetation and parent rock across a significant period of time

How can soil types be identified?

By looking at the layers in the soil profile, which are known as soil horizons

Where do podzols occur?

Cool temperate climates in the northern hemisphere where there is more precipitation than evapotranspiration

Where are podzols usually found?

Under coniferous woodland or heather moorland

What are the O and A horizons?

The O horizon is a layer of needles from coniferous trees or heather leaf litter, and below this is a narrow, acidic A horizon- nutrients are leached from this horizon by water

What is the E horizon?

Because of the acidity, water travelling through the soil is more able to dissolve certain minerals such as iron and aluminium compounds. Leaching of these minerals creates a pale E horizon formed mainly of quartz sand and silt

How does a ‘hard pan’ form in the B horizon?

Minerals accumulate here, forming a reddish-brown layer. In very well-developed podzols, a ‘hard pan’ layer forms in the B horizon- this is a hard, continuous layer of deposited iron

Why is arable farming difficult in areas with podzols?

• acidity and lack of nutrients means few crops are able to grow

• Formation of a hard pan can prevent water draining away, making the soil vulnerable to water logging, damaging crops

• Water logging also makes ploughing difficult because machinery sinks into the ground

• Arable farming here would require treatment with lime to reduce acidity and extensive artificial fertilisation

Why is forestry a common human activity in podzols?

Coniferous trees grow successfully here. Low soil temperatures mean it can take up to 100 years for a tree to reach maturity and be ready to harvest

Where are latosols found?

Under tropical rainforests

How is chemical weathering of bedrock encouraged?

High temperature and humidity. This forms soils up to 30-40m deep

Why is the O horizon thick and the A horizon thin in latosols?

Year round plant growth makes a thick O horizon. As soon as leaf litter decomposes to humus, its nutrients are absorbed by vegetation rather than staying in the soil- this means the fertile A horizon is very thin

Why is there lots of leaching of latosols?

Soil moisture surplus due to high rainfall. Silicate minerals are leached from the B horizon, but less soluble iron and aluminium compounds are left behind. The iron compounds give the B horizon a red colour

What is formed by a build up of minerals in the soil?

A laterite horizon, which acts like clay

Why are latosols poor for agriculture?

Low nutrient content. Once the rainforest trees are removed, the soil has no protection from the heavy rainfall- leaching increases and the latosol becomes even more nutrient poor.

How have humans adapted to latosols?

Traditional agriculture using slash and burn clears one small area for growing crops at a time. Burning vegetation to clear the plot adds nutrients to the soil. After one growing season, a new plot is cleared, and the first is left to recover fully.

How is permanent soil degradation caused?

Large areas of land are cleared for agriculture, and soil isn’t given a chance to recover

Why are latosols useful for building?

The laterite horizon is soft when it is moist, but hard when it dries out

How does clearing vegetation make soil more vulnerable to erosion?

Rain falls directly onto the soil instead of being intercepted by plants, and the roots that bind the soil together are removed. Vegetation also slows down the wind, so removing it exposed the ground surface to stronger winds.

How does topography make soil more vulnerable to erosion?

Soil is more likely to be washed down a steep slope

How does climate make soil more vulnerable to erosion?

High rainfall increases water erosion. Low rainfall and high temperatures mean soil is dry, making it more vulnerable to wind erosion.

How does land use make soil more vulnerable to erosion?

Ploughing loosens soil and exposes it to wind and rain, making it more vulnerable to erosion

Why is soil erosion a threat to agriculture?

It removes nutrients and reduces the soil’s ability to hold water. In the last 40 years, almost a third of the world’s arable land has become unproductive because of soil erosion.

How can crop rotation reduce soil erosion?

Farmers plant cover crops which maintains the soil until a main crop is sown again

How can windbreaks reduce soil erosion?

Hedges or trees can be planted around feels as barriers against wind erosion

How can terracing reduce soil erosion?

Steps can be cut into a steep hillside to slow down the movement of water down the slope

How can contour ploughing reduce soil erosion?

Ploughing across the slope instead of downslope stops rainwater flowing downhill as quickly

How can mulching reduce soil erosion?

Covering the soil with a layer of plant material protected the soil from wind and rain, and slows down runoff

What are the causes of waterlogging?

• soils with few airspaces fill up with water quickly

• Laterites hinder drainage which causes waterlogging of the soil above

• Precipitation is higher than evapotranspiration

• Too much irrigation

What are the agricultural problems caused by waterlogging?

• plant roots are surrounded by water, which limits their growth and can rot them

• Water decreases soil temperature, which can reduce crop growth

• Crops may be out-competed by weeds that can cope better with the wet conditions

• Land is hard to plough

What are the management strategies for waterlogging?

• avoid over-watering crops

• Drain the soil using underground pipes or ditches around the fields

• Change the composition of the soil

What are the causes of salinisation?

• high temperatures draw water to the surface, where it evaporates and leaves behind salts

• In dry climates, there isn’t enough rainfall to leach salts away

• Irrigation water contains salts- when the water is absorbed by plants or evaporated, the salts are left behind

• Some fertilisers contain salts- applying too much means some salts are left in the soil

What are the agricultural problems caused by salinisation?

• salt can stop crops absorbing the water they need from the soil

• Some salts are toxic to plants so they can reduce the yield or kill the crop

• Water flows from areas of low salinity to areas of high salinity- high soil salinity means water may flow from plant roots to the soil, dehydrating plants

What are the management strategies for salinisation?

• avoid waterlogging

• Only use as much water for irrigation as is needed

• Add the appropriate amount and type of fertiliser

What are the causes of structural deterioration?

• uses of heavy machinery, or trampling by livestock or people can compact soil

• Removal of vegetation, as plant roots help to maintain soil structure

• Salinisation in clay soils, as salt causes clay particles to clump together

What are the agricultural problems caused by structural deterioration?

• if the soil is too compacted, it’s difficult for plant roots to grow

• A loss of pore spaces in the soil means there is reduced capacity for water, sp plants can dry out

• Land is hard to plough

What are the management strategies for structural deterioration?

• avoid compaction by moving livestock regularly

• Maintain vegetation cover

• Change the structure of soil by adding sand to clay soil

• Avoid salinisation

What does food security depend on?

• food availability- a country must produce or import a sufficient amount of food

• Food access- people must be able to regularly obtain food by buying or producing it

• Food quality and use- the food that people consume must be nutritious enough for them to maintain a healthy life. It must be stored and prepared in a safe and hygienic way

How can agricultural expansion increase food production?

More land can be converted to agricultural use, but this destroys ecosystems

How can intensive farming increase food production?

This means producing as much food as possible from the land available. This reduces the needs for clearing natural land, but it may result in artificial chemicals damaging the natural environment.

How can changing the types of food produced increase food production?

Producing plants needs less land and water than producing meat and dairy, so converting to arable farming means more food can be produced. However, as countries become more developed, people tend to eat more meat so demand is increasing.

How can technology increase food production?

Crops can be genetically modified to produce higher yields or resist pests and diseases. This limits the need for artificial pesticides, but it reduces biodiversity. Hydroponics (growing plants in a nutrient solution rather than soil) means crops can be grown in places where there’s a lack of fertile soil. However, this is expensive so may not increase food production in poorer countries.

How can trade increase food access?

Food can be imported to countries that don’t have enough. However, prices have to be low enough for countries to be able to afford sufficient food. Cheap imports may undercut local farmers and make it hard for them to earn a living.

How can improving market access increase food access?

Improving transport links makes it easier for farmers to sell their produce, but some countries can’t afford to invest in infrastructure needed

How can aid increase food access?

Food can be donated, e.g. during a famine. However, this isn’t sustainable in the long term.

How can waste be reduced in production?

Crop loss due to pests and disease can be decreased by educating farmers on prevention and providing them with better resources, e.g. equipment and pesticides

How can waste be reduced in distribution?

Many shops discard food that they don’t sell. Improving storage and packaging and speeding up the time it takes for food to reach consumers increases shelf life. Some supermarkets donate surplus food to food banks

How can waste be reduced in consumption?

Campaigns can encourage consumers to be less wasteful, e.g. by sharing recipes to use up leftovers. However, it can take a long time for populations to change their behaviour on a large scale.

What is health?

Physical, mental and social well-being, and the absence of disease.

How can health be measured?

Indicators such as HALE- this is the number of years a newborn child can expect to live in full health without major disease. This is highest in more developed countries and lowest in less developed countries.

What does health depend on?

How much disease there is in the country, and what types of diseases there are

What is morbidity and what are the morbidity indicators?

The rate of disease in a population. Prevalence is the total number of cases in a population at a particular time, and incidence is the number of new cases in a population during a particular time period.

Morbidity pattern of infectious diseases

High morbidity of infectious disease in less developed countries include lack of clean water, sanitation and healthcare, limited health education and overcrowded conditions in urban areas.

Morbidity pattern of non-communicable diseases

High morbidity of non-communicable disease in more developed countries- higher proportion of older people means more people are likely to suffer from diseases associated with old age. Unhealthy lifestyle means risk of some diseases increases if you’re overweight, eat unhealthy food or don’t do enough exercise.

What are mortality rates?

How many people die in a population over a period of time

Why is the risk of dying from a disease higher in less developed countries?

Malnutrition- reduces the body’s ability to fight disease

Poor access to healthcare- people can’t access the drugs or treatments they need to treats the disease

What is the epidemiological transition model?

States that the main cause of mortality changes from infectious diseases to non-communicable diseases over time

What is stage one of the epidemiological transition model?

Age of pestilence and famine. High number of deaths from infectious diseases. Low average life expectancy (under 50 years)

What is stage two of the epidemiological transition model?

Age of receding pandemics. Number of deaths from infectious diseases falls due to better living conditions and healthcare. Average life expectancy starts to increase (60 years or less)