Changing Land Use

The increase in population led to an increase in the demand for agricultural and industrial land. Urbanisation also occurs since more people prefer living in cities. The change in land use causes an increase in greenhouse gas emission.

Increase in Agriculture

Agriculture is the practice of cultivating land, producing crops and raising livestock. Agriculture produces the third most amount of greenhouse gas. 

In the production of crops, tractors are used to plough the land. It uses fossil fuels which release carbon dioxide. Inorganic fertilisers are also used to fertilise the soil. This increase the amount of nitrous oxide in the soil. The nitrous oxide from the soil is released when the soil is ploughed or when rain flows through the soil. Organic matters in agriculture fields decay and release methane. In rice fields, decomposition is very fast since lots of water is used in the soil. This cause rice fields to produce large amount of methane
The farming of cattle also contribute to an increase in greenhouse gas emission. This is because cattle release methane as waste gas. Millions of tonnes of methane are released annually from cattle farming.

Increase in Industries 

Industries is the production of goods and service within a country. Secondary industries refer to industrial economic activities. Secondary industries involve the burning of fossil fuels for goods to be produced. This lead to an increase in greenhouse gas emission. Greenhouse gases may also be released as a waste gas when producing goods.
The countries emitting the largest amount of greenhouse gas from industrial processes are North America, Central America, Europe and Asia, due to the concentration of industries in these countries.
In the past, Europe, North America and Central America were emitting the most amount of carbon dioxide from industrial processes since these countries were heavily involved in manufacturing. Countries like China and India are experiencing industrailisation, causing more carbon dioxide to be emitted from those countries.

Urbanisation

Urbanisation is the process in which more and more people are living in urban areas like cities or towns. The demand for energy in these urban areas is high, causing there to be large amount of fossil fuels to be burnt to provide energy for various human activities such as heating, cooling, cooking, lighting etc. The large number of vehicles in urban areas also contribute to an increase in emission in greenhouse gases.  

Constructing infrastructure and producing construction materials also release large amount of greenhouse gases into the atmosphere.

Deforestation

Deforestation is the cutting down of trees in forested areas. Trees are cut down for wood, used to make papers, building materials etc. Forests are also deforested so that there is more space available for human activities like mining, grazing of animals, planting of crops, construction of infrastructure and for many other purposes.
Trees absorb carbon dioxide, a greenhouse gas, to produce oxygen during photosynthesis in the trees. The trees absorb a significant amount of carbon dioxide, in turn reducing a significant amount of global greenhouse gas emission.
Deforestation cut down trees and plants that photosynthesise. This make there an increase in the carbon dioxide in the atmosphere.
Soil contains one of the most amount of carbons in the world. The decay of organic accumulates carbon in the soil. The trees in the forest originally block the soil from sunlight; without the trees, the soil is exposed to sunlight. This increases the temperature of the soil which in turn increase the rate of carbon oxidation, a process where carbon oxidise to form carbon dioxide. This is another way how deforestation increase the amount of greenhouse gases.
Deforestation causes the second greatest increase in greenhouse gases.
Between 2000 and 2010, 52000 km² of forest was lost annually; 142.5 km² of forest is lost everyday.
Afforestation is done in many countries to reduce the problem of deforestation. 

Burning Fossil Fuels

Fossil fuels are fuels formed from dead organic matter that has decomposed over millions of years. Oil, coal and natural gas are examples of fossil fuels. Human activities such as industrial, transportation, domestic and commercial activities  require large amount of energy; fossil fuels are burnt to produce large amount of energy essential for human activities. 

Fossil fuels contain high content of carbon and by burning it, it releases large amount of carbon dioxide, a greenhouse gas. The burning of fossil fuels produces the most amount of greenhouse gases. The burning of fossil fuels releases billions of tonnes of carbon dioxide into the atmosphere annually. 

The world's usage of fossil fuels has increased in recent years.

In 2010, the global carbon dioxide emission is 30.6 billion tonne, 1.62 billion tonnes more than the carbon dioxide emission in 2009.