7.3 Biodiversity & the Effect of Human Interaction on Ecosystems

Deforestation causes an increase in the level of carbon dioxide (CO₂) in the atmosphere.

Give two reasons why.

A dairy farmer hoses down the floors of his milking shed at the end of each day's milking. The effluent flows from the shed floor and is pumped into a waste water storage tank. The effluent contains urine and faeces from the cattle.

On one occasion, the effluent overflows his waste water storage tank and finds its way into a nearby stream.

Explain the effect that the effluent will have on the plants and animals living in the stream.

The oil palm is a tree that grows in tropical areas, whose oil has many uses in cooking, food preparation and as a detergent. It is also used in the manufacture of biofuels. Figure 2 shows the annual production of palm oil in Colombia (South America) since 2010. 

Figure 2

Calculate the mean increase in palm oil production per year for the three year period 2014 to 2017. Show clearly how you work out your answer.

Give your answer in thousands of metric tonnes per year.

The replacement of forests with oil palm plantations to produce biofuels will change the composition of the atmosphere.

Explain how.

When palm oil plantations are created, native forest is cut down and the biodiversity in the forest reduces dramatically. Even when demand for palm oil is low, there is still a benefit to the palm oil manufacturers in cutting down the native forest.

Suggest what that benefit is. 

Conservationists concerned about the loss of habitats caused by oil palm plantations are urging farmers to use methods that allow humans to take what they need from the land but to do so in a way that oil palms can coexist with native species.

What is the name of this kind of farming?

Table 2 gives data about how the carbon dioxide (CO₂) concentration of the air has changed over time. 

Year	CO2 concentration in parts per million
1800	282
1900	295
1950	310
2000	370
2020	410
2022	420

Plot the data from Table 2 in the graph paper provided below. 

Explain why carbon dioxide concentrations in the atmosphere are changing.

In 2022, a climate activist claimed that, to arrest global warming, the atmospheric CO₂ level should be brought back to the level of the year 1900.

Using the data from Table 2, calculate the percentage decrease that the climate activist claims would be needed to return the atmospheric CO₂ level to its 1900 level. 

Figure 3 shows some damage to a piece of furniture caused by woodworm. 

Figure 3

State how the action of woodworm can contribute to global warming. 

When fossil fuels are burned, they release carbon dioxide (CO₂) into the atmosphere. In addition, because they contain levels of sulfur, sulfur dioxide gas (SO₂) can also be released into the atmosphere. 

Flue gases from the burning process can be captured and desulfurised, which traps the flue gases and reacts the sulfur dioxide with calcium hydroxide. 

Ca(OH)_2(s) + SO_2(g) → CaSO_3(s) + H₂O_(l)

A further step results in the formation of calcium sulfate which is a major component of plasterboard used in the building industry. 

Apart from supplying the building industry, state and explain the advantage of the process of flue gas desulfurisation. 

Another product of burning fossil fuels, especially the heavier fractions of crude oil like diesel, are so-called particulates. 

Explain what particulates are and describe their detrimental effect on people who come into contact with them. 

There are currently two main ways in which domestic trash is disposed of by local authorities in the UK. These are:

1. Landfill
2. Incineration (burned at 1000°C)

Table 3 below outlines some of the features of both ways of disposing of trash. 

Table 3

Landfill	Incineration
Traditional, trusted	More recent method
Needs a large hole in the ground eg. a disused quarry	Involves a high-tech incineration plant
Generates CO2 and methane	Generates a lot of CO2
Causes odours and insect/rat infestations	Clean-burning; few pollutants emitted to the atmosphere/rivers
Requires waste to be transported a long way, even exported	Generates heat and electricity for the local grid
Suitable sites running out	Unpopular but effective
	Can be set up in all localities

Use the data in Table 3 and your knowledge of waste treatment to evaluate both methods of waste disposal and to recommend a policy to a UK local authority. 

Deforestation is a major contributor to the general decline of biodiversity worldwide. 

Suggest two ways in which deforestation impact biodiversity negatively. 

With an increased need for food security due to a rapidly increasing population, farmers are keen to maximise their crop yields. 

One way in which they can achieve this is to prevent the growth of weeds using plant growth hormones. 

Evaluate the use of plant growth hormones by farmers, considering the impact of such hormones on biodiversity.

There is a general consensus amongst the scientific community that increased levels of carbon dioxide emissions as a result of human activity are causing global warming due to an enhanced greenhouse effect. 

Explain how increases in the proportions of greenhouse gases in the atmosphere have led to global warming.

Global warming, and the climate change that it brings, have an overall detrimental effect on biodiversity and ecology in general.

Suggest and explain one effect of global warming that may be beneficial to an individual species.

Peat bogs are areas of wetland that contain partially-decomposed plant material (peat). 

The conditions in a peat bog are usually acidic, which is one of the reasons why the decay of plant material is so slow (forming peat). 

Peat is an excellent natural fertiliser. 

Suggest why the destruction of peat bogs is controversial. 

Data from the United Nations suggests that globally, we are losing 88,000 km² of natural forest every year to timber and paper production, and to clearance of land for crops and livestock grazing.

A football pitch has an area of 7 140 m².

Calculate the time taken, at the current rate of deforestation, for a football pitch-sized piece of land to be deforested. Give your answer to the nearest whole second. 

Humans are reducing the area of land available for other living species. 

Give two ways in which humans are doing this. 

Growth in demand for biofuel has led to large areas of rainforest being cleared in South America to grow sugarcane. 

Sucrose is extracted from sugarcane and is fermented by microorganisms to produce ethanol, which is used in biofuels for cars.

The graph in Figure 1 shows how the production of sugarcane has changed for one country in South America. 

Calculate the percentage change in sugarcane growth over a 10 year period between 2007 and 2017.

Show clearly how you have worked out your answer. 

Clearing rainforests to create sugarcane plantations to produce biofuels for cars is controversial, with some scientists arguing that biofuels are not carbon neutral. 

Explain why. 

Almost 70% of the world’s almond supply is grown in California. 

Intensive farming of almonds in California has decreased the quality of the soil. 

To combat this, and to meet demand, farmers are increasingly reliant on fertilisers.

Excess fertiliser ends up running off into rivers and streams. 

Suggest the consequences of excess fertiliser ending up in the water supply.