Biodiversity & the Effect of Human Interaction on Ecosystems Practice Questions

Biodiversity is important for the future of the human species on Earth.

The human population is growing rapidly and the standard of living in many countries is rising. This means that more resources are used and more waste is produced.

A wildlife trust bought an area of damaged heathland in 2009 and began a programme to regenerate the habitat.

Figure 1 shows the number of breeding pairs of a rare bird counted on the heathland in four different years.

Peat bogs are waterlogged areas of land containing thick layers of partly decayed plant material called peat. Large areas of peat bog are drained and dug up so that the peat can be sold as garden compost.

Table 1 shows the size of the human population and the area of land used for farming in four different years.

Year	Human population / billions	Area of land used for farming / million km²
1961	3.1	42.0
1981	4.5	46.2
2001	6.2	48.6
2021	7.9	48.0

Large areas of tropical forest have been cut down in recent years.

A company has applied for permission to extract peat from a lowland bog in the north of England.

The local council has been given the following information.

• The bog covers 90 hectares. It is home to 20 plant species that are found nowhere else in the county, as well as rare insects and birds.
• The peat in the bog is estimated to store 250 000 tonnes of carbon.
• Extracting the peat would create 45 full-time jobs in an area where unemployment is high.
• Compost made from peat is cheaper for gardeners than peat-free compost, and gardeners say plants grow better in it.
• The company has promised to re-wet and restore 30 hectares of the bog after 15 years of extraction.
• If permission is refused, the company says it will buy peat from bogs in another country and transport it to the UK.

Sewage from a small town is treated at a sewage works and the treated water flows into a river. Water from fields that are sprayed with fertiliser also drains into the river, just below the sewage works.

A student sampled the river at four sites on one day in July. The results are shown in Table 2.

Site	Position	Nitrate concentration / mg dm$^{-3}$	Number of invertebrate species found
A	2 km upstream of the sewage outflow	5	24
B	0.5 km downstream of the sewage outflow	42	6
C	3 km downstream of the sewage outflow	30	11
D	10 km downstream of the sewage outflow	12	20

The student concluded:

'The sewage works has caused a large fall in the biodiversity of the river.'