Health and environment
Health and environment

This free course is available to start right now. Review the full course description and key learning outcomes and create an account and enrol if you want a free statement of participation.

Free course

Health and environment

4 Changes in relative abundance of species

4.1 Human predation and extinctions

There are a number of ways in which humans have altered ecosystems, that have led to the decline of particular species. We will leave to one side any major interference such as felling forests to provide land for agricultural and urban development, and instead begin by looking at examples where we have eroded or eradicated stocks of particular species. This has notably been a consequence of the over-exploitation of food species (prey items). Predators do not normally eliminate their prey (see Figure 4), but the use of sophisticated tools, such as guns and fishing gear, has led to our being over-successful as hunters. The disappearance of the dodo must surely be the best-known example, but it is not an isolated occurrence. Table 2 shows some other vertebrate extinctions that correlate with human activity. This table gives a selection of species only. For example, around 100 species of bird are known to have become extinct since 1600.

Table 2 Some vertebrate extinctions.

Species Former distribution Last recorded in wild Probable cause of extinction
dodo Mauritius c. 1680 hunting
great auk North Atlantic 1844 hunting by sailors
passenger pigeon North America 1889 hunting and habitat destruction
pink-headed duck Bengal 1936 hunting
auroch Europe 1627 hunting and habitat destruction
Caribbean monk seal Caribbean c. 1960 hunting
Steller's sea cow North Pacific 1768 hunting
Tasmanian wolf Tasmania 1900s hunted as a ‘pest’
harelip sucker rivers of North America 1893 fishing and habitat destruction
blue pike Great Lakes, North America 1970 over-fishing, pollution, predation by introduced fish species
St Croix racer St Croix, US Virgin Isles 1900s

Take your learning further

Making the decision to study can be a big step, which is why you'll want a trusted University. The Open University has nearly 50 years’ experience delivering flexible learning and 170,000 students are studying with us right now. Take a look at all Open University courses.

If you are new to university level study, find out more about the types of qualifications we offer, including our entry level Access courses and Certificates.

Not ready for University study then browse over 900 free courses on OpenLearn and sign up to our newsletter to hear about new free courses as they are released.

Every year, thousands of students decide to study with The Open University. With over 120 qualifications, we’ve got the right course for you.

Request an Open University prospectus