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Studying mammals: Food for thought
Studying mammals: Food for thought

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7 The threat of extinction

DA ends his book by writing eloquently of the dangers of extinction faced by mammals, from habitat loss as we exploit our environment to produce more and more food, for our growing population. However bleak the picture, there is still time and opportunity to save mammal species from extinction. Although bison in the USA and Canada were reduced to barely 1000 individuals in 1900, their numbers have now risen to well over 150 000 thanks to the efforts of First Nation indigenous peoples, and ranchers and conservationists.

Unfortunately, the news is not so good for primates, especially apes. The Primate Specialist Group of the World Conservation Union, states that one in three of all primate species is now threatened with extinction. Half of the world's most endangered primates live in Asia; one of those species is the Sumatran orangutan. On their website, the Sumatran Orangutan Society (SOS) reports that orangutans may become extinct in the wild within 10 years. SOS documents the tragic consequences on the Sumatran orangutan population, of illegal logging and the deliberate starting of fires for forest clearance for timber and palm oil plantations. Such activities account for the loss of over 80% of orangutan habitat over the last 20 years. The loss of forest forces orangutans to stray into farms or palm oil plantations where they are captured or killed. Some captured orangutans, along with those that were kept as pets until 'owners' tired of them, are taken to rescue centres, similar to Camp Leakey which featured in the TV programme. There is another rescue centre at Bohorok, adjacent to the Gunung National Park, but rescued orangutans cannot be released into the park because of the risk of spreading infectious diseases. The loss of orangutans from the forest ecosystem would have severe consequences. They play a crucial role in forest regeneration because of their diet; the fruits and seeds they eat are dispersed in their faeces - without orangutans in the forest, many species of plants could disappear.

The Gunung National Park in northern Sumatra is part of the vast Leuser Ecosystem, which occupies two million hectares and includes swamp forest, lowland forest, lakes, rivers, and two active volcanoes. The rainforest in the area is considered to be sacred by the local people. The Sumatran orangutan, genetically different from the Bornean orangutan, lives in the swamp and lowland forests of the National Park. In the TV programme, you saw a group of Sumatran orangutans feeding in the swamp forest. Other species living in the National Park include the Sumatran tiger (you caught a brief glimpse of this species in the programme from 03.42-03.50), elephant, rhinoceros, clouded leopard, sun-bear, slow loris, gibbons and monkeys. Even though one-third of the Leuser Ecosystem, including the swamp forest, is National Park, it is under threat. In September 1999, the Suaq Balimbing research station in the Park was abandoned by the staff, at a point where it was entirely surrounded by illegal logging activity. Despite requests for help from the authorities, no assistance was provided and illegal logging continued without interruption. The area around Suaq Balimbing had a high density of orangutans, seven individuals per square kilometre. Researchers had been studying the growth and productivity of the trees used by the orangutans as sources of fruit. All trees with a trunk diameter greater than 20 cm were removed by the illegal loggers.

Even planned selective logging would cause problems, as removal of the mature fruit trees that orangutans depend on for food puts the animals at risk of malnutrition. To date, over 25% of the Gunung National Park has already been damaged by the illegal logging that is still ongoing. The damage to the Leuser ecosystem has been exacerbated by the large-scale flooding and landslides in northern Sumatra and Aceh in 2000, which destroyed thousands of hectares of rice fields and killed ten people. During the initial preparation of this course (2003), the local Acehnese authority planned to build a network of roads in the park. The one road that now crosses the Gunung National Park is used by illegal loggers and poachers as an entry route into the heart of the Leuser ecosystem.

Figure 9
Figure 9: Courtesy of the Sumatran Orangutan Society
Figure 9 extract from the website of the Sumatran Orangutan Society. For an enlarged version, click on 'View document' below

Click 'View document' to open a larger version of Figure 9

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Activity 8

Study Figure 9, which shows an extract from the SOS website, including the map of the Leuser Ecosystem showing the plans for the new roads (depicted in orange through the green rainforest areas). Predict two likely effects of the roads, listing your ideas as bulleted points.


Four possible effects are listed here; you may have thought of others.

  • From the map, it looks as if the roads will split the Leuser Ecosystem into nine unconnected parts, isolating the animals in each part. Orangutans move around the forest, harvesting fruits as they come into season and the roads will block their access to important sources of food.

  • Animals will follow their traditional routes around the ecosystem and will be at risk of being killed by traffic.

  • The roads will provide an even easier route for poachers and illegal loggers to gain access for their activities.

  • Increased illegal logging is likely to exacerbate the problem of flooding - not surprising, since much of the swamp forest is regularly inundated.

Given the vulnerability of so many of the mammalian species discussed in the 'Studying mammals' units, the topic of conservation is an appropriate one with which to close this course, and indeed the series as a whole. This information about the Sumatran orangutans was obtained from the web source identified. Such websites are invaluable for gaining up-to-date information about conservation issues. I hope you will feel prompted to find out more about these pressing issues on your own initiative.