Learning Unit 13: Biodiversity Loss

1. Learning Unit 13: Biodiversity Loss

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3. Learning Outcomes • Explain what "biodiversity" means • Name six fundamental causes of the loss of biodiversity due to human activities • Explain how threatened species are classified • Explain how the loss and modification of habitats, specifically deforestation, contribute to the loss of biodiversity • Explain how the overexploitation of biotic resources contributes to the loss of biodiversity • Briefly discuss the efforts being made to counteract the loss of biodiversity

4. Understanding biodiversity Pages 341-343 in Middleton • Biodiversity refers to the number, variety and variability of living organisms. It is defined in terms of genes, species and ecosystems: • Genetic diversity: variation between individuals and between populations within a species • Species diversity: different types of animals, plants and other life-forms within a region. • Ecosystem diversity: variety of habitats found in an area • Definition of the Convention on Biological Diversity: the variability among living organisms from all sources, including terrestrial, marine and other aquatic ecosystems; this includes diversity within species, between species and of ecosystems

5. Threats to biodiversity Pages 343-344 in Middleton • Biodiversity is threatened by: • Human population growth • Habitat loss and degradation • Climate change • Excessive nutrient load and pollution • Over-exploitation of resources • Invasive alien species

6. Threatened species Pages 344-345 in Middleton IUCN Red Data List

7. Habitat loss and degradation Pages 345-348 in Middleton Pandas • Habitat destruction, fragmentation and degradation is regarded as the most severe threat to biodiversity • The giant panda has been driven to the edge of extinction by human encroachment into its habitat • There are extreme difficulties with captive breeding of pandas • Continued destruction of panda habitats – even in conservation areas (Wolong Nature Reserve) • Nature reserve attracts tourists which also increase human population • Trees are cut for fuel, which further destroys panda habitats

8. Habitat loss and degradation • Fragmentation of the panda’s habitat has affected the number of bamboo species remaining (pandas rely on a specialized bamboo diet) • Small, isolated populations of pandas face risk of inbreeding • Inbreeding may reduce resistance to disease, less adaptability to environmental change and decrease reproduction rates • Habitat fragmentation increases dangers from outside disturbances (fires and diseases) and invasion by competitors or predators

9. Habitat loss and degradation Dung beetles in the Amazon basin • Dung beetles are a keystone species in the forest ecosystem. Burying dung and carrion as a food source for their larvae facilitates the rapid recycling of nutrients and germination of seeds defecated by fruit-eating animals and reduces diseases levels by killing parasites that live in the dung • The dung beetles are significantly affected by forest fragmentation in the Amazon which causes lower population densities for each species and smaller-sized beetles together with fewer species of beetles

10. Climate change Page 348 in Middleton • Warming temperatures, increased frequency of extreme weather events and changing patterns of rainfall and drought has significant impacts on biodiversity. • Warming climate is a significant threat to polar bears because of its effect on sea ice • Loss of sea ice in the Arctic – which is the primary habitat of polar bears – negatively affects the survival of polar bears • It is estimated that two-thirds of the world’s polar bears could be extirpated by 2050 • Large-scale warming of sea surface and air temperatures contributed to the extinction of the Monteverde harlequin frog and the golden toad from the mountains of Costa Rica. • The demise of the harlequin frog, golden toad and other endemic amphibians in the American tropics occurred due to a fungus that has thrived in higher temperatures. • The processes of climate change and habitat loss are happening concurrently (at the same time)

11. Pollution Pages 348-349 in Middleton Marine ‘dead zones’ • Rivers carrying heavy nutrient loads severely degrade coastal water quality by creating ‘dead zones’ where decomposing algae use up oxygen in the water to leave large areas completely without marine life. • The number of dead zones increased dramatically over the past 100 years

12. Overexploitation Pages 123 and 349-351 in Middleton • Scientific evidence of the overexploitation of fauna from the Stone Age to the Late Pleistocene • Overexploitation from Roman times (elephant, rhino and zebra in Africa north of the Sahara) • Death of the last dodo by seafarers on Mauritius meant that the tembalocque tree (an endemic species) has been unable to reproduce for the past 300 years because the dodo prepared the tree’s fruit in its gizzard for germination • The advent of the firearm enhanced humans’ ability to exterminate fauna in large numbers – resulting to the decimation of the buffalo and extinction of the passenger pigeon in North America • The North American passenger pigeon is believed to have been the most abundant bird to ever have inhabited the planet – about 10,000 million in the first half of the 19th century • They were killed for their meat and together with the destruction of breeding habitats, were driven to extinction

13. Overexploitation • Migrating birds are killed by hunters in Italy and Malta. • Overhunting pose a big threat for large mammals, whose products fetch high prices in local and international markets. • The African elephant population was cut by half during the 1980s before a ban on international trade in ivory was introduced in 1989. • The market for whale products (whale oil and meat) fuelled the hunting of whale species. • An estimated 250,000 blue whales were killed in the Southern Ocean leaving around 1000 today. • The market for floral species can also lead to overexploitation. • Cacti and orchids are at risk from collectors and many species of tree have been reduced in their range by selective logging (sandal tree from Juan Fernàndes island and bois de prune blanc of Mauritius and Réunion)

14. Invasive alien species Pages 351-352 and 372-376 in Middleton • Increased trade, travel and transport have facilitated the spread of invasive alien species • The movement of people has assisted biological invasions both deliberate and unintentional. • Examples of plants and animals deliberately transported for subsistence and commercial purposes are: pigs, chickens, yams, taro, coconuts, potatoes and maize. • Unintentional dispersal is when species are transported by automobiles, aircrafts and ships. Examples include alewife, lamprey, zebra mussel and little red fire ant.

15. Invasive alien species Introduction of the alewife and lamprey • Invasion of the alewife and sea lamprey following the completion of the Erie Canal and the Welland Canal • Atlantic salmon, lake charr, lake trout and lake herring (all of commercial importance) have been severely depleted by competition for food from the alewife and predation by the sea lamprey • The Great Lakes Fishery Commission currently spends about US$25 million per year in lamprey control (use of barriers, traps, periodic applications of a toxicant in their spawning areas and release of sterile males)

16. Invasive alien species Unintentional dispersal of the zebra mussel • Arrival of zebra mussel in the ballast tank of a European ship from the Caspian Sea to the Great Lakes • Within two years, zebra mussel densities had reached 70,000 individuals per square metre in parts of Lake Erie, choking out native mussels in the process • The mussels have spread to all five of the Great Lakes as well as numerous other inland lakes and rivers • The zebra mussel can now be found in the waters of 23 US states and two Canadian provinces and may cause damage to drinking water treatment plants, electric power generation facilities, dams, boats and fisheries and endemic aquatic communities • Economic losses from aquaculture amounts to US$32 million per year

17. Invasive alien species Examples of invasive plant species that altered ecosystem properties

18. Island species Pages 352-355 in Middleton • Island species are threatened and vulnerable to extermination • Many island species are endemic and extremely vulnerable to invasive alien species, diseases and predators • The small size of islands means human activities can rapidly degrade large portions of ecosystems and have great impacts on the small island populations • The likelihood of island birds to become extinct is 40 times greater than continental bird populations

19. Island species • Nine genera, at least 17 species of giant lemurs, several species of flightless birds and giant tortoises have become extinct since humans arrived on Madagascar • Resource overuse, fire-mediated vegetation change and invasive species continue to endanger several lemur species on Madagascar today • Goats were introduced to St Helena by explorers and colonizers • St Helena’s endemic plants had evolved without large grazing animals and had few defences against them • Seven endemic species are extinct and today another seven endemic plant species are endangered and nine are critically endangered on St Helena

20. Island species • Polynesians were responsible for the loss of numerous species by hunting, habitat modification and the introduction of predators • Damage to wildlife of the Hawaiian islands began before the arrival of Europeans • Polynesians cleared lowland areas for cultivation and introduced rats, dogs, pigs and jungle fowl • At least half of the known total of 83 species of birds in Hawaii became extinct in the pre-European period • The introduction of the brown tree snake to a number of Pacific islands had devastating effects on endemic birds • It was accidentally introduced to the island of Guam from New Guinea • The exponential growth of the brown tree snake lead to rapid declines in bird species, two bat species and six species of lizard

21. Habitat protection Pages 357–361 in Middleton • 13% of the earth's surface is currently covered by conservation areas • Some countries give protection to more than one-quarter (25%) of their land area (Bhutan, Botswana and New Zealand), while other countries protect less than 1% of their national space (Uruguay, Yemen). The world’s largest protected area is the Northeast Greenland National Park – covering 972,000 km2 of Arctic desert and icecap that has a very small human population. • The top five largest protected areas are: • Rub al Khali Wildlife Management Area in Saudi Arabia – 640,000 km2 of sandy desert • Chang Tang Nature Reserve – 290,000 km2 on the Tibetan Plateau consisting of alpine and desert steppe at elevations of 4,800 m and higher • Phoenix Islands Protected Area in Kiribati – 410,500 km2 • Great Barrier Reef Marine Park in Australia – 344,400 km2 • North-western Hawaiian Islands in the USA – 341,400 km2 • The total protected sea area is only about 0,65% of the surface area of the oceans

22. Off-site conservation practices Pages 363-365 in Middleton • Off-site conservation techniques complement on-site approaches by providing individuals for research, the results of which can be fed back into management techniques in the wild • Individuals are also provided that can be re-introduced into the wild • Off-site programmes are of educational value • Off-site programmes can be expensive, logistically demanding and require long-term management and monitoring • Plant reintroductions have relatively low rates of long-term success • Reintroduction of animals is also a difficult task • Examples of reintroduction: • The Arabian oryx to Oman • The Przewalski horse to Mongolia