Human Impacts on the Biosphere

1. Human Impactson the Biosphere Chapter 49

2. Impacts, IssuesA Long Reach • Humans threaten other species by competing for resources, overharvesting, introducing nonnative competitors, and degrading habitats – even at the ends of the globe

3. 49.1 The Extinction Crisis • Extinction is a natural process, but humans are accelerating it • In mass extinctions, many organisms in different habitats become extinct in a short period • Species diversity takes millions of years to recover after a mass extinction

4. The Sixth Great Mass Extinction • Five great mass extinctions mark boundaries of geologic time periods • Previous mass extinctions occurred as a result of global catastrophes • Many species are currently endangered or threatened as a result of human activity, in what is being called the sixth great mass extinction

5. Endangered and Threatened Species • Endangered species • A species that has population levels so low that it faces extinction in all or part of its range • Threatened species • A species that is likely to become endangered in the near future

6. Extinct as the Dodo • When humans arrived on Mauritius in 1600, dodos were plentiful – 80 years later, they were extinct

7. Living or Extinct? • The ivory-billed woodpecker was believed driven to extinction by lumbering in the 1940s – reports of sightings are not conclusively confirmed

8. 49.2 Current Threats to Species • Species with highly specific resource requirements are particularly vulnerable to habitat alterations • Endemic species • A species confined to the limited area in which it evolved, often by resource requirements

9. Habitat Loss, Fragmentation, and Degradation • Species decline when humans destroy or fragment natural habitat, or degrade it through pollution or withdrawal of an essential resource • Example: Development of prairies and meadows threatens the eastern fringed prairie orchid Example: Excessive withdrawals and pollution of an aquifer endanger the Texas blind salamander

10. Two North American Species Under Threat • Eastern fringed prairie orchid and Texas blind salamander

11. Giant Panda: An Endangered Species • Giant pandas are endemic to bamboo forests • As bamboo forests were destroyed or fragmented, pandas began to disappear • Current efforts to save giant pandas: • Protecting existing habitat, creating corridors of suitable habitat to connect isolated preserves, and captive breeding programs

12. Giant Panda: An Endangered Species • Pandas feed almost exclusively on bamboo

13. Overharvesting and Poaching • Overharvesting has caused the collapse or extinction of many commercially valuable species • Commercial hunting (passenger pigeon) • Commercial fishing (cod, abalone) • Poaching – the illegal harvest of species – is a particular threat in less-developed countries • Food sources, black market profits

14. Species Introductions • Exotic predators, such as rats and snakes, endanger many island species • Intentionally introduced exotic species, such as kudzu and European brown trout, often outcompete native ones • Exotic pathogens, such as avian malaria, are carried by introduced species

15. Interacting Effects • Most endangered species are affected by multiple threats • Example: When buffalo were hunted to near extinction, running buffalo clover declined, and is now near extinction due to habitat conversion, competition from introduced plants, and attacks by introduced insects and pathogens

16. 49.1-49.2 Key ConceptsThe Newly Endangered Species • Human activities have accelerated the rate of extinctions • Habitat loss, degradation, and fragmentation lead to extinctions, as do species introductions and overharvesting

17. 49.3 The Unknown Losses • Existing endangered species lists focus on vertebrates; we have only begun to evaluate the threats to invertebrates and plants • Our impact on protists and fungi is essentially unknown; prokaryotes are not even addressed

18. 49.4 Assessing Biodiversity • Three levels of biodiversity • Genetic, species, and ecosystem diversity • Three goals of conservation biology • Survey the range of biodiversity • Investigate evolutionary and ecological origins of biodiversity • Maintain and use biodiversity to benefit humans

19. Monitoring Indicator Species • Indicator species • A species that alerts biologists to habitat degradation and impending loss of diversity when its populations decline • Example: Lichens are indicators of habitat quality; they absorb mineral ions from the air and are harmed by air pollution

20. Identifying Regions at Risk • Hot spots • Habitats that are rich in endemic species and face a high degree of threat • Hot spots take priority in conservation efforts • Ecoregions • Larger areas characterized by physical factors and species composition • Ecoregions represent all of Earth’s biomes

21. 49.3-49.4 Key ConceptsAssessing Biodiversity • Our knowledge of species is biased toward large land animals • Conservation biologists assess the state of ecosystems and their biodiversity, with the goal of preserving as much of it as possible

22. 49.5 Effects of Development and Consumption • As human populations soar, their need for energy and other resources puts pressure on native species • Developed areas displace wild species and also harm them indirectly, as by introducing competing plants or causing light pollution

23. Negative Impact on Biodiversity • Cities displace wild species and require huge amounts of resources

24. Effects of Resource Consumption • Processes that extract or capture energy can destroy or degrade habitat • Oil spills, coal runoff, hydroelectric dams • Obtaining raw materials used in consumer products frequently involves degradation of the environment, which can reduce biodiversity • Petroleum for plastics, copper for electronics

25. 49.6 The Threat of Desertification • Human activities have potential not only to harm individual species, but to transform entire biomes • Desertification • Conversion of productive grassland or woodland into a desertlike region in which little grows • Result of poor agricultural practices or overgrazing

26. Mid 1930s: The Dust Bowl • Prairies of the southern Great Plains were plowed for crops, exposing rich topsoil to winds • Billions of tons of topsoil darkened the skies, until the entire region was labeled the Dust Bowl • Soil fell to earth as far away as New York – an ecological and economic disaster

27. The Dust Bowl • Drought and poor agricultural practices allowed winds to strip tons of topsoil from the ground

28. Desertification Around the World • Desertification now threatens vast areas • Africa: Sahara desert is expanding south into the Sahel, due to overgrazing • Northwest China: Gobi desert is expanding due to overgrazing and overplowing • The best way to avoid desertification: • Avoid farming in areas with high winds and periodic drought

29. Modern Dust Clouds • Dust from the Sahara desert, blowing out over the Atlantic Ocean, falls as far away as the southern US and Caribbean

30. 49.7 The Trouble With Trash • The US generates millions of tons of garbage • Plastics, which can persist for more than 100 years, often end up in the oceans where they harm marine life • You can minimize your environmental impact by avoiding disposable goods, and by recycling

31. Eat Plastics and Die • Its parents fed this albatross chick more than 300 pieces of plastic gathered from the ocean

32. 49.5-49.7 Key ConceptsHarmful Practices • Building homes, using energy, purchasing products, raising crops, and discarding trash all have harmful environmental effects that endanger species and ecosystems

33. 49.8 Maintaining Biodiversity and Human Populations • Some people oppose environmental protections for economic reasons • Sustainable practices allow people to benefit economically from biological resources without destroying them

34. Sustainable Uses of Biological Wealth • Using genetic biodiversity • Mexico set aside a reserve for wild maize, which might help domesticated corn resist viruses • Discovering useful chemicals • Costa Rica searches native plants for new medical or commercial chemicals • Ecotourism • Costa Rica created the Monteverde Cloud Forest Reserve as a profitable sanctuary

35. Sustainable Use of Biological Wealth • Strip logging yields sustainable economic benefits while minimizing erosion

36. Sustainable Use of Biological Wealth • Excluding cattle from riparian zones (narrow corridors of vegetation along river banks) has many benefits • Flood protection • Water conservation • Habitat for wildlife • Preservation of biodiversity

37. Riparian Restoration • San Pedro River before and after restoration

38. 49.8 Key Concepts Sustainable Solutions • All nations have biological wealth that can benefit human populations • Recognizing the value of biodiversity and putting it to use in sustainable ways is good for Earth and all of its species