Chapter 6: Habitat degradation and loss

1. Chapter 6: Habitat degradation and loss

2. Biggest threat to biodiversity; over 80% of land on Earth is affected by humans to some extent; at least 60% is used unsustainably and/or is damaged. Aquatic systems too: e.g., over 1/5 of coral reefs gone, another 1/5 degraded.

3. Degradation vs. loss: Many human factors, direct or indirect (e.g., some forms of pollution; global warming). Degradation: Some species affected, not all; not necessarily permanent. Loss: All or most species affected; recovery time (if even possible) usually long.

4. Habitat conversion (transformation): Usually some variation on degradation or loss; change land from one type to another -- e.g, forest to grassland, grassland to agriculture. Degradation often escalates to loss.

5. Fig. 6.1: For many biomes, much of loss was pre-1950; since then, biggest effects have been in tropics. Projection (at current rates): degradation/loss of approx. 50% of most by 2050.

7. Terrestrial: Can track history of vegetation using pollen cores; satellite imagery now allows tracking in real time. Evidence of forest to agriculture started at least 7,000 years ago in parts of the Old World; some permanent by 2,000 years ago.

11. Degradation and loss increases exponentially with human population growth. Only about 40% of natural vegetation left in U.S.; some habitat types almost gone; similar patterns in Europe, now SE Asia, and other areas, especially with rapid urbanization and agriculture.

13. In last 300 years, 50% of worldwide forests cleared; most gone in Europe by 1700; now over 70% of forest loss per year is in the tropics. Forests critical for biodiversity; also filter and protect drinking water, carbon sequestration, climate (e.g., evapotranspiration and rainfall patterns, temperature), control of erosion/prevention of flooding, contribute to soil fertility...

15. Grasslands/shrublands: over 40% of Earth’s terrestrial area; easily transformed for agriculture; heavy grazing by livestock changes vegetation and can increase erosion and desertification.

16. Freshwater: Affected by dams, rerouting, changes in flow rates, pollution. Over 90% of U.S. threatened or endangered fishes due to water development, use for agriculture and urban areas, etc.

17. Consider Aral Sea in Kazakhstan: combined effects of water use: Rivers diverted for agricultural use (especially cotton); lose fishes (including ones used for food); salt concentrates in water; dry areas that accumulated pesticides etc. create toxic dust. Quality of life declines (and cotton industry will probably decline too).

18. Wetlands: Major effect to decrease loss; over 50% lost in US, and 70% in Europe.

20. Marine: About 20% of coastal habitats extensively modified; drained, dredged, used for aquaculture, polluted by runoff etc.; diversion of rivers can decrease nutrient input and increase erosion due to loss of sediments. Runoff can cause eutrophication, algal blooms, loss of biodiversity.

21. Tropical coastal mangrove forests severely damaged; important for breeding fishes and other organisms; many cleared or used for aquaculture (especially shrimp in SE Asia). Unsustainable: Massive pollution, nutrient input, destruction... huge areas of mangrove forests disappearing.

22. Other coastal ecosystems: seagrass beds (important e.g., for larval fishes even if species richness of plants is low); coral reefs -- inherent species richness.

23. 6.13 The Exxon Valdez oil spill contaminated over 1900 km of shoreline in Alaska

24. Recall that some of the major types of habitat destruction are due to agriculture; extraction, including coal, mining; exploitation -- fishing, timber etc.

26. Agriculture: Growing rapidly; uses water for irrigation; often heavy use of pesticides, fertilizers. Worst are monocultures (large areas of one species; e.g., corn, soybeans). Better: polyculture; use of agricultural matrices, creation/maintenance of habitat corridors.

27. Huge areas used to produce grain for livestock -- better to use pasture land (and of course, reduce demand for meat and dairy products).

28. Distribution of cultivated systems worldwide

29. 6.19 Distribution of the 305 crisis ecoregions that are at-risk of elimination

30. 6.17 Biodiversity hotspots (dark gray) and major tropical wilderness areas (light gray)

31. Case 6.2 Table A

32. Extraction: mining, oil, gas, coal -- often very damaging. Logging is also “extraction” in a sense; some improvements, e.g., selective logging in tropics. Intensive fishing (especially trawling of sea floor) is also a form of extraction; often causes medium- to long-term damage (usually less so than logging).

35. 6.21 Economic value from managing ecosystem in sustainable ways vs. unsustainable uses

36. 6.20 How habitat degradation caused by land use change is based on economic and social drivers

37. Development: Building cities etc. usually completely destroys habitat. Roughly 3% of land on Earth is urbanized; this is occupied by at least 50% of world population. But -- can consider this in terms of actual surface area covered, or by the “ecological footprint”.

38. Ecological footprint: how far do the effects of the city extend? Estimate for Vancouver B.C.: Footprint is about 174 times the city area. UN estimate for the Earth (2007): human ecological footprint = 1.5 Planet Earths (i.e., people are using resources 50% faster than they can be renewed). Per person (UK): about 5.5 “global hectares” (worldwide range 1-10).

39. Case study (from Chapter 18): Approaches to pollution, sustainability, etc.: how can cities reduce their impact? Many answers.

40. Cities historically have been built near sources of good water and agricultural land. Influenced by the industrial revolution, starting in the 1700s; exponential growth and spread to developing countries. More and more people moved to cities; trend continues in 3rd world.

41. “Urban sprawl”: not just cities; suburbs, more cars, pollution, inefficient land use, demands on natural resources. All of this increases the “ecological footprint”. How to change? W. Europe especially active: change patterns of use of food, goods, and energy.

42. Changes in agriculture: organic, or at least low pesticide/herbicide. How much food is wasted? In developed countries, up to 1/3 of food purchased. “Food miles”: How far does food travel, on average, from producer to consumer? U.S.: about 1300 miles. So -- think local/seasonal.

43. Case 18.2 Table A

44. Many cities are getting better at getting people to separate garbage: recycling, organic matter for composting (and make compost available for local vegetable growing). Vienna and other European cities: urban gardens/allotment gardens = local fresh produce, low cost. And -- recycling and urban agriculture can boost local economies.

45. Recycling: can be very complex, but overall, especially useful if materials don’t have to be transported long distances. Make it economically viable for local people to collect recyclables and profit (aluminum cans are a prime example). Especially effective in some 3rd World cities.

46. Compacted living: Urban sprawl (suburbs etc.): bigger ecological footprint, more cars -- “build up, not out”. Concentrate more people in smaller areas, and increase efficiency of transportation, energy use etc. Urbanization may even lead to restoration of natural areas (at least locally).

47. Case 6.1 (B) The landscapes of New England land use and population density (black line)

48. “Ecoprocurement”: Evaluate use of goods used by local governments, ecologically AND economically: often saves money and encourages local production.

49. Poverty: People who can’t afford expensive goods and services may have a negative impact disproportionate to their income. Poor sanitation may lead to pollution. Clearing local areas for (often inefficient) agriculture. Production/use of charcoal (e.g., Madagascar).

50. What if the land could be used for sustainable purposes? Example: Kenya: Use natural forest areas to raise butterflies. Big market in rich countries; also encourages ecotourism. Sustainable, and has doubled average income.