BIOL 570

Discussion of Jackson et al

Historical overfishing and the collapse of coastal ecosystems

1. From what you have seen of food webs elsewhere in the course, what would be your prediction of the effects of adding a top level consumer on the food webs in Fig 1?

2. What are the major changes in kelp forest habitats that have occurred in the past 10,000 years (See Table 1)? How strong is the evidence that humans are responsible for the change? How does cod body size (Fig 2 A) relate to this?

3. What are the major changes in coral reefs that have occurred in the past 50 years (see Table 1)? How strong is the evidence that humans are responsible? How does Fig 2B relate to the conjecture that humans are responsible?

4. What are the major changes in estuaries like the Chesapeake Bay (Maryland, Delaware, Virginia) and Pamlico Sound (North Carolina) that have occurred in the past 1000 years (See Table 1)? How strong is the evidence that humans are responsible? How does Fig 2C relate to this conjecture?

5. The authors argue that the ecological extinction of entire tropic levels makes ecosystems more vulnerable to other disturbances. How does this argument fit with the ideas of Paine on food web complexity and species diversity?

6. What are the prospects for ecosystem restoration in these habitats?