The land-sea connection
The idea that changes to fishing can result system wide changes often assumes strong top-down effects. The existence of such trophic cascades requires 'key-stone' species at each trophic level. Strong control of tropical and temperate habitats via benthic grazing, as a function of direct or indirect fishing pressure, has had a persuasive influence on coastal managers throughout Australia.
We have tremendous difficulty with the application of these ideas to much of Australia's south coast. Instead, many of need to be as concerned about what we add to our coast (coastal run-off) as we are about what we remove (abalone, urchins, fish). Our research has identified land-to-sea connections that links intensity of land-use to extent to subtidal habitat-degredation (kelp loss).
Comparison of south-coast recovery (after >5 years):
Good water quality
Poor water quality
Ecosystem change across 30+ years
- Connell SD, BD Russell et al. 2008. Recovering a lost baseline: missing kelp forests from a metropolitan coast. Marine Ecology Progress Series. 360:63-72
- Connell, S. D. 2007. Water quality and the loss of coral reefs and kelp forests: alternative states and the influence of fishing. Pages 556-568 in S. D. Connell and B. M. Gillanders, editors. Marine Ecology. Oxford University Press, Melbourne
Cause of change
- Gorman, Russell & Connell SD 2009 Land-to-sea connectivity: linking human-derived terrestrial subsidies to subtidal habitat change on open rocky coasts. Ecological Applications 19: 114-1126. (download)
Gorgula, SK & Connell, SD 2004. Expansive covers of turf-forming algae on human-dominated coast: the relative effects of increasing nutrient and sediment loads. Marine Biology 145: 613-619. (request)
Uncertainty about the science
Gorman & SD Connell 2009 Recovering subtidal forests in human-dominated landscapes. J Applied Ecology 46: 1258-1265. (request)
Elsdon & SD Connell 2009 Spatial and temporal monitoring of coastal water quality: refining the way we consider, gather, and interpret patterns. Aquatic Biol 5:157-166
Russell, BD & Connell SD 2007. Response of grazers to sudden nutrient pulses in oligotrophic v. eutrophic conditions. Marine Ecology Progress Series 349:73-80. (request)