EcosystemEcosystem EffectsEffects ofof OverfishingOverfishing OutlineOutline
• Human exploitation: Land vs Sea • Altered Food webs • Escalating Human Impacts, from hunter gatherer to Globalization. American bison
New Zealand Moas Australian diprotodont Sirenia But our exploitation of the sea is different • On the land, we replaced wild species with domestic species, and rebuilt the structure of terrestrial ecosystems • In the sea, we made important species functionally extinct and did not replace them Coral reefs Coral reefs Prehistoric Stock Depletion
1200 St. Thomas 1000 St. Martin 800
600 Saba
400 Nevis
200 Puerto Rico Average reef fish weight (g) Average reef fish weight 0 2000 1500 1000 500 0 Years before present Fishing Down the Food Chain
3.8
St. Thomas 3.7 Puerto Rico
3.6 Saba
3.5 St. Martin Trophic level index
Nevis 3.4 2000 1500 1000 500 0 Years before present
The working hypothesis: Three distinct transitions Three distinct transitions
1. Loss of macrofauna 2. Loss of structure 3. Rise of “pests” Human Impacts on Ecosystems
5 Climate change
4 Introductions 3 Human Mechanical population habitat Altered growth destruction ecosystems 2 Pollution 1 Fishing
Then Now Global Demand Roving Bandits Expansion of the live fish trade Serial expansion and depletion of live fish trade ContributionContribution ofof fourfour speciesspecies toto thethe livelive fishfish tradetrade overover timetime
8
7
Plectropomus leopardus 6 Lepoard Coral Trout Epinephelus coioides Green Grouper 5 Plectropomus maculatus Coral Trout Epinephelus lanceolatus 4 Giant Qld Grouper kg/year) 6 Cheilinus undulatus Humphead Wrasse (10 3
2 Mass of live fish imported to Hong Kong imported to Hong Mass of live fish
1
0 1998 2000 2002 Year Summary
• Human exploitation of the Land and Sea has altered foodwebs. • Even early human societies had an impact. • Population growth and emerging technologies have escalated the problem to a global scale Produced by
For