rarity and extinction risk in the sea (marine lecture 4)

Question 1

Why do people incorrectly assume marine species aren’t at risk of extinction?

Answer 1

bc perception that they are:

• abundant and widespread/no dispersal barriers: many marine endemics & highly structured population
• high fecundity: doesn’t predict recovery potential
• naturally variable and resilient, depleted populations recover: no more than many terrestrial species, they may they may not
• lower extinction in fossil record: untested

Question 2

What is the reality?

Answer 2

• oceans are far from uniform
• physics/biology define distinct marine ecosystem at a range of scales
• most marine surveys show a large number of singletons
• some species only known from one individual ever

Question 3

What are the threats unique to marine ecosystems?

Answer 3

• overfishing: industrial scale hunting
• ocean acidification
• plastics: production/use still rising. plastic ingestion v high

Question 4

What are consequences unique to marine ecosystems? What areas are most threatened?

Answer 4

• coral bleaching: warm water destroying entire reefs

- coral reefs, mangroves, sea grass, deep sea

Question 5

What is the extinction risk for marine species?

Answer 5

• low absolute numbers not cause for complacency
• in well known groups marine risk matches that on land
• do data deficient species have similar risk also?

Question 6

How does trade affect marine species? How are elasmobranchs threatened?

Answer 6

• large marine animals as threatened by trade in luxury products as terrestrial animals
• marine species have larger geographic ranges but this does not lower extinction risk
• life histories don’t protect either
• elasmobranchs (sharks & rays) most threatened
• exploited in largely unregulated fisheries
• luxury product trade
• large, slow growing, late to mature

Question 7

What is marine defaunation? Where is it worst?

Answer 7

• human caused animal loss in ocean
• relatively recent and few global extinctions
• but many significant range retractions/ population reductions
• coastal systems hit harder than ocean/deep sea
• but coastal ecosystems also better studied

Question 8

What are implications for conservation?

Answer 8

• many marine systems highly mobile
• conservation efforts need to span ecosystems/jurisdiction
• diversity not necessary predictable by comparison to land, especially in deep sea

Question 9

Summary

Answer 9

• many myths about marine extinctions
• less hard data than land
• what data there is implies marine species not at lower extinction risk
• many groups of marine species and marine ecosystems are under high threat